Applied wetlands science and technology

Kent, Donald M. “Frontmatter” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

Library of Congress Cataloging-in-Publication Data Kent, Donald M. Applied wetlands science and technology / edited by Donald M. Kent.—2nd ed. p. cm. Includes bibliographical references. ISBN 1-56670-359-X (alk. paper) 1. Wetland conservation. 2. Ecosystem management. 3. Wetlands. 4. Water quality management. I. Kent, Donald M. QH75 .A44 2000 333.91'8—dc21

00-030927 CIP

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© 2001 by CRC Press LLC Lewis Publishers is an imprint of CRC Press LLC No claim to original U.S. Government works International Standard Book Number 1-56670-359-X Library of Congress Card Number 00-030927 Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 Printed on acid-free paper

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Preface Compared to other ecosystems, wetlands have received an unprecedented amount of attention. Much of this attention has occurred as a result of, and subsequent to, passage of Section 404 of the U.S. Clean Water Act in 1977. The Act recognizes the importance of wetlands to the societal good. That is not to suggest that wetland values were institutionally unrecognized prior to this time. Beginning in the 1930s, wetlands were recognized as valuable for the production and protection of wildlife, especially waterfowl and furbearers. In the 1960s, wetlands were recognized as important for attenuating floodwaters. Now, wetlands are recognized for providing these and other functions, including nutrient and contaminant retention and transformation, groundwater recharge, and production export. Ironically, and coincident with this recognition of wetland value is an awareness that wetlands are disappearing at an alarming rate. Between 1780 and 1980, an estimated 47 million ha of wetlands were lost in the contiguous United States. Of the north central wetlands 75 percent, mostly prairie potholes, were lost between 1850 and 1977. Bottomland hardwood forests were cleared at a rate of 67,000 ha per year between 1940 and 1980. Gulf coast wetlands disappeared at a rate of 10,000 ha per year. Of those wetlands that remain, many are degraded from channelization, damming, and agricultural and urban runoff. Remaining wetlands are fragmented or isolated. This awareness of wetland loss and degradation, and the promulgation of laws and regulations for protecting wetlands and regulating their use, has spawned the development and growth of the wetland professions. This book is for working wetland professionals and nonprofessionals alike. It is intended for managers, regulators, consultants, and developers responsible for effective decision making. The book also is intended for anyone interested in how wetlands function, how wetlands can be protected, and how wetlands can be managed. In some ways, this is a “how to” book, in that it is a guide for working with wetlands. However, we understand that each and every wetland, and each and every situation, is unique and requires a unique solution. As such, the book seeks to provide the guidelines for effective decision making. This second edition of the book, as was the first, was written by practicing wetland professionals. In this manner, the most relevant, up to date information on applied wetland science and technology is available. Each chapter is fully referenced, providing the reader with an opportunity to seek out more detailed information. The book has 14 chapters—2 fewer than the first edition. The reduction in the number of chapters is due to consolidation, and not a reduction, in material. In fact, three new chapters have been added, and several chapters appearing in the first edition have been partly or completely revised. Several new authors have participated in the revision. Chapter 1 provides an introduction to wetland management, including definition and classification. The chapter also discusses legislation and regulation in the United States to provide the context for subsequent chapters. Chapter 2, Wetland Identification and Delineation, is a consolidation of Chapters 2 and 3 from the first edition. ©2001 CRC Press LLC

Carl Tammi has updated the subject in response to recent legislation and policy. Wetland functions and values are discussed in Chapter 3. The subject has been totally revised from the first edition, with an emphasis on evaluating wetland functions and values, including economic values. Chapter 4 is an updated version of the ecological risk assessment material. As in the first edition, David Kent and his coauthors discuss evaluating wetland impacts from anthropogenic chemical, physical, or biological stressors. Chapter 5 discusses avoiding and minimizing impacts to wetlands from anthropogenic activities. Wetlands impacted by anthropogenic activity will require remediation. Enhancement, restoration, and creation of wetlands are methods for remediating impacts. John Zentner, author of Chapter 6, has consolidated the freshwater and coastal enhancement, restoration, and creation chapters from the first edition. Another remediation option is mitigation banking. Chapter 7—Wetland Mitigation Banking, authored by Mike Rolband, Ann Redmond, and Tom Kelsch, is a chapter new to this edition. Chapter 8, Monitoring Wetlands, is a carryover from the first edition. Monitoring is an important component of remediation efforts, as well as fundamental to treatment wetland programs. Tom and Bill DeBusk have written Chapter 9 on treatment wetlands. The chapter is completely new and consolidates the discussions of three distinct chapters in the first edition. Chapters 10 through 13 discuss wetland management. Chapter 10 consolidates Chapters 13 and 14 from the first edition in discussing design and management of wetlands for wildlife. The chapter addresses design issues based upon modern conservation principles and specific management techniques for existing wetlands. Coastal Marsh Management (Chapter 11) continues to be an important issue, and Robert Buchsbaum’s chapter from the first edition is again included in this edition. A new chapter on Watershed Management is included in the second edition. Effective management of wetlands is constrained without consideration of surrounding activities. The theme of broadened perspectives is expanded even further in Chapter 13, Managing Global Wetlands. This new chapter, coauthored by Annette Paulin, recognizes that some wetlands are of international importance and discusses mechanisms for managing these wetlands. The final chapter, Wetlands Education, is the anchor for the book. Karen Ripple has completely revised the chapter. Nevertheless, the intent of the chapter remains the same as that of the first edition—effective wetland management and regulation depends ultimately upon educating the general populace on the value of wetland functions. In closing, I am indebted to the contributing authors. Their contributions are invaluable to those who may read this book and hopefully will influence the way wetlands are managed. I am pleased and honored to have worked with each author and proud to share this book with them. As always, a work of this sort is the result of numerous discussions both past and present. To all those who have stimulated and influenced my thinking, thanks. Donald M. Kent, Ph.D.

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About the Authors Dr. Robert Buchsbaum is Massachusetts Audubon Society’s coastal ecologist and is responsible for applied research on coastal habitats and providing technical analysis on coastal issues. He has published technical papers on a variety of topics including herbivory by Canada geese on saltmarsh plants, nitrogen dynamics in decomposing marsh plants, and on eelgrass wasting disease, and nontechnical papers for the lay public. His recent work includes studies of human impacts on wildlife and water quality in salt marshes and investigations into the role of the environment in the ability of eelgrass to resist disease. Thomas A. DeBusk is the President of Azurea, Inc. and DB Environmental Laboratories, Inc., environmental consulting and research firms located in central Florida. He has 23 years experience with the use of aquatic plants and wetlands for water treatment. Dr. William F. DeBusk is Assistant Professor in the Department of Soil and Water Sciences, University of Florida, Gainesville. He specializes in elemental cycling, wetland ecology, and analysis of ecosystem processes along spatial gradients. Dr. James F. Hobson is Senior Project Advisor for Arcadis Geraghty & Miller in Millersville, MD. He has significant experience in environmental toxicology and testing programs in support of existing and new chemical product registrations under U.S. federal, state, Canadian, and European regulations. He is a diplomate of the American Board of Toxicology and has frequently spoken at and chaired industrial and academic conferences on environmental toxicology issues. Dr. Kenneth D. Jenkins is Director of the Molecular Ecology Institute at California State University and principal in the consulting firm of JSA Environmental in Long Beach, CA. He has been directly involved in numerous ecological risk assessments, especially for hazardous waste sites, and is widely published in the field of ecological assessments. Tom Kelsch is Director of the Conservation Education Initiative which he joined in 1998. Previously, he worked for 8 years as an environmental scientist with the U.S. Environmental Protection Agency’s Office of Wetlands, Oceans and Watersheds in Washington, D.C., including 3 years as Chief of the Wetlands Regulatory Policy Section. He also has extensive experience as an environmental planner for a private consulting firm. He earned a master’s degree in Environmental Studies from Yale University and holds a bachelor’s degree in Landscape Architecture from Michigan State University. David J. Kent is currently an environmental toxicologist and consultant with THE WEINBERG GROUP INC. in Washington, D.C. He formerly was manager of the aquatic toxicology laboratory and project manager on field assessments for ©2001 CRC Press LLC

International Technology Corporation. He has extensive experience in performing and managing ecological assessments for a wide variety of regulatory programs including ecological risk assessments for the pesticide industry and RCRA and Superfund sites. He has numerous scientific presentations and publications to his credit in the areas of aquatic toxicology and ecological risk assessment. Dr. Donald M. Kent is Principal Technical Staff Director with Walt Disney Imagineering Research and Development’s Environmental Science and Technology Group and a consultant. His broad experience includes ecological and environmental research, conduct of functional ecological assessments and impact analyses, design and implementation of mitigation projects, training of international decision makers, and expert technical review. He continues to investigate and develop various applied ecological and biotechnological techniques for integrating land use and natural resource protection. Kevin McManus is Manager of Technical Services for the Massachusetts Water Resources Authority’s Toxic Reduction and Control Program. He has 17 years experience in the environmental field, working in both the public and private sectors. He has specialized in environmental impact assessment, wetlands permitting and mitigation, facility siting, NEPA compliance, pollution prevention, and oil spill response technologies. Annette M. Paulin is a Project Manager with Azurea, Inc., where she conducts original research and develops and implements environmental management and training programs. Her research experience includes studies of nuisance aquatic plants, contaminant removal by natural systems, and copper impacts on aquatic communities. She has also developed training programs for international decision makers. Presently, her duties include managing a volunteer-based water quality monitoring program in central Florida. Ann Redmond is Vice President of Development for Wetlandsbank, Inc. She is responsible for Wetlandsbank’s expansion into new markets, as well as its regulatory and legislative activities. She was with the Florida Department of Environmental Protection for 12 years as the agency’s expert on mitigation and mitigation banking, leading the development and implementation of rules and legislation in these areas. She has worked in ecosystem management initiatives, the conceptual framework for restoration planning, development of functional assessment methods, and sustainability of mitigation projects. She also has worked with a regional water management agency and as an environmental consultant. She earned her bachelor and master of science degrees in Biological Science from the Florida State University with emphases on botany and ecology. Karen L. Ripple is Education Director for Environmental Concern Inc., a nonprofit nonadvocacy corporation devoted to wetland education, wetland research, and the development and application of technology in the construction, restoration, and enhancement of wetlands. She has extensive experience as a public school ©2001 CRC Press LLC

environmental educator and national teacher trainer specializing in wetlands. She has authored several articles and coauthored a book of wetland activities for educators. Prior to her concentration on wetland education, she contributed to a variety of fisheries research projects. Michael Rolband is the president of Wetland Studies and Solutions, Inc. which specializes in water resource issues. He is a member of the Virginia Chesapeake Bay Local Assistance Board, serves on the Fairfax County Stormwater Utility Advisory Group, and is on the boards of the Northern Virginia Chapter of the National Association of Industrial and Office Properties and the National Mitigation Banking Association. He has taught courses on wetland mitigation, permitting, and Chesapeake Bay Preservation Ordinances. He has a bachelor of science and master of engineering degree in Civil and Environmental Engineering, and a master of business administration degree from Cornell University. Carl E. Tammi is a Senior Wetlands Project Manager in the Water Resources Department of ENSR, Inc. He has over 12 years of professional experience in wetland assessment, delineation, permitting, mitigation and restoration design, construction, monitoring, and treatment design. He manages a group of wetland scientists who routinely work throughout the United States on capital projects, remediation and restoration projects, biological monitoring, and applied wetland science research. He is a Certified Professional Wetland Scientist, and received his Provisional Delineator Certification from the U.S. Army Corps of Engineers, Baltimore District. John Zentner is a principal with Zentner and Zentner, a professional consulting firm with offices in California. Zentner and Zentner specializes in planning and restoration throughout the western United States. He specializes in wetland science, land planning, permit processing, and restoration of natural resources. Among other accomplishments, he is President of the Western Chapter of the Society of Wetland Scientists and has participated in various federal, state, and local wetland working groups.

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Contents Chapter 1 Definition, Classification, and U.S. Regulation Donald M. Kent Chapter 2 Wetland Identification and Delineation Carl E. Tammi Chapter 3 Evaluating Wetland Functions and Values Donald M. Kent Chapter 4 Ecological Risk Assessment of Wetlands David J. Kent, Kenneth D. Jenkins, and James F. Hobson Chapter 5 Avoiding and Minimizing Impacts to Wetlands Donald M. Kent and Kevin McManus Chapter 6 Wetland Enhancement, Restoration, and Creation John Zentner Chapter 7 Wetland Mitigation Banking Michael S. Rolband, Ann Redmond, and Tom Kelsch Chapter 8 Monitoring Wetlands Donald M. Kent Chapter 9 Wetlands for Water Treatment Thomas A. DeBusk and William F. DeBusk Chapter 10 Design and Management of Wetlands for Wildlife Donald M. Kent Chapter 11 Coastal Marsh Management Robert Buchsbaum ©2001 CRC Press LLC

Chapter 12 Watershed Management Donald M. Kent Chapter 13 Managing Global Wetlands Annette M. Paulin and Donald M. Kent Chapter 14 Wetlands Education Karen L. Ripple

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Kent, Donald M. “Definition, Classification, and U.S. Regulation” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

CHAPTER

1

Definition, Classification, and U.S. Regulation Donald M. Kent

CONTENTS Definition Classification Classification of Wetlands and Deepwater Habitats of the United States A Hydrogeomorphic Classification for Wetlands U.S. Regulation Regulating Agencies Army Corps of Engineers Environmental Protection Agency Fish and Wildlife Service National Resource Conservation Service National Marine Fisheries Service References

DEFINITION Wetlands are defined directly or implicitly in a variety of ways. Several factors, including personal perspective, position in the landscape, and wetland diversity and function, contribute to the tractable nature of the definition. Each individual or group brings to the definition its own perspective based upon cumulative experience and personal needs (Figures 1 to 4). For example, the lay person asked to define wetlands may envision a deep-water marsh teeming with

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ducks, or alternatively a dark swamp. To an engineer a wetland may be a place that will require a specialized construction design to accommodate poorly drained soils. The scientist likely has a functional perspective, defining a wetland as a place where anaerobic processes occur, and plants are adapted specially for living in saturated or inundated conditions. Finally, those charged with regulating wetland use are likely to have a structural perspective, defining wetlands by characteristic soil, hydrology, and plants so as to facilitate permit decision making.

Figure 1

Salt marsh is an emergent, interdial estuarine wetland system characterized by persistent plant species such as cordgrass (Spartina alterniflora). Saltmarsh has a fringe geomorphic setting, and the water source and hydrodynamics are predominantly surface or near surface bidirectional flows.

Defining wetlands is further complicated by their position in the landscape. Wetlands are transitional habitats in the sense that they are neither terrestrial nor aquatic, but exhibit characteristics of both. Their boundaries are part of a continuum of physical and functional characters, and may expand or contract over time depending upon factors such as average annual precipitation, evapotranspiration, and modifications to the watershed. The transitional nature of wetland characteristics and the shifting of wetland boundaries renders precise identification of wetland boundaries difficult if not impossible. The diversity of wetland types also contributes to the tractable nature of the definition. Wetlands include such familiar habitats as marsh and swamp, as well as less familiar seasonal wetlands such as vernal pools and intermittent streams. They may be tidal or nontidal, saline or fresh, lotic or lentic, permanent or impermanent. Vegetation may consist of herbaceous or woody species, or there may be no vegetation.

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Figure 2

This marsh is an emergent, palustrine wetland with a depressional setting. It is subject to vertical fluctuations in water level, and derives its water from precipitation and groundwater discharge.

Figure 3

Palustrine wetlands may also be wooded as illustrated by this hardwood swamp. Swamps frequently have a riverine setting and unidirectional, surface or nearsurface flows.

Wetlands also defy a unifying functional definition. Each wetland is unique with respect to its size, shape, hydrology, soils, vegetation, and its position in the landscape. As such, wetlands exhibit a wide range of functional attributes, including provision of aquatic and wildlife habitat, retention of sediments and toxicants, flood

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Figure 4

This vernal pool in California is inundated or saturated for a short time in early spring. It occurs in a depressional setting and is dependent upon precipitation for water.

attenuation, nutrient metabolism, groundwater recharge, and production export. Individual wetlands may exhibit some of these attributes, all of these attributes, or in rare instances, none of these attributes. Moreover, individual wetlands of similar attributes are likely to provide functions to differing degrees. Despite the difficulty in singularly defining wetlands, several formal definitions have been proposed. The earliest definition was for managers and scientists, particularly those concerned with waterfowl and wildlife (Shaw and Fredine, 1956). Largely a structural definition, it uses language understandable to the lay person. The term wetland … refers to lowlands covered with shallow and sometimes temporary or intermittent waters. They are referred to by such names as marshes, swamps, bogs, wet meadows, potholes, sloughs, and river-overflow lands. Shallow lakes and ponds, usually with emergent vegetation as a conspicuous feature, are included in the definition, but the permanent waters of streams, reservoirs, and deep lakes are not included. Neither are water areas that are so temporary as to have little or no effect on the development of moist-soil vegetation.

The definition established two parameters essential for a habitat to be a wetland: the presence of surface water and the development of moist-soil vegetation. At a workshop of the Canadian National Wetlands Working Group, 23 years later, a definition evolved that recognized a third parameter, hydric soils, and which noted the functional attributes of wetlands (Tarnocai, 1979). Furthermore, it expanded the previous definition of wetland to include not only those habitats with surface water but also those having saturated soils. ©2001 CRC Press LLC

Wetland is defined as land having the water table at, near, or above the land surface or which is saturated for a long enough period to promote wetland or aquatic processes as indicated by hydric soils, hydrophilic vegetation, and various kinds of biological activity which are adapted to the wet environment.

That same year, the U.S. Fish and Wildlife Service adopted a definition that also recognized wetland hydrology, hydric soils, and hydrophytic vegetation as defining parameters (Cowardin et al., 1979). Intended for wetland scientists, the definition is distinguished from the Canadian definition in that a wetland need not exhibit characteristics of all three parameters. Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. For purposes of this classification wetlands must have one or more of the following three attributes: (1) at least periodically, the land supports predominantly hydrophytes; (2) the substrate is predominantly undrained hydric soils; and (3) the substrate is nonsoil and is saturated with water or covered by shallow water at some time during the growing season each year.

The three-parameter approach developed for scientists and managers is reflected in Section 404 of the Clean Water Act, forming the basis for regulatory decision making. The term “wetlands” means those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.

CLASSIFICATION Classification is the act or process of classifying; systematically arranging in groups or categories according to established criteria. For example, Linnaean taxonomy is a binomial nomenclature providing for orderly classification of plants and animals according to their presumed natural relationships. Classification schemes may be hierarchical or nonhierarchical. If hierarchical, the classification scheme may be divisive or agglomerative, and monothetic or polythetic. Hierarchical, divisive, polythetic classifications are common and lend themselves to a wide range of scientific applications. Regardless of the scheme used, the effect of classification is to provide a common language. Many wetland classification schemes have been developed (e.g., Martin et al., 1953; Stewart and Kantrud, 1971; Golet and Larson, 1974). The classification system developed by Cowardin et al. (1979) and the classification system developed by Brinson (1993) have received wide acceptance by scientists, policymakers, and managers. These classifications can be applied across broad geographic areas and in large part encompass many other classification schemes. ©2001 CRC Press LLC

Classification of Wetlands and Deepwater Habitats of the United States In 1974, the U.S. Fish and Wildlife Service directed its Office of Biological Services to design and conduct a national inventory of wetlands. Existing classification systems were considered too simplistic (Martin et al., 1953) or too geographically limited (Stewart and Kantrud, 1971; Golet and Larson, 1974; Odum et al., 1974; Zoltai et al., 1975) to satisfy the requirements of a national inventory. Cowardin et al. (1979) developed a classification of wetlands and deepwater habitats of the United States to support the national inventory. The objectives of the classification were to describe ecological units with homogeneous natural attributes, to arrange these units in a system that would aid resource management decisions, to furnish units for inventory and mapping, and to provide uniformity in concepts and terminology throughout the United States. Their classification of wetlands and deepwater habitats of the United States is hierarchical, divisive, and polythetic (Table 1). Wetland and deepwater systems are made up of subsystems, subsystems of classes, and classes of subclasses. Dominance types (plants and animals) are attributed to subclasses. Water regime, water chemistry, and soil modifiers are applied to classes, subclasses, and dominance types. For example, according to the classification, a cordgrass (Spartina sp.) saltmarsh would be estuarine (system), intertidal (subsystem), emergent (class), and persistent (subclass). Systems are a complex of wetlands and deepwater habitats that share hydrology, geomorphology, chemistry, and biology. The classification has five major systems: marine, estuarine, riverine, lacustrine, and palustrine. Subsystems are more specific categories of systems and provide hydrological information. Marine and estuarine systems encompass subtidal and intertidal subsystems. The riverine system includes a tidal subsystem, as well as lower perennial, upper perennial, and intermittent subsystems. Limnetic and littoral subsystems comprise the lacustrine system. The palustrine system is not divided into subsystems. The class describes the general appearance of the habitat. Classes are defined by either the dominant vegetation form or the physiography and composition of the substrate. Examples include rock bottom, aquatic bed, emergent wetland, and forested wetland. Cowardin et al. (1979) intended that the classes be discernible without extensive biological knowledge, and in many cases recognizable by remote sensing. Finer differences in vegetation form or substrate are recognized at the subclass level. For example, rock bottom is divided into bedrock and rubble, and emergent wetland is divided into persistent and nonpersistent. Dominance type is the most precise category and reflects the dominant plant species or dominant sedentary or sessile macroinvertebrate. Class, subclass, and dominance type levels of the classification are more fully described by modifiers. Water regime modifiers describe hydrological characteristics and require detailed knowledge of duration and timing of surface inundation. Salinity in all habitats, and pH in freshwater habitats, are water chemistry modifiers. Soil modifiers are mineral and organic. The classification also includes special modifiers to describe man-made wetlands, and wetlands modified by the activity of persons or beavers. ©2001 CRC Press LLC

Table 1

A Classification of Wetlands and Deepwater Habitats of the United States (Cowardin et al., 1979)

System Marine

Subsystem Subtidal

Intertidal

Estuarine

Subtidal

Intertidal

Riverine

Tidal

Lower perennial

Upper Perennial

Lacustrine

Intermittent Limnetic

Littoral

Palustrine

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Class Rock bottom Unconsolidated bottom Aquatic bed Reef Aquatic bed Reef Rocky shore Unconsolidated shore Rock bottom Unconsolidated bottom Aquatic bed Reef Aquatic bed Reef Streambed Rocky shore Unconsolidated shore Emergent wetland Scrub–shrub wetland Forested wetland Rock bottom Unconsolidated bottom Aquatic bed Rocky shore Unconsolidated shore Emergent wetland Rock bottom Unconsolidated bottom Aquatic bed Rocky shore Unconsolidated shore Emergent wetland Rock bottom Unconsolidated bottom Aquatic bed Rocky shore Unconsolidated shore Streambed Rock bottom Unconsolidated bottom Aquatic bed Rock bottom Unconsolidated bottom Aquatic bed Rocky shore Unconsolidated shore Emergent wetland Rock bottom Unconsolidated bottom Aquatic bed Unconsolidated shore Moss–lichen wetland Emergent wetland Scrub–shrub wetland Forested wetland

Cowardin et al. (1979) designed the classification for use over a broad geographic area, and for use by individuals and organizations with varied interests and objectives. Information about the wetland or deepwater area to be classified is obtained directly from site inspections, or indirectly from maps, aerial photographs, and other sources. The type and extent of information necessarily determine the level to which the area is classified. Cowardin et al. (1979) intended the classification to be openended and incomplete below the class level. Users are expected to identify additional dominance types and add subclasses as necessary. A Hydrogeomorphic Classification for Wetlands A hydrogeomorphic classification for wetlands presented by Brinson (1993, 1995) emphasizes the abiotic characteristics of wetlands. The abiotic characteristics are intended to be indicators of wetland functions. Brinson (1993) suggests that a functionally based classification of wetlands is needed for two reasons. First, the concept of wetlands needs to be simplified to improve communication among researchers, managers, and the public, and this communication is best achieved by focusing on processes that are fundamental to sustained existence. Second, paradigms that clarify the relationship between ecosystem structure and function must be developed to support monitoring of ecosystem health. A hydrogeomorphic classification for wetlands was developed to support ongoing efforts at assessing the physical, chemical, and biological functions of wetlands subject to U.S. Army Corps of Engineers permit. It has its scientific origins in a coastal ecosystem classification system based upon biological, geological, chemical, and physical factors (Odum et al., 1974); a mangrove classification system relying on vegetation and on water source, quality, and flow (Lugo and Snedaker, 1974); and a study by Brown et al. (1979) that found that differences among freshwater forested wetlands are attributed to the amount of water flow. Kangas (1990), who developed a wetland classification system based upon energy flow and landscape properties, also influenced the classification. The classification is nonhierarchical and has three interdependent components: geomorphic setting, water source and its transport, and hydrodynamics (Table 2). Geomorphic setting is defined as the topographic location of the wetland within the surrounding landscape. The seven geomorphic settings tend to have distinct combinations of hydroperiod, dominant direction of water flow, and zonation of vegetation. An individual wetland may have characteristics of more than one geomorphic setting category. Also, a small wetland (e.g., less than or equal to 1 ha) may be difficult to assign to a geomorphic setting category if it is part of a larger wetland complex. Water sources include precipitation, groundwater discharge, and surface or nearsurface flow. The latter include flooding from tides, overbank flow from stream channels, and interflow or overland flow from higher potentiometric surfaces. Precipitation is, of course, a contributor to all wetlands and its relative importance is a function of the contribution of groundwater and surface water. The relative importance of the three sources of water can be determined by construction of a water budget, or more quantitatively by interpreting a hydrograph of the wetland. Bogs

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Table 2

Hydrogeomorphic Classification for Wetlands (Brinson, 1993, 1995)

Geomorphic setting Riverine Depressional Slope Mineral soil flats Organic soil flats Estuarine fringe Lacustrine fringe Water source Precipitation Groundwater discharge Surface or near-surface inflow Hydrodynamics Vertical fluctuations Unidirectional flows Bidirectional surface or near-surface flows

and pocosins are heavily influenced by precipitation, fens and seeps by groundwater discharge, and riverine and fringe wetlands by surface and near-surface flow. Hydrodynamics refers to the direction of flow and strength of water movement within the wetland. There are three qualitative categories of hydrodynamics: vertical fluctuations, unidirectional flows, and bidirectional flows. Astronomic tides, wind, or a combination of both generate the latter. The classification makes inferences about hydrodynamics based upon velocity of flow, rate of water table fluctuations, particle size distribution of bedload sediments, and the capacity to replace soil moisture deficits created by evapotranspiration. These correspond, respectively, to the depressional, riverine, and fringe geomorphic settings. Implementing the classification requires use of indicators of wetland ecological significance, profile development, and comparison to reference wetlands. Indicators are observed in the field, or derived from maps, photographs, water quality data, or other sources. Representative indicators of ecological significance include water characteristics such as suspended sediment and salinity, water color, pH, nutrient status, and soil or sediment characteristics (Table 3). Ecological significance, as determined from direct observation of wetland function or from indicators, is then used to develop a profile for the wetland. A profile may be either narrative or tabular, and is the end point of the classification. Brinson (1993) recommends that profile development be tied to the establishment of reference wetlands that would be used to facilitate assessment, training, and mitigation. The classification emphasizes the interpretation of wetland ecological significance based upon geomorphic setting, water source, and hydrodynamics, and illustrates how fundamental knowledge about water flows and sources can reveal ecological functioning. It does not allow the user to take it to the field for the purpose of matching indicators with functions (Brinson, 1993). Also, the interpretation of ecological significance results in the description of wetland function without necessarily placing the wetland into a discrete category. Brinson (1993) expects that the ©2001 CRC Press LLC

Table 3

Hydrogeomorphic Classification for Wetlands Indicators of Ecological Significance (Brinson, 1993) Water characteristics Suspended sediments Salinity Color Clear Black pH Acid Circumneutral Nutrient status Low Medium High Soil or sediment characteristics Mineral Organic sediments

classification will be used in conjunction with locally recognized wetland names or with classification of wetlands and deepwater habitats of the United States developed by Cowardin et al. (1978).

U.S. REGULATION Numerous federal statutes have been enacted which impact activities in and around wetlands (Table 4). These statutes encompass regulation, acquisition, and restoration of wetlands, incentives and disincentives to use of wetlands, and other programs. Far from being a cohesive collection of synergistic laws, the statutes have been initiated and enacted piecemeal over the years by various federal agencies. Federal authority to regulate wetlands derives principally from Section 404 of the Federal Water Pollution Control Act of 1977 (33 U.S.C. 1344). Section 404 requires landowners and developers to obtain permits prior to dredge and fill activities in navigable waters. The definition of navigable waters has been extended to include adjacent wetlands. However, the Water Pollution Control Act exempts normal agriculture, silviculture, and ranching activities, provided these activities do not convert areas of U.S. waters to uses to which they were not previously subject, do not impair the flow or circulation of such waters, or do not reduce their reach. Due in part to the aforementioned exemptions, Section 404 regulates only about 20 percent of the activities that impact wetlands. The Food Security Act of 1985 (P.L. 99–198 Statute 1354) compensates, in part, for this lack of regulation through three provisions: Swampbuster, the Conservation Reserve Program, and the Wetlands Reserve Program. Swampbuster denies federal farm program benefits to producers who plant an agricultural commodity on wetlands that were converted after December 23, 1985. Although Swampbuster is the only legislative provision that directly affects eligibility for other federal benefits, the policy allowed ©2001 CRC Press LLC

producers to plant a commodity crop in wetlands when prices were high enough to make federal farm program benefits unnecessary, and to plant converted wetlands with a noncommodity crop in years when federal program benefits might be needed. To overcome this deficiency, the Food, Agriculture, Conservation, and Trade Act of 1990 was enacted to make noncomplying producers ineligible for federal benefits for that year and all subsequent years. By contrast, the Conservation Reserve Program authorizes the federal government to enter into contracts with agricultural producers to remove highly erodible cropland from production for 10 to 15 years in return for annual rental payments. Producers are required to implement a conservation plan that usually includes planting cover such as grass or trees to hold soil in place and to reduce erosion. The program was expanded in 1989 to make cropped wetlands eligible for enrollment. Similarly, the Wetlands Reserve Program offers financial incentives for landowners to enhance wetlands in exchange for retiring marginal agricultural land. Landowners may sell a conservation easement or enter into a cost-share restoration agreement to restore and protect wetlands. The landowner continues to control access to the land, and may lease the land for undeveloped recreational activities (e.g., hunting, fishing). Another program that removes land from use is authorized by The Water Bank Act of 1970 (16 U.S.C. 1301). The Water Bank Program provides funds to purchase 10-year easements on wetlands and adjacent areas for the purpose of preserving, restoring, and improving the wetlands. Private landowners enter into agreements with the federal government in which they promise not to drain, fill, level, burn, or otherwise destroy wetlands, and to maintain ground cover essential for the resting, breeding, or feeding of migratory waterfowl. Implementation of the program is concentrated in the prairie pothole region of the United States. Two other programs having a significant affect on the preservation of wetlands are the Migratory Bird Hunting and Conservation Stamp Act of 1934 (16 U.S.C. 718) and the Coastal Barrier Resources Act of 1982 (16 U.S.C. 3501). The Stamp Act uses proceeds from duck stamps to preserve wetlands and adjacent uplands important to waterfowl through purchase or perpetual easement. The Coastal Barrier Resources Act attempts to minimize the loss of human life, wasteful expenditure of federal revenues, and damage to fish, wildlife, and other natural resources by prohibiting federal expenditures and financial assistance for development of coastal barriers. Regulating Agencies Army Corps of Engineers The Corps is responsible for issuing Section 404 permits authorizing dredge or fill activities in waters of the United States and adjacent wetlands. Approximately 15,000 project-specific permit applications and 40,000 minor activities associated with regional and nationwide general permits are evaluated each year (United States General Accounting Office, 1991). Wetland determinations and delineations are also the responsibility of the Corps, including verification of the accuracy of delineations performed by consultants for permit applicants. Public interest reviews are conducted to determine the efficacy of permits. Consideration is given to economics, aesthetics, ©2001 CRC Press LLC

Table 4

Significant Federal Wetlands-Related Legislation Legislation

Date

Effect on Wetlands

Section 10, Rivers and Harbors Act

1899

Migratory Bird Hunting and Conservation Stamp Act Federal Aid to Wildlife Restoration Act

1934 1937

Fish and Wildlife Act

1956

U.S. Fish and Wildlife Coordination Act

1958

Land and Water Conservation Fund Act

1965

National Wildlife Refuge System Administration Act National Flood Insurance Act

1966 1968

National Environmental Policy Act

1969

Water Bank Act Endangered Species Act

1970 1973

Resource Conservation and Recovery Act

1976

Section 402, Federal Water Pollution Control Act Section 404, Federal Water Pollution Control Act Coastal Barrier Resources Act

1977

Requires permits from U.S. Army Corps of Engineers for dredge and fill activities in navigible waterways and wetlands Proceeds of duck stamps used to acquire habitat Assistance to states and territories for restoring, enhancing, and managing wildlife Established U.S. Fish and Wildlife Service Requires all federal projects and federally permitted projects to consider wildlife conservation Purchase of natural areas at federal and state levels Established National Wildlife Refuge System Requires communities to develop floodplain management programs Requires Environmental Impact Statements for federal actions Purchase easements on wetlands Prohibits federal agencies from undertaking or funding projects which threaten rare or endangered species Controls disposal of hazardous waste, reducing threat of contamination to wetlands Authorized national system for regulating sources of water pollution Regulates dredge and fill activities

1977 1982

Food Security Act Swampbuster Conservation Reserve Program Wetland Reserve Program

1985

Emergency Wetlands Resources Act

1986

Agricultural Credit Act

1987

Everglades National Park Protection and Expansion Act North American Wetlands Conservation Act

1989

Food, Agriculture, Conservation and Trade Act

1990

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1989

Prohibits federal expenditure or assistance for development on coastal barriers Discourages farming on wetlands Removes erodible crop land from use Restores and protects wetlands on private property Promotes conservation through intensified cooperation and acquisition efforts Preserves land reverting to Department of Agriculture’s Farmers Home Administration Increased water flow to park and acquired more land Increased protection and restoration of wetlands under the North American Waterfowl Plan Strengthened Swampbuster, Conservation Reserve Program, and the Wetland Reserve Program

Table 4 (continued) Significant Federal Wetlands-Related Legislation Legislation

Date

Effect on Wetlands

Water Resources Development Act

1990

Coastal Wetlands Planning, Protection and Restoration Act

1990

Coastal Zone Management and Improvement Act

1990

Requires federal agency development of action plan to achieve no-net loss Restoration of coastal wetlands and funds North American Waterfowl Management projects Sets guidelines and provides funding for state coastal zone management programs

historic value, fish and wildlife value, value for attenuating floods, navigation, recreation, water supply and quality, and other needs and welfare of the public. Compliance inspections are conducted following permit issuance to ensure permit conditions are met. The Corps has the authority to seek civil or administrative remedies for violation of permit conditions, or for other unauthorized discharges into wetlands. Environmental Protection Agency The Environmental Protection Agency has statutory enforcement authority to deal with unpermitted dredge and fill activities. In addition, the Agency determines the scope of navigable waters and interprets the scope of exemptions under the Section 404 Program. In consultation with the Corps, the Agency developed the guidelines for selection of sites for disposal of dredged or fill materials. The Agency has veto authority under Subsection 404(c) if disposal of dredged or fill material will have an unacceptable adverse effect on municipal water supplies, shellfish beds and fishery areas, and wildlife or recreational areas. Fish and Wildlife Service The Fish and Wildlife Service is an advisor to the Corps with regard to the Section 404 Program, making recommendations for approval or disapproval of permits, and recommending conditions for permits to be approved. In addition, the Fish and Wildlife Service is active in a number of programs designed to protect, restore, and enhance wetlands. The Fish and Wildlife Service helps the National Resource Conservation Service map agricultural wetlands and select and manage wetlands protected under the Farmers Home Administration Conservation Program and the Wetlands Reserve Program. The Fish and Wildlife Service also implements restoration projects on highly erodible cropland under the Conservation Reserve Program and assists the Department of Agriculture and individual farmers in designing wetland conservation plans necessary to qualify for Farm Bill incentives. Other activities of the Fish and Wildlife Service include management of the National Wildlife Refuge System, research, and development of National Wetlands Inventory maps.

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National Resource Conservation Service The U.S. Department of Agriculture National Resource Conservation Service administers and enforces Swampbuster, the Conservation Reserve Program, and the Wetland Reserve Program. This includes providing wetlands information to producers and third parties, identifying and delineating wetlands, monitoring compliance with regulations, responding to public complaints and producer’s appeals of decisions, and dealing with violations. Operations are carried out in conjunction with other federal and state agencies and county committees. National Marine Fisheries Service The National Marine Fisheries Service is active in coastal wetland issues and makes recommendations to the Corps regarding Section 404 permits under authority of the Fish and Wildlife Coordination Act. Field staff also work closely with state fish and wildlife agencies and water quality agencies.

REFERENCES Brinson, M. M., A Hydrogeomorphic Classification for Wetlands, Technical Report WRP-DE-4, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 1993. Brinson, M. M., The HGM approach explained, Natl. Wet. Newsl., November/December, 7, 1995. Brown, S., Brinson, M. M., and Lugo, A. E., Structure and function of riparian wetlands, in Strategies for the Protection and Management of Floodplain Wetlands and Other Riparian Ecosystems, Johnson, R. R. and McCormick, J. F., Tech. Coord., Forest Service General Technical Report WO-12, U.S. Department of Agriculture, Washington, D.C., 1979, 17. Cowardin, L. M., Carter, V., Golet, F. C., and LaRoe, E. T., Classification of Wetlands and Deepwater Habitats of the United States, U.S. Department of the Interior, Fish and Wildlife Service Biological Services Program FWS/OBS-79/31, 1979. Golet, F. C. and Larson, J. S., Classification of Freshwater Wetlands in the Glaciated Northeast, U.S. Fish and Wildlife Service, Resource Publication 116, 1974. Kangas, P. C., An energy theory of landscape for classifying wetlands, in Lugo, A. E., Brinson, M. M., and Brown, S., Eds., Forested Wetlands, Elsevier, Amsterdam, 1990, 15. Lugo, A. E. and Snedaker, S. C., The ecology of mangroves, Ann. Rev. Ecol. Syst., 5, 39, 1974. Martin, A. C., Hotchkiss, N., Uhler, F. M., and Bourn, W. S., Classification of Wetlands of the United States, U.S. Fish and Wildlife Service, Special Scientific Report, Wildlife 20, 1953. Odum, H. T., Copeland, B. J., and McMahan, E. A., Eds., Coastal Ecological Systems of the United States (4 Volumes), The Conservation Foundation, Washington, D.C., 1974. Shaw, S. P. and Fredine, C. G., Wetlands of the United States, Their Extent, and Their Value for Waterfowl and Other Wildlife. U.S. Department of Interior, Fish and Wildlife Service, Circular 39, Washington, D.C., 1956. Stewart, R. E. and Kantrud, H. A., Classification of Natural Ponds and Lakes in the Glaciated Prairie Region, U.S. Fish and Wildlife Service, Resource Publication 92, 1971.

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Tarnocai, C., Canadian wetland registry, in Proceedings of a Workshop on Canadian Wetlands Environment, Rubec, D. D. A. and Pollett, F. C., Eds., Canada Land Directorate, Ecological Land Classification Series, No. 12, 1979, 9. United States General Accounting Office, Wetlands Overview: Federal and State Policies, Legislation and Programs, GAO/RCED-92–79FS, Washington, D.C., 1991. Zoltai, S. C., Pollett, F. C., Jeglum, J. K., and Adams, G. D., Developing a wetland classification for Canada, Proc. N. Am. For. Soils Conf., 4, 497, 1975.

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Tammi, Carl E. “Wetland Identification and Delineation” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

CHAPTER

2

Wetland Identification and Delineation Carl E. Tammi

CONTENTS Off-Site Wetland Identification Identification Resources Interpreting Resources U.S. Geological Survey (USGS) Topographic Maps U.S. Fish and Wildlife Service (USFWS) National Wetland Inventory Maps U.S. Department of Agriculture Natural Resources Conservation Service Soil Surveys and the Hydric Soils of the United States List Comparison and Corroboration Aerial Photographs U.S. Geological Survey Surficial Geologic Maps Individual State Wetland Maps On-Site Wetland Delineation Wetland Hydrology Hydrological Field Indicators Hydric Soils Hydric Soil Field Indicators Hydrophytic Vegetation Indicators of Hydrophytic Vegetation Identifying and Delineating Wetlands Undisturbed Areas Disturbed Areas Difficult Areas Aids to Delineation References

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Wetland identification and the science of delineation are regulatory-driven activities that are commonly required in land-use development, planning, exploration, and a host of related activities involving future site expansion. Although federally mandated wetland regulatory statutes have been in existence for over 25 years, the science of identifying and delineating the extent and types of wetlands has been consistently evolving. As the science has evolved, a greater awareness of the functions and values wetlands provide has occurred with the resultant development of extensive wetland identification and delineation resources within the last 10 years. Today, the land-use planner, wetland scientist, and manager have a range of tools in print, graphic, and electronic format available to assist in making wetland determinations and defendable jurisdictional delineations. Typically, the science of identifying and delineating wetlands is a two-tiered process. An initial office-based off-site assessment is conducted for identification purposes. A legally binding jurisdictional determination requires an on-site field assessment called a wetlands delineation. Identifying the location and determining the areal extent of jurisdictional wetlands is an important consideration for those involved in land use management, development, remediation, or assessment. Today, defining wetland limits and boundaries is primarily driven by comprehensive federal and, where applicable, state and local land-use laws and regulations. Section 404 of the Clean Water Act is the principal tool that the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency use to regulate the discharge of dredged or fill material into waters of the United States, including wetlands (33 CFR 320–330). At the federal level, wetlands are further defined from a regulatory viewpoint as, “Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas” (33 CFR 328.3). In identifying and delineating federal jurisdiction wetlands, three essential technical criteria or factors are applied: the presence of wetlands hydrology through surficial or groundwater; a prevalence of wetland vegetation (hydrophytes) that typically has specialized morphological and physiological adaptations to tolerate saturated or inundated conditions; and wetland soils (hydric soils), which in their undrained condition exhibit characteristics of somewhat poorly drained, poorly drained, or very poorly drained soils. Other major federal legislation that drives wetland identification includes Section 401 Water Quality Certification (delegated to the individual states), Section 10 of the Rivers and Harbors Act of 1899 and the National Environmental Policy Act. Many states have promulgated and adopted wetland protection legislation for inland, and where applicable, coastal wetlands. Identification and delineation techniques vary slightly from state to state, although most have adopted the principles of the federal methodology (to be described in greater detail later). Given the regulatory framework behind wetland protection, it is incumbent upon project proponents and land-use managers to determine, locate, and identify wetland resources on a subject parcel. Furthermore, it is important to adequately and accurately determine the location and approximate areal extent, as well as the predominant wetland cover type, early in project planning stages to avoid wetland impacts ©2001 CRC Press LLC

and resultant time-consuming permit decisions. This action can streamline the permitting process during more advanced stages of project design through avoidance and minimization of wetland impacts. An off-site macroscale wetland determination makes a positive or negative wetland determination for a subject parcel, and determines the approximate location of wetland and deepwater areas. It also determines the approximate areal extent and distribution of wetland and deepwater areas, and the predominant wetland cover type (Cowardin et al., 1979). Finally, an off-site macrosite wetland determination assesses the need for continued analysis and approximate level of effort associated with any analyses. In some instances, information relative to the potential presence of hydric soils, surficial hydrology, and site disturbance can be determined from off-site wetland determinations. Historical and current land use as it pertains to wetland resources can also be ascertained in many circumstances. By making initial determinations and preliminary conclusions regarding the aforementioned factors, a project proponent can make informed decisions, save valuable time and expense, and determine if detailed on-site investigations are necessary. The level of effort to conduct off-site investigations can vary greatly, and can be tailored to suit individual site permitting or project requirements.

OFF-SITE WETLAND IDENTIFICATION For the purposes of this chapter, off-site identification of wetlands is defined as assembling and interpreting readily available natural resource mapping and reports and other documents, both published and unpublished, from existing sources, for the sole purpose of identifying, locating, and describing wetland resources on a given site or parcel of land. By applying existing resource document information, the researcher can make initial determinations relative to the perceived presence or absence of one, two, or sometimes three of the parameters necessary for an area to be considered a jurisdictional wetland. In instances where on-site inspection is not necessary or is beyond the scope of the investigation (e.g., National Environmental Policy Act wide range alternatives analyses, or limited environmental assessments), off-site wetlands determinations may be the only source of information for environmental planning decisions. The overall accuracy of off-site wetland determinations is a function of the quality of the information (sources) used and the ability of an individual(s) to interpret the data. The keys to conduct of an effective and technically valid analysis include the following: • • • •

Define the project scope and goals prior to conducting the analysis. Ensure that a wide range of available sources are investigated and used. Emphasize comparison and corroboration between different sources for the same site. Obtain recent data, but also data that cover many different years to assist in understanding the site history. • Understand individual resource document symbols and interpretation keys. • Understand regulatory requirements for documentation. ©2001 CRC Press LLC

The primary objective of off-site wetland determinations is identifying and determining whether wetlands exist on a parcel, followed by the approximate distribution and areal extent. In determining and quantifying these parameters, the key is corroboration between different sources. That is, not only locating wetlands on a subject parcel from a single source, but corroborating the identification through multiple sources. Another important objective of off-site determinations is documenting the dominant wetland cover type on parcels that have been preliminarily determined to have wetlands within their boundaries. Depending on the source, an interpreter can determine whether the wetlands are forested, scrub–shrub, emergent, aquatic bed, or open water. Detailed interpretation requires a greater level of effort and expertise but can result in greater detail, such as evergreen forest vs. deciduous forest, or persistent emergent vs. nonpersistent emergent, or artificially created vs. naturally occurring. Classification schemes can be tailored to an individual state’s system, or the widely accepted federal system developed by the U.S. Fish and Wildlife Service (Cowardin et al., 1979) and now recognized as the Unified Federal Classification Scheme (Federal Geographic Data Committee, 1995). Site soil characterizations and surficial hydrological features can also be recognized and described from off-site resources. Published sources exist which reveal site soils mapping to varying levels of detail and accuracy. Determining the hydrological regime, or simply the hydrology of a wetland, is a significant feature in determining the areal extent of wetlands both in the field and from mapped sources. Off-site interpretation can reveal a wetland’s hydrological source, as well as its drainage features. Identification Resources The first step in offsite wetland interpretation studies is identifying and obtaining readily available sources of information. Resources are generally diverse, with varying levels of accuracy. Also, resources have been dramatically expanded in recent years with many new tools available to the interpreter. These resources are generally available and provide a baseline of information from which to work. • U.S. Geological Survey (USGS) Topographic Maps, Standard Edition and Provisional Edition (7.5 minute or 15 minute quadrangles, scales 1:24,000 or 1:25,000, continental United States, 1:20,000 Puerto Rico, 1:63,360 Alaska), U.S. Department of the Interior Geological Survey National Mapping Division. • U.S. Department of the Interior/Fish and Wildlife Service (USFWS) National Wetland Inventory Maps (scale 1:24,000, continental United States, 1:63,360, Alaska), interpreted and adapted from High Altitude Aerial Photography and superimposed on U.S. Geological Survey Topographic Maps. • U.S. Department of Agriculture Natural Resources Conservation Service County Soil Surveys, in cooperation with individual state agriculture experiment stations; used in conjunction with the hydric soils of the United States, 1991, National Technical Committee for Hydric Soils, U.S. Department of Agriculture Natural Resources Conservation Service.

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• Aerial photography (stereo-paired, black and white, color, color infrared; positive transparency/aero negative; various scales and dates), Federal, State, and Commercial Suppliers. • U.S. Geological Survey Surficial Geologic Map Quadrangles (7.5 minute quadrangles, scale 1:24,000), U.S. Department of the Interior Geological Survey. • Individual state wetland maps (limited coverage and level of accuracy).

Interpreting Resources This section describes in more detail the analysis and interpretation of the resources listed above. Although the level of detail and accuracy varies with each source, a first-time evaluator should be able to extract sufficient information to reasonably determine if wetlands are present on-site, and the approximate historical or current location and extent of wetlands. U.S. Geological Survey (USGS) Topographic Maps The U.S. Department of the Interior, Geological Survey National Mapping Division generates 7.5- and 15-minute topographic maps through the National Mapping Program. Available are two separate editions, the Standard Edition Maps and the Provisional Edition Maps, each produced at 1:24,000 (English units) or 1:25,000 (metric units) for the continental United States. Standard Edition Quadrangles represent a finished product with the earth’s topographic relief depicted by contours. Provisional Edition Quadrangles represent an updated draft format, including hand lettering and limited descriptive labeling of some physical features. Stereoplotting field verified, high altitude aerial photographs produce both editions. Some quadrangles are mapped by a combination of orthophotographic images and map symbols, with orthophotographs derived from aerial photographs by removing image displacements owing to camera tilt and terrain relief variations (USGS, 1991). The use of USGS Topographic Maps for off-site wetland identification is often the first step to evaluate a site’s physical features. In addition to topographic, hypsographic, infrastructure, and other physical features, the USGS Topographic Maps provide detailed information relative to vegetation cover types, surface features, coastal features, hydrographic features such as rivers, lakes, and canals, and submerged areas and bogs. Figure 1 is a section of an USGS Quadrangle and depicts some of these features. The section includes wooded marsh or swamp in the western and southern parts of the site, perennial ponds or lakes in the central part of the site, and perennial streams associated with cranberry bogs in the northeast part of the site. Although most of the wetland and open water interpretation keys that accompany the maps are self-explanatory, the individual submerged areas and bogs keys require a little elaboration to distinguish among different wetland cover types. Marsh or swamp designations are wetlands characterized by saturated soil conditions in the root zone (as opposed to inundation), with emergent, herbaceous, or aquatic bed vegetation as the dominant cover class. An example would be a rush (Juncus spp., Scirpus spp.) and sedge (Carex spp.) dominated wet meadow. ©2001 CRC Press LLC

Figure 1

A U.S. Geological Survey topographic map.

Submerged marsh or swamp designations indicate an inundated root zone condition with emergent, herbaceous, or aquatic bed vegetative dominants. A typical example is a broad-leaved cattail (Typha latifolia) or pickerelweed (Pontederia cordata) marsh. Wooded marsh or swamp is a wetland characterized by saturated soil conditions with shrub, sapling, or mature forest as the dominant cover class. A saturated red maple (Acer rubrum) swamp is an example. Submerged wooded marsh or swamp indicates root zone inundation (ponding) as the dominant water regime with shrub, ©2001 CRC Press LLC

sapling, or mature forest as the dominant cover class. A bottomland hardwood forest dominated by cypress (Taxodium spp.) trees is an example. Land subject to inundation can be floodplain and flood-prone areas that may support wetland hydrology and wetland vegetation (hydrophytes). Rice fields and cranberry bogs are examples of anthropogenically influenced wetland areas. Some of the advantages to using USGS Topographic Maps include the relative accuracy of the topographic contours in undisturbed areas, photointerpretation documentation is groundtruthed at regular intervals, and individual quadrangles are periodically photorevised which assists in chronological evaluation of a site’s history. The limitations in using USGS Topographic Maps include interpretation problems associated with the small scale (1 in. equals 610 m) of the maps, and smaller wetlands often are frequently unmapped. In some parts of the country, quadrangles may be too outdated to be of use. U.S. Fish and Wildlife Service (USFWS) National Wetland Inventory Maps The USFWS initiated the National Wetland Inventory (NWI) program and mapping in 1975 to assess, measure, and characterize the extent of wetlands and open water areas throughout the United States. The NWI Maps are produced from photointerpretation of high altitude, stereo, aerial photographs. High altitude aerial photographs were selected over satellite imagery because of the problems satellite imagery had in capturing optimum water conditions for wetland detection, detecting smaller wetlands, and identifying forested wetlands (Tiner and Wilen, 1983). The NWI Maps are developed from 1:60,000 color-infrared aerial photographs. Photointerpretation of the aerials provides a three-dimensional image, thus allowing the interpreter to identify trees from shrubs, while considering shade and slope. Wetland and open water types are differentiated based on their characteristic photographic signatures. NWI Maps are developed according to a comprehensive evaluation process (Tiner and Wilen, 1983). The preliminary field investigations and photointerpretation of high altitude aerial photographs is the initial step, with review of existing wetland information and quality control of the interpreted photographs completing the first phase. Draft map production is initiated with a subsequent interagency review of draft maps and final map production. Available are two series of NWI Maps: the 1:100,000/1:250,000 scale and large scale 1:24,000. The USGS Topographic Map Quadrangle is used as a base map with wetland and deepwater areas depicted as overlays. A new wetland classification was developed by USFWS to correspond with the NWI Maps. Classification of wetlands and deepwater habitats of the United States (Cowardin et al., 1979) describes individual wetland ecological attributes and arranges them in a hierarchical system that facilitates resource management and inventory. The three key components in the ecological hierarchy are hydrophytes, hydric soils, and hydrology. The use of NWI Maps in off-site wetland identification typically provides the greatest level of detail and accuracy with the least amount of interpretation effort ©2001 CRC Press LLC

and expertise. The USFWS Classification System is a comprehensive and progressive inventory that groups wetlands into one of five major systems, marine, estuarine, lacustrine, riverine, and palustrine, based upon hydrologic, geomorphologic, chemical, and biological factors (Cowardin et al., 1979, see Chapter 1). The hierarchy progresses through subsystems, classes, and subclasses that further refine and describe specific wetland structural (vegetation, hydrology, dominant life form, etc.) components. Figure 2 depicts a representative section from an NWI Map that corresponds with Figure 1, and that indicates several different wetland classes within the palustrine system. Comparing Figure 2 with Figure 1, and using the interpretive key that accompanies the map, the interpreter is able to determine that the wooded swamp or marsh of the USGS Map has been further defined as palustrine forested broad-leaved deciduous wetland. An interpreter can become familiar with this system with a little practice resulting in quick characterizations of site conditions relative to wetland types. The accuracy of NWI Maps varies between systems and classes, with the highest degree of accuracy occurring for large marine, lacustrine, and estuarine systems. Less accurate are smaller mapped units for palustrine wetlands, specifically palustrine forested wetlands. The latter can be misstated owing to photointerpretation difficulties encountered as a result of leaf-in periods, when the interpreter cannot accurately describe the forest floor (MacConnell et al., 1989). NWI Maps provide the greatest diversity of all off-site references, with the possible exception of aerial photographs. However, the latter require a greater degree of photointerpretation expertise, and the NWI maps were prepared for the express purpose of identifying and classifying wetlands. Through use of the USFWS Classification system, an interpreter can characterize a wetland’s system, the dominant vegetative structural life form (e.g., forested, emergent, aquatic bed), its hydrological regime (e.g., intermittent vs. perennial), and substrate (e.g., rock bottom or unconsolidated bottom). The taxonomy also has provisions for documenting anthropogenic influence on created or farmed wetlands (e.g., palustrine farmed cranberry bogs and palustrine open water artificially excavated). The limitations of NWI Maps for off-site wetlands identification include the small scale (1 in. equals 2000 ft), errors associated with photointerpretation of select cover types (principally deciduous forest), limited field verification, and the lack of photorevision since initial production. NWI Maps are beneficial as a qualitative reference and are one of the only federally produced and readily available documents for the sole purpose of identifying, inventorying, and characterizing wetlands. U.S. Department of Agriculture Natural Resources Conservation Service Soil Surveys and the Hydric Soils of the United States List The U.S. Department of Agriculture Natural Resources Conservation Service produces County Soil Surveys in cooperation with the individual state’s agricultural experiment station. Programs have mapped individual soil series based on comprehensive field investigations conducted by Natural Resources Conservation Service and State soil scientists. To produce the maps, soil scientists observe the steepness, length and shape of slopes, the size and velocity of streams, the kinds of native ©2001 CRC Press LLC

Figure 2

A National Wetland Inventory map.

plants and rocks, and evaluate soil profiles (U.S. Department of Agriculture Natural Resources Conservation Service, 1978). Soil profiles are examined to the depth of the parent material and are compared to soil profiles examined in other counties for the purpose of comparing and contrasting known soil series. A unified soil taxonomy, the U.S. Department of Agriculture Soils Classification, is used across the nation to characterize and classify soil types. Soil series and soil phase are the most common terms used in describing individual soil types. A soil ©2001 CRC Press LLC

series is a grouping of soils that have similar profiles and major horizons and are named after the town in which the series was first discovered (U.S. Department of Agriculture Natural Resources Conservation Service, 1978). Phases further refine the series based on the texture in the surface layer, slope, or stoniness (U.S. Department of Agriculture Natural Resources Conservation Service, 1978). Soil mapping units and boundaries are depicted as overlays on high altitude aerial photography and are originally drafted by the field soil scientists. These boundaries are further refined following laboratory analysis of soil properties. The finished product indicates soil boundary delineations, soil series descriptions, and biophysicochemical properties. Additional sections of the soil survey provide information about recommended use and management of the soils, soil properties, and soil formation. Use of soil surveys for off-site wetland identification is limited to the identification and distribution of hydric soils. Hydric soils, one of the three essential characteristics of a federal jurisdictional wetland, have unique physical properties that set them apart from nonhydric soils. A hydric soil is defined as “a soil that is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part” (U.S. Department of Agriculture Natural Resources Conservation Service, 1991). The development of hydric soils is ultimately driven by the presence of wetland hydrology, and under sufficiently wet conditions (root zone saturation and inundation), hydric soils support the growth of hydrophytic vegetation. The U.S. Department of Agriculture Natural Resources Conservation Service has developed a list of hydric soils of the United States by applying criteria (e.g., drainage class, organic vs. mineral, etc.) of the National Technical Committee for Hydric Soils (U.S. Department of Agriculture Natural Resources Conservation Service, 1991). Included in this list are most of the somewhat poorly drained soil series, and all of the poorly drained and very poorly drained soils. Hydric soil classifications have been developed based on taxonomic and morphologic features. Tools subsequently have been developed for assisting in the field determination of drainage classes (New England Hydric Soils Technical Committee, 1998). Through the use of individual soil surveys, an interpreter can determine all mapped soil series on-site and then cross-reference the list of soils with Hydric Soils of the United States. Figure 3 is a soil survey map of the site depicted in previous figures. Examination of the site and cross-reference with the hydric soils list indicates that Sanded Muck (SB), Peat (Pe), Freshwater Marsh (Fr), Scarboro Sandy loam (ScA), Muck (Mv), and Au Gres and Wareham loamy sands (AuA) are hydric soil. The occurrence of hydric soils corresponds with the wooded swamp or marsh, perennial lakes or ponds, and cranberry bogs of the USGS Map, as well as the palustrine forested broad-leaved deciduous, palustrine farmed wetlands, and palustrine open water of the NWI Map. Although soil mapping involves an intensive field effort, the accuracy of the soil maps is quite variable, and areas mapped as hydric soils (a hydric soil series) can contain inclusions of nonhydric soils. Conversely, areas of nonhydric soils may contain hydric inclusions. The soil mapping information is best used as a macroscale assessment tool and should not be used for definitive boundaries of hydric soils. An

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Figure 3

A U.S. Department of Agriculture Soil Conservation Service soils survey.

advantage in using soil surveys and the list of hydric soils is that the interpreter does not need to spend time learning the U.S. Department of Agriculture Soils Classification and taxonomy system to be able to locate areas of mapped hydric soils on a site, although it is recommended that the interpreter understand the basic principles underlying the criteria for listing a soil as a hydric soil. ©2001 CRC Press LLC

Comparison and Corroboration USGS Topographic Maps, USFWS NWI Maps, and U.S. Department of Agriculture Natural Resources Conservation Service Soil Surveys are typically the most accessible resources and require the least amount of technical knowledge to interpret. The effectiveness and level of accuracy in conducting off-site wetlands interpretation studies using these resources is a function of the time needed to obtain each source and interpreting the information. Emphasis should be placed on comparing and contrasting individual sources: that is, comparing and corroborating the results from USGS to NWI to the Soil Survey, being sure to consider the years each source was initially produced. For example, the USGS indicates wooded marsh or swamp throughout the western and southern sections of the reference site (Figure 1), the NWI indicates palustrine forested broad-leaved deciduous wetland in the western and southern sections of the site (Figure 2), and the U.S. Department of Agriculture Natural Resources Conservation Service indicates hydric soils in the western and southern sections of the site (Figure 3). Therefore, the interpreter can be reasonably confident that wetlands, and most likely forested wetlands, exist at the site. In an effort to further refine the information already obtained from these resources, additional resources can be consulted and evaluated. Aerial Photographs Aerial photography has been used since the 1860s for remote sensing land-use patterns and activities through the use of hot-air balloons (McKnight, 1987). These actions spawned the development of photogrammetry, the science of obtaining reliable and defensible measurements from photographs and mapping from aerial photographs (Ritchie et al., 1988). Historically, the interpretation of aerial photography has fallen under the term remote sensing, with the net result being that aerial photographs were the only tool used in remote sensing. Contemporary views have altered the term to include a wide range of tools and analytical devices. One recent definition stated remote sensing is the measurement of reflected, emitted, or backscattered electromagnetic radiation from the earth’s surface using instruments stationed at a distance from the site of interest (Roughgarden et al., 1991). Nonetheless, aerial photography is used today as a powerful source for remote sensing land use, including wetland identification, characterization, and perturbation as a result of anthropogenic activities. Stereo-paired vertical contact prints provide the most useful and scientifically defensible information as a three-dimensional image of the earth’s surface is presented to the interpreter via a stereoscope. This three-dimensional image is obtained through photographs taken in stereo pairs with end overlap. The photographs are interpreted with a stereoscope, which allows the interpreter to closely examine site conditions by adding depth of field, and provides the ability to distinguish wetland cover types. Different cover types have characteristic signatures that can be quantified based on observable color, tone or hue, shadow, texture, and depth of field. Color signatures can be further refined using the Inter-Society Color Council and

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National Bureau of Standards (ISCC-NBS) method of color description, using Centroid Color Charts (Smith and Anson, 1968). Permanently and seasonally inundated forested, scrub–shrub, emergent, and open water areas are relatively easy to distinguish from upland habitats using aerial photographs. Surface water has a different reflectance pattern than dry areas. The difficulty comes when trying to identify seasonally saturated wetlands, particularly seasonally saturated forested wetlands. Aerial photographs are available in many formats, scales, and geometry (Figure 4). The most common photograph types used for wetland identification are vertically oriented black and white, color, and color infrared using aerographic film. Aerial photograph geometry (i.e., basis of the angular relationship to the earth’s surface) can be divided into two major categories: oblique (including low oblique and high oblique) and vertical (see Figure 5 and Hudson and Lusch, 1990). Oblique aerial photographs have an advantage to the interpreter, in that ground features can be interpreted from a familiar point of view (McKnight, 1987). In addition, owing to the orientation of the camera for oblique photos, the stereoscopic effect is reduced, thereby negating the three-dimensional effect. However, due to measurement inadequacies and scale development, vertically oriented photographs are used for determining quantitative information and provide more useful and defensible information for wetland identification. Combining aerial photographs with groundtruthing can be a very effective and cost-efficient means to identifying and delineating wetland boundaries on large parcels. Film types are also an important consideration in identifying wetlands. Panchromatic black and white photographs are the least expensive and most common. However, color infrared photographs have a demonstrated and significant advantage. Color infrared discriminates between living and dead vegetation, enhances open water areas, and discriminates natural features from man-made features. Larger scale, low-altitude aerial photography is recommended over smaller scale, high-altitude aerial photography for clarity, ease of interpretation, distinguishing ground features, and general resolution. The most useful and accurate interpretations are made through chronological analysis of a site. Aerial photographic coverage and availability significantly limit its use for offsite wetland identification. Federal and State agencies have inventories with spotty coverage, which may not be available for purchase. The National Archives (in Utah) maintains an active database and inventory of aerial photographs (black and white, color infrared, stereo-paired) covering the entire continental United States for select years, and these photographs are available for purchase. They are generally highaltitude, small-scale aerial photographs. Private commercial suppliers often maintain inventories, and usually specialize within a region (i.e., New England, Northwest, Southeast). Coverage is largely unpredictable varying from complete chronological coverage over several years to no coverage at all. Purchase costs can be quite high, with some firms charging access fees for database reviews. Because aerial photography provides the base map and framework for most other off-site resources, it is apparent how important it can be when used in its unrevised form. Stereo aerial photographic interpretation has evolved into a scientific and technical discipline of its own and, in some instances, requires considerable expertise ©2001 CRC Press LLC

Figure 4

A vertical black and white aerial photograph.

to extract valid information. Nonstereo paired aerial photographs can be used to supplement the other off-site information in a qualitative manner. There is much variability among nonstereo aerial photographs, especially relative to geometry, ©2001 CRC Press LLC

HIGH OBLIQUE

LOW OBLIQUE

VERTICAL

90o

Figure 5

Aerial photography angular orientation.

scales, film types, and coverage. When conducting preliminary qualitative off-site wetland reviews, interpretation of aerial photographs may not be necessary. However, if the goal is to quantify wetland site conditions over time, aerial photographs may prove to be an indispensable tool. U.S. Geological Survey Surficial Geologic Maps The U.S. Geological Survey produces surficial geologic maps primarily for use as indicators of geologic zonation above bedrock. These maps provide some detail relative to soil and subsurface composition and are helpful in locating and identifying swamp deposits, alluvium, surface water bodies, and other wetland features. Figure 6 ©2001 CRC Press LLC

illustrates the location of surface waterbodies, swamp deposits (Qs), and cranberry bogs on the reference site. The swamp deposit designations are indicative of organic matter, clay, silt, and sand accumulating in swamps (USGS, 1967).

Figure 6

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A U.S. Geological Survey surficial geologic map.

Individual State Wetland Maps Several individual states have produced wetland maps for use in macroscale planning, and at least in one instance (MacConnell et al., 1989), for jurisdictional purposes. Most of the maps are developed based on interpretation of stereo-paired aerial photography, similar to the process used by the National Wetland Inventory. Representative states that have produced wetland maps include Maine, Vermont (based on NWI), Massachusetts (Wetlands Restriction Program), New York, and New Jersey. Coverage, interpretation keys (classification systems), and accuracy are variable from state to state.

ON-SITE WETLAND DELINEATION The ability to document wetland site conditions without detailed on-site investigations has a demonstrated need from a natural resources planning perspective as well as from a jurisdictional perspective. Documentation of anthropogenic influence on wetlands is another demonstrated need for using off-site materials for wetland identification. By using the resources and methods discussed above, a reviewer can generally make a positive or negative determination regarding the presence or absence of wetlands, estimate the areal extent of wetlands, and, in some cases, determine major cover types (although a follow-up site inspection is always recommended for full confirmation). However, off-site wetland identification is not a substitute for on-site wetland delineation when the goal is a definitive demarcation or delineation of wetlands for site development and project planning purposes. The need to identify jurisdictional wetlands and delineate wetland/upland boundaries in the United States is principally driven by Section 404 of the Clean Water Act by state and municipal wetland protection statutes. The wetland protection statutes, and associated regulatory policies, dictate that wetland boundaries be established and, in many cases, confirmed, prior to site development and related land management activities. Therefore, project proponents are required to characterize and quantify the differences between wetlands and uplands so that the boundary can be identified with some certainty and repeatability. This is accomplished by field assessment of vegetation, soils, and hydrology. Through interagency consensus, three characteristics or parameters have been selected to distinguish wetlands from uplands. First, wetlands are characterized by the presence of water, typically from a surface or groundwater source. Water levels in wetlands are typically dynamic, with the frequency of saturation and inundation varying among wetland types and varying temporally within wetland types. Second, wetlands are characterized by the presence of unique soils that are diagnostic of wetland conditions. These soils display properties that indicate anaerobic conditions in the root zone resulting from prolonged saturation or inundation. Finally, wetlands are characterized by the presence of wetland vegetation that possesses morphological

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adaptations that enable them to tolerate frequent root zone saturation or inundation and anaerobic conditions. Earlier in this chapter, the regulatory definition of wetlands was provided. More recently, the National Academy of Sciences (National Research Council, 1995) proposed another definition of wetlands. A wetland is an ecosystem that depends on constant or recurrent, shallow inundation or saturation at or near the surface of the substrate. The minimum essential characteristics of a wetland are recurrent, sustained inundation or saturation at or near the surface and the presence of physical, chemical and biological features reflective of recurrent, sustained inundation or saturation. Common diagnostic features of wetlands are hydric soils and hydrophytic vegetation. These features will be present except where specific physicochemical, biotic, or anthropogenic factors have removed them or prevented their development.

There are many factors that affect the presence of these features. Topographical relief and overall landscape position are significant physical factors that often dictate the source for wetland hydrology. For example, topographical depressions often correspond closely with water table elevation in glaciated wetlands of the northeastern United States. Headwaters of streams and rivers are often the result of sheet runoff from watersheds that emanate from mountainous regions. Palustrine and riverine wetlands are often associated with these surface water bodies. Other factors that influence the formation of the three wetland factors include stratigraphy, surficial and bedrock geology, and watershed and climatological conditions including precipitation and evapotranspiration. In identifying and delineating wetlands, it is important to establish in advance the overall goal and scope of the wetland investigation. The investigator should determine if it is necessary to conduct a comprehensive on-site delineation of the entire wetland and upland boundary or simply confirm the presence or absence of wetlands. A wetland determination is the process by which the evaluator makes a positive or negative assumption that wetlands are extant on a site. This assumption is based on identifying whether or not wetland characteristics are present anywhere within the site’s boundaries. Wetland delineation is the process by which the investigator identifies and locates wetlands, then qualitatively or quantitatively assesses the areal extent of wetlands on the site. This is accomplished through consideration of hydrological field indicators, soil profiles, and vegetation sampling and inventory. Wetland delineation techniques and methodologies vary from place to place in response to local and state jurisdictional requirements. Nevertheless, almost without exception, local and state mandated procedures are predicated upon parameters defined by the federal agencies. These factors, and their associated technical criteria, are expressed in the Corps of Engineers Wetland Delineation Manual (Environmental Laboratory, 1987), the Wetland Identification and Delineation Manuals, Volumes I and II (Sipple, 1988), the Federal Manual for Identifying and Delineating Jurisdictional Wetlands (Federal Interagency Committee for Wetland Delineation, 1989), the National Food Security Act Manual (U.S. Department of Agriculture, 1994), and the National Research Council (1995).

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As federal legislation has evolved, resultant modifications to the jurisdictional definitions and limits have occurred, and likely will continue to occur, with ensuing performance standard modifications (U.S. Army Corps of Engineers, 1991; U.S. Army Corps of Engineers, 1992). Other sources (Tiner, 1991; Sipple, 1992) discuss the importance of the dynamic nature (e.g., seasonality, degree of wetness) of wetlands as it relates to the individual factors and the ability to effectively recognize wetland boundaries. Tiner (1993) proposed an innovative approach to delineating wetlands based on identifying primary indicators of hydrophytes and hydric soils in undrained wetlands. Also in 1993, the National Academy of Sciences was tasked by Congress to conduct an independent assessment of current wetland delineation practices, with their findings published in 1995 (National Research Council). The National Research Council report emphasized regionalizing standard approaches and evaluation criteria. This section discusses the three factors associated with wetlands, with an emphasis placed on conducting field assessments that evaluate and characterize each factor. Techniques are presented which assist the investigator in assessing each factor, including recognizing field indicators of wetland hydrology, hydric soils, and hydrophytes. In conducting these analyses, it is important that the methodology be practical, reproducible, efficient, and cost effective. The following sections describe each factor in depth, and an evaluation procedure for assessing all these in conducting a wetland delineation. Wetland Hydrology Wetland hydrology is the single greatest impetus driving wetland formation (Mitsch and Gosselink, 1986; Federal Interagency Committee for Wetlands Delineation, 1989; Tiner and Veneman, 1989; Tiner, 1993), and has historically been the most controversial (U.S. Environmental Protection Agency, 1991; Environmental Law Institute, 1991). Wetland hydrology is characterized by permanent, temporary, periodic, seasonal, or tidally influenced inundation or soil saturation within the root zone. This water may derive from surface water (e.g., streams, rivers, ponds, lakes, ocean), groundwater, overbank flooding, precipitation, sheet flow, or tidal flooding. Wetland hydroperiod is a term used to characterize the hydrological condition of a wetland and is a function of flood duration and flood frequency. All wetlands are dynamic systems from a hydrological viewpoint. The hydrology of perennial wetlands varies irregularly on an annual basis. Ephemeral wetlands such as vernal pools typically have seasonally varying hydroperiods. Tidally influenced wetlands experience daily periodic hydrologic fluctuations. Keeping in mind this inherent variation, a wetland’s net hydroperiod can be represented by the following equation (Mitsch and Gosselink, 1986). V = Pn + Si + Gi – Et – So) – Go ± T

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where V equals the change in volume of water storage. Pn equals the net precipitation. Si equals the surface inflows (stream flow and sheet flow). Gi equals the groundwater inflows. Et equals the evapotranspiration. So equals the surface outflows. Go equals the groundwater outflow. T equals the tidal inflow (+) or outflow (–).

Wetland hydrology drives the development and distribution of the other two indicator parameters. Permanent or periodic inundation or saturation of the root zone during the growing season results in the development of anaerobic conditions, which is one of the chief determinants of hydric soil conditions. Root zone saturation is, in turn, responsible for the occurrence and distribution of vegetation that can withstand these conditions. There has been much debate regarding the duration of time required for anaerobic conditions to develop from root zone saturation or inundation. Until recently, the U.S. Army Corps of Engineers required a minimum of 2 weeks of continuous saturation or inundation within the root zone for an area to be considered to possess wetland hydrology (U.S. Army Corps of Engineers, 1991). Presently, the Corps stipulates that the root zone be saturated or inundated for more than 12.5 percent of the growing season for an area to have wetland hydrology (U.S. Army Corps of Engineers, 1992). Areas inundated or saturated for 5 to 12.5 percent of the growing season may or may not have wetland hydrology. The National Research Council, in their 1995 study, Wetlands: Characteristics on Boundaries, proposed that the threshold for duration of saturation can be approximated as 14 days during the growing season in most years. Historically, the definition of the root zone and its maximum vertical extent has been critical to determining jurisdictional limits. This vertical extent is a direct function of soil series drainage class and permeability. The Corps of Engineers Wetlands Delineation Manual defines major portions of the root zone to be that area within 30 cm of the soil surface (Environmental Laboratory, 1987). The ability to identify and delineate wetlands relative to the hydrology parameter relies on the investigator’s ability to recognize field indicators of wetland hydrology. Generally, quantitative studies and hydrological modeling are not required for onsite wetland identification and delineation. Although many of the technical aspects of the scientific discipline of hydrology are widely applicable to wetland formation, only a rudimentary knowledge of the underlying principles is crucial to wetland delineation. Proficiency in recognizing wetland hydrological indicators, however, is required. Hydrological Field Indicators On-site wetland inspection and delineation require the ability to recognize and distinguish wetland hydrological field indicators (Table 1). The indicators provide ©2001 CRC Press LLC

visual or assumed evidence of soil saturation or surface inundation. Certain indicators provide strong evidence of the frequency and duration of saturation or inundation and can be interpreted to support wetland boundary determinations. Field indicators include the direct observation of wetland hydrological conditions (during the growing season), soil characteristics, morphological plant adaptations, and evidence of water movement (Environmental Laboratory, 1987; Federal Interagency Committee for Wetland Delineation, 1989). Table 1

Wetland Hydrological Field Indicators Widely Used for Identifying Wetlands, and Delineating the Wetland and Upland Boundary

Direct observation of inundation Direct observation of soil saturation Wetland drainage patterns Plant morphological adaptations Adventitious roots Aerenchyma Hypertrophied lenticels Leaf adaptations Multiple trunks Oxidized rhizospheres Pneumatophores Shallow roots Stooling Tree buttressing Water marks and drift lines Surface scouring and water-borne sediment deposits Field confirmed hydric soils Water-stained leaves

The strongest field indicator of wetland hydrology is the direct observation of surface inundation or soil saturation within the root zone during the growing season (Figure 7). This indicator represents a real-time visual observation of wetland diagnostic conditions. Inundation is a valid indicator of wetland hydrology; however, the boundary or areal extent of a wetland may, indeed, extend far beyond the limit of the inundated area. Typically (especially in groundwater discharge wetlands), as topographic elevation increases, the areal extent of inundation decreases, with soil saturation within the root zone becoming the dominant defining characteristic. The depth to which soil saturation is present, and its persistence, determine whether the area is a jurisdictional wetland. Depth is also related to the hydric soil criterion, specifically its drainage class and permeability. Generally, the soil should be saturated within 0 to 46 cm of the surface during the growing season. Soil saturation can be field confirmed through an auger boring to a depth of 46 cm to determine the water table elevation. Saturated soils will occur below this elevation and slightly above due to capillary action (Environmental Laboratory, 1987). Careful attention needs to be paid to extremely fine textured soils (silty clays and clays) which can have a very high capillary fringe and not be good indicators of the actual water table elevation. Soils can also be squeeze tested to extract free water to determine saturation. Wetland drainage patterns occur along riverine, estuarine, palustrine, and some lacustrine wetlands. They are typically associated with moving or fluctuating water systems such as streams, rivers, creeks, etc. Visual indicators include drainage channels, eroded areas, the absence of litter, litter deposits, and characteristic meandering. ©2001 CRC Press LLC

Figure 7

The strongest field indicator of wetland hydrology is the direct observation of surface inundation or soil saturation.

Many wetland plants have developed specialized morphological adaptations that enable them to survive and proliferate with their roots in an anoxic environment. These adaptations have developed in response to root zone saturation and are, therefore, treated as wetland hydrology indicators (Federal Interagency Committee for Wetlands Delineation, 1989). The adaptations typically are specialized structures enabling the plants to capture molecular oxygen and transport it to stems and roots. This is true of buttressed trees (swollen base of the trunk), pneumatophores (above ground root structures), adventitious roots (above ground roots), shallow roots, multiple trunks and stooling, hypertrophied lenticels (exaggerated lenticels on stems), aerenchyma (air-filled tissue), and leaf adaptations (floating and polymorphic leaves). An oxidized rhizosphere is also indicative of wetland hydrology. Evidenced by channels that have developed along the roots for the transport of oxygen, rhizopheres are difficult to observe and clearly identify unless iron oxide concretions are present. Watermarks are visible indications of inundation on woody vegetation and other permanent structures within wetlands. These are considered strong indicators of the presence of wetland hydrology owing to their confirmation of inundated conditions. Drift lines are visible lines indicating the extent of hydrologically driven actions. Tidal marshes typically display drift lines with debris and driftwood extending up to the spring high tide elevation. Drift lines also accumulate along riverbanks and floodplains. Surface scouring occurs in wetlands with widely fluctuating hydroperiods. Scouring also occurs in areas subject to storm or tidal forces that expose soils, remove leaf litter, and cause surficial erosion. Sediment deposits on vegetation also indicate that inundated conditions have occurred in the recent past. ©2001 CRC Press LLC

Observations of wetland hydrology are typically performed at the time of the on-site inspection. However, in cases where long-term observation may be necessary to confirm precise wetland boundaries, wetland hydrology should be assessed for longer periods such as entire growing seasons. Long-term hydrological monitoring can be a labor intensive and costly process unless historical groundwater and surface water elevation data are available. In situations where the jurisdictional limits of a wetland have been debated or questioned and precise boundaries are required (e.g., real estate transactions), hydrological monitoring can typically be accomplished in a cost-effective manner through the installation and monitoring of hand-set groundwater monitoring wells. Typically, 5 cm diameter slotted screen PVC monitoring wells, 60 to 75 cm long, are installed at random locations along a transect line extending from within the recognizable wetland area out to recognizable upland. Hand augers are sufficient to install wells, and borings should be backfilled with washed sand to allow unrestricted passage of groundwater. Well locations and elevations should be surveyed and plotted on a site plan, and monitoring of groundwater elevations should be conducted weekly throughout the growing season. Water level recording can be accomplished using a sounder mechanism and an incremented cord or tape rule. Precipitation should be recorded throughout the monitoring period. Regulatory agencies may require several growing seasons’ worth of data, which can be impractical from the standpoint of project timing and cost. Nevertheless, long-term hydrological information represents the strongest evidence for the extent of wetlands. Hydric Soils The soils found in wetlands have unique morphological and other observable properties that differentiate them from upland soils. A hydric soil by definition is a soil which is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part (U.S. Department of Agriculture Natural Resources Conservation Service, 1991; New England Hydric Soils Technical Committee, 1998). Hydric soil properties are a direct function of the frequency and duration of saturation and inundation, specifically in the root zone. Soils that display flooded and saturated conditions for an extended period (2 weeks or more) during the growing season create an environment where free oxygen is deficient and, ultimately, unavailable to plants. As a result of this saturation and inundation, hydric soils display observable field indicators that are diagnostic of wetland conditions. The U.S. Department of Agriculture Natural Resources Conservation Service has developed a classification system that provides criteria for listing a hydric soil as well as categories of the listed hydric soils. This list, Hydric Soils of the United States, categorizes hydric soils into two major groups: organic soils and mineral soils (U.S. Department of Agriculture Natural Resources Conservation Service, 1991). Generally, soils with at least 46 cm of organic matter in the upper part of the soil profile are considered organic soils, or histosols (Tiner and Veneman, 1989). Organic soils are divided into groups based on the degree to which plant fibers and material are decomposed. Fibrists (peats), hemists (mucky peats and peaty mucks), and saprists (muck) are organic hydric soils listed in increasing order of plant ©2001 CRC Press LLC

material decomposition. Folists are the fourth group of organic soils, but they are not considered hydric soils because the organic component does not derive from long-term saturation or inundation (Tiner and Veneman, 1989). Mineral soils generally have less organic material in the upper part of the profile than organic soils and have different field indicators. Mineral hydric soils are also taxonomically arranged and include soils in Aquic suborders, Aquic subgroups, Albolis suborder, Salorthids great groups, and Pell great groups of Vertisols (shrinking or swelling dark clay soils, Federal Interagency Committee for Wetlands Delineation, 1989; U.S. Department of Agriculture Natural Resources Conservation Service, 1991). Mineral soils are considered hydric soils when any of several criteria are satisfied (Tiner and Veneman, 1989). Somewhat poorly drained soils with a water table less than 15 cm from the surface for a significant period during the growing season are hydric. Poorly drained or very poorly drained soils are hydric if the water table is at or less than 30 cm from the surface for a significant period during the growing season if permeability is equal to or greater than 15 cm/hr in all layers within the top 50 cm, or the water table is less than 46 cm from the surface for a significant period during the growing season if permeability is less than 15 cm/hr in any layer within the top 50 cm. Mineral soils are also hydric if water is ponded for a long duration (more than 7 days) or a very long duration (greater than 1 month) during the growing season. Mineral soils frequently flooded for a long duration (more than 7 days) or a very long duration (more than 1 month) during the growing season are also considered hydric. A significant period is defined as at least 15 consecutive days of saturation or 7 days of inundation during the growing season (U.S. Army Corps of Engineers, 1992). The 1987 Corps Manual, which is the current manual guiding federal jurisdictional technical delineation, defines growing season as that portion of the year when soil temperatures at 50 cm below the soil surface are higher than biologic zero (5˚C). For ease in determination, the growing period can be estimated to occur when air temperature exceeds 22˚C (U.S. Army Corps of Engineers, 1992). Drainage classes are a significant criterion when determining the presence of hydric soils, as the soils relate to individual taxonomic groups (New England Hydric Soils Technical Committee, 1998; Smith, 1973; Tiner and Veneman, 1989). In addition, field determination of drainage classes has been made easier through the use of manuals such as the Field Indicator for Identifying Hydric Soils in New England (New England Hydric Soils Technical Committee, 1998). All very poorly and poorly drained soils are hydric soils, assuming the soils have not been drained. A very poorly drained soil is a soil where water is removed from the soil so slowly that free water remains at or near the surface during most of the growing season. A poorly drained soil is a soil where water is removed so slowly that the soil is saturated periodically during the growing season or remains wet for long periods. Many somewhat poorly drained soils are also hydric. A somewhat poorly drained soil is one where water is removed slowly enough that the soil is wet for significant periods during the growing season. Soil mapping provided by the U.S. Department of Agriculture Natural Resources Conservation Service indicates the soil series drainage class which can be field confirmed using criteria developed by the U.S. Army Corps of Engineers (1991). ©2001 CRC Press LLC

Essential to the investigation of soils for hydric properties is an understanding of soil horizons. Soil horizons, or layers, develop in response to localized chemical and physical processes resulting from the activities of soil organisms, the addition of organic matter, precipitation, and percolation. Horizons can be distinguished based upon color, texture, and composition (Environmental Laboratory, 1987). However, the soil horizon is essentially a continuum and there is no clear distinction between one horizon and another. Soils typically have four major horizons: an organic layer (O) and three mineral layers (A, B, and C); see Figure 8. The O horizon is the surface layer and is composed of fresh or partially decomposed organic material. The A horizon is characterized by an accumulation of organic matter and the loss of clay, iron, and aluminum. Together, the O and A horizons constitute the zone of maximum biological activity. The B horizon is characterized by the accumulation of silicates, clay, iron, aluminum, and humus, whereas the C horizon contains weathered material either similar or dissimilar to the parent material. Soil colors also provide critical information on soil wetness, and the degree of saturation and inundation. The Munsell Color Chart standardizes three aspects of color: hue, value, and chroma (Kollmorgen Corporation, 1975). Hue describes the soil based on its relation to the spectral colors (i.e., red, yellow, green, blue, purple, or a mixture of these colors), value describes the degree of lightness, and the chroma indicates the strength or purity of the color. The Munsell Color Chart depicts individual hues on separate pages, with the corresponding value on the vertical axis and the chroma on the horizontal axis. Soil color is reported as hue, value/chroma — for example, 7.5 YR 2/1. A relatively new standard soil color is the earth tones book that has an increased number of soil color chips and is being used more commonly for hydric soil determinations. Soil colors are an important field indicator for field verification of mapped hydric soils as well as hydric soil inclusions in mapped, nonhydric soils. Both soil matrix, the predominant color derived from the parent material or deposits, and redoximorphic features and concretions, contrasting spots within the matrix, should be characterized. Soil colors are diagnostic of wetland conditions when the matrix chroma immediately below the A horizon is two or less in redoximorphic features (e.g., mottled soils), or one or less in soils without redoximorphic features (Environmental Laboratory, 1987). In some soils, though, it is now recognized that carbon soils with a chroma of three and the presence of redoximorphic features indicate a hydric soil. Hydric Soil Field Indicators Hydric soils display certain field indicators that provide clues to the degree of saturation and inundation. These clues are, in turn, indicative of the presence or absence of wetlands hydrology (e.g., indicate that the root zone has experienced saturation or inundation). The field indicators presented in Table 2 are nationally accepted and were developed based on U.S. Department of Agriculture Natural Resource Conservation Service factors (Environmental Laboratory, 1987; Federal Interagency Committee for Wetland Delineation, 1989; Tiner and Veneman, 1989). Since that time, there have been several attempts to develop regional hydric soil ©2001 CRC Press LLC

Figure 8

A generalized soil profile. Actual horizons represent a continuum and will not appear this distinct in the field.

field indicators (New England Hydric Soils Technical Committee, 1998). Recognizing and applying these field indicators will enable the wetland scientist to field confirm or refute the hydric soil criterion. Most of these field indicators are used when attempting to recognize hydric mineral soils, and some, such as a high organic content at the surface, subsurface streaking, and wet spodosols, are particularly useful when attempting to recognize sandy hydric mineral soils. As mentioned previously, all organic soils except folists are considered hydric soils. Organic soils are readily identifiable in the field due to the relatively high percentage of poorly decomposed organic matter such as vegetative material and litter in the soil matrix. Organic soils also often possess dark hues and very dark chromas (7.5 YR 2/0, 10 YR 2/1, etc.).

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Table 2

Field Indicators of Hydric Soils

Organic soils (histosols) Histic epipedons Sulfidic material Aquic or peraquic moisture regime Reducing condition Soil color Mottling or concretions High organic matter content in surface horizon Subsurface streaking Spodic horizon Note: Indicators are applied to the soil profile within the root zone.

Histic epipedons are thick (20 to 40 cm) organic surface layers overlying hydric mineral soils. They develop as a result of prolonged saturation within the root zone, at least 30 consecutive days or more in most years (Environmental Laboratory, 1987). The presence of sulfidic material is a strong indicator of permanently saturated soil conditions. Sulfidic material is evidenced by a rotten egg-like odor, typically following soil disturbance. The odor occurs as a result of sulfates being reduced to sulfides under anaerobic conditions associated with prolonged root zone saturation. This indicator is especially common in tidal marshes. Elevated groundwater levels characterize aquic and peraquic moisture regimes. Aquic moisture regimes are mostly reducing, and are nearly free of dissolved oxygen as a result of saturation due to groundwater or the capillary fringe. A part or all of the root zone is reduced and totally deficient in dissolved oxygen during the growing season. Peraquic moisture regimes occur when groundwater is always at or near the soil surface. Reducing conditions can be observed in hydric mineral soils of high iron content using a calorimetric test kit. In a reducing environment, ferrous (reduced) ions are detected using a-adipyridil (Environmental Laboratory, 1987). It should be understood that this test only reveals reducing conditions during the time of the field investigation and may not reflect conditions typical of a significant part of the growing season. Repeated sampling over an extended temporal scale is required to satisfy the hydric soil criterion. Soil colors typically provide the most useful and diagnostic field indicators for hydric mineral soils. When water is at or near the soil surface for most or all of the year, soils may become gleyed and take on a lighter dull gray or bluish color. The color arises from the conversion of oxidized (ferric) iron to its reduced (ferrous) state, and the subsequent removal of the latter from the soil. Oxidizing conditions are apparent only along root channels in gleyed soils. The formation of redoximorphic features (e.g., mottles, concretions, and depletions) occurs in soils where the water table fluctuates periodically. Saturated, anaerobic conditions cause the solubilization of iron compounds. Subsequent depressions in the water table create an aerobic environment and iron ions are converted to insoluble oxides that appear as orange or red mottles in the soil matrix. Relatively longer periods of soil saturation and anaerobic conditions followed by aerobic conditions convert manganese ions to ©2001 CRC Press LLC

oxides. The manganese oxides are deposited as concretions and are evidenced by small, dark brown or black nodules interspersed with the soil matrix. Both mottles and concretions persist for long periods after formation and may not reflect current conditions. However, a combination of redoximorphic features and a low matrix chroma is generally indicative of hydric conditions. Accumulations of iron and manganese are now generally referred to as redox concentrations (New England Hydric Soils Technical Committee, 1998). Redox depletions are areas within the soil with low chromas without iron and manganese oxides. Soil color is a poor indicator of hydric condition in sandy soils and other indicators must be used. A high organic matter content in the surface horizon is indicative of hydric conditions because it is caused by prolonged inundation or saturation. This prolonged inundation or saturation greatly reduces oxidation of organic matter, leading to its accumulation. Subsequent lowering of the water table may cause streaking of the subsurface horizons as organic matter is moved downward through the sand. Eventually, this downward moving organic matter may accumulate at a point coinciding with the most commonly occurring depth to groundwater. The organic matter may become cemented with aluminum, forming a less permeable, hardened, spodic horizon. Each of these characteristics, high organic matter content in the surface horizon, streaking, and a spodic horizon, is indicative of hydric conditions. When examining the soil component during wetland identification and delineation, minimum equipment needs include a hand auger, Munsell Color Chart, delineation data sheets, pencil, and camera. Borings need to be hand augured at locations along the perceived upland and wetland sides of the boundary, keeping hydrological and topographical indicators in mind. Borings should extend to depths between 30 to 46 cm to adequately characterize O, A, and B horizons. Diagnostic observations include depth to groundwater or depth of inundation, and examination for each of the field indicators for mineral and organic hydric soils. The hydric soil boundary should be identified based upon the wetland side having observable characteristics of hydric soils and the upland side having a general lack of these characteristics. Visible hydrology will influence the number of borings needed to adequately define the soil boundary. Hydrophytic Vegetation Probably the most visible and easily recognizable diagnostic feature of wetlands is hydrophytic (water-loving) vegetation. Hydrophytic vegetation is the sum total of macrophytic plant life that occurs in areas where the frequency and duration of inundation or soil saturation are of sufficient duration to exert a controlling influence on the plant species present (Environmental Laboratory, 1987). Hydrophytes possess anatomical and physiological adaptations that allow them to survive and thrive in saturated or inundated soils, where oxygen depletion is the primary factor limiting vegetation occurrence (Figure 9). Adaptive structures of hydrophytes include aerenchyma, adventitious roots, stooling, hypertrophied lenticels, and buttressing. Plant species with a demonstrated ability to achieve maturity and reproduce where the root zone is inundated or saturated during the growing season are listed in the National List of Plant Species that Occur in Wetlands (Reed, 1988, 1995). ©2001 CRC Press LLC

Figure 9

Hydrophytes, such as this skunk cabbage (Symplocarpus foetidus ) possess anatomical and physiological adaptations that allow them to survive in saturated soils.

Approximately 7000 species of hydrophytes are listed. Originally designed as an appendix to Classification of Wetlands and Deepwater Habitats of the United States (Cowardin et al., 1979), the list was modified to assist in determining the probability that a vegetation community is a wetland (Wentworth and Johnson, 1986). This is accomplished by assigning each plant to an indicator category which reflects the probability, expressed as a frequency of occurrence, of a species occurring in wetland or upland (Table 3). Modifiers (+ or –) are also assigned to the categories to further refine individual species affinity toward wet conditions. A ‘+’ indicates an increased probability of wetland tolerance, and a ‘–’ indicates an affinity for drier conditions (Reed, 1988). The categories should not be equated to degrees of soil wetness. For example, many obligate wetland species occur in permanently flooded wetlands, whereas other obligate plants occur in seasonally or temporarily flooded wetlands. Indicators of Hydrophytic Vegetation Dominance by hydrophytes is the most reliable indicator for determining whether hydrophytic vegetation is present. It has its basis in the current federal definition of wetlands which includes the phrase a prevalence of vegetation typically adapted for life in saturated soil conditions. Vegetation is said to be prevalent when it is dominant, that is, the species contribute more to the character of a plant community than other species (Environmental Laboratory, 1987). If the dominant species are hydrophytes, the community consists of hydrophytic vegetation. The standard for determining if the vegetation is hydrophytic is the 50 percent rule—more than 50 percent of the dominant vegetation is OBL, FACW, or FAC (excluding FAC–) on the appropriate

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Table 3

Indicator Category and Frequency of Occurrence in Wetlands for Plants Listed (in Reed 1988) Frequency of Occurrence in Wetlands > 99 percent

Indicator Category Obligate Wetland (OBL) Facultative Wetland (FACW) Facultative (FAC)

67–99 percent 34–66 percent

Facultative Upland (FACU) Obligate Upland (UPL)

1–33 percent < 1 percent

Representative Species Cattail (Typha spp.) Button bush (Cephalanthus occidentalis ) Soft rush (Juncus effusus ) Speckled alder (Alnus rugosa ) Red maple (Acer rubrum ) Sweet pepperbush (Clethra alnifolia ) American beech (Fagus grandifolia ) White pine (Pinus strobus ) Black oak (Quercus veltina ) Staghorn sumac (Rhus lyphina )

Note: Upland species are not listed.

list of plant species that occur in wetlands (Environmental Laboratory, 1987; U.S. Army Corps of Engineers, 1991; U.S. Army Corps of Engineers, 1992). Various ecologically based methods are acceptable for determining dominant plant species. Hays et al. (1981) provides operational descriptions of several techniques suitable for quantitatively measuring habitat variables. The Corps of Engineers recognizes various techniques that consider individual vegetation strata (Table 4). Consistent with the Corps of Engineers (Environmental Laboratory, 1987; U.S. Army Corps of Engineers, 1992), trees and lianas within a 9.1 m (30 ft) radius of a sample point are identified and measured for basal area at breast height (1.4 m or 4.5 ft). The basal area of all individual tree species and all individual liana species are summed and tree species and liana species separately ranked in descending order based upon total basal area. As an alternative to measuring the basal area of lianas, the number of individual stems of each species may be counted. As many lianas branch, stem counts should be conducted at ground level. Lianas are then ranked in descending order of dominance based upon number of stems. Table 4

Categories Used in the Assessment of Vegetation Communities

Story Woody overstory Woody understory

Stratum Tree Liana Sapling Shrub

Herbaceous understory

Seedlings and herbs Mosses and liverworts

Definition Woody, nonclimbing, at least 12.7 cm dbh and at least 6.1 m tall Woody vines, climbing Woody, nonclimbing, at least 1 cm dbh but less than 12.7 cm dbh and at least 6.1 m tall Woody, nonclimbing, at least 0.9 m tall but less than 6.1 m tall Woody, less than 0.9 m tall, or nonwoody and any height Small, green, nonflowering

Other strata are typically evaluated based upon percent areal coverage. According to the Corps of Engineers (Environmental Laboratory, 1987; U.S. Army Corps of Engineers, 1992), saplings and shrubs are assessed within a 4.5 m (15 ft) radius, ©2001 CRC Press LLC

and seedlings and herbs are assessed within a 1.5 m (5 ft) radius, of a sample point. For each stratum, the species are ranked in descending order of dominance based upon percent cover. Mosses and liverworts are only considered when they constitute an important component of the vegetation community. In determining whether hydrophytic vegetation is present, the Corps of Engineers (Environmental Laboratory, 1987; U.S. Army Corps of Engineers, 1992) suggests using the three dominant species from each vegetation stratum and five species if only one or two strata are present. The indicator status of each species is recorded. If the majority of dominant species are OBL, FACW, or FAC (excluding FAC–), then the vegetation is said to be hydrophytic and, therefore, indicative of wetlands. A variation of the dominance method requires calculation of a prevalence index (Federal Interagency Committee for Wetland Delineation, 1989). Each indicator category is assigned an index value: OBL equal to 1.0, FACW equal to 2.0, FAC equal to 3.0, FACU equal to 4.0, and UPL equal to 5.0. Dominant vegetation is identified based upon its relative frequency of occurrence or relative areal coverage. An index value is assigned to each species and weighted by its relative dominance in the community. If the sum of the index value is less than 3.0, then the vegetation is considered to be hydrophytic. Although dominance by hydrophytes is the most reliable indicator of hydrophytic vegetation, other indicators exist. In general, these other indicators should be applied only after application of the dominant species method. Nevertheless, visual observation of plant species growing in areas of prolonged inundation or soil saturation, particularly if those species have been observed in other wetland areas, suggests hydrophytic vegetation. This approach may be applied with some reliability for OBL, and to a lesser extent FACW species, but it is considerably less reliable for FAC species. The presence of standing water or saturated soil is, in many cases, insufficient evidence that the observed species are capable of tolerating anaerobic conditions for an extended period. When in doubt, determine hydrology and soil characteristics. Morphological adaptations to inundation or soil saturation such as buttressed tree trunks, adventitious roots, and shallow root systems are also suggestive of hydrophytic vegetation (see Table 1). Most individuals of the dominant species should exhibit morphological adaptations for this indicator to be reliable. However, not all hydrophytic species have obvious morphological adaptations. Conversely, apparent morphological adaptations may develop in response to factors other than soil wetness.

IDENTIFYING AND DELINEATING WETLANDS Undisturbed Areas When a site is relatively undisturbed, identifying and delineating wetlands are accomplished by simultaneously applying the criteria for wetland hydrology, hydric soils, and hydrophytic vegetation. Typically, the best time to identify or delineate wetlands is during the growing season, when dominant vegetation (especially ©2001 CRC Press LLC

annuals) are evident and hydrology can be directly observed. Nevertheless, identification and delineation of wetlands can be reasonably accomplished at any time of the year, although the process is made infinitely more difficult by snow or ice cover. To facilitate wetland identification and delineation, it is helpful to establish a working baseline. The baseline should extend parallel to any major watercourses or waterbodies or to any potential wetland areas (Figure 10). It is also helpful to establish the baseline perpendicular to the topographical gradient. Transects are established perpendicular to the baseline, with the number of transects depending upon the length of the baseline and the diversity of plant communities on the site. Minimally, at least one transect should sample each plant community type. The Corps of Engineers (Environmental Laboratory, 1987) offers guidelines for establishing transects. A number of observation points should be established along each transect. Again, the Corps of Engineers (Environmental Laboratory, 1987) offers guidelines for establishing observation points. An experienced investigator will minimize effort by establishing one observation point in recognizable wetlands and a second point in recognizable upland. Using observed hydrological, soil, and vegetation characteristics at these two observation points as references, the investigator can then focus his or her efforts on areas that are less readily discernible.

Figure 10

Establishment of a baseline parallel to observed watercourses and perpendicular to the topographical gradient facilitates wetland identification and delineation. Transects are established perpendicular to the baseline, and at least one transect should sample each plant community type.

At each observation point, hydrology, soil, and vegetation are simultaneously characterized and a determination is made as to whether the area constitutes wetlands or uplands. More precisely, the observation point is inspected for indicators of wetland hydrology, indicators of hydric soil, and hydrophytic vegetation. Under normal conditions, indicators of wetland hydrology, hydric soil, and hydrophytic vegetation must all be present for an area to be considered a wetland. A determination ©2001 CRC Press LLC

that the observation point constitutes a wetland is sufficient if the purpose of the exercise is only identification of wetlands. For the purpose of delineation, subsequent observation points along the transect, upgradient of the wetland observation point, must be characterized until wetland indicators are absent. Conversely, initial identification of an upland observation point requires subsequent investigation of downgradient observation points until all wetland indicators are present. Disturbed Areas When a site is disturbed, identifying and delineating wetlands through application of the criteria for wetland hydrology, hydric soils, and hydrophytic vegetation may be impossible. The disturbance may have been intentional or inadvertent, the result of unauthorized activities or natural events. Site hydrology may be altered due to dam construction, water diversion, channelization, or groundwater withdrawal, resulting in a site that is wetter or drier than normal. Soil may be buried, removed, or mixed, whereas vegetation may be cut, burned, or converted to agricultural crops. In many cases, normal application of the methods discussed above will lead to the conclusion that the site is not a wetland because one or more of the wetland indicators are likely to be absent. If one or more wetland indicators cannot be assessed and the site clearly has been disturbed, it is appropriate to evaluate the remaining indicators and to identify other sources of information regarding the missing indicator(s). In general, as many sources as possible should be considered prior to any determination. There are several avenues of investigation for determining normal site hydrology. Recent aerial photographs of the site, taken during the growing season, may provide relatively conclusive information about site inundation and somewhat less conclusive information about soil saturation. In some instances, a stream or tidal gauging station may be located in close proximity to the site, allowing calculation of high and low water elevations. Certain field indicators of wetland hydrology, such as plant morphological adaptations or high water marks, may be visible. Less reliable but of some usefulness are historic records, floodplain management maps, and the personal knowledge of local officials or residents. If fill has been placed on the site, buried soils can reasonably be examined for hydric soil indicators. Conversely, the removal of surface soil layers may allow for examination of the exposed subsurface horizons. Plowed soils can be examined immediately beneath the plow zone. Although inconclusive, review of soil survey maps, or examination of adjacent, undisturbed soils of the same series may be useful. Information relative to the preexisting vegetation community varies in its reliability. The most reliable information comes from examination of vegetation communities only partially removed or from review of recent documentation of site vegetation. Somewhat less reliable is examination of recent aerial photography and examination of vegetation in adjacent, undisturbed areas. Least reliable are review of soil survey plant community descriptions, review of National Wetland Inventory maps, and the recollection of local officials or residents.

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Difficult Areas Some wetlands are inherently more difficult to identify and delineate than other wetlands. The difficulty arises because one or more of the wetland indicators may be impermanent. Slope wetlands in glaciated wetlands have thin soils over relatively impermeable till or varying hydraulic conditions that produce groundwater seepage. Hydric soils and hydrophytic vegetation are generally readily apparent, but wetland hydrology is present only during wetter parts of the growing season. Seasonal wetlands such as vernal pools also lack wetland hydrology during all but the wettest part of the growing season. Prairie potholes have standing water for the majority of the growing season in normal or wet years, but they may be dry in years of below average precipitation. Vegetated flats are dominated by annual plant species during the growing season, but they are devoid of vegetation outside of the growing season. Almost without exception, identification and delineation for each of these wetland types, as well as other difficult wetlands, can reasonably be accomplished by conducting the evaluation at the appropriate time of the year or in a year of normal precipitation. Aids to Delineation In the last several years, many tools have been developed or improved which have facilitated the technical procedures associated with wetland delineation. Differential Global Positioning System (GPS) software has widely expanded reference or landscape point location capability, including wetland boundaries. Use of GPS technology as it applies to wetland jurisdictional delineations has largely involved the ability to electronically locate wetland boundaries and data points (flags or transect locations) and place these data points on a site plan or other underlay in an efficient and reproducible manner. Use of GPS for locating wetland boundaries allows an operator to collect significant line and point features, and attribute data for objects or points in the natural landscape, in a relatively short period of time. GPS data collection is often undertaken using a backpack unit consisting of handset data logger and an antenna with differential beacon receiver allowing the operator to cover large areas and areas with difficult access to record the jurisdictional wetland boundary. GPS raw data typically needs to be downloaded onto computers for storage and differential correction but can be readily integrated with Geographic Information Systems (GIS) software to create site plans or base maps. The most common limitation of GPS for wetland assessment is human operational error. Inexperienced operators should understand basic settings and how to maximize the GPS’s efficiency. In order to maximize the effective use of GPS, a digital plan should be utilized with specific horizontal and vertical control. Other limitations include signal obstruction from the satellite constellation that impairs the ability of the receiver to collect a position. This can occur under heavy forest cover, against buildings, or when the sky is effectively blocked. However, satellite positions change in relation to the operator’s location on the earth so returning to a position at a later time may solve the problem.

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Technical resources and wetland delineation software also facilitate wetland delineation. A number of federal, state, and private vendor internet sites have made it much easier to acquire wetland delineation technical information. This information includes access to the various wetland delineation manuals, various technical publications, maps and soil surveys, and delineation software (Table 5). Table 5

Internet Sites with Wetland Delineation Technical Information Site

Information

www.fws.gov/fgdcwet.html www.nwi.fws.gov/qanda.html www.statlab.iastate/edu/soils/hydric www.nwi.fws.gov www.wssinc.com www.libweb.wes.army.mil

U.S. Fish and Wildlife Service publications Wetland classification Hydric soil list National Wetland Inventory maps, plant list WetForm software U.S. Corps of Engineers Waterways Experiment Station publications U.S. Department of Agriculture publications

www.itis.usda.gov/itis/index.html

Wetland Studies and Solutions, Inc. have developed specialized wetland delineation software, WetForm. A windows-based application, WetForm provides to field delineators a U.S. Army Corps of Engineers-accepted data form consistent with the data collection needs of the 1987 Corps Manual. Electronic data entry fields for observation plot, vegetation, soils, hydrology, and wetland determination are included and also are consistent with the Corps of Engineer Policy guidance issued subsequent to the 1987 Manual. The software package includes a vegetation database and all numerical calculations (e.g., vegetation dominance, percent cover, dominance ratio) are automatically calculated. Vegetation data fields include common and scientific names of wetland species from the applicable USFWS regions in the continental United States. The soils database is not comprehensive, but it does have inputs for matrix and redoximorphic Munsell color, texture, and structure. Soils series from the U.S. Deparment of Agriculture Soil Conservation Soil Surveys are also in the database. Hydrological indicator fields are essentially identical to the Corps of Engineer forms, but related keys are triggered when answers to consistent indicators are given.

REFERENCES 33 CFR 320–330, 1986 Code of Federal Regulations, U.S. Army Corps of Engineers, 1986. Cowardin, L. M., Carter, V., Golet, F. C., and LaRoe, E. T., Classification of Wetlands and Deepwater Habitats of the United States, U.S. Department of the Interior, Fish and Wildlife Service Biological Services Program FWS/OBS-79131, 1979. Environmental Laboratory, Corps of Engineers Wetland Delineation Manual, Technical Report Y-87–1, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 1987. Environmental Law Institute, What is a jurisdictional wetland? Nat. Wet. Newsl., September/October, No. 5, 1991. Federal Geographic Data Committee (Wetlands Subcommittee), Proposal to Establish the Cowardin System as the Federal Wetland Classification Standard, 1995. ©2001 CRC Press LLC

Federal Interagency Committee for Wetland Delineation, Federal Manual for Identifying and Delineating Jurisdictional Wetlands, U.S. Army Corps of Engineers, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and U.S. Department of Agriculture Natural Resources Conservation Service, Washington, D.C., 1989. Hays, R. L., Summers, C., and Seitz, W., Estimating Wildlife Habitat Variables, U.S. Department of the Interior Fish and Wildlife Service, FWS/OBS-81/47, 1981. Hudson, W. D. and Lusch, D. P., Airphoto/satellite imagery—an introduction, in Proceedings of the Remote Sensing and GIS Applications to Nonpoint Source Planning Conference, sponsored by the U.S. Environmental Protection Agency and the Northeast Illinois Planning Commission, Chicago, IL, 1990. Kollmorgen Corporation, Munsell Soil Color Charts, Baltimore, MD, 1975. MacConnell, W., Goodwin, D., Jones, K., Stone, J., Foulis, D. B., Springston, G., and Swartout, D., Wetland Restriction Program: Mapping Standards for Wetlands Restriction Maps in Massachusetts, Technical Memorandum published by the Massachusetts Department of Environmental Protection, 1989. McKnight, T., Physical Geography: A Landscape Appreciation, 2nd ed., Prentice-Hall, Englewood Cliffs, NJ, 1987. Mitsch, W. J. and Gosselink, J. G., Wetlands, Van Nostrand Reinhold, New York, 1986. National Research Council, Wetlands: Characteristics and Boundaries, National Academy Press, 1995. New England Hydric Soils Technical Committee, Field Indicators for Identifying Hydric Soils in New England, 2nd ed., New England Interstate Water Pollution Control Commission, Wilmington, MA, 1998. Reed, P. B., Jr., National List of Plant Species that Occur in Wetlands: National Summary U.S. Fish and Wildlife Service, Biological Report 88(24), Washington, D.C., 1988. Reed, P. B., Jr., National List of Plant Species that Occur in Wetlands: National Summary, U.S. Fish and Wildlife Service, Biological Report, Washington, D.C., 1995. Ritchie, W., Wood, M., and Wright, R., Surveying and mapping for field scientists, in Aerial Surveying Techniques, Longman Scientific and Technical, 1988. Roughgarden, J. S., Running, W., and Matson, P. A., What does remote sensing do for ecology? Ecology, 72(6), 1918, 1991. Sipple, W. S., Wetland Identification and Delineation Manual, Vol. 1, Rational, Wetland Parameters, and Overview of Jurisdictional Approach, U.S. Environmental Protection Agency, Office of Wetlands Protection, Washington, D.C., 1988. Sipple, W. S., Wetland Identification and Delineation Manual, Vol. 2, Field Methodology, U.S. Environmental Protection Agency, Office of Wetlands Protection, Washington, D.C., 1988. Sipple, W. S., Time to move on, Nat. Wetl. Newsl., 14, 4, 1992. Smith, G. D., Soil moisture regimes and their uses in soil taxonomies, in Field Soil Water Regime, Bruce, R. R., Flach, K. W., and Taylor, H. M., Eds., Soil Scientist Society of America, Madison, WI, 1973. Smith, J., Jr. and Anson, T. A., Eds., Manual of Color Aerial Photography, 1st ed., American Society of Photogrammetry, VA, 1968. Tiner, R. W., Wetland delineation, in Proceedings of the 1991 Stormwater Management/Wetlands/Floodplain Symposium, Aron, G. and White, E. L., Eds., Pennsylvania State University, Department of Civil Engineering, University Park, PA, 1991. Tiner, R. W., The primary indicators method—a practical approach to wetland recognition and delineation in the United States, Wetlands, 13(l), 50, 1993.

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Tiner, R. W. and Wilen, B. O., The U.S. Fish and Wildlife Service’s National Wetland Inventory Project, Technical Memorandum, USFWS, Washington D.C. and Newton Corner, MA, 1983. Tiner, R. W. and Veneman, P. L., Hydric Soils of New England, University of Massachusetts Cooperative Extension, Revised Bulletin C-183-R, Amherst, MA, 1989. U.S. Army Corps of Engineers, Questions and Answers on the 1987 Corps of Engineers Manual, CECW-OR 7, October 1991. U.S. Army Corps of Engineers, Technical Memorandum: Clarification and Interpretation of the 1987 Manual, CECW-OR, USCOE/Washington, D.C., March 1992. U.S. Department of Agriculture Natural Resources Conservation Service, Soil Survey of Kennebec County, Maine, USDAISCS Cooperative Publication with the Maine Agricultural Experiment Station, 1978. U.S. Department of Agriculture Natural Resources Conservation Service, Hydric Soils of the United States, National Technical Committee for Hydric Soils, Publication No. 1491, Washington, D.C., 1991. U.S. Department of Agriculture Natural Resources Conservation Service, National Food Security Act Manual, 3rd ed., 180-V-NFSAM, 1994. U.S. Environmental Protection Agency, Proposed revisions to the Federal Manual for Delineating Wetlands, Fed. Regist., 58, 157, August 14, 1991. U.S. Geological Survey, Surficial Geologic Map, Hanover, MA Quadrangle, 1967. U.S. Geological Survey, Topographic Map, Hanover, MA Quadrangle, 1974. U.S. Geological Survey, Topographic Map, Duxbury, MA Quadrangle, 1975. U.S. Geological Survey, Topographic Map Index, 1991. Wentworth, T. R. and Johnson, G. P., Use of Vegetation for the Designation of Wetlands, U.S. Fish and Wildlife Service, Washington, D.C., 1986.

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Kent, Donald M. “Evaluating Wetland Functions and Values” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

CHAPTER

3

Evaluating Wetland Functions and Values Donald M. Kent

CONTENTS Functions and Values Aquatic and Wildlife Habitat Educational and Scientific Venue Elemental Transformation and Cycling Flood Flow Alteration Groundwater Recharge Particle Retention Production Export Raw Materials Recreation Soil Stabilization Evaluating Functions and Values Representative Evaluation Techniques Expert Opinion Wetland Evaluation Technique Rapid Assessment of Wetlands (RAW) Wetlands Integrated Monitoring Condition Index (WIMCI) Hydrogeomorphic Assessment (HGM) Habitat Evaluation Procedures (HEP) Virtual Reference Wetlands (VRW) Economic Valuation Economic Valuation Methodologies Direct Economic Valuation Indirect Economic Valuation

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The Value of the World’s Ecosystem Services and Natural Capital References

As do all ecosystems, wetlands have functions and values. Functions are processes that are inherent to a wetland. They derive from the wetland’s hydrological, geological, biological, and chemical characteristics. For example, groundwater recharge is a wetland function that occurs when water in the wetland, derived from precipitation, surface runoff, or both, infiltrates downward through permeable soils to the groundwater table. Wetland functions occur regardless of whether there are people present to benefit from these processes. Wetland values are functions that prove useful or are important to people. The aforementioned wetland functioning to recharge groundwater will possess a groundwater recharge value only if the recharged groundwater is used by local or regional populations. Values may be provided within the confines of the wetland, for example, recreation, or beyond the wetland boundaries, for example, flood protection. Another characteristic of wetland values is that they vary with time and circumstances. Again returning to the example of a groundwater recharge wetland, a downstream community drawing drinking water from a surface impoundment does not view the wetland as valuable to its drinking water supply. Should the surface water supply diminish or become contaminated, and groundwater withdrawal become necessary, that wetland now takes on value. Clearly, wetland functions and values are inextricably linked. Values cannot be provided without there first being a function. Conversely, a function has no value until someone exploits that function. Recognizing the confounding nature of the relationship between wetland function and value, many functions and values have been attributed to wetlands (Amman et al., 1986; Mitsch and Gosselink, 1993; Adamus et al., 1987; Reimold, 1994; Brinson, 1995). Some of the commonly recognized functions and values of wetlands are listed in Table 1 and described briefly below. Table 1

Wetland Functions and Values

Aquatic and wildlife habitat Educational and scientific venue Elemental transformation and cycling Flood flow alteration Groundwater recharge Particle retention Production export Raw materials Recreation Soil stabilization

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FUNCTIONS AND VALUES Aquatic and Wildlife Habitat All wetlands, with the exception of those that have been severely degraded, provide habitat for wildlife. And wetlands with seasonal or permanent surface water support fish and other aquatic vertebrates and invertebrates. Many threatened and endangered species are associated with wetlands. The type and degree to which aquatic and wildlife habitat is provided is dependent upon local and landscape characteristics including water depth and permanence, vegetation type and cover, habitat size, and the nature of the surrounding environment (Forman and Godron, 1986; Kent, 1994). Educational and Scientific Venue Numerous public and private organizations exist for the purpose of educating people about the importance of wetlands. Educational topics include awareness, regulations and legislation, conservation and planning, and science and management (Drake and Vicario, 1994). Wetlands provide an opportunity for studying fundamental biological and ecological principles including energy flow, biogeochemical cycling, population biology, and community structure. As well, wetlands are the focus of more specific studies related directly to inherent functions and values such as pollutant removal, habitat provision, and flood attenuation. Elemental Transformation and Cycling Wetlands serve as sinks, sources, or transformers of many inorganic and organic chemicals, including those of ecological and socioeconomic importance such as nitrogen and phosphorus, carbon, sulfur, iron, and manganese. Chemicals enter the wetland through hydrologic pathways such as precipitation, surface or groundwater, tidal exchange, or alternatively through biotic pathways including photosynthetic fixation of atmospheric carbon and bacterial fixation of nitrogen, respectively. Wetlands export or lose chemicals by burying in the sediment, outflow in surface or groundwaters, denitrification, atmospheric loss of carbon dioxide, ammonia volatilization, or methane and sulfide release. While within the wetland, chemicals may become part of the litter, remineralized, translocated in plants, or transformed by changes in redox potential or biotic components. Flood Flow Alteration Wetlands have the potential for reducing downstream peak flows and delaying the timing of peak flows. Water from precipitation, overbank flow, overland flow, and subsurface flows may be detained in wetlands by depressions, plants, and debris, or as the result of the wetland slope. Alternatively, water may be retained in the wetland, infiltrate, and recharge surficial groundwater. The importance of wetlands

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for reducing downstream flooding increases with an increase in wetland area, distance the wetland is downstream, size of the flood, closeness to an upstream wetland, and the lack of other upstream storage areas (Ogawa and Male, 1983, 1986). Coastal wetlands also have the capacity to alter flood flows as well as reduce flood wave severity. In this case, salt marshes and mangrove forests absorb the energy of coastal storms, thereby protecting inland areas. Groundwater Recharge Wetlands with pervious underlying soils recharge underlying materials, groundwater, or aquifers. Recharge is thought to occur primarily around the edge of wetlands, making groundwater recharge relatively more important in smaller wetlands. As most wetlands are thought to have impervious underlying soils, the majority of wetlands may not exhibit this function and value (Larson, 1982; Carter and Novitzki, 1988). Particle Retention Wetlands trap and retain sediments, nutrients, and toxicants, primarily through physical processes. Reduction in water velocity causes sediments, and chemicals sorbed to sediments, to settle. Dissolved elements and compounds are retained with inorganic and organic particulates after sorption, complexation, precipitation, and chelation. In contrast to chemical transformation and cycling, incoming particles are subject to long-term accumulation or permanent loss from incoming water sources through burial in the sediments or uptake by vegetation. Production Export Some wetlands, especially those with high primary productivity, export dissolved and particulate organic carbon to downslope aquatic ecosystems. Plant material and other organic matter are leached, flushed, displaced, or eroded from the wetland, providing the basis for microbial and detrital food webs. Raw Materials Wetlands are a source of plants and animals that serve as raw materials for various domestic, commercial, and industrial activities. Forested wetlands, for example, bottomland hardwoods and cypress swamps, are a source of lumber. Lower quality timber and woody shrubs are used for the production of other wood products, paper pulp, or firewood. Marsh vegetation is used for food (e.g., rice), fodder, thatch for roofs, and other commodities. Wetland wildlife, fish, and shellfish are consumed as food, and wildlife skins are used for clothing and related items. Because of the extractive nature of this function and value, the provision of raw materials is likely to have serious impacts on other wetland functions and values. Sustainable practices can minimize these impacts.

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Recreation Wetlands provide passive and active recreation including fishing, hunting, birdwatching, hiking, canoeing, photography, and others. The opportunity for recreation is related to access and landscape heterogeneity. Recreation can at times be incompatible with other functions. Soil Stabilization Vegetated wetlands have the potential for stabilizing underlying soils. Stems, trunks, and branches dissipate water energy through frictional resistance and reduce erosive forces. Roots bind soil. The dissipation of erosional forces and binding of soil affords protection to nonwetlands in coastal and in riverine areas.

EVALUATING FUNCTIONS AND VALUES The white and gray literature is replete with methods for evaluating wetland functions and values. Differences among the methods are reflected in the precision, accuracy, and reliability of conclusions. Critical factors to consider when selecting or interpreting evaluation methods are whether functions and values are measured directly or implied through indicators, whether evaluated data are qualitative or quantitative, whether the evaluation was conducted off-site or on-site, and whether assumptions and limitations are clearly stated. In general, a method should be selected based upon the type and level of information desired, available labor and economic resources, and the required time scale. Several representative evaluation methods are described below. In many circumstances, a combination of two or more of these methods, or development of an original method, may be most appropriate. Representative Evaluation Techniques Expert Opinion Expert opinion is perhaps the simplest, quickest, and least expensive technique for evaluating wetland function and value. The technique is most applicable when a functional assessment is required on short notice, when money is a limiting factor, and a precise or accurate evaluation is not essential. However, when a group of experts is convened and empirical information is available, expert opinion can represent actual function and value with fair accuracy. At its simplest, expert opinion consists of the professional judgment of an individual conversant with wetland ecological processes. Individual professional judgment should not be the entire basis for decision making when the decision can have serious consequences. More commonly, expert opinion consists of a convention of experts that come together with the goal of reaching consensus. The

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consensus opinion can be given more weight, and more reasonably be used in critical decision making. The two expert opinion techniques that have enjoyed widespread use are the Nominal Group Technique and the Delphi Technique (Delbecq et al., 1975). The two techniques are similar, except that the Nominal Group Technique requires faceto-face meeting(s) of participating experts, whereas the Delphi Technique is typically conducted through correspondence. The Nominal Group Technique is the quicker and more cost-effective technique if the convening experts are proximally located. Conversely, the Delphi Technique may be less costly and less time consuming for participants that interact poorly or are geographically disjunct. In general, the Delphi Technique will require more time to conduct and complete. The Delphi Technique is described to illustrate the Nominal Group and Delphi Techniques process. Delphi was the meeting site in Greece where Oracles met to discuss matters of the time and issue opinions. In modern times, the Delphi process consists of a discussion among knowledgeable individuals with the goal of reaching an agreeable conclusion (Pill, 1971). There are two assumptions fundamental to the process: 1. Expert opinion is sufficient input to decision making when absolute answers are unknown. 2. The collective decision of a group of experts will be more accurate than the professional judgment of an individual.

Involved in a Delphi process are three separate groups: the decision makers, a moderator, and experts (Turoff, 1970). Decision makers initiate the process by posing a question, and then seek an individual or group to moderate the process. The moderator identifies experts, designs the initial and follow-up questionnaires, and summarizes the expert responses. The experts respond to the question posed by the decision makers and transmitted by the moderator. Generally, the experts are polled, responses are tabulated, analyzed, and returned to the experts, and the experts respond again based upon the aggregate responses. The process is repeated until a consensus is reached. The identity of the experts may remain hidden to all parties except the moderator throughout the process. Delbecq et al. (1975) indicated that the quality of Delphi responses is strongly influenced by the interest and commitment of the experts. One area in which the Delphi Technique has been applied with some success is in the development, habitat suitability curves for fish (Crance, 1985, 1987a, 1987b). Habitat suitability curves describe the relationship between a habitat variable (e.g., water temperature or bottom substrate) and the probability that a fish will use a habitat with that particular characteristic. Crance (1987b) has offered guidelines for developing habitat suitability curves, based in part upon general recommendations by Delbecq et al. (1975). The guidelines are believed to be applicable to terrestrial species as well. The number of experts is governed by the number of respondents needed to constitute a representative pooling of judgments, and the information processing capabilities of the monitor. A total of 8 to 10 experts are likely an optimal number, ©2001 CRC Press LLC

although more or less may be sufficient. Crance (1987b) develops a list of 15 to 20 experts, and then prioritizes the list based upon best knowledge of the species’ habitat requirements, geographical coverage, and enthusiasm. The experts should represent a diversity of knowledge about the habitat use by the species, and overrepresentation by any single stakeholder group should be avoided. Experts are mailed an information packet that reiterates the purpose of the exercise and provides guidelines for responding. A response time of about 10 days is established. A second information packet is sent after 4 to 6 weeks which summarizes the results of the first round and includes the preliminary suitability index curves for each variable and life stage considered to be important, new questions, and instructions for the second round. Experts review the preliminary suitability index curves and indicate their agreement or disagreement. Disagreement with a preliminary curve requires sketching of a new curve and providing explanatory comments. Responses to the second round are summarized by the monitor and returned to the experts for further review and comment. The process continues until an acceptable level of agreement is reached. A final report is generated which includes feedback to the experts, and which summarizes exercise goals, process, and results. Crance (1985) has concluded that Delphi exercises are not a replacement for empirical curve development, but provide a more updated and interactive exchange of scientific information than can be achieved with a literature search. Also, Delphiderived curves tend to represent average values of habitat quality for a species and, therefore, will be useful only for predicting average suitability indices. Wetland Evaluation Technique The Wetland Evaluation Technique (WET, Adamus et al., 1987) was developed upon recognition that professional expertise may not always be available, and can be difficult to reproduce. WET’s objectives are to assess most recognized wetland functions and values, be applicable to a wide variety of wetland types, be rapid and reproducible, and have a sound technical basis in the scientific literature. There are 11 functions and values assessed by WET (Table 2). In addition, WET assesses the suitability of wetland habitat for 14 waterfowl species groups, 4 freshwater fish species groups, 120 species of wetland-dependent birds, 133 species of saltwater fish and invertebrates, and 90 species of freshwater fish. Adamus et al. (1987) suggest that WET can be used to compare different wetlands, estimate impacts from wetland modification, prioritize wetlands for acquisition or more detailed study, develop conditions for permits, and compare enhanced, restored, or created wetlands with reference wetlands. Geographically, WET is designed for use in the contiguous United States. Users should, at a minimum, have an undergraduate degree in biology, wildlife management, environmental science or a related discipline, or have several years of experience in one of these areas. Knowledge of the Fish and Wildlife Service classification system (Cowardin et al., 1979, see Chapter 1) and an ability to delineate wetlands are also recommended. WET evaluates functions and values in terms of social significance, effectiveness, and opportunity. Social significance assesses the value of a wetland to society due to its special designations, potential economic value, and strategic location. For ©2001 CRC Press LLC

Table 2

Functions and Values Assessed by the Wetland Evaluation Technique (WET, Adams et al., 1987)

Groundwater recharge Groundwater discharge Floodflow alteration Sediment stabilization Sediment/toxicant retention Nutrient removal/transformation Production export Wildlife diversity/abundance Aquatic diversity/abundance Recreation Uniqueness/heritage

example, a wetland would have a high social significance value for groundwater recharge if it were a sole source aquifer, Class II Groundwater, or had wells, and if it were used as a source of water by a nearby population. Effectiveness assesses the capability of a wetland to perform a function owing to its physical, chemical, or biological characteristics, and opportunity assesses the opportunity for a wetland to perform a function to its level of capability. For example, wetlands with a high effectiveness and opportunity for recharging groundwater would have permeable substrata, a negative discharge differential, and no outlet or a restricted outlet. Functions and values are characterized based upon physical, chemical, or biological processes and attributes. Characterization is accomplished by identifying threshold values for predictors—simple or integrated variables that directly or indirectly measure the physical, chemical, or biological processes and attributes of a wetland and its surroundings. Predictors are chosen for ease of measure or evaluation and vary in directness and accuracy. Threshold values for predictors are established by answering questions, and the responses to the questions are analyzed in a series of interpretation keys. The interpretation keys define the relationship between predictors and functions and values based upon information found in the technical literature. Functions and values are assigned a qualitative probability rating of high, moderate, or low. The ratings are not direct estimates of the magnitude of a wetland function or value, but are an estimate of the probability that a function or value will exist or occur. In practice, WET requires three steps: preparation, question response, and interpretation (Figure 1). Preparation includes obtaining resources, establishing the context, and defining the assessment and surrounding areas. Type and level of evaluation are also determined at this time. The Social Significance Evaluation has two levels: the first level has 31 questions and can be completed in 1 to 2 hr. The second level refines the probability rating for Uniqueness/Heritage function and value, and requires several hours to several weeks to complete depending upon the availability of information.

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Figure 1

Evaluation process for the Wetland Evaluation Technique (WET, Adamus et al., 1987).

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Effectiveness and opportunity are evaluated concurrently at three levels. Each level consists of a series of questions, and successive levels build upon previous levels to develop an increasingly detailed characterization. The level selected depends upon available time and information, and the desired confidence in the evaluation results. Level 1 can be conducted off-site in 1 to 2 hr. Level 2 requires a site visit and 1 to 3 hr. Level 3 requires a site visit and detailed physical, chemical, and biological monitoring data. The second level is recommended as an appropriate level in most circumstances. Interpretation is accomplished through a series of keys; each key consists of a series of boxes. Within each box are coded references to a question or group of questions, and each coded reference is followed by a specified answer of “yes” or “no.” A “true” or “false” arrow leads from each box to either another box or to a probability rating. The user proceeds through each key until a probability rating has been assigned to each function and value for each type of evaluation. There are social significance keys for 11 functions and values, effectiveness keys for 10 functions and values, and opportunity keys for 3 functions and values. The Habitat Suitability Evaluations are accomplished in the same manner using answers to questions in Effectiveness and Opportunity Evaluations 1, 2, and 3. Dougherty (1989) evaluated the applicability of WET to high elevation wetlands in Colorado. Two subalpine wetland complexes, Cross Creek and Willliams Fork, at similar elevations but of differing hydrologic regime, size, and geomorphology were studied in 1985 to evaluate WET’s ability to distinguish between similar wetlands and to compare WET’s evaluations to collected data. At both sites, data were available on groundwater level and surface water stage, groundwater and surface water quality, vegetation cover and standing crop, and stream gauging. The wetlands were assessed using WET Social Significance Levels 1 and 2, Effectiveness and Opportunity Levels 1, 2, and 3, and Habitat Suitability. The evaluation indicated differences in ratings between the two wetland complexes and differences between the WET probability ratings and empirical data. Of the 24 WET probability ratings, 13 were considered questionable, 4 were supported by empirical data, and 7 were rated moderate and thus considered neutral by Dougherty (1989). The 13 questionable ratings centered on three issues. First, WET is insensitive to the degree of overbank flooding which is a major hydrologic distinguishing characteristic of montane and subalpine wetlands in Colorado. Second, WET does not consider snowmelt which drives high elevation wetland hydrology. Third, WET’s heavy reliance on locality (“a relatively small political or hydrologic area”) as a predictor of social significance functions and values may have artificially applied different probability ratings for floodflow alteration and nutrient removal/transformation to the two wetland complexes. In the opinion of the author, WET was most accurate in instances where more detailed data were available (e.g., groundwater measurement) to support the Effectiveness and Opportunity Level 3 assessment. However, the application of WET to this situation is limited by questions that do not appear to be well suited for assessment of high elevation wetlands. In part, this may be attributed to the reliance of WET on the technical literature which is sparse for this region. In closing,

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Dougherty (1989) cautions that WET should be considered as a broad-brush tool for the organization of information and decision making, and not an end in itself. Rapid Assessment of Wetlands (RAW) Kent et al. (1990) developed a macroscale wetland function and value assessment technique to facilitate preliminary land-use planning efforts. The technique was designed to assess widely recognized wetland functions and values, provide expeditious field application, apply to a variety of wetland types, and to be reproducible. The function and value assessment incorporates functions and values, and critical criteria identified in WET (Adamus et al., 1987) and in the “Method for the Evaluation of Inland Wetlands in Connecticut” (Amman et al., 1986). There are 11 functions and values, identical to those of WET, assessed using available resources (e.g., U.S. Geological Survey maps, soil surveys, National Wetland Inventory maps, etc.) and one or more field visits. Each function and value is assessed relative to critical criteria (Table 3), which are used to determine whether or not a wetland potentially provides a function and value under consideration. A wetland is presumed effective for a function and value if the assigned criteria are satisfied. Conversely, a wetland is presumed ineffective for a function and value if the assigned criteria are not satisfied. The cumulative value of a wetland is determined by summing the number of positive responses, dividing this sum by the number of functions and values being assessed (less than or equal to 11), and multiplying the resultant quotient by 100. Wetland systems with percents ranging from 1 to 20 are assigned a poor value, 21 to 40 a below average value, 41 to 60 an average value, 61 to 80 a high value, and 81 to 100 a very high value. The State of Connecticut Department of Transportation, Bureau of Planning, conducted a macroscale delineation and function and value assessment of wetlands at Bradley International Airport in 1990. The purpose of the delineation and assessment was to develop a wetland resource map that would provide guidance to the Department in the development of the Bradley Master Plan, and to facilitate future planning by identifying areas requiring more detailed investigation at a later date. The area covered by the determination and assessment was approximately 405 ha (1000 acres). Identified were 18 separate wetland complexes, the majority of which were broad-leaved, deciduous forested wetlands. Wetlands at the airport were assessed using RAW in the spring of 1990. The majority of the wetlands were assessed as poor value. These wetlands were primarily small, isolated wetlands effective only for flood storage and groundwater recharge. Two larger, contiguous wetlands were assessed as high value, effective for all wetland functions and values except for aquatic diversity and abundance, recreation, and uniqueness and heritage. Intermediate size wetlands with a hydrological connection to other wetlands were assessed as below average and average value. RAW adequately satisfied the planning goals of the Connecticut Department of Transportation, Bureau of Planning. The assessment was conducted in a relatively short period of time and at low cost. Wetland experts with the Bureau of Planning reviewed the assessment and found its conclusions consistent with their opinions of site functions and values. Nevertheless, the authors caution that this technique is ©2001 CRC Press LLC

Table 3

Functions and Values and Assessment Criteria for the Rapid Assessment of Wetlands (RAW, Kent et al., 1990) Function and Value

Aquatic diversity and abundance

Flood flow alteration or flood storage

Groundwater discharge Groundwater recharge Nutrient removal and transformation Production export

Recreation Sediment stabilization Sediment and toxicant retention Uniqueness and heritage Wildlife diversity and abundance

Criteria Permanent open water; open water and vegetation interspersion, water quality suitable for aquatic organisms Regulated outflow, perceived outflow less than perceived inflow, greater than 200 acres and at least 70 percent vegetation coverage Pervious substrate, nonfringe wetlands with outlet only Pervious substrate, permanent inlet and no outlet, impermanent inundation Sediment retention, well-vegetated, low water flow velocity Permanent outlet, high primary productivity, potential erosive conditions, permanent or periodic high water flow velocity Public use permitted Potential sediment sources, reduced water inflow velocity, well-vegetated Potential sediment and toxicant source, absent or constricted outlet, well-vegetated Critical habitat for threatened and endangered species, historical or archaeological site Large and vegetatively diverse, moderate-sized oasis, floodplain

applicable only to planning efforts, and that there is no scientific basis for assigning a cumulative wetland value. Wetlands Integrated Monitoring Condition Index (WIMCI) The Wetlands Integrated Monitoring Condition Index (WIMCI) was intended to provide a framework for cost effective, scientifically responsive monitoring of enhanced, restored, and created wetland functions and values, particularly those associated with local, state, and federal permit activities (Kent et al., 1992). The authors recognized that the standard for measuring success was based largely on structural parameters related to vegetation, and that functional approaches for monitoring wetland ecosystems or addressing impacts were largely nonexistent (Kusler and Kentula, 1989). WIMCI was designed to directly assess the majority of wetland functions, to be flexible, simple to use, produce repeatable results, relatively inexpensive, and to be accomplished in a reasonable period of time. WIMCI assessed eight functions (Table 4). Values, such as uniqueness, heritage, recreation, and education, for which insufficient published literature suitable for objective assessment was lacking, were excluded. So, too, consumptive functions and values (e.g., agriculture, forestry) inconsistent with the intended use of the index were also excluded. The eight assessed functions and values are measured directly and expressed as a fraction of a reference wetland function and value. Individual ©2001 CRC Press LLC

functions and values can then be averaged to produce the WIMCI. Condition index values range from zero for a monitored wetland that does not provide any functions, to one for a monitored wetland that functions at a level comparable to the reference wetland. Instances in which the monitored wetland functions and values exceed that of the reference wetland are also assigned a value of one. Table 4

Wetlands Integrated Monitoring Condition Index (WIMCI) Functions, Values, and Measurements (Kent et al., 1992)

Function and Value

Measurement

Aquatic habitat Flood attenuation Groundwater recharge Nutrient metabolism Production export Sediment retention Toxicant retention

Animal species list Flood storage capacity Recharge volume Total nitrogen or total phosphorus Total suspended organics Total suspended solids Heavy metals, volatile organics, and petroleum hydrocarbon analysis Animal species list

Wildlife habitat

As the overall WIMCI averages individual functions and values, it is compensatory in nature. A high function and value can offset an absent or low individual function and value. The converse is also true. WIMCI does not allow one function and value to be an absolute limiting factor to overall wetland condition. The WIMCI approach is flexible in two ways. First, WIMCI can use more or less functions than described above. Second, WIMCI can be easily modified to assign weights to individual functions and values. The authors note that WIMCI has not been applied in its entirety but is based upon commonly used measurement and assessment techniques. Hydrogeomorphic Assessment (HGM) The HGM assessment was designed to accurately and rapidly measure the net change in wetland function resulting from degradation and restoration (Brinson, 1995, 1996). Changes in function are measured by comparing an impacted or degraded wetland with reference wetlands. The assessment differs from many other evaluation techniques by measuring only functions and not values and by requiring that functions be sustainable. A number of regional guidebooks presenting examples of how to assess wetlands are in press, in development and testing, or being planned (Brinson et al., 1997). HGM first classifies wetlands into functional categories based upon the position of the wetland in the landscape, dominant sources of water, and the flow and fluctuation of the water. A total of seven wetland classes have been recognized: riverine, depressional, slope, mineral soil flats, organic soil flats, estuarine fringe, and lacustrine fringe (see Chapter 1). The classification is intended to simplify the development and conduct of the assessment.

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For a given wetland class, a series of indicators and variables are developed to reflect the measurable properties of the wetland’s functions. Variables are either hydrologic, representing inflow processes, or structural, representing removal processes, and are derived from measurements and visual indicators of wetland function (Table 5). Level of functioning is estimated by combining variables in equations. Variables scale from zero, indicating no function, to one, indicating function equivalent to a reference standard. Focal wetland functions exceeding the reference standard are also assigned a value of one. Unlike other evaluation approaches, the user has the option of reducing the estimated value if the function is determined to be nonsustainable. Table 5

Hydrogeomorphic (HGM) Assessment Functions (Brinson et al., 1995)

Hydrologic Short-term surface water storage Long-term surface water storage Maintenance of high water table Biogeochemical Transformation, cycling of elements Retention, removal of imported substances Accumulation of peat Accumulation of inorganic sediments Habitat and food web support Maintenance of characteristic plant communities Maintenance of characteristic energy flow

Reference wetlands are the most critical component of the HGM assessment. Reference standards are established based upon observations and measurements of wetland sites of the same class. The reference wetlands are intended to be selfsustaining and representative of the highest levels of overall performance. Reference wetlands must be established, at a minimum, for regional subclasses in each physiographic province. Because professional judgment and local knowledge are required to select appropriate reference wetlands, assessment teams comprised of members with complementary scientific skills are recommended. The assessment concludes with a calculation of replacement ratios. To demonstrate its use, Brinson et al. (1995) developed a guidebook for applying the HGM approach for functional assessment to riverine wetlands. To develop the guidebook, wetland sites were studied in the glaciated northeast, Gulf coastal plain, Southwest, Rocky Mountains, Olympic Peninsula, and Puget Sound. The guidebook is to be used by teams of individuals who adapt the information to riverine wetlands of their physiographic region. The information in the guidebook must be modified, calibrated, and tested to determine its effectiveness under local and regional conditions. The guidebook identified 15 functions of riverine wetlands in 4 major categories: hydrologic, biogeochemical, plant habitat, and animal habitat (Table 6). A total of 44 variables were identified: 14 for hydrologic functions, 16 for biogeochemical

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functions, and 27 for habitat functions. From two to nine measurements are required to determine the value of an individual variable. Table 6

Riverine Wetland Functions (Brinson et al., 1995)

Hydrologic Dynamic surface water storage Long-term surface water storage Energy dissipation Subsurface storage of water Moderation of groundwater flow or discharge Biogeochemical Nurtient cycling Removal of imported elements and compounds Retention of particulates Organic carbon export Plant habitat Maintain characteristic plant communities Maintain characteristic detrital biomass Animal habitat Maintain spatial structure of habitat Maintain interspersion and connectivity Maintain distribution and abundance of invertebrates Maintain distribution and abundance of vertebrates

HGM limits include an inability to compare wetland functions between wetland classes. Also, the development of a reference wetland set can require tens of thousands of dollars and several months time, limiting the applicability of HGM to relatively large or controversial projects (Magee, 1996). Criticisms of the HGM assessment approach include poorly defined terminology (e.g., self-sustaining ecosystems, sustainable, ecological stability), and an inability to quantify levels of functions greater than that of reference wetlands (Hruby, 1997). Additional development may be necessary before HGM can be widely used (Opheim, 1996). Habitat Evaluation Procedures (HEP) HEP was developed in response to a need to document the nonmonetary value of fish and wildlife resources and is based upon the assumption that habitat quality and quantity can be numerically described (U.S. Fish and Wildlife Service, 1980a). The assessment procedure is a species-habitat approach to impact assessment. Habitat quality for selected evaluation species is documented with the Habitat Suitability Index (HSI) which is derived from an evaluation of the species’ key habitat components. HSI values are multiplied by area and aggregated to obtain a Habitat Unit (HU). HUs provide the basis for comparison of the relative value of different wetlands at the same point in time, or the relative value of the same wetland at two different points in time. The time and costs associated with a HEP analysis are highly variable, and depend upon size of the study area, number of cover types, number of evaluation species, and the number and types of proposed actions. ©2001 CRC Press LLC

The steps required to conduct a HEP analysis are depicted in Figure 2 (U.S. Fish and Wildlife Service, 1980b). Study limits are defined initially. This includes defining the study area, delineating cover types, and selecting evaluation wildlife species. The study area should include areas where direct or indirect biological changes are expected to occur. The level of delineation of cover types depends upon mapping constraints and the level of detail required for the analysis. A cover type classification applicable to the region is recommended. Evaluation wildlife species can be a single species, a group of species, a species life stage, or a species life requisite. There are two approaches to the selection of species: selection of species with high public interest or economic value and selection of species providing a broad ecological perspective of the assessment area. Examples of the latter include species sensitive to land-use changes, keystone species, and species that represent guilds. HUs are determined next. HUs are the product of the total area of available habitat and the HSI. The total area of available habitat includes all areas that can be expected to provide some support to the evaluation species. The recommended method of describing HSI values is through the use of models which may be in word or mathematical form. Calculating an HSI requires establishing HSI model requirements, acquiring an HSI model, and determining HSI for available habitat. Index values are an estimate of habitat conditions in the subject area relative to a standard of comparison, typically optimal habitat conditions. Values range from 0.0 (no habitat) to 1.0 (optimal habitat). Ideally, HSI models produce an index with a proven, quantified, positive relationship to carrying capacity. Model development is described in Habitat Evaluation Procedures (U.S. Fish and Wildlife Service, 1980b). Figure 3 is an example of an HSI. Schroeder (1982) developed a HSI model for the yellow warbler (Dendroica petechia) to facilitate consideration in HEP evaluations. The model is applicable to the breeding range, season, and habitat of the species. Breeding habitat was determined to be deciduous shrubland and deciduous scrub–shrub wetland (U.S. Fish and Wildlife Service, 1981). There are three variables that describe the suitability of breeding habitat for the yellow warbler: percent deciduous shrub crown cover (variable 1), average height of deciduous shrub canopy (variable 2), and percent of deciduous shrub canopy comprised of hydrophytic shrubs (variable 3). Optimal habitat is considered to exist at shrub densities of 60 to 80 percent, shrub heights of 2 m, and 100 percent hydrophytic vegetation. Other levels of suitability are described by the equation (variable 1 × variable 2 × variable 3)1/3. Baseline HUs describe the existing ecological conditions which facilitate landuse planning and alternatives analysis. Baseline HUs can be compared among areas or to predictions of future HUs for a single area following some change in land use. The latter application constitutes an impact assessment. Application of HEP to impact assessments requires predictions of changes in physical, vegetative, and chemical variables. The same HSI models must be used to determine habitat value at all points in time. HEP allows the incorporation of value judgments through the use of a Relative Value Index (RVI). RVIs are applied as weighting values to the HUs calculated for each evaluation species. Calculation of RVIs requires defining the perceived significance of RVI criteria, rating each evaluation species against each criterion, and

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Figure 2

Habitat Evaluation Procedures (HEP) evaluation process (U.S. Fish and Wildlife Service, 1980b).

transforming the perceived significance of each criterion and each evaluation species’ rating into a RVI. HUs are no longer directly related to carrying capacity after adjustment by RVIs. Unavoidable HU losses can be offset by the development of compensation plans that apply specified management measures to existing habitat to effect a net increase in HUs. Compensation may be in kind, in which the goal is to offset the HU loss for each evaluation species. Alternatively, the compensation plan may have a goal of equal replacement, in which HU losses may be compensated by a gain of an equal number of total HUs, regardless of individual evaluation species’ HUs. ©2001 CRC Press LLC

Figure 3

Suitability index graphs for the yellow warbler (Schroeder, 1982).

Virtual Reference Wetlands (VRW) VRW (Kent et al., 1999) offer an alternative or supplemental approach to assessing wildlife. An idealized standard, the VRW, is established by compiling a list of ©2001 CRC Press LLC

all wildlife species occurring in regional wetlands. Compilation can be accomplished using field guides, agency lists, scientific publications, the gray literature, or expert opinion. The VRW can represent wildlife of all wetland types or can be partitioned by wetland type. Also, the VRW can represent wildlife of all seasons or any one season. Wildlife of the focal wetland, determined by direct observation, is compared to the VRW. The approach is applicable to assessing the success of enhancement, restoration, and creation efforts, or establishing the relative value of a population of wetlands as part of an alternative analysis. The VRW approach is repeatable and, because it is based upon direct observation, allows for evaluation of actual rather than potential function and value. The use of an idealized standard eliminates the need to identify an appropriate reference wetland and facilitates comparison and extrapolation to other wetlands. VRW also provide for calculation of various metrics including relative richness, similarity, and the proportion of upland–wetland species and habitat generalists–specialists. The metrics can be applied at several temporal and spatial scales. The most serious limitation of the VRW approach is the inability to compare wildlife abundance. Kent et al. (1999) applied the VRW approach to evaluation of wildlife in a created wetland. The created wetland wildlife community was found to be relatively rich, due in part to the occurrence of upland birds. The wildlife community most closely resembled that of freshwater marshes of the region consistent with the wetland’s physical characteristics. Habitat specialists were just as likely to occur in the wetland as habitat generalists.

ECONOMIC VALUATION There has been recognition in recent years that wetlands provide ecosystem services, and that these ecosystem services can be economically valued (e.g., Thibodeau and Ostro, 1981; Danielson and Leitch, 1986; Costanza et al., 1997). The total economic value of a wetland consists of its use value and its nonuse value (see Table 7 and Pearce and Moran, 1994). Use value represents the value arising from the actual use of the wetland and is further divided into direct use, indirect use, and option values. Direct use values include recreation, fishing, and forest products. Indirect use values derive from ecosystem functions such as water quality renovation. Option values represent an individual’s willingness to pay for the option to use a value at a later date. Table 7

Categories of Wetland Economic Values (Pearce and Moran, 1994)

Total Economic Value Use values Nonuse values Direct use Indirect use Option values

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Bequest values Existence values

Nonuse values, by contrast, accrue independent of on-site or off-site use of the wetland. Somewhat more difficult to estimate, nonuse values are divided between bequest values and existence values. Bequest values accrue to an individual from the knowledge that others might benefit from the wetland in the future. Existence values derive simply from the knowledge that the wetland exists, even if the individual never sees the wetland. Nonuse value may be quite large relative to use value (Brown, 1993) and has become increasingly accepted. For example, nonuse values have been recognized by the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA, 26 U.S.C. 4611 et seq.) and the 1990 Oil Pollution Act (35 U.S.C. 2701 et seq.). In practice, total economic value is almost impossible to calculate. Unlike financial analyses, which consider whether a project will be profitable for investors, economic analyses must consider the value of a project to society as a whole. All economic analyses rely on the accuracy of costs and an accurate prediction of the future. In practice, many environmental costs are difficult, if not impossible, to estimate. Existing valuation techniques can reasonably distinguish use values from nonuse values but cannot reliably distinguish between option, bequest, and existence values (Pearce and Moran, 1994). Economic valuation is also unlikely to accurately account for underlying, holistic, ecosystem functions, and for intrinsic value (Pearce and Moran, 1994; Pimm, 1997). Economic Valuation Methodologies Direct and indirect approaches are used to estimate the economic value of environmental goods including wetlands (Pearce and Moran, 1994). Direct approaches establish values directly from individuals through surveys or experiments and can be used to determine both use and nonuse values. Indirect approaches establish values from actual, observed market-based information. Nonuse values cannot be determined from indirect approaches. All of the valuation techniques have advantages and limitations that should be understood prior to use. In general, users should select and use techniques that are institutionally acceptable, that consider the needs of the end user(s), and that balance costs against the level of information required (Pearce and Moran, 1994). Direct Economic Valuation Experiments offer the most reliable method for establishing the economic value of a wetland. For example, to determine the recreation value of a wetland, the wetland could be enclosed and an entrance fee charged. In practice, it is difficult to design and establish experiments to determine the economic value of a wetland. Individuals may be asked to rank their preferences as in the Contingent Ranking Method. More commonly the Contingent Valuation Method (CVM) is used and individuals are asked to state what they are willing to pay for some change in the provision, or what they are willing to accept to forgo a change in the provision, of a wetland function or value.

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The CVM has three parts. First, a hypothetical description of the terms under which the function or value is to be offered is presented to the respondent. Second, the respondent is asked questions to determine how much they value the function or value. Respondents may be asked whether or not they want to pay for a function or value if it costs a specified amount or how much they would be willing to pay for the function or value. And third, relating responses to socioeconomic and demographic characteristics tests response validity. CVM willingness to pay responses are analyzed for the frequency distribution of the responses to the valuation questions and relationships between willingness to pay and socioeconomic variables. The CVM is not without its shortcomings (Batie and Shabman, 1982; Diamond and Hausman, 1994; Pearce and Moran, 1994). The quality and presentation of information described to the respondent can have a significant effect on results. The method inherently establishes a hypothetical market which may or may not reflect the behavior of respondents if they had to make actual payments. Also, respondents may not be familiar with the commodity being valued, and responses are sensitive to the described method of payment. Arrow et al. (1993) offer guidelines which improve the reliability of the Contingent Valuation Method. Stevens et al. (1995) used the CVM to estimate the total value of preserving different types of wetlands in New England. A survey was mailed to 2,510 randomly selected New England residents. Each group was asked for their opinions about the importance of wetlands and about rules and regulations governing wetland preservation in New England. Respondents were also asked to rank four types of wetlands: 1. 2. 3. 4.

Wetlands Wetlands Wetlands Wetlands

that provide recreation containing rare species of plants that provide food that provide flood protection, water supply, and water pollution control

Surveyed individuals were asked one of five versions of a contingent valuation question about the amount of sales tax they were willing to pay to prevent wetland loss. The first version asked respondents if they would accept a sales tax of $N each year for the next 5 years for their highest priority wetland type. The second version asked for the respondents’ willingness to pay for all four types of wetland. Version three asked about the willingness to pay to preserve wetlands containing rare species of plants. Version four was the same as version two except less information was provided, and version five asked about willingness to pay for wetland restoration rather than preservation. The survey response rate was 34 percent and 90 percent of respondents said that wetland preservation was very important to them. Of the respondents, 48 percent gave top priority to wetlands that provide flood protection, water supply, and water pollution control; 38 percent gave top priority to wetlands containing rare species of plants; only 9 and 4 percent gave top priority to wetlands providing recreational opportunities and food, respectively. Of the respondents, 64 percent were willing to pay to preserve wetlands. The average respondent was willing to pay between US$73.89 and US$80.41 per year for wetlands that provide flood protection, water

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supply, and water pollution; between US$80.77 and US$96.07 for wetlands containing rare species of plants, and approximately US$114 to preserve all wetland types. The aggregate value of New England wetlands was estimated to be between US$242 and US$261 million per year for wetlands providing flood protection, water supply, and water pollution control, and between US$264 and US$313 million per year for wetlands containing rare species of plants. There was no significant difference in willingness to pay for wetland preservation compared to restoration. The majority of respondents who would not pay were opposed to the special sales tax. The authors concluded that a substantial economic value is associated with wetland preservation and restoration by New England residents. Nevertheless, the response rate, combined with the tendency for respondents to be better educated than the average resident, may have influenced the willingness to pay amount. Indirect Economic Valuation Indirect valuations elicit values from observed market-based information, that is, an individual purchases a good to which the wetland function or value can be related (Pearce and Moran, 1994). Obtained values will be sufficient for cost–benefit purposes. Indirect valuations can be divided into two categories: surrogate market and conventional market. Surrogate market techniques consider markets for private goods and services that are related to environmental goods and services. Individuals reveal the value they place on the environmental goods and services by the value they place on the private goods and services. Surrogate market approaches include household production functions and the hedonic pricing method. Household production functions use expenditures for goods or services that are substitutes for the environmental goods or services. The travel cost approach is perhaps the most commonly applied household production function and uses expenditures for travel to recreation sites. Money and time spent by individuals to get to a site are used to estimate willingness to pay for a site’s functions and values. Data requirements for the travel cost approach are extensive and include the number of visitors to a site, the visitor’s place of origin, socioeconomic characteristics, journey duration, direct travel expenses, and purpose of the visit (Pearce and Moran, 1994). Nevertheless, the travel cost approach can value the demand for recreation function and value. Another surrogate market technique, the hedonic pricing method, estimates an implicit price for an environmental good or service, that is, a use value, by looking at real markets in which those goods or services are traded (Pearce and Moran, 1994). For example, house or land values are used to establish a relationship between property prices and proximal environmental attributes. As with the travel cost approach, data requirements are substantial and may be difficult to obtain. Conventional market techniques use market prices, or shadow market prices, to establish the value of an environmental good or service. Recognized are two approaches: dose–response and replacement cost (Pearce and Moran, 1994). The dose–response technique establishes a dose–response function by relating damage to the environment (the response) to the cause of the damage (the dose). A monetary ©2001 CRC Press LLC

damage function is established by multiplying the dose–response function by the price or value per unit of damage. The approach is applicable to environmental changes that have impacts on marketable goods; for example, pollution impacts on fisheries, forestry, and agriculture. Cost of application ranges from inexpensive to expensive depending upon the availability of dose–response functions. The approach is not suited to valuing nonuse benefits. As the name implies, the replacement cost approach estimates the cost of replacing or restoring a damaged environment to its original condition. Replacement costs can be determined by observing actual spending on replacement efforts, or estimation of the cost of replacement. Incomplete assessment of actual damage, and the practical inability to replace all functions and values, can lead to underestimation. Conversely, use of replacement cost to assign value may underestimate ancillary benefits of the replacement. The Value of the World’s Ecosystem Services and Natural Capital Costanza et al. (1997) estimated the value of the world’s ecological services and natural capital stocks to make the range of potential values more apparent, to establish a first approximation of the relative magnitude of global ecosystem services, to establish a framework for further analysis, and to point out those areas in need of more research. Ecological services are defined as the “flows of materials, energy, and information from capital stocks that combine with manufactured and human capital services to produce human welfare.” Capital stocks are “a stock of materials or information that exists at a point in time.” Trees, minerals, ecosystems, and the atmosphere are examples of the latter. Ecosystem services were grouped into 17 major categories and applied to 16 biomes. Only renewable services were considered. The unit value of ecosystem services was estimated by synthesizing previous studies which used a variety of methods including direct observation, contingent valuation, and replacement cost. The areal extent of the 16 ecosystems was determined and multiplied by the unit value of the ecosystem services to estimate the total value of the world’s ecosystem services and natural capital. This value is estimated to be in the range of US$16–54 trillion per year, with an average of US$33 trillion per year. Wetlands were estimated to have a value of US$29,571 per hectare per year and a total value of US$4.9 trillion per year. This is approximately 15 percent of total global ecosystem services. For purposes of the study, the wetland biome consisted of freshwater wetlands (swamps, bogs, riparian wetlands, and floodplains) and coastal wetlands (tidal marshes and mangroves). Assigned to freshwater wetlands were 10 ecosystem services which had a total value of US$19,580 per hectare per year and a total global value of US$3.2 trillion per year (Table 8). Water supply and disturbance regulation (i.e., storm protection) were the most significant ecosystem services of freshwater wetlands. Assigned to coastal wetlands were 6 ecosystem services which had a total value of US$9990 per hectare per year and a total global value of US$1.6 trillion per year. Waste treatment was the most significant ecosystem service provided by coastal wetlands, accounting for 67 percent of the total value.

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Table 8

Average Global Value of Annual Wetland Services (Costanza et al., 1997)

Services Gas regulation Disturbance regulation Water regulation Water supply Waste treatment Habitat/refuge Food production Raw materials Recreation Cultural Total

1994 US$ per Hectare per Year Freshwater Coastal Total 265 7,240 30 7,600 1,659 439 47 49 491 1,761 19,581

1,839

6,696 169 466 162 658 9,990

265 9,079 30 7,600 8,355 608 513 211 1,149 1,761 29,571

Costanza et al. (1997) consider their estimate of the value of ecosystem services to be a minimum estimate because of a number of uncertainties, including the exclusion of the infrastructure value of ecosystems. Pimm (1997) agrees that the estimate is clearly an underestimate, in part because ecosystems are exceedingly complex and poorly understood and, therefore, cannot reasonably be replicated. Pimm (1997) also questions the moral right to place monetary values on sustaining the environment for future generations. Both Costanza et al. (1997) and Pimm (1997) recognize that the value of ecosystem services will increase exponentially as they become scarcer. Constanza et al. (1997) conclude that their (and subsequent) valuation of ecosystem services will help modify systems of national accounting and provide a basis for project appraisal.

REFERENCES Adamus, P. R., Clairain, E. J., Smith, R. D., and Young, R. E., Wetland Evaluation Technique (WET), Vol. II, Methodology, Operational Draft Department of the Army Waterways Experiment Station, Vicksburg, MS, 1987. Amman, A. P., Franzen, R. W., and Johnson, J. L., Method for the Evaluation of Inland Wetlands in Connecticut, Connecticut Department of Environmental Protection, Bulletin No. 9, 1986. Arrow, K., Solow, R., Portney, P. R., Leamer, E. E., Radner, R., and Schuman, R., Report of the NOAA panel on contingent valuations, Fed. Regist., 58(10), 4602, 1993. Batie, S. and Shabman, L., Estimating the economic value of wetlands: principles, methods, and limitations, Coastal Zone Manage. J, 10, 255, 1982. Brinson, M., The HGM approach explained, Nat. Wetl. Newsl., November/December, 7, 1995. Brinson, M., Assessing wetland functions using HGM, Nat. Wetl. Newsl., January/February, 10, 1996. Brinson, M. M., Hauer, F. R., Lee, L. C., Nutter, W. L., Rheinhardt, R. D., Smith, R. D., and Whigham, D., A Guidebook for Application of Hydrogeomorphic Assessments to Riverine Wetlands, Final Report to the U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS, 1995.

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Brinson, M., Lee, L., Ainslie, W., Rheinhardt, R. D., Hollands, G. G., Smith, R. D., Whigham, D. F., and Nutter, W. B., Common misconceptions of the hydrogeomorphic approach to functional assessment of wetland ecosystems: scientific and technical issues, Wetl. Bull., 14(2), 16, 1997. Brown, T., Measuring nonuse value: a comparison of recent contingent valuation studies, W-133 Benefits and Cost Transfer in Resource Planning, 6th Interim report, Department of Agricultural and Applied Economics, University of Georgia, Athens, 1993. Carter, V. and Novitzki, R. P., Some comments on the relation between ground water and wetlands, in The Ecology and Management of Wetlands, Vol. 1, Ecology of Wetlands, Hook, D. D., McKee, W. H., Jr., Smith, H. K., Gregory, J., Burrell, V. G., Jr., DeVoe, M. R., Sojka, R. E., Gilbert, S., Banks, R., Stolzy, L. H., Brooks, C., Matthews, T. D., and Shear, T. H., Eds., Timber Press, Portland, OR, 1988. Costanza, R., D’Arge, R., de Groots, R., Farber, S., Grasso, M., Hannon, B., Limburg, K., Naeem, S., O’Neill, R. V., Paruelo, J., Raskin, R. G., Sutton, P., and van den Belt, M., The value of the world’s ecosystem services and natural capital. Nature, 387, 253, 1997. Cowardin, L. M., Carter, V., Golet, F. C., and LaRoe, E. T., Classification of Wetlands and Deepwater Habitats of the United States, U.S. Fish and Wildlife Service Publication FWS/OBS-79/31, Washington, D.C., 1979. Crance, J. H., Delphi Technique Procedures Used to Develop Habitat Suitability Index Models and Instream Flow Suitability Curves for Inland Stocks of Striped Bass, U.S. Fish and Wildlife Service WELUT-85/WO7, 1985. Crance, J. H., Habitat suitability curves for paddlefish developed by the Delphi technique, N. Am. J. Fish. Manage., 7, 123, 1987a. Crance, J. H., Results on the use of the Delphi technique for developing category I habitat suitability criteria for redbreast sunfish, in Proceedings of Species Criteria Workshop, Fort Collins, CO, December 10–12, 1986, 1987b. Danielson, L. E. and Leitch, J. A., Private versus public economics of prairie wetland allocation, J. Environ. Econ. Manage., 13(1), 1986. Delbecq, A. L., Van de Ven, A. H., and Gustafson, D. H., Group Techniques for Program Planning—A Guide to Nominal Group and Delphi Processes, Scott Foresman, Glenview, IL, 1975. Diamond, P. and Hausman, J., Contingent valuation: is some number better than no number? J. Econ. Perspect., 8(4), 45, 1994. Drake, K. and Vicario, M., Wetlands education, in Applied Wetlands Science and Technology, Kent, D. M., Ed., Lewis Publishers, Boca Raton, FL, 1994, 363. Dougherty, S. T., Evaluation of the applicability of the Wetland Evaluation Technique (WET) to high elevation wetlands in Colorado, in Wetlands: Concerns and Successes, American Water Resources Association, 1989, 415–427. Forman, R. T. T. and Godron, M., Landscape Ecology, John Wiley & Sons, New York, 1986. Hruby, T., Continuing the discussion: scientific and technical issues regarding the hydrogeomorphic approach to function assessment of wetlands, Wetl. Bull., 14(3), 23, 1997. Kent, D. M., Designing wetlands for wildlife, in Applied Wetlands Science and Technology, Kent, D. M., Ed., Lewis Publishers, Boca Raton, FL, 1994, 283. Kent, D. M., Reimold, R. J., And Kelly, J. M., Macroscale Wetlands Delineation and Assessment, Technical report to the Connecticut Department of Transportation, Bureau of Planning, Metcalf and Eddy, Inc., 1990. Kent, D. M., Reimold, R. J., Kelly, J. M., and Tammi, C. E., Coupling wetland structure and function: developing a condition index for wetlands monitoring, in Ecological Indicators, McKenzie, D. H., Hyatt, D. E., and McDonald, V. J., Eds., Elsevier Applied Science, London, 1992. ©2001 CRC Press LLC

Kent, D. M., Schwegler, B. R., and Langston, M. A., Virtual reference wetlands for assessing wildlife, Fla. Sci., 62, 222, 1999. Kusler, J. A. and Kentula, M. E., Eds., Wetland Creation and Restoration: The Status of the Science, U.S. Environmental Protection Agency, Report No. 600/3–89/038a, 1989. Larson, J., Wetland value assessment—state of the art, in Wetlands: Ecology and Management, Gopal, B., Turner, R. E., Wetzel, R. G., and Whigham, D. F., Eds., National Institute of Ecology and International Scientific Publications, Jaipur, India, 1982. Magee, D. W., The hydrogeomorphic approach: a different perspective, Wetl. Bull., June, 12, 1996. Mitsch, W. J. and Gosselink, J. G., Wetlands, 2nd ed., Van Nostrand Reinhold, New York, 1993. Ogawa, H. and Male, J. W., The Flood Mitigation Potential of Inland Wetlands, Water Resources Research Center Publication No. 138, University of Massachusetts, Amherst, 1983. Ogawa, H. and Male, J. W., Simulating the flood mitigation role of wetlands, J. Water Res. Plan. Manage., 112, 114, 1986. Opheim, T., HGM: the beast is unleashed, Nat. Wetl. Newsl., May/June, 2, 1996. Pearce, D. and Moran, D., The Economic Value of Biodiversity, Earthscan Publications Ltd., London, 1994. Pill, J., The Delphi method: substance, context, a critique and an annotated bibliography, Socio-Econ. Plan. Sci., 5, 57, 1971. Pimm, S. L., The value of everything, Nature, 387, 231, 1997. Reimold, R. J., Wetlands functions and values, in Applied Wetlands Science and Technology, Kent, D. M., Ed., Lewis Publishers, Boca Raton, FL, 1994. Schroeder, R. L., Habitat Suitability Index Models: Yellow Warbler, U.S. Department of the Interior, Fish and Wildlife Service FWS/OBS-82/10.27, 1982. Stevens, T. H., Benin, S., and Larson, J. S., Public attitudes and economic values for wetland preservation in New England, Wetlands, 15(3), 226, 1995. Thibodeau, F. and Ostro, B., An economic analysis of wetland protection, J. Environ. Manage., 12(1), 19, 1981. Turoff, M., The design of a policy Delphi, Technol. Forecast. Soc. Change, 2, 149, 1970. U.S. Fish and Wildlife Service, Habitat as a Basis for Environmental Assessment, Division of Ecological Services, Department of the Interior, Washington, D.C., 1980a. U.S. Fish and Wildlife Service, Habitat Evaluation Procedures (HEP), Division of Ecological Services, Department of the Interior, Washington, D.C., 1980b. U.S. Fish and Wildlife Service, Standards for the Development of Habitat Suitability Index Models, 103 ESM, U.S. Department of the Interior Fish Wildlife Service, Division Ecological Services, 1981.

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Kent, David J. et al “Ecological Risk Assessment of Wetlands” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

CHAPTER

4

Ecological Risk Assessment of Wetlands David J. Kent, Kenneth D. Jenkins, and James F. Hobson

CONTENTS The Human Health Risk Assessment Paradigm Ecological Risk Assessment The Ecological Risk Assessment Framework Problem Formulation Phase Choosing Biological Endpoints Spatial and Temporal Considerations Other Considerations Analysis Phase Exposure Characterization Ecological Effects Characterization Risk Characterization Phase Predictive Ecological Assessments Problem Formulation Exposure Characterization Ecological Effects Characterization Risk Characterization The Quotient Method for Risk Characterization Retrospective Ecological Assessments Problem Formulation Exposure Characterization Ecological Effects Characterization Risk Characterization Summary References

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Until recently, the term risk assessment generally was applied to the estimate of risk to human health, typically from chemical exposure. For example, a cancer risk assessment is an estimate of the risk to humans from carcinogenic compounds. Recently, however, the term risk assessment has been applied to ecological systems. An ecological risk assessment is an estimate of the adverse effect to an ecosystem from chemical, physical, or biological stressors resulting from anthropogenic activity. This recent interest in assessing ecological health is evidenced by several publications (Bartell et al., 1992; Cairns et al., 1992; Suter, 1993; Newman and Strojan, 1998; Lewis et al., 1999) including two documents produced by the U.S. Environmental Protection Agency (USEPA, 1992, 1998). The first of these USEPA documents, Framework for Ecological Risk Assessment (1992), was intended as the first step in a long-term program to develop guidelines for the performance of ecological risk assessments. The second document, Guidelines for the Ecological Risk Assessment, provided more detailed information and is the current guidance on the subject. The principles of ecological risk assessment can be applied to any ecosystem, although they may be particularly relevant to wetlands. The extent and rate of wetland loss, as well as the biologic, economic, and social importance of wetlands, are well documented (Mitsch and Gosselink, 1986). Moreover, the transitional nature of wetlands may make them especially sensitive to stress. Despite the uniform application of assessment principles to ecological systems, individual wetlands are sufficiently different in their spatial, temporal, and physiochemical characters to warrant site-specific sampling and analysis (Figures 1 and 2). These differences will influence the design and interpretation of the ecological risk assessment.

Figure 1

Risk assessment can be broadly applied to a variety of ecosystems. Nevertheless, individual wetlands are sufficiently different in their spatial, temporal, and physicochemical characters to warrant site-specific samping and analysis. A New England saltmarsh is shown here.

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Figure 2

An Arkansas riverine system wetland.

To understand the use of ecological risk assessment for wetland ecosystems, an introduction to the principles of risk assessment is necessary. The current basis for risk assessment is derived from the National Research Council Risk Assessment paradigm (1983). Following this, an in-depth discussion of the USEPA Ecological Risk Assessment Framework (USEPA, 1992) is presented as is a discussion of the challenges and strategies associated with carrying out assessments. Finally, examples of specific applications to wetland ecosystems are provided.

THE HUMAN HEALTH RISK ASSESSMENT PARADIGM The risk assessment paradigm has been used for some time to evaluate the chronic impacts of environmental pollutants on human health. This strategy was initially conceptualized by the National Research Council Risk Assessment Panel (NRC, 1983) and formalized by the USEPA in its 1986 Guidelines (USEPA, 1986a–e). This risk assessment paradigm consists of several components:

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• Hazard identification: does a chemical contaminant represent a specific threat to human health? Establishment of cause–effect relationships is central to this component. • Defining dose–response: what is the relationship between the magnitude of the exposure and the probability of an adverse health effect? • Exposure assessment: what is the potential for human exposure to the chemical of concern? • Risk characterization: what is the potential magnitude of risk to human health given the predicted exposure and dose–response data? What is the uncertainty associated with this risk estimate?

Standard methodologies are employed to evaluate potential threats to human health. The methodologies usually involve determining all relevant effects and then summing those effects to get a total effect value.

ECOLOGICAL RISK ASSESSMENT Ecological risk assessments (ERA) examine the probability that undesirable ecological effects are occurring or may occur as a result of exposure to a stressor or a combination of stressors. The term stressors is used here to reflect the broad range of anthropogenic factors that can result in ecological perturbations. Stressors may include any chemical, physical, or biological factor resulting from anthropogenic activities that can cause an ecological disturbance. Most often, however, the term stressor refers to toxic chemicals. ERAs can be used to address a wide range of issues and are generally classified as predictive or retrospective. Predictive ERAs are designed to assess the risks associated with proposed actions, such as the introduction of new chemicals into the environment and the establishment of new sources of stressors or hypothetical accidents (USEPA, 1991). Predictive risk assessments have usually followed the NRC human health paradigm relatively closely while emphasizing the choice of biological endpoints and related stressor–response data. In contrast, retrospective ERAs address the risks associated with stressors released due to current or previous anthropogenic activities. Examples of retrospective assessments include evaluating the ecological impact of hazardous waste sites and previous releases or spills. The goal of this type of risk assessment is to establish and define the relationship between the pollution source, the distribution of stressors, the exposure of biological endpoints, and the level of effects of this exposure on the ecosystem. Retrospective assessments often take advantage of field data to define contaminant sources and measure adverse biological effect. Various levels of data collection or site-specific assessment may be necessary to provide the information required to design and conduct the retrospective ecological risk assessment, and to achieve a given level of confidence. The challenge here is to establish cause–effect relationships between the source of stressors and any observed ecological effects. Some ERAs, such as those used for wetlands, may involve both predictive and retrospective aspects. For example, in an assessment of a hazardous waste site, the ©2001 CRC Press LLC

current status of the site may require a retrospective evaluation, but the long-term impact of various repetition scenarios would be addressed in a predictive fashion. As the type of risk assessment to be conducted is dependent upon the ultimate application of the results, a clear understanding of the objectives of the risk assessment is essential. The move to ERAs by the regulatory community is driven by a number of factors. From a legal standpoint, many of the underlying statutes require some form of evaluation of ecological risk. For example, the Superfund Amendment and Reauthorization Act (1987) specifies that the actual and potential risk to public health and the environment must be assessed for each hazardous waste site. The use of a basic risk assessment paradigm would provide a structural framework for ecological assessment and a consistent strategy for managing various types of risk. This issue is particularly important when comparing the sensitivity of ecological endpoints relative to the human endpoint. In some cases, nonhuman endpoints may prove to be more sensitive than human endpoints, and would, thus, drive the overall risk assessment. This type of comparison is facilitated by consistency in the strategies used to carry out risk assessments for both types of endpoints. Although human health risk assessment strategies provide a useful model, assessing ecological risk has proven to be more complex. A number of factors contribute to this complexity. • Multiple biological endpoints: these could include multiple species, and various levels of biological organization (e.g., subcellular, individual, population, community, and ecosystem). • More complex exposure pathways: these are determined by the biological endpoints of concern. • Indirect effects: indirect effects such as habitat impairment or disruption of intertrophic relationships may be more important than direct exposure to chemicals. • Evaluating impacts on ecosystems: ecosystems are complex, their function is often not tightly coupled to stressor inputs, and they show resilience and recovery to varying degrees of stress.

In spite of these complexities, there are some distinct advantages to estimating risk to ecological endpoints. Exposures and hazards can often be estimated directly on the species of concern or a closely related surrogate species. This may result in a more accurate estimate of risk, because there is no need for extrapolation from more distantly related species as is almost always the case in human risk assessment. This is particularly useful when multiple stressors or complex exposure matrices are involved. In ERAs, the biological endpoints of interest can often be tested directly against the specific stressor or mixture of stressors of concern, thus eliminating the need to estimate such factors as stressor interactions, chemical form (speciation), and bioavailability. Despite the aforementioned advantages, the added complexity associated with ERAs results in a higher degree of uncertainty than is normally associated with human health-based risk assessments. This complexity requires more effort in the initial planning stages so that the final assessment is well focused. Furthermore, ©2001 CRC Press LLC

some modifications of the basic NRC risk assessment paradigm are required. The Risk Assessment Forum within the USEPA has developed the framework (and now guidelines) for ecological risk assessment which addresses these issues, yet is conceptually consistent with human health risk assessment strategies. It is important to note that slight differences in terminology exist between the various ERA structures currently promoted. However, the elements are fairly analogous. For the sake of simplicity, the discussions in this chapter will utilize the USEPA framework terminology, although the concepts may be drawn from multiple sources. The Ecological Risk Assessment Framework Two major elements that form the basis of the ERA framework are the characterization of exposure and the characterization of ecological effects. Aspects of the two elements are considered in all phases of the framework process. While carrying this common thread throughout the paradigm, the framework is divided into three phases. The phases are problem evaluation, analysis, and risk characterization (Figure 3). Problem Formulation Phase The first step in this process requires defining the specific purpose of the ERA. Although this may seem trivial, many ERAs suffer from lack of clear focus and, as a result, may be ambiguous and misleading. Once the specific purpose of the assessment is defined, the specific goals that must be met to achieve this purpose are formulated. These goals provide a basis for establishing a precise conceptual study design. In undertaking the study design, a number of questions must first be addressed. • • • • •

Is the ERA to be predictive or retrospective? Is the ERA to be site-specific or generic? What type of ecosystem(s) is at risk? What types of stressors are involved? What are the potential source(s) for a given stressor or set of stressors?

Addressing these questions requires a rigorous review of available data. Where existing data are unavailable or incomplete, it may be necessary to carry out a preliminary study, particularly to establish the types of potential stressor. Most important, ecological risk assessment is often an iterative process. A given level of information is required for developing the design and objectives (i.e., the problem formulation). Additional data may be required for the complete ERA. Ultimately, the level of information needed and the extent of new data collection are dependent upon the objectives, such as the level of certainty desired. As well, the level of information is dependent upon the outcome of the previous iterations, for example, how much ecological impact has occurred at a given site or how hazardous a new chemical may be based on laboratory toxicity studies.

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Figure 3

From the Framework for Ecological Risk Assessment (USEPA, 1992).

Choosing Biological Endpoints An important issue at this stage is determining the appropriate suite of biological endpoints to be used in the evaluation. Biological endpoints should be carefully chosen specifically to address the overall goals of the assessment. The parameters to be considered in choosing these endpoints should include the ecological relevance of the endpoint and the spatial and temporal occurrence of the endpoint relative to the distribution of the stressors and potential biological receptors.

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In ecological assessments the distinction is often made between assessment endpoints and measurement endpoints (Warren-Hicks et al., 1989; Suter, 1993). Assessment endpoints represent the ultimate resource(s) or final environmental values that are to be protected. They should have social or biological relevance, be quantifiable, and provide useful information for resource management or regulatory decisions. For example, successful reproduction of a species in danger of extinction is an appropriate assessment endpoint. For populations that are valued for commercial or sport uses such as anadromous fish (e.g., salmon) or estuarine or marine shrimp, the important assessment endpoints could be growth, reproduction, or overall productivity. Other potential assessment endpoints include yield and productivity, market or sport value, recreational quality, and reproductive capability (see WarrenHicks et al., 1989). In general, assessment endpoints focus on population and community parameters because ecological risk assessments are usually concerned with protecting these higher levels of biological organization rather than individual organisms. However, when there is concern for endangered species, the assessment endpoints may indeed focus on the individual organism. In contrast, measurement endpoints represent the specific parameters that are to be measured in a given assessment. They are often chosen based upon practical considerations such as availability and ease of measurement. It is often impossible from a practical sense to measure some endpoints (e.g., endangered species) and other more obtainable measurement endpoints are chosen as surrogates for the actual assessment endpoints of interest. Such measurement endpoints should be well characterized and take into account exposure pathways and temporal factors. Ideally, measurement endpoints should be chosen so that the data from these endpoints can be linked directly or indirectly to appropriate assessment endpoints. This latter issue is often the most difficult to address in ERAs. At the level of the individual, measurement endpoints may include mortality, growth, and fecundity. Abundance and reproductive performance are measurement endpoints on a population level. Other measurement endpoints include species evenness and diversity on a community level and biomass and productivity on an ecosystem level. Assessment of endangered species poses a special problem. Because exposure for an endangered species cannot usually be directly assessed, the residues of a contaminant in a principal food item can be a measurement endpoint. Alternatively, if exposure to a chemical and its potential impact on an endangered species is the assessment endpoint, then a co-existing species with similar life history habits might be used as a surrogate measurement endpoint. Spatial and Temporal Considerations Ultimately, the problem formulation phase should result in the establishment of the study design which will form the basis of the assessment. The design must take into account a number of environmental and ecological factors that may affect the stressors or their potential impact on biological systems. Many of these factors have spatial or temporal components that must be taken into account in the design. Spatial

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factors include potential routes of exposure, other sources of stressors, location of sensitive biological resources, and factors that may modify contaminant mobility or availability. The changing composition of sediments is an example of the latter. Temporal factors may include seasonal changes in physical, chemical, or biological aspects of ecosystems that may influence the magnitude or form of the stressor or its potential to cause a biological effect. For example, increased surface water movement in the wet season in riparian habitats can dramatically affect contaminant migration and the potential for exposure. Also, seasonal variation in physical or chemical parameters such as temperature or pH can modify the bioavailability of contaminants, thus changing the nature of the exposure. The biological characteristics of the exposure matrix may also change temporally. Species may be present only seasonally as is typical of migratory waterfowl, anadromous fishes, or species that migrate seasonally within a local area. Exposure to a given species, population, or community may vary with seasonal changes in life history habits such as seasonal feeding patterns or reproductive cycles. Thus, temporal changes in the biological components of an ecosystem may influence the distribution of the stressor or the availability of the biological endpoint within the ecosystem. Temporal variation would affect the ultimate risk assessment. Therefore, these temporal patterns must be addressed in designing the sampling scheme and data collection for the risk assessment. Temporal considerations may also include long-term historical or predicted trends in stressor influence and potential seasonal variation in stressor impact. Historical or predicted trends are very important to understanding the overall impact of stress on an ecosystem and may be important to the application of risk information in risk management decisions such as remediation plans, wetland restoration, and registration of a new pesticide. Other Considerations Another factor to consider is the presence of biological resources that are either sensitive to stressor impact or may be of particular economic or social importance. Wetlands are nursery areas for many species that inhabit adjacent terrestrial and aquatic communities. Other resources may include populations of economically important species such as anadromous fish populations or endangered species which are protected by law. In completing the problem foundation phase of the ERA, these issues must be addressed in rigorous and systematic fashion. The ultimate goal is the development of a conceptual model that will serve as a basis for the ERA. The model should address the spatial and temporal distributions of potential stressors, appropriate biological endpoints, as well as probable routes and levels of exposure. Finally, the model should be precisely linked to the goals and purposes of the risk assessment. A well-conceived conceptual model is essential to the effective implementation of the subsequent component of the risk assessment.

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Analysis Phase The analysis phase consists of two distinct activities: characterization of exposure and characterization of ecological effects. It is here that the two main elements of an ecological risk assessment are most prominent and most closely interrelated. Exposure Characterization The goal of exposure characterization is to develop an accurate appraisal of the potential for exposure to important biological resource or receptors, as represented by the measurement endpoints, to the identified stressors. Spatial and temporal factors are particularly important in this stage of the ERA. Issues associated with multiple routes of exposure must also be addressed at this time. Both the stressor and the ecosystem must be characterized with regard to the distribution and pattern of change. This is accomplished through the use of modeling or monitoring data, or both, depending on whether the ERA is predictive or retrospective. Stressors can be characterized from direct sampling, laboratory or field testing, or through remote sensing. At this stage, it is important to evaluate the means by which stressors can be modified in the ecosystem through biotransformation or other environmental fate processes such as photolysis, hydrolysis, and sorption. Transport and fate models are often employed, including interactive mass balance models like the Exposure Analysis Modeling System (EXAMS) developed at the USEPA research laboratory in Athens, GA (Burns et al., 1982). Characteristics of the ecosystem that can affect exposure also need to be evaluated. These can include habitat requirements, food preferences, reproductive cycles, and seasonally influenced activities. After stressor and ecosystem characteristics are defined, the spatial and temporal distributions are combined to evaluate exposure. Finally, the magnitude and distribution patterns are quantified for the scenarios developed during the problem formulation phase of the ERA. All sources of uncertainty should also be quantified to the degree possible for the input into the ERA. Recently, probabilistic techniques have been used to characterize uncertainty under various exposure conditions (Burmaster and Anderson, 1994; Power, 1996). Ecological Effects Characterization The goal of this portion of the analysis phase is to identify and characterize any adverse ecological effects that are associated with exposure to a particular stressor or stressors. To the extent possible, these effects should be quantified and any cause and effect relationships evaluated. Initially, an evaluation must be made of all effect data that are relevant to the stressor. The types of data that are relevant will depend upon the characteristics of both the stressor and the ecological component and also on whether the ERA is to be predictive or retrospective. Commonly used data types include aquatic toxicity tests, computer models, quantitative structure activity relationships (QSARs), microand mesocosms, species diversity analyses, artificial substrate comparisons, the ©2001 CRC Press LLC

Wetland Evaluation Technique (Adamus et al., 1987), and others (Suter, 1993; USEPA, 1992; McKim et al., 1987; Barnthouse et al., 1986). Data from laboratory and field observations, as well as from controlled studies, may be used. These data are considered based upon their relevance to the measurement and assessment endpoints. Evaluating the quality of the data, that is, the adequacy of sampling and statistical design, is an important component of this stage. The next step is to quantify the ecological response in terms of the stressor–response relationship. The aim is to describe the relationship between the magnitude, frequency, and duration of the stressor, and the magnitude of the response. The dose–response curve in laboratory aquatic toxicity tests is an example of this type of analysis. Determining relative differences in productivity, biomass, species composition, and diversity between contaminated and reference sites is also a commonly used means of defining this relationship. Any extrapolations required between the stressor and measurement endpoints must be evaluated as well as any extrapolations between measurement and assessment endpoints. The strength of the causal relationship must be quantified to the extent possible. Finally, as with the exposure analyses, quantitative estimates of uncertainty such as natural variability in ecological characteristics and responses should be included in the analyses. Often this analysis of uncertainty can be done probabilistically (Moore, 1996). However, it should be emphasized that although the goal is to provide quantification of the stressor–response relationship, in many cases, it can only be described qualitatively and, therefore, professional judgment plays an important role in most ERAs. Risk Characterization Phase The ultimate purpose of the ERA is to estimate the risk that unacceptable adverse ecological effects will occur due to exposure to anthropogenic stressors. The risk characterization phase provides an estimate of the likelihood that an adverse impact has occurred or will occur. It also should address the relative ecological consequences that are associated with the various levels of risk. Ideally, risk characterization should be quantitative and include estimates of uncertainty. However, the complexity of ecological risk assessments may often preclude precise quantification. Under these circumstances, qualitative estimates of risk are often employed. In the risk characterization phase a hazard-exposure matrix is developed. This matrix represents a fusion of the exposure predictions developed in the exposure characterization phase and the estimates of effects developed in the ecological effects characterization phase. Ultimately, the risk characterization phase should evaluate the ecological consequences or ecological significance of predicted or observed effects. This is simpler in some cases for retrospective risk assessments, because the changes can be documented and quantified in situ. Also, the ecological effects, that is, the resulting changes at higher levels of biological organization or in the ecosystem as a whole can be monitored directly with the proper sampling design and appropriate reference sites. In predictive ecological risk assessments, these effects or changes in ecosystems must be predicted. The degree of uncertainty for such predictions is relatively large in most situations. As the historical database for ecotoxicology and ©2001 CRC Press LLC

ecological risk assessment increases, especially field data sets, these predictions will be made with higher levels of confidence. Especially important is the field validation of risk assessments based on laboratory-based hazard assessments and modeled exposure assessments. As a result of the inherently different goals of predictive and retrospective ecological risk assessments, the remainder of this chapter will provide illustrations of how ERAs may be applied for each of these types with regard to wetland ecosystems. The first type of ERA to be discussed will be the current tiered assessment design, a predictive approach employed by the USEPA in the pesticide regulation program. The second describes a retrospective approach more common in the assessment of hazardous waste sites or spills. Predictive Ecological Assessments A practical example of a predictive risk assessment can be seen in evaluating the potential ecological impact of the introduction of a new herbicide. Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and its amendments, all new pesticides and herbicides must be registered for each specific use. The Office of Pesticide Programs of the USEPA prepared the Standard Evaluation Procedure for Ecological Risk Assessment (SEP) (Urban and Cook, 1986) to define the procedures to be used for the ecological risk assessment process. In short, this document presents a tiered approach to determining the potential for unreasonable adverse effects on the environment as a result of the use of pesticides and herbicides. Additional information for the testing of new pesticides and herbicides can be found in the Pesticide Assessment Guidelines (USEPA, 1982a, b). To illustrate this example, consider a new herbicide for control of weeds in rice paddies adjacent to riparian and emergent wetlands. The goal here is to assess the potential risk of the new herbicide on the wetland ecosystem based on the toxicology and environmental fate of the pesticide under the proposed use pattern. Problem Formulation The first activity in this predictive ERA is to define the scope of the problem. The planned use pattern for the herbicide requires its application to fields that have a great dependence on water flow and, thus, have a large potential for transport of chemicals into adjacent aquatic habitats. It is important that the inherent toxicity of herbicides be assessed in relation to the likely exposure to various ecological compartments. In simple terms, the questions to be answered are how toxic is it and will there be enough exposure for the toxicity to be realized? The typical rice field (Figure 4) may be 10 to 60 ha in size and laser-leveled to control water flow. The fields are not allowed to get too dry and, if sufficient rainfall is lacking, they may be flushed with water to depth of 2.5 cm or so on a fairly regular basis. Once the rice is adequately established, the field is typically flooded to a depth of 7.5 to 15 cm, which is then maintained until harvest. The temporary flush and permanent floodwaters are drained to an adjacent ditch that runs within 100 m to a small bayou. Emergent and riverine wetlands are associated ©2001 CRC Press LLC

with the bayou. Approximately 400 ha of rice drainage enter into the bayou above and below our hypothetical field. For this example, let us assume that the herbicide has a maximum application rate of 2.7 kg (5 lb) active ingredient per hectare and is applied only once a year, just prior to the permanent flood.

Figure 4

The typical rice field may be 10 to 60 ha in size and laser-leveled to control water flow. Flooding and drainage are accomplished through use of the ditch in the foreground.

Exposure Characterization Essentially, there are four means by which the herbicide could enter the adjacent wetland habitats. First, exposure may occur if the pilot applying the material oversprays the field and deposits some of the herbicide directly on the wetland. Second, small droplets of the substance have the potential to drift in the wind during application. Third, owing to the nature of rice culture, periodic releases of water are made from the fields. And finally, severe storms could potentially create an overflow of paddy water into nearby wetlands. Each of these routes should be examined in the ERA. In most cases, measured concentrations of the new herbicide in the field will not be available at this point. Therefore, the potential exposure must be estimated. The endpoint of interest in the exposure characterization is the determination of an estimated environmental concentration (EEC). The EEC provides the risk assessor with a concentration of the herbicide that may be present in the environment. A tiered approach is commonly used to determine the EEC, moving from simple to more complex depending on the need for additional information. ©2001 CRC Press LLC

The simplest way to determine the EEC is to assume that the herbicide is applied directly to the water in the wetlands adjacent to the rice fields. Although this is unlikely, it is possible if, for example, the pilot applying the herbicide overshoots the field. In any case, it provides an extreme worst-case exposure scenario. At the given application rate, and assuming a direct application to water that is 0.6 m deep, the EEC immediately following application would be 919 ppb (Urban and Cook, 1986). Comparing this EEC to ecological effects would allow a cursory assessment of risk to be made. However, this simple method of determining the EEC does not consider variables that could modify the actual concentrations in the adjacent wetland system. For example, normal use practices of the herbicide would preclude direct application to water bodies. Rather, the application would be directly to the field and transport of the chemical would be a function of water flow off the field. In addition, physiochemical and environmental fate characteristics of the herbicide may allow it to partition to the sediments or be metabolized or degraded into either more or less persistent compounds. This method represents a screening level estimation of the worst case environmental concentration. Should some concern remain following the screening level EEC determination, then a more realistic determination is required which may incorporate additional tiers of evaluation. For example, a second level may incorporate additional variables such as drainage basin size, surface area, and percent runoff into the simple equation. A still more complex EEC determination can be made utilizing computer models such the Pesticide Root Zone Model (PRZM) and EXAMS (Burns et al., 1982) to predict herbicide concentrations in aquatic systems resulting from runoff. Finally, in the event that some concern still exists, the last tier EEC determination may include conducting an actual field residue monitoring study in which the herbicide is applied at the maximum label-allowed rate in a test field and residues are measured periodically around the field. The spatial and temporal factors associated with the introduction of a pesticide are important to consider. For the herbicide example, these can include the application and use rates, water flow dynamics in the rice field (e.g., is water released immediately after application or held for a significant time period before release), mobility and persistence of the herbicide (e.g., water solubility, hydrolysis/photolysis rates, metabolism rates, etc.), and potential for bioaccumulation. Other factors include the timing of application with respect to seasonal biological cycles and the type and number of organisms that could potentially be affected. Ecological Effects Characterization The purpose of this segment of the ERA is to characterize any adverse impacts that may be associated with the pesticide. Because this is a herbicide, it is designed to be toxic to certain broadleaf weeds. Therefore, the effects characterization should be limited to nontarget flora and fauna that may be exposed to the herbicide either during use or following runoff. To test all of the species that may come in contact with the herbicide at all of the potential sites of application is unrealistic. Therefore, a series of standard surrogate species are typically tested. ©2001 CRC Press LLC

As with the determination of the EEC, a tiered approach is usually taken to quantify the toxicity of the herbicide to nontarget organisms. Results from the first tier testing determine the need for second tier testing, and so on. Each tier normally examines increasingly sensitive endpoints. Tier I addresses acute toxicity to warm water and cold water fish, as well as to aquatic invertebrates and plants (World Wildlife Fund, 1992). Acute oral and dietary dosages to game birds such as bobwhites and mallards are also evaluated for toxicity. Additional tests of toxicity to estuarine species, honeybees, and others may be required depending on the use pattern and environmental fate of the compound. Tier II testing is sometimes required to determine a no-observable-effect concentration (NOEC) for effects such as reduced survival, growth, and reproduction. Tier II tests for toxicity to fish early life stage or invertebrate life cycle can be triggered by acute toxicity where the median lethal concentration (LC50) is less than 1.0 ppm. These tests can also be triggered by high EEC levels (where EEC is greater than 0.01 of the lowest Tier I LC50 value), chemical persistence in the environment, continuous or recurrent exposures, or high potential for bioaccumulation or reproductive effects. Tier II studies are automatically required for any aquatic use of herbicides. Tier II avian reproduction studies may also be triggered if Tier I avian tests indicate toxicity. Tier III full life-cycle tests with fish may be required if the EEC is more than 0.1 of the NOEC from the Tier II fish early-life-stage study, or if data suggest that there is a potential for impairment of fish reproduction. Finally, Tier IV field or mesocosm studies may be invoked if the expected concentrations in the environment exceed the Tier III NOEC determination. Tier IV field testing with avian or mammalian species may also be required. It is important to note that recent guidance by the USEPA suggests that decisions on the reregistration of existing pesticides and herbicides can be made without requiring Tier IV studies (Fisher, 1992). However, companies wishing to reregister existing pesticides and herbicides where a hazard for aquatic organisms has been presumed may want to conduct Tier IV testing in an effort to rebut this presumption. Risk Characterization Phase By comparing the estimates of environment concentrations developed in the exposure characterization section and the estimates of toxicity developed in the ecological effects characterization section, an assessment of risk of the rice herbicide to the adjacent wetlands can be generated. There are several methods for examining the relationship between the EEC and environmental effects (Barnthouse et al., 1982a, b). One of these is the quotient method of risk analysis. The Quotient Method for Risk Characterization The quotient method is often employed for predictive risk characterizations of single compounds such as pesticides and herbicides. This method is based on a simple comparison of the estimated exposure to a stressor response value (SRV) for a specific endpoint. The SRV represents a level of exposure that has been demonstrated to have unacceptable toxicological effects. When the estimated exposure ©2001 CRC Press LLC

derived from the exposure assessment exceeds the SRV, the associated risk is considered unacceptable. Clearly the choice of the SRV is critical to this approach. Usually SRVs are derived from laboratory toxicity studies and are estimates of threshold toxicity for appropriate endpoints, such as 1/10 the acute median lethal concentration (LC50) or the chronic NOEC. The use of the quotient method is straightforward and is useful for single chemicals. However, there are a number of disadvantages to this approach. The estimate of risk from the quotient method is only as good as the hazard and exposure estimates. The latter is often based on cursory environmental fate information and has a low confidence level. The hazard assessment data for ecological endpoints are often based on acute effects (i.e., mortality) rather than subacute effects such as inhibition of growth rates or impaired reproduction. Moreover, these so called aquatic hazard assessments are usually based on clean water laboratory tests which may not accurately reflect in situ exposure conditions. Finally, and most importantly, the quotient method is not useful in estimating risk from multiple stressors. Most ecological risk assessments, especially retrospective assessments, involve more than one stressor. Risk from multiple stressors cannot be accurately addressed by adding the stressor–response values due to stressor interactions (e.g., synergism, antagonism, potentiation). In these cases, the hazard assessment and the exposure assessment phases of the ERA must be modified and tailored to the suite of stressors. This assumes that the suite of stressors is known or identified in the preliminary characterization carried out as of the conceptual framework. The Ecological Effects Branch of the USEPA uses a similar methodology. However, where the quotient method uses the resultant quotient in a relative ranking to indicate adverse effects, the Ecological Effects Branch compares the EEC and an effect level (e.g., LC50) to regulatory risk criteria. Many of the risk criteria summarized in Table 1, incorporate safety factors derived from a toxicological model presented in the FIFRA regulations. These safety factors are included to allow for the differential variability and sensitivity among resident fish and wildlife species (Urban and Cook, 1986). Based on the results of the risk characterization, a determination is made as to whether to register the herbicide for use on rice, restrict its use (through required labeling) to certified applicators, restrict its use to areas with limited wetland habitat proximal to the fields, or deny registration of the herbicide (World Wildlife Fund, 1992). It should be noted that recent debate has centered on the development and use of probabilistic ecological risk assessment techniques. A cooperative effort between industry, environmental advocacy groups, and the USEPA, referred to as ECOFRAM, has prepared draft documentation of various probabilistic ERA tools (ECOFRAM, 1999a, b). The actual use of these tools by pesticide risk assessors remains to be seen. Retrospective Ecological Assessments An example involving an ecological assessment of wetlands adjacent to a hazardous waste site will demonstrate how the principles of ecological risk assessment ©2001 CRC Press LLC

Table 1

The Regulatory Risk Criteria* No Risk

Acute toxicity

Chronic toxicity

Risk Limited by Restricted Use

Unacceptable Risk Non-Endangered Species EndangeredSpecies

Mammals EEC <1/5 LC50

Mammals EEC > 1/5 LC50

EEC > LC50

Birds EEC <1/5 LC50

Birds 1/5 LC50 < EEC < LC50

EEC > LC50

Aquatic EEC <1/10 LC50

Aquatic 1/10 LC50 < EEC < 1/2 LC50

EEC > 1/2 LC50

EEC < chronic no effect level

NA

EEC > chronic effect levels

EEC or EEC EEC or EEC EEC or EEC EEC

> 1/10LC50 > 1/5 LC10 > 1/10LC50 > 1/5 LC10 > 1/20LC50 >1/10 LC10 > chronic effect levels

* The criteria listed in this table can be compared to the estimated environmental concentration (EEC) and the effect level to characterize risk. Adapted from Urban and Cook, (1986).

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are applied in a site-specific retrospective study. The principles developed in the USEPA framework and guideline documents (USEPA, 1992, 1998) can be applied to retrospective risk assessments as well as, and in some cases better than, the predictive ERAs (Pascoe et al., 1993). In addition, several other USEPA documents provide guidance applicable to ecological assessments at hazardous waste sites (USEPA, 1988, 1989a; Warren-Hicks et al., 1989). Finally, guidance specific to the Superfund program was issued in 1989 (USEPA, 1989b, c). This guidance, commonly referred to as RAGS (for Risk Assessment Guidance for Superfund), has become the main source of procedural information for both human and environmental health risk assessments. Problem Formulation For the purposes of this example, consider a hazardous waste site that is a longterm chemical manufacturing facility. The facility is located on 2 ha of commercial land that includes a nontidal marsh. In addition, a levee separates the site from an adjacent tidal marsh and a large estuarine bay. The primary objective is to assess the degree of risk that contamination from the site poses for the adjacent wetland ecosystem. Another objective of this sitespecific assessment is to provide information for the development and evaluation of an ecologically sound remedial action plan for the site. In the case of the nontidal wetland, these data can be used to help define the strategy required to address any effects of the contamination from the site on the nontidal wetland ecosystem. For the tidal marsh, these data would provide a basis for determining if contaminantrelated impacts are occurring and whether remediation is necessary. Moreover, if required, these data could be used to determine the appropriate type and extent of remediation. The following specific goals can be established for performing an assessment of risk to the tidal wetlands. • Assess the potential for exposure to the contaminants of concern for ecologically and socially important species from the tidal wetland. • Determine the potential for acute and chronic toxicological effects from accumulated contaminants on these species. • Evaluate the structure of the populations and communities of plants, benthic invertebrates, and small mammals in the tidal wetland. • Relate the exposure, bioaccumulation, and toxicity data obtained in this assessment with population, community, and ecosystem data to provide an integrated picture of the impact of contamination from the site on the adjacent tidal wetland. • Evaluate the source or sources of any stressors that may be identified by examining the distributional patterns of those stressors in the tidal wetland in relation to identified sources including the site and the bay. That is, do the stressors come from the site or from the other sources via the connection to the bay?

Exposure Characterization The retrospective approach to exposure characterization is usually more direct than in the predictive approach. In a retrospective ERA, stressors are already present ©2001 CRC Press LLC

in the environment. The goal is to determine which stressors are present and in what concentrations, rather than attempting to predict which stressors might enter the environment. The potential for exposure can be determined by measuring the actual accumulated dose of stressor in environmental matrices, including the tissues of native or transplanted organisms. The first step in the exposure characterization phase is to determine the nature and distribution of the stressors. As indicated above, this is accomplished by collecting samples of the various environmental matrices and analyzing them for the suspected contaminants. In our waste site example, sampling should be performed within the site proper, in the on-site nontidal marsh, and at near field and far field locations within the adjacent tidal wetland. Additionally, external reference sites should be sampled to provide a comparison to the zones within the site and adjacent wetlands (Figure 5).

Figure 5

For hazardous waste sites, initial sampling commonly requires extra protection for team personnel.

The precise sampling strategy employed will be dependent upon the exact goals of the ecological assessment, the structure and function of the ecosystem involved, and the nature of the contaminants of concern. One approach is a random sampling strategy that is designed to evaluate differences over relatively broad areas of the wetland. A grid system comprised of relatively large quadrats is set up within each zone to be examined. The use of randomly selected sampling stations within each grid facilitates statistical comparisons between zones, and the number of samples to be taken per unit area can be calculated (Warren-Hicks et al., 1989). Statistical comparisons of data from the nontidal marsh, the near field tidal marsh and far field tidal marsh grids allow for spatial comparisons of the different measurement endpoints ©2001 CRC Press LLC

relative to their distances from the site. This provides a basis for an internally controlled evaluation of the spatial effects of the site. Data on these three zones can also be compared to the remote reference sites. This strategy provides two independent methods for evaluating the broad scale effects of the site on the adjacent wetlands. A second approach for evaluating the impact of the site on the adjacent tidal wetlands can be used in parallel with the random sampling approach described above. In this approach, the sampling focus is on the potential route by which onsite stressors may be transported off-site and into the tidal wetland. In this nonrandom sampling strategy, a series of stations can be established in the major drainage slough to provide a spatial gradient of contamination moving from the site to the bay. The types of sample measurements that are commonly taken at stations such as those described should include concentrations of contaminants in the sediments, soils, and surface waters. Measurements of actual concentrations of the stressors in plants and animals are also helpful. The combined database from all of the sites will provide the basis for interpreting the extent and magnitude of the stressors on the site and in the adjacent wetlands. The exposure characterization discussion thus far has been limited to determining the nature and distribution of stressors on the site and neighboring wetlands. An equally important component of this phase of the ERA is to evaluate the potential routes by which organisms may be exposed to the stressor. In the example, routes of potential exposure include direct exposure in the sediments and surface waters and indirect exposure via the food chain. Soils and sediments commonly serve as sinks for chemical stressors and, thus, will need to be examined closely. The bioavailability of stressors sequestered in the sediments should also be evaluated because this could have a profound effect on the actual ecological effects observed. The degree to which the stressor is bioaccumulated or depurated is also very important to the evaluation of actual exposure. Finally, the temporal aspects of the stressors must be considered. For example, the standing waters of the nontidal wetland would likely recede during the dry season. Marsh plants commonly exhibit a rapid growth period at the end of the wet season and continue this growth into the dry season. As available water diminishes, plant growth subsides, and eventually the plants senesce and die. These and other seasonal changes could modify stressor distribution and bioavailability. Therefore, it is often necessary to perform the ecological assessments during both the growing and nongrowing seasons. Some inherent complicating factors must be addressed in order to establish cause–effect relationships between stressors in the environment and observed changes in biological endpoints. For example, in highly commercial areas, extensive anthropogenic activities can result in numerous stressors from multiple sources. Moreover, these stressors may have differential mobility within ecosystems and the ratios of one stressor to another may change with distance from the source. This complexity makes it difficult to relate any observed biological effects to specific stressors or to a specific source. The spatial and temporal sampling schemes described above should provide a basis for determining if the concentrations of chemical contaminants and biological parameters in the wetlands show significant correlation with one another and specific relationships to the site. ©2001 CRC Press LLC

Ecological Effects Characterization To accomplish the retrospective ecological assessment, it is necessary to determine if the stressors from the site have produced adverse effects on the structure and function of the adjacent wetland ecosystems. In the predictive ERA example, the emphasis was on performing laboratory studies to determine potential ecological effects, followed by increasingly higher tier modeling or field dissipation studies if warranted by the laboratory data. Conversely, with the retrospective ERA, the emphasis is on determining actual ecological effects on the site and in the adjacent wetlands. This is accomplished by emphasizing field evaluations of community structure and the toxicity of soils, sediments, and surface waters. It is important to co-ordinate the ecological effects sampling with the exposure sample collection on both a spatial and a temporal scale. In other words, samples for chemical analysis and ecological effects should be taken at the same time and place whenever possible. Examples of the types of ecological effects sample measurements commonly taken are provided in Table 2. Table 2

Retrospective Ecological Risk Assessment (ERA) Emphasizing Field Evaluations*

Bioaccumulation of contaminants in dominant plant species Bioaccumulation of contaminants in dominant benthic invertebrate species Bioaccumulation of contaminants in small mammals Bioaccumulation of contaminants in dominant fish species Sediment toxicity (pore water, elutriates, or solid phases) Water toxicity Plant population and community structure within each grid Benthic infaunal invertebrate population and community structure Histopathological evaluation of native small mammals or fish Fish population survey * Typical ecological effects sample measurements are listed in the table and should be collected at the same time and place as the chemical measurements.

As can be seen in Table 2, the emphasis is on measuring actual effects in the field whenever possible. Nevertheless, laboratory toxicity tests can play an important role in the evaluation of wetlands water and sediments affected by hazardous waste sites (Zimmer et al., 1988; Durda, 1993; Woodward et al., 1988; see Figure 6). The toxicity of field collected samples is used to define the extent of contamination with regard to direct biological significance. On-site studies such as cage studies may also provide valuable information in the delineation of ecological effects. Measurement endpoints should be chosen for relevant characteristics. Endpoints may be key ecosystem components that are sensitive to stressors, accumulate the stressor of concern, or are food resources for higher trophic levels. Other endpoints include key indicators of ecosystem structure and function or surrogates for stressor impacts to endangered species or other assessment endpoints that cannot be directly monitored. Species continuously exposed to contaminated sediment or water have the greatest potential for contaminant uptake and serve as excellent indicators of ©2001 CRC Press LLC

Figure 6

Ecological effects characterization emphasizes measurement of actual effects in the field. Nevertheless, laboratory toxicity tests, such as this sediment test, can play an important role.

bioaccumulation potential. In wetland sites, marsh plants, benthic invertebrates, and filter-feeding mollusks are particularly useful indicators of bioavailability. Transfer of contaminants along the food chain should also be considered. The biological effects of accumulated contaminants are also complex. Contaminants may be stored in an inactive form, mobilized, or excreted. Alternatively, they can interact with cellular macromolecules causing metabolic perturbations and cellular damage that impact the function of the organism. Thus, while bioaccumulation of contaminants reflects the potential for toxicity, supplemental approaches with greater resolution are needed to determine actual toxicity to the organism. Sublethal impacts on the organism can affect higher levels of biological organization through inhibition of such physiological processes as growth and reproduction. Changes in these parameters can impinge upon populations and communities. In addition, if the marsh plant populations are adversely affected, the ecological impact could result in habitat disturbance for birds and small mammals, including endangered species. As in the previous cases, impact at these higher levels of organization can be inferred or measured directly. Risk Characterization Comparison of the exposure and ecological effects characterizations is performed to provide an assessment of risk to both the on-site nontidal wetland and the tidal estuarine wetland adjacent to the site. Because of the complexity of the linkages ©2001 CRC Press LLC

between contaminant distribution and ecosystem effects, the ecological assessment must be designed to carefully examine the correlations between the concentrations of contaminants in sediment, soil and water, and biological function observed at any of several levels of biological organization. The collection of matched samples for measuring contaminant concentrations in the sediments, bioaccumulation, toxicity, and population and community status is important to allow a rigorous examination of the relationships among these endpoints. The specific procedures used in the risk characterization phase will depend on the design chosen to determine exposure and ecological effects, as well as the overall purpose for performing the ERA. In the retrospective example, the primary objective is to assess the degree of risk that contamination from a hazardous waste site will have on the on-site and adjacent wetland ecosystems. Data collected includes chemical concentrations in the sediments and surface waters, bioaccumulation of the stressors in dominant plant and animal species, sediment and surface water toxicity, fish and wildlife population surveys, and plant and benthic invertebrate population and community structure. Initially, the stressor concentration data can be tabulated and plotted on both the spatial and temporal scales to evaluate trends in concentration. Are the concentrations higher near the site and lower away from the site? Do concentrations appear to follow a gradient associated with one or more transport routes away from the site? Has the stressor partitioned into the sediments or has it been dispersed for some distance? Furthermore, how do these concentrations relate to water quality standards and criteria established for wetlands (USEPA, 1990)? Similarly, the sediment and surface water toxicity data should be tabulated and plotted to show spatial and temporal trends. Are any trends evident and, if so, do they correlate with the stressor concentration trends? Bioavailability can be established by comparison of contaminant levels in the abiotic matrices and biota exposed to these matrices. Ecological effects on the population and community level can be evaluated using several statistical procedures designed for these types of data (Ludwig and Reynolds, 1988). Species diversity, richness, and abundance can be compared using ANOVA and cluster analyses to determine if differences in these parameters can be correlated with stressor concentration. A picture should begin to emerge regarding the levels of exposure and the degree of effect after comparing all of the collected data. If the picture is sufficiently muddled because of extensive anthropogenic inputs into the systems under investigation, techniques such as the principal components analysis may be used to help define the key contaminants associated with specific effects. In addition, fate and transport processes can often be modeled based on data collected in the field and the physicochemical characteristics of the stressors of concern. Ultimately, the actual assignment of ecological risk will often depend on the professional judgment of the risk assessor.

SUMMARY ERA is a rapidly developing and increasingly important discipline that can be used as a management tool in the protection of wetlands. It is a process that estimates ©2001 CRC Press LLC

the impact of anthropogenic activities on ecosystems. The results of ERAs are used by managers and regulators to determine the appropriate action for the wetland or site in question. The application of the ERA paradigm as described provides a framework for assessing risk to ecological resources for a variety of scientific and regulatory purposes. The principles of ERA can be applied to a variety of situations including retroactive analysis of anthropogenic activities and predictive assessment of future actions. Additional definition of the principles and procedures of ERA is needed to help risk assessors standardize their methods as much as possible. With this objective in mind, the American Society for Testing and Materials (ASTM) has undertaken an effort to develop standards for the assessment and valuation of wetlands (Ethier, 1993). The use of a standard approach with standard terminology will facilitate communication and interpretation of results and concepts. Furthermore, this standard approach will allow for balanced risk management of human health and environmental concerns under a variety of regulatory programs. However, it is important to understand that even with increased standardization of the ERA framework, ERAs will still need to be designed on a site- or chemical-specific basis to address the specific concerns.

REFERENCES Adamus, P. R., Clairain, Jr., E. J., Smith, R. D., and Young, R. E., Wetland Evaluation Technique (WET), Vol. II, Methodology, Department of the Army, Waterways Experiment Station, Vicksburg, MS, 1987. Barnthouse. L. W., Bartell, S. M., DeAngelis, D. L., Gardner, R. H., O’Neill, R. V., Powers, D. D., Suter, G. W., Thompson, G. P., and Vaughan, D. S., Preliminary environmental risk analysis for indirect coal liquefaction, Draft Report, Oak Ridge National Laboratory, Oak Ridge, TN, 1982a. Barnthouse, L. W., DeAngelis, D. L., Gardner, R. H., O’Neill, R. V., Powers, C. D., Suter, G. W., and Vaughan, D. S., Methodology for Environmental Risk Analysis, ORNL/TM 8167, Oak Ridge National Laboratory, Oak Ridge, TN, 1982b. Barnthouse, L. W., Suter, G. W., Bartell, S. M., Beauchamp, J. J., Gardner, R. H., Linder, E., and Rosen, A. E., User’s Manual for Ecological Risk Assessment, Publication Number 2679, ORNL-6251, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 1986. Bartell, S. M., Gardner, R. H., and O’Neill, R. V., Ecological Risk Estimation, Lewis Publishers, Chelsea, MI, 1992. Burmaster, D. E. and Anderson, P. D., Principles of good practice for the use of Monte Carlo techniques in human health and ecological risk assessments, Risk Anal., 14, 477, 1994. Burns, L. A., Cline, D. M., and Lassiter, R. R., Exposure Analysis Modeling System (EXAMS): User Manual and System Documention, EPA/600/3-82-023, 1982. Cairns, Jr., J., Niederlehner, B. R., and Orvos, D. R., Eds., Predicting Ecosystem Risk, Princeton Scientific, Princeton, NJ, 1992. Durda, J. L., Ecological risk assessments under Superfund, Water Environ. Technol., 45, 42, 1993. ECOFRAM, Aquatic draft report, The Ecological Committee on FIFRA Risk Assessment Methods, May 10, 1999. ©2001 CRC Press LLC

ECOFRAM, Terrestrial draft report, The Ecological Committee on FIFRA Risk Assessment Methods, May 10, 1999. Ethier, W. H., New wetlands standards: providing great tools for policymakers, Stand. News, 21, 26, 1993. Fisher, L., Memo re: decisions on the biological, fate and effects task force, Program Guidance on Ecological Risk Management, 1992. Lewis, M. A., Mayer, F. L., Powell, R. L., Nelson, M. K., Klaine, S. J., Henry, M. G., and Dickson, G. W., Ecotoxicology and Risk Assessment for Wetlands, SETAC Press, Pensacola, FL, 1999. Ludwig, J. A. and Reynolds, J. F., Statistical Ecology, John Wiley & Sons, New York, 1988. McKim, J. M., Bradbury, S. P., and Niemi, G. J., Fish acute toxicity syndromes and their use in the QSAR approach to hazard assessment, Environ. Health Perspect., 71, 171, 1987. Mitsch, W. J. and Gosselink, J. G., Wetlands, Van Nostrand Reinhold, New York, 1986. Moore, D. R. J., Perspective: using Monte Carlo analysis to quantify uncertainty in ecological risk assessment: are we gilding the lily or bronzing the dandelion? Hum. Ecol. Risk Assess., 2, 628, 1996. National Research Council, Risk Assessment in the Federal Government: Managing the Process, National Research Council, National Academy Press, Washington, D.C., 1983. Newman, M. C. and Strojan, C., Risk Assessment: Logic and Measurement, Lewis Publishers, Chelsea, MI, 1998. Pascoe, G. A., Blanchet, R. J., Linder, G., and Ingersoll, C. G., Assessment of ecological risks of contaminated wetland, a Superfund case study, Presented at the 1st SETAC World Congress, Lisbon, Portugal, March 1993. Power, M., Probability concepts in ecological risk assessment, Hum. Ecol. Risk Assess., 2, 650, 1996. Superfund Amendments and Reauthorization Act, Fed. Regist., 52, 13378, April 22, 1987. Suter, G. W., Ecological Risk Assessment, Lewis Publishers, Chelsea, MI, 1993. Urban, D. J. and Cook, N. J., Hazard Evaluation, Standard Evaluation Procedure, Ecological Risk Assessment, EPA 540/9-85-001, 1986. U.S. Environmental Protection Agency, Pesticide Assessment Guidelines, Subdivision E, Hazard Evaluation: Wildlife and Aquatic Organisms, EPA 540/9-82-024, 1982a. U.S. Environmental Protection Agency, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate, EPA 540/9-82-021, 1982b. U.S. Environmental Protection Agency, Guidelines for carcinogen risk assessment, Fed. Regist., 51, 33992, September 24, 1986a. U.S. Environmental Protection Agency, Guidelines for mutagenicity risk assessment, Fed. Regist., 51, 34006, September 24, 1986b. U.S. Environmental Protection Agency, Guidelines for health risk assessment of chemical mixtures, Fed. Regist., 51, 34014, September 24, 1986c. U.S. Environmental Protection Agency, Guidelines for health assessment of suspect developmental toxicants, Fed. Regist., 51, 34028, September 24, 1986d. U.S. Environmental Protection Agency, Guidelines for exposure assessment, Fed. Regist., 51, 34042, September 24, 1986e. U.S. Environmental Protection Agency, Review of Ecological Risk Assessment Methods, EPW23O-10-88-O41, 1988. U.S. Environmental Protection Agency, Rapid Bioassessment Protocols for Use in Streams and Rivers: Benthic Macroinvertebrates and Fish, EPA/444/4-89-001, 1989a. U.S. Environmental Protection Agency, Risk Assessment Guidance for Superfund, Vol. I, Human Health Evaluation Manual, Part A, EPA/540/l-89/002, 1989b.

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U.S. Environmental Protection Agency, Risk Assessment Guidance for Superfund. Vol. 11, Environmental Evaluation Manual, 1989c. U.S. Environmental Protection Agency, Water Quality Standards for Wetlands: National Guidance, EPA 440/S-90-011, 1990. U.S. Environmental Protection Agency, Summary Report on Issues in Ecological Risk Assessment, EPA/625/3-91/018, 1991. U.S. Environmental Protection Agency, Framework for Ecological Risk Assessment. Risk Assessment Forum. EPA/630/R-92/001, 1992. U.S. Environmental Protection Agency, Guidelines for Ecological Risk Assessment, Risk Assessment Forum, EPA/630/R-95/002F, 1998. Warren-Hicks, W., Parkhurst, B. J., and Baker, Jr., S. S., Ecological Assessment of Hazardous Waste Sites: a Field and Laboratory Reference Manual, EPA/600/3/89/013, 1989. Woodward, D. F., Snyder-Conn, E., Riley, R. G., and Garland, T. T., Drilling fluids and the arctic tundra of Alaska, U.S.A.: assessing contamination of wetlands habitat and the toxicity to aquatic invertebrates and fish, Arch. Environ. Contam. Toxicol., 17, 683, 1988. Zimmer, R. D., Buchanun, G., Charters, D., Ferretti, J., and Kent, D. J., Aquatic toxicological evaluation of soils collected from a mid-western Superfund site, presented at the 61st Annual Conference of the Water Pollution Control Federation, Dallas, TX, 1988. World Wildlife Fund, Improving aquatic risk assessment under FIFRA: report of the Aquatic Effects Dialogue Group, Washington, D.C., 1992.

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Kent, Donald M. et al “Avoiding and Minimizing Impacts to Wetlands” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

CHAPTER

5

Avoiding and Minimizing Impacts to Wetlands Donald M. Kent and Kevin McManus

CONTENTS Planning Design and Construction Design Construction Erosion and Sedimentation Nitrogen Loading Planning Guidelines Estimating Nitrogen Loads Stormwater Runoff Planning and Nonstructural Practices Structural BMPs Pretreatment Detention Basins/Retention Ponds Vegetated Treatment Infiltration Filtration References

Recent estimates of the extent of global wetlands range from 5 to 8.6 million ha (Mitsch, 1995). Increasing evidence suggests that the historic extent of global wetlands was substantially greater. For example, in Japan, 45 percent of tidal flats have been destroyed since 1945 (Hollis and Bedding, 1994). Northern Greece has lost

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94 percent of its marshland since 1930. In the conterminous United States, an estimated 47 million ha of wetlands have been lost over the last 200 years — an average rate of 235,000 ha per year (U.S. Office of Technology Assessment, 1984; Dahl, 1990; Hollis and Bedding, 1994). This rate of loss appears to have decreased dramatically in recent years, to about 32,000 ha per year, coincident with recognition of the importance of wetlands and a “no net loss” government policy (Heimlich and Melanson, 1995). Wetland losses are attributed to filling and draining, primarily in support of development and agricultural activities. An unknown number of wetlands, not filled or drained, have been otherwise impacted by changes in watersheds or adjacent land uses. Alterations to wetland plant communities lead to increased erosion and sedimentation. Construction of buildings, parking lots, and other impervious surfaces increases the quantity and decreases the quality of surface runoff to wetlands. Septic systems and fertilizers increase the concentration of nitrogen in groundwater flow to wetlands. Activities adjacent to wetlands can disturb wildlife. Wetland impacts, both direct and indirect, can be avoided or minimized by appropriate planning, design, and construction. In this chapter, planning is discussed as a means for avoiding or minimizing direct impacts to wetlands. Design and construction techniques are discussed as a means to avoid or minimize indirect impacts to wetlands. Discussed in some detail are three design and construction issues. They are erosion and sedimentation, nitrogen loading, and stormwater.

PLANNING Planning to avoid or minimize direct impacts to wetlands is fundamentally a three-step process. The first step is to identify the wetland resource. Discussed in detail in Chapter 2, this step requires applying hydrology, soils, and vegetation criteria to undeveloped areas. For large areas, off-site resource identification is an effective and appropriate approach for preliminary planning. Greater resource resolution, typically requiring on-site identification, is more appropriate for smaller areas and for detailed planning. Characterization and classification (e.g., palustrine forested wetland, emergent marsh; see Chapter 1) of wetland resources are also helpful at this stage. The second step in effective planning is to assign functions and values to identified wetland resources. Common techniques for determining functions and values include professional opinion, the use of indicators, direct measurement, and economic analysis (see Chapter 3). As with resource identification, off-site and less detailed approaches are most appropriate for large areas during preliminary planning, whereas on-site assessments are most appropriate for small areas and detailed planning. Assigning functions and values will facilitate prioritization in the event that not all resource areas can be preserved and reveal functions and values that need to be protected or replaced during construction and operation. Finally, wetlands identified and evaluated for functions and values are incorporated into a site selection process. Site selection typically includes identification of

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several alternative sites and development of site selection criteria. Alternative sites satisfy minimal, implicit criteria such as availability and location. At a minimum, the site selection process should consider the criteria listed in Table 1 (McManus, 1994). Direct and indirect impacts to wetland and other environmental resources should be identified. Other environmental resources include fish and wildlife, navigation channels, and recreation areas. Projects not dependent upon access to water should be sited elsewhere. The minimum size required to satisfy the project purpose should be determined and project configuration and layout evaluated to further reduce project size. Constructability refers to project topographic, slope, soil, and backfill requirements. Extensive grading, blasting, or filling are typically associated with environmental impacts and should be avoided. Proximity to supporting infrastructure, such as utilities and roadways, affects project size, configuration and layout, and cost. Cost prohibitive sites should be eliminated; thereafter, the costs of development should be weighed against the costs of environmental impacts. The opportunity for successfully satisfying the requirements of various international, national, regional, and local entities such as regulatory agencies and lending institutions should also be evaluated. Table 1

Representative Site Selection Criteria (Adapted from McManus, 1994)

Wetland impacts Other environmental impacts Water dependency Site size Constructability Supporting infrastructure Costs Regulatory/institutional issues

Larger and more complex projects will require a more detailed site selection process. In the United States, the National Environmental Policy Act (U.S. Congress/NEPA, 1978) provides guidance as to appropriate criteria for evaluating project impacts to wetlands and other environmental resources. In addition to environmental impacts, this approach considers impacts to human uses and the technical, economic, and institutional feasibility and merits of the site. Table 2 represents a hypothetical site-screening matrix consistent with the NEPA (McManus, 1994). In the example, Site 1 is technically and economically feasible, but will likely impact the environment and human use of the site, and is not publicly acceptable. Site 2 has no significant environmental, human use, or institutional constraints but has technical and economical issues. Site 3 is the preferred site, having no significant environmental or human use impacts, being technically and economically feasible and acceptable to the public.

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Table 2

A Hypothetical Site Selection Matrix (Adapted from McManus, 1994) ScreeningCriteria

Site 1

Site 2

Site 3

0 0 0 – – –

0 0 0 0 0 0

0 0 0 0 0 0

– – 0 0 –

0 0 0 0 0

0 0 0 0 0

0 – – – – 0 – 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0

+ +

– – –

+ + +

+ + 0

– – –

+ + 0

– 0

0 0

+ 0

Environmental Aquatic Ecosystem Substrate Water quality Water circulation Normal water fluctuations Threatened and endangered species Other aquatic organisms and wildlife Special Aquatic Sites Sanctuaries/refuges Wetlands Mudflats Vegetated shallows Riffle and pool complexes Human Uses Water supplies Recreational and commercial fisheries Water–related recreation Aesthetics Parks, preserves, wilderness areas Archaeological or historical sites Compatibility with adjacent land uses Potential noise impacts Potential odor impacts Public health Traffic increase Technical Suitable foundation/soils conditions Adequate land area Access to existing roads and utilities Economic Land acquisition Operation and maintenance Capital cost—construction Institutional Public acceptance Compliance with existing regulations

Note: + indicates an expected positive impact; – is an expected negative impact; 0 is an insignificant or no impact.

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DESIGN AND CONSTRUCTION Design Once the site selection process has been completed, the focus can shift to design details, site layouts, construction methods, and other specific engineering requirements to minimize unavoidable wetland impacts. A reasoned assessment of the minimum economically and functionally viable size for a proposed structure(s) should be made, particularly if the project is not water dependent. Even for water dependent projects, such as marinas or dredging projects, project scope should be evaluated with an eye toward minimizing wetland impacts. The project should have an accurate wetland delineation line depicted on site plans to facilitate evaluation of layout options. For projects that may involve clearing of trees and other existing vegetation, care should be taken to minimize the limits of clearing to the minimum acreage needed for the project. Maintenance of existing vegetative buffers, particularly within wetland areas, is not only a valuable means of providing a visual and auditory buffer for the facility, but it also may reduce overall facility wetland impacts. This is particularly true along active coastal shorelines, such as eroding bluffs, beaches, and dune environments. The orientation and layout of a project are generally a function of its intended purpose and use. Many projects, such as railways, roads, and retaining walls, being linear features, have limited flexibility with regard to basic configuration. However, their actual alignment, relative to wetland areas, can often be optimized to reduce impacts to insignificant levels. Similarly, layouts of buildings and ancillary structures such as garages, walkways, and decks can be adjusted to minimize direct wetland impacts. Specific design details for a project can also be important factors in reducing wetland impacts. For example, use of the maximum safe slopes for site preparation will minimize incursions into wetland areas. Maximum safe slopes can be achieved using vertical retaining walls, cellular confinement, sheet piling, or gabion rock walls. Backfill and other construction materials should ensure good drainage and scour protection (Nelson, 1995). Another method for minimizing impacts is to use boardwalks supported by posts or post-like anchors. Waterway crossings offer another opportunity to minimize wetland impacts. Typically, culverts are used when crossing small waterways. Culverts should be designed to pass expected flows (e.g., 100-year flood event), and to avoid changes to flow velocity and increased erosion and scour. Bridges can minimize impacts to larger waterways, especially if construction is accomplished in midair using a crawler crane. Construction For many projects, such as subsurface water, sewage, and other utility pipelines, the primary impacts to wetlands occur during construction. The use of temporary

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access materials, specialized construction equipment, and the placement of staging areas can all affect the level of wetland impacts. Temporary pile-supported construction trestles can be used to significantly reduce direct wetland impacts through ecologically sensitive wetland areas such as estuarine and fresh-water marshes, beach or dune environments, and peat bogs (Figure 1). These trestles can be located either directly above, or directly adjacent to, the work area. Equipment can be brought to the work area using rail-mounted transport platforms, and the trestle can be constructed in stages to accommodate the construction schedule. Trestles provide a stable temporary work platform that directly impacts little wetland acreage.

PLAN VIEW pipeline wood planking upland

wetland

sheet piling construction trench PROFILE

wood planking sheet piling

pipeline

Figure 1

Temporary pile-supported construction trestles can be used to significantly reduce wetland impacts. The trestles may be located either directly above or immediately adjacent to the work area.

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Another effective construction technique uses steel sheet piling to isolate the active work area, and temporary wood decking placed directly on top of the sheet piling. This allows construction equipment to access the work areas without compacting wetland soils. Compacted wetland soils lose their original productivity and hydrologic functions. For smaller projects that may not warrant the use of sheet piling, geotextile fabric, clean granular material, and wood decking can be placed within the project alignment. Sheet piling can also be used in intertidal or shallow freshwater areas. Combined with siltation curtains, piling can prevent the release of sediment-laden water to surrounding wetlands and waterways. The use of barge-mounted equipment can also be used in intertidal and shallow freshwater areas to access sensitive sites. Work barges can be floated into place on rising tides, and grounded out to provide suitable access with minimal or no long-term impacts. For construction of trenches in wetland areas, utility workers have developed specialized, tracked, trenching vehicles that can operate on soft, unstable soils. The vehicles work directly within the project alignment. Wide, low-pressure tires on vehicles that distribute loads across wetland soils and vegetation also reduce vehicle impacts. For dredging within wetlands, waterways, and waterbodies, clamshell dredge equipment fitted with covers and watertight buckets minimizes sediment washout and turbidity. Large construction projects typically require staging areas. Staging areas should be located outside wetlands and their designated buffer zones and should be paved to minimize erosion and groundwater impacts. Also, staging areas should include stormwater management systems designed to trap suspended sediments and to contain accidental releases of fuel oil, lubricants, and other potentially hazardous releases from equipment. Scheduling can minimize temporary, construction-related impacts. As a general rule, wetland work in temperate climates should be scheduled during winter and early spring when plants are dormant and the soils are frozen or well consolidated. Soil compaction is minimized, and site cleanup and rehabilitation during the coming peak growing season are facilitated. Other seasonal restrictions are often applied for work within coastal environments based upon the expected presence of commercially and recreationally important fish and wildlife species. Species susceptible to illtimed construction include spawning and migrating anadromous fish and shrimp, overwintering groundfish, and migratory waterfowl. Another method for minimizing the impacts of construction within wetlands is proper work sequencing. For example, minimizing the extent of clearing in front of the active trenching operation will reduce the potential for soil erosion into adjacent wetlands and reduce impacts to wildlife using the existing vegetative cover. Wherever possible, work that is required within wetland areas should be completed as quickly as possible, without excessive delays between the initial disturbance and rehabilitation. Trenching should be conducted as a single, continuous operation, involving clearing, installation, backfilling, and soil restoration. An open trench can act as a channel to dewater adjacent wetland areas and increase erosion and runoff impacts.

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EROSION AND SEDIMENTATION Sedimentation of wetlands can be avoided or minimized by preventing soil erosion and controlling already eroded sediments. There are numerous methods for erosion and sedimentation control, all of which seek to isolate and contain, to the maximum extent possible, sediment-laden runoff generated during project construction activities. The performance of these various methods in the field varies considerably depending upon the type of soils, water flows, exposure, and other site specific factors. Figure 2 summarizes some of the more popular sedimentation control methods. Critical elements of effective erosion and sediment control plans are listed in Table 3 (Brown and Caraco, 1997). Erosion and sedimentation control methods can be used singly or in combination. By limiting the amount of incremental and total land clearing, and maintaining existing ground cover to the maximum extent possible, potential runoff, gully creation, rutting, and airborne dust formation can be reduced to acceptable levels. Cleared land produces as much as 2000 times more sediment than uncleared land (Paterson et al., 1993). Where feasible, a project site layout should take advantage of existing vegetation between the clearing limits and adjacent wetlands. Buffers of at least 25 m in width are the most effective in filtering sediment from construction site runoff (Woodward, 1989). Vegetative buffers should also be preserved for projects with shoreline frontage to protect structures from wave and flooding impacts. Installation of hay bales within shallow cut-off trenches upgradient of wetland areas can be an effective and inexpensive perimeter control method. Bales should be staked to the ground, without gaps between bales. Bales should be routinely monitored, and bales damaged, moved, or destroyed during construction should be repaired. Construction specifications should provide for regular checks of the condition and effectiveness of the hay bale protection systems. Geotextile siltation fences can be wrapped around hay bales and staked into the ground to provide an extra measure of protection against the release of fine-grained materials. Siltation fence efficiency ranges from 35 to 86 percent depending upon site conditions (Horner et al., 1990; W&H Pacific and CH2M-Hill, 1993). Siltation curtains can also be used effectively in both wetlands and open water environments. Curtains can be used to surround subaqueous dredging operations, particularly those occurring within sheet piling, to isolate trench water from the surrounding environment. Curtains with flotation can also be installed around shoreline construction projects and anchored in place to isolate the work area. However, the effectiveness of these structures decreases significantly in areas of strong river currents, tidal flows, and large tidal ranges, particularly if the curtain is installed perpendicular to the current flow. In such cases, the siltation curtain experiences rollover or submergence and is susceptible to damage from debris. Therefore, siltation curtains are most effective in ponds, lakes, and other sheltered water bodies with little or no variation in water height. In any construction project, regardless of the proximity to wetlands or other adjacent sensitive habitats, construction specifications should require prompt stabilization of newly exposed soils, including stockpiled soil. Seeding and sodding are relatively inexpensive, and up to 99 percent effective in reducing erosion (Brown ©2001 CRC Press LLC

Figure 2

Erosion and sedimentation control methods (McManus, 1994). Black indicates the method is suitable for use in the environment; gray indicates the method is suitable with limitations.

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Table 3

Critical Elements of an Erosion and Sediment Control Plan (Adapted from Brown and Caraco, 1997)

Minimize clearing and grading Protect waterways and stabilize drainage ways Phase construction to limit soil exposure Stabilize exposed soils immediately Protect steep slopes and cuts Install site perimeter control to filter sediments Use settlement traps and basins for larger volumes Use experienced contractors to implement the plan Tailor the plan to specific site conditions Assess plan effectiveness after storms

and Caraco, 1997). Seeding is the least expensive option and is appropriate when temporary stabilization is required. Seeds can be broadcast by hand or hydroseeded. The latter is a mixture of seeds, water, fertilizer, lime, and mulch sprayed onto the soil. Sodding is more appropriate for permanently vegetated areas and provides immediate cover and greater resistance to higher flow velocities. The construction schedule should allow time for vegetation to become reestablished prior to the end of the growing season. In cases where this is not possible, more expensive but generally less effective measures, such as mulching or covering exposed areas with erosion control blankets, jute mats, or geotextile mats, should be employed. Mulches, blankets, and mats protect seeds from erosion, dehydration, and animals until the next growing season (Brown and Caraco, 1997). Mulches, consisting of straw, hay, fiber, or wood chips, are effective on flat or gently sloping areas. Erosion control blankets consist of a mulch material held together by a plastic netting, and jute mats are sheets of woven jute fiber. Effective on relatively level ground, both the blankets and the mats are stapled to the ground after seeding and degrade over time. Geotextile mats are more appropriate for steeper slopes and channels. The mats are typically laid on the soil surface and covered with topsoil and seed. As previously discussed, isolation of the active work area in both wetlands and open water areas is an effective method to limit the horizontal extent of disturbance, particularly in areas where significant dredging is required. In such cases, dredging open trenches beyond 1 m in depth requires side slopes which can range from 3:1 to 5:1 or greater, meaning that a 3-m-deep trench would disturb a minimum 20- to 33-m width of sediments. Clearly, this size dredging operation would require the handling and disposal of large amounts of excess dredged material. Conducting this work within sheet pilings allows a vertical sidewall, thereby reducing the volume of material to be handled and isolating the silt-laden trench water from surrounding marsh and other wetland areas. Open dredging within or adjacent to wetland areas can produce significant amounts of turbidity. If typical dredging equipment is used, for example, a bargemounted crane with a clamshell dredge bucket, methods are available which can reduce turbidity. These include establishing requirements that all lifts of a clamshell dredge bucket through the water column are vertical, that dredge buckets be used ©2001 CRC Press LLC

with covers and gasket seals to prevent washout of sediments and suitable filtering of water released from stockpiled dredged material. Hydraulic dredging can also be used in certain unconsolidated sediments to reduce turbidity. With this method, sediments are removed and pumped as a slurry to a settling barge or disposal site. While initial turbidity at the point of dredging is minimal, large amounts of water must be filtered and removed from sediments at the disposal site, and pumping limitations require that disposal occur in close proximity to the point of dredging. Construction will often require temporary stockpiling of soils, and care should be taken to continually spray these piles with water, or cover them, in order to prevent wind erosion and transport of fines. Similarly, newly graded access roads should be frequently sprayed with water or dust suppressants to reduce dust formation. The construction schedule should attempt to minimize the period of time where exposed stockpiles or unpaved road surfaces are required. Site grading and excavation activities in areas already served by drainage systems are a potential concern for sedimentation. Many parking lots, roadways, and other facilities use stormwater drainage systems that discharge directly into adjacent wetland areas. In order to minimize the impacts from run-off of sediment-laden water, existing catch basins and storm drains should be completely ringed with staked haybales and a layer of filter fabric. Other inlet protection methods include concrete block wrapped with wire and stones and placing geotextile fabric and stones directly over the inlet (Brown and Caraco, 1997). These sediment traps will allow stormwater flow to pass through, but will filter out significant amounts of suspended sediments. These structures also provide protection in the event of an accidental fuel oil spill, hydraulic hose rupture, or other hazardous material release, providing some measure of initial containment upgradient of adjacent wetland areas. As with all hay bale structures, the sediment traps need to be maintained and periodically replaced to ensure their effectiveness. Excavation for foundations, utility trenches, and other facilities will often extend below the existing water table, resulting in collection of groundwater within the excavation. In order to dewater these areas and prevent discharge of sediment-laden water into surrounding areas, various types of settling basins and detention structures can be constructed. Sediment removal efficiencies generally range from 60 to 90 percent, with higher efficiencies associated with wet storage (Brown and Caraco, 1997). These structures allow particulate matter to settle and gradually discharge filtered runoff. Figure 3 is a schematic representation of a typical settling basin which can be constructed upgradient of a wetland area using filter fabric and clean rip-rap material to effectively filter silts and sediments at a construction site. Concrete or fiberglass settling basins are also available for use as sedimentation control structures during dewatering operations and are often used on barges during dredging operations to filter water discharged from stockpiled dredged materials. Geotextile wetland filter bags have also been developed to serve as sedimentation and erosion control devices on construction sites (Figure 4). The true test of any sedimentation and erosion control plan will occur during the first significant rainfall event during construction. Thus, it is recommended that on-site resident inspectors monitor the success of the installed erosion control devices ©2001 CRC Press LLC

Ground Slope

15' - 20 (Typ.) or as Directed

Suitable Device to Dissipate Velocity

To Natural Water Course

Sediment Laden Water Sediment Free Water Pump Discharge Flat Stone Ground Slope Approved Filter fabric Mat Baled Hay or Straw

10'-15' (Typ.) or as Direcled

Pump Discharge Line

Suitable Velocity Dissipator Clean Stones (If Required) Flat Stone

Approved Filter Fabric Mat Sediment

Baled Hay or Straw as Directed

TYPICAL SECTION

SEDIMENT TRAP Figure 3

Settling basins are used in conjunction with dewatering operations to prevent discharge of sediment-laden water into wetlands. The basins are constructed upgradient of wetlands using filter fabric and clean rip-rap material.

during and immediately after a rainstorm or snowmelt. The hay bales, siltation fences, and other structures should be observed on, at least, a weekly basis to detect damage from wildlife, machinery, or other activities on site. Equally important, resident inspectors should conduct frequent visual observations of the adjacent wetlands or open water bodies to detect turbidity plumes resulting from on-site runoff. For certain subaqueous activities, significant shortterm increases in turbidity are unavoidable. Nevertheless, attention should focus on the effectiveness of the siltation curtains, dredging methods, and dewatering

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Wetland Filter Bag

Flow Pipe Water flowing out from the bag

Figure 4

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A geotextile bag can be used on construction sites to remove sediments from site runoff.

practices to ensure that surrounding background levels of turbidity are not significantly increased. For deepwater areas, the use of a Secchi disk or similar device will provide a qualitative measure of the water clarity and amount of suspended sediments during construction.

NITROGEN LOADING Nitrogen occurs in wetlands in various inorganic and organic forms (Mitsch and Knight, 1997). Ammonia, nitrate, and nitrite are the most important forms for wetland processes. Ammonia is an important nutrient for most wetland plants and autotrophic bacteria and is a growth limiting compound in coastal waters. Coastal waters are the most highly fertilized ecosystems on earth (Nixon, 1986; Kelly and Levin, 1986). In natural waters, ammonia is readily oxidized resulting in oxygen consumption. Ammonia in its unionized form (NH3) is toxic to many forms of aquatic life at low concentrations (0.2 ppm). Nitrate is reduced to nitrite in oxygen-poor environments and is conservative in groundwater. In infants, nitrite combines with fetal hemoglobin preventing oxygen transport. This potentially fatal condition is known as methemoglobinemia. High nitrate concentrations have also been linked to carcinogenic effects (U.S. Environmental Protection Agency, 1990). The primary source of nitrogen, particularly in residential areas, is domestic wastewater (Cape Cod Commission Water Resources Office, 1992; Valiela et al., 1997). For residential septic systems, the concentration of nitrogen depends upon soil characteristics, loading rates, distance to the impervious stratum, distance to the water table, time of year, and depth below the leach field (Suffolk County Department of Health Services, 1983; Canter and Knox, 1985). Typical nitrate nitrogen concentrations range from 33 to 41 ppm (Cape Cod Planning and Economic Development Commission and U.S. Environmental Protection Agency, 1978; Nassau-Suffolk Regional Planning Board, 1978; Suffolk County Department of Health Services, 1983; IEP, 1988; Robertson et al., 1991). Nitrogen concentrations in nonresidential areas are less well known and vary widely in character and quantity. In general, nitrate nitrogen concentrations are higher when no gray water (i.e., sinks and showers) is present. Secondary sources of nitrogen include lawn fertilizer, atmospheric nitrogen, and runoff from impervious surfaces. Nitrogen levels from lawn fertilizer vary with soil type, application rate, precipitation, temperature, turf type, and nitrogen form. Typical fertilizer application rates range from 0.8 to 1.7 kg/100 m2 (1.7 to 3.8 lb nitrogen/1000 ft2) up to 4.7 kg/100 m2 (9.6 lb nitrogen/1000 ft2) for golf course greens (Nassau-Suffolk Regional Planning Board, 1978; Cape Cod Planning and Economic Development Commission, 1979; Eichner and Cambareri, 1990). Nitrogen leaching rates vary widely, from 0 to 60 percent (Nassau-Suffolk Regional Planning Board, 1978; Brown et al., 1982; IEP, 1988; Petrovic, 1990). Controlled application of fertilizer to healthy turf can eliminate or minimize leaching (Petrovic, 1990).

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Atmospheric nitrogen loading, largely from precipitation, is relatively minor compared to potential loading from wastewater and fertilizers. Precipitation concentrations in the United States range from 0.14 to 1.15 ppm nitrate nitrogen (Loehr, 1974). Dry deposition of nitrogen may double this concentration (Valiela et al., 1997). Nitrogen loading off of impervious surfaces is, however, significant, ranging from 0.41 to 1.75 ppm nitrate nitrogen and 1.13 to 10 ppm total nitrogen (IEP, 1988). Recharge rate off of impervious surfaces is poorly understood. The TR-55 stormwater modeling program assumes a recharge rate of 98 percent (Soil Conservation Service, 1986) and the Water Resources Office of the Cape Cod Commission (1992) assumes a 90 percent recharge rate. Planning Guidelines Based upon the threat of methemoglobinemia and cancer, the U.S. Environmental Protection Agency has established a limit of 10 ppm nitrate nitrogen in drinking water (U.S. Environmental Protection Agency, 1990). Studies on Long Island, NY, revealed that average nitrate nitrogen concentrations of 6 ppm led to violation of the 10 ppm criteria 10 percent of the time, and that average concentrations of 3 ppm led to violation of the 10 ppm criteria 1 percent of the time (Nassau-Suffolk Regional Planning Board, 1978; Long Island Regional Planning Board, 1986). Based upon this information, Long Island recommended that areas be sewered if the average nitrate nitrogen concentration exceeds 6 ppm. The Cape Cod Planning and Economic Development Commission (1978) and Cape Cod Commission Water Resource Office (1992) adopted a 5 ppm nitrate nitrogen standard. A second consideration in the establishment of nitrogen standards is protection of coastal embayments. Each embayment has a unique critical nitrogen loading rate dependent upon embayment morphology and flushing rate. For example, U.S. Environmental Protection Agency and the Massachusetts Executive Office of Environmental Affairs (1991) developed recommended nitrogen loading limits for Buzzards Bay (Table 4). Recommended nitrogen loads are lower in shallower embayments than deep embayments and in higher quality waters than lower quality waters. Based upon studies of Waquoit Bay, MA, Valiela et al. (1997) offer general recommendations that wastewater disposal within 200 m of shore be limited, that homes be required to use multiple leaching fields or septic systems, and that fertilizer use be controlled on near-shore lawns. Estimating Nitrogen Loads Several methods have been used to estimate nitrogen loading to groundwater and coastal embayments. For example, the Cape Cod Commission Water Resources Office (1992) recommends a site-specific mass balance analysis for relatively small sources and a cumulative loading analysis for proposed sources in groundwater recharge zones and relatively large sources. The former estimates nitrogen and water uses within the boundaries of a development, whereas the latter is a recharge zone-wide analysis for

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Table 4

Recommended Nitrogen Loading Limits for Coastal Embayments (Adapted from U.S. Environmental Protection Agency and Massachusetts Executive Office of Environmental Affairs, 1991) Embayment

Shallow Flushing < 4.5 Flushing > 4.5 Deep Select rate resulting in lesser annual loading

Outstanding Resource Areas3

SB Waters1

SA Waters2

350 mg/m3/Vr4 30 g/m2/yr

200 mg/m3/Vr 15 g/m2/yr

100 mg/m3/Vr 5 g/m2/yr

500 mg/m3/Vr 45 g/m2/yr

260 mg/m3/Vr 20 g/m2/yr

130 mg/m3/Vr 10 g/m2/yr

1

Excellent for fish, other aquatic life and wildlife, primary and secondary contact recreation, and shellfish harvesting with depuration.

2

Excellent for fish, other aquatic life and wildlife, primary and secondary contact recreation, and shellfish harvesting without depuration.

3

Outstanding socioeconomic, recreational, ecological, or aesthetic value.

4

Vollenweider flushing term; Vr equals r /1 +

r r equals flushing time (years).

existing and proposed conditions. The models estimate the nitrate nitrogen load by totaling the nitrogen inputs from wastewater, impervious surfaces (roof and paved), and fertilizer, and dividing nitrogen inputs by total water inputs. Figure 5 illustrates a mass balance analysis process for a hypothetical 20 house residential development. In this example, as typically occurs, the majority of nitrate nitrogen originates in wastewater. Valiela et al. (1997) developed a model to estimate atmospheric, fertilizer, and wastewater nitrogen loading to watersheds and receiving waters. Based upon data from the Waquoit Bay Land Margin Ecosystems Research Project and syntheses of published information, the model estimates nitrogen inputs to surfaces of the major types of land use within the landscape. Nitrogen losses in the various watershed compartments are then estimated. For example, atmospheric and fertilizer nitrogen are lost in vegetation, soils, the vadose zone, and aquifer. Wastewater nitrogen losses occur in septic systems and effluent plumes and during diffuse transport in aquifers. Nitrogen loss calculations are conducted separately for each major type of land cover. The model was developed for Waquoit Bay, MA, but is believed applicable to other rural to suburban watersheds underlain by unconsolidated sandy sediments. According to the model, the atmosphere is the largest contributor of nitrogen to the watershed, but wastewater is the largest source of nitrogen to receiving estuaries (Table 5). The model implies that estuary management should focus on wastewater disposal, particularly within 200 m of shore. The authors also suggest that installation of multiple conventional leaching fields or septic systems in high flow parcels could be beneficial. Other recommendations include control of fertilizer use on near-shore lawns and conservation of parcels of accreting natural vegetation. The latter effectively intercept atmospheric nitrogen.

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Model Parameters Impervious Surfaces Wastewater NO3 35 mg/L Roof Area 2,000 m2 Roof runoff NO3 0.75 mg/L Paved Area 4,000 Paved runoff NO3 1.5 mg/L Natural Area 20,000 m2 Fertilizer 1000 g/100 m2 Lawn Area 10,000 m2 Fertilizer leach rate 0.25 Wastewater 400 L/bedroom Impervious surface recharge rate 1 meter/year Natural area recharge rate 0.45 meter/year Roof 2,000 m2 × 1 m/yr × 1,011 L/m3 × 1 yr/365 day L runoff/day × 0.75 mg NO3/L =

5,539.7 L/day 4,154.8 mg/day

Paved 4,000 m2 × 1 m/yr × 1,011 L/m3 × 1 yr/365 day L runoff/day × 1.5 mg NO3/L =

11079.5 L/day 16,619.3 mg/day

Natural 20,000 m2 × 0.45 m/yr × 1,011 L/m3 × 1 yr/365

24,928.8 L/day

Lawn 10,000 m2 × 1000 mg/100 m2/yr × 1 yr/365 days 68.5 mg/day Wastewater 3.5 bedrooms × 400 L/bedroom × 20 bedrooms L wastewater per day × 35 mg NO3/L=

28,000 L wastewater per day 980,000 mg/day

Cumulative nitrate nitrogen load 4, 154.8 + 16, 619.3 + 68.5 + 980, 000 mg ------------------------------------------------------------------------------------------------------------ = 14.39 mg/L 5, 539.7 + 11079.5 + 24, 928 + 28, 000 liters Figure 5

Table 5

Nitrate nitrogen loading calculations for a hypothetical 20 house residential development with an average of 3.5 bedrooms per house.

Percent Nitrogen Input to the Watershed, Loss within the Watershed, and Input to Estuaries According to the Waquoit Bay Land Margin Ecosystems Research Model (Adapted from Valiela et al., 1997)

Source

Input to Watershed

Losses within Watershed

Input to Estuaries

Atmospheric Fertilizer Wastewater

56 14 27

89 79 65

30 15 48

STORMWATER RUNOFF Development is accompanied by an increase in impervious surfaces which increases stormwater runoff and decreases infiltration and evapotranspiration. This decreases the time for the runoff to reach wetlands and streams, increasing the

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frequency and severity of erosion and downstream flooding. During periods of prolonged dry weather, water tables and stream flows are reduced leading to a loss of wetland and aquatic habitats. Hydraulic and biological changes to streams occur when 10 to 20 percent of a watershed has impervious surfaces [Massachusetts Department of Environmental Protection and Massachusetts Office of Coastal Zone Management (DEP/CZM), 1997]. Typical impervious area percentages range from 20 to 40 percent for low density residential developments to 95 to 100 percent for business districts (Brach, 1989). Stormwater runoff is contaminated with a variety of pollutants that have various effects on wetland and aquatic habitats (Bingham, 1994; DEP/CZM, 1997). Nutrients from animal wastes, human wastes, and fertilizers induce algal growth and lower dissolved oxygen. Sedimentation also lowers dissolved oxygen as well as increasing turbidity and smothering aquatic life. Pathogens contaminate drinking water, swimming areas, and shellfish. Metals, hydrocarbons, organic chemicals, and salt increase the toxicity of the water column and sediments and may bioaccumulate in aquatic organisms. Stormwater impacts to wetland and aquatic habitats can be avoided or minimized through careful planning, use of nonstructural practices, and use of structural best management practices (BMPs). These measures reduce the volume of runoff, store runoff water, promote infiltration of stormwater to groundwater, and remove pollutants. Planning and Nonstructural Practices Effective stormwater management planning will minimize the size and cost of structural requirements. Planning and nonstructural practices can mitigate most stormwater impacts to wetlands and aquatic habitats for small developments. For larger developments, planning and nonstructural practices can significantly reduce the extent and, therefore, the cost of structural BMPs. Perhaps the most important planning technique available is minimizing impervious surfaces. Minimization of impervious surfaces is critical in recharge areas, especially those associated with drinking water supplies. Methods for minimizing impervious surfaces include the maintenance of natural buffers and drainageways. This allows infiltration of runoff, reduces runoff velocity, and removes suspended solids. Other methods include minimizing steep slopes, reducing building footprints and parking areas, limiting the width of roadways and the use of sidewalks, using shallow grassed roadside swales and parking lot islands, using turf pavers, gravel, and other porous surfaces, and maintaining as much predevelopment vegetation as possible (DEP/CZM, 1987). Other planning techniques are also available for managing stormwater. Developments can be “fit” to the terrain by designing road patterns that match the landform. Grassed waterways, vegetated drainage channels, and water quality swales can be constructed along roadways to channel runoff (DEP/CZM, 1987). Similarly, natural,

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vegetated drainageways can be preserved, helping to maintain predevelopment flood volumes, peak discharges, and base flows. Pollutants will be filtered by vegetation and will bind to underlying soils and organic matter. The planning process should also attempt to mimic predevelopment hydrologic conditions including peak discharge, runoff volume, infiltration capacity, base flow levels, groundwater recharge, and water quality. Several nonstructural techniques can also be effective in managing stormwater quantity and quality. Developments, especially commercial developments, will benefit from preparation of a pollution prevention plan that identifies potential sources of pollution and ensures implementation of practices that reduce pollutants in stormwater discharges (DEP/CZM, 1987). Example techniques include proper pesticide and fertilizer application, pet waste management, the proper storage, use, and disposal of hazardous chemicals, and proper operation and maintenance of septic systems. Areas accustomed to winter snowfalls use sand and salt to mitigate icy roadways. Street and parking lot sweeping can reduce total suspended solids like sand and salt by 5 to 80 percent. Vacuum sweepers tend to be more effective than mechanical sweepers. Much of the solids also ends up in catch basins, which benefit from regular cleaning. Salt (NaCl) toxicity can be minimized by using alternative de-icing compounds such as calcium chloride (CaCl2) and calcium magnesium acetate (CMA), and by designating “low salt” areas on roadways near wetlands and streams. Deicing compounds should be stored on sheltered, impervious pads, and stored snow should be placed where it can slowly infiltrate into the ground. Structural BMPs Structural BMPs are required when planning and nonstructural practices alone are insufficient to mitigate stormwater impacts. There are five major categories of stormwater structural BMPs: pretreatment, detention basins/retention ponds, vegetated treatment, infiltration, and filtration (Table 6). As with planning and nonstructural practices, the goals of a stormwater management design using structural BMPs should be to approximate predevelopment runoff rates and volume and to maximize pollutant removal. In many instances, the most effective design will incorporate several BMPs in series. Selecting a BMP requires consideration of the quantity of stormwater runoff to be produced, the water quality to be achieved, the proximity of critical areas (e.g., wetlands, aquatic habitats), maintenance requirements, aesthetics, cost, and site constraints (DEP/CZM, 1987; Schueler, 1987; Horner et al., 1994). In many instances, site physical characteristics limit or determine BMP selection. For example, sandy soils will inhibit the use of ponds but will facilitate infiltration BMPs. Pond BMPs require a relatively large contributing drainage area, whereas infiltration BMPs are restricted to a relatively small drainage area. A water table at or near the surface is essential for wetlands and wet ponds but will preclude infiltration BMPs. Swales and trenches are most effective when slopes are greater than 5 percent but less than 20 percent. Wet ponds and wetlands should not outflow to cold water streams, and infiltration BMPs should not be located close to foundations.

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Table 6

The Major Types of Structural Best Management Practices for Stormwater Pretreatment Sediment traps Water quality inlets Catch basins Detention/retention ponds Extended detention ponds Wet retention ponds Vegetated treatment Drainage channels Water quality swales Constructed wetlands Infiltration Dry wells Trenches Basins Filtration Basins

Pretreatment Sediment traps, water quality inlets, and catch basins remove debris, oil, and grease, and sediment and associated pollutants. Settling is the primary treatment mechanism. Sediment traps are on-line units, whereas water quality inlets and catch basins are off-line units. Pretreatment BMPs should only be used as pretreatment devices for other stormwater management technologies because they have limited storage capacity, short detention times, and do not remove soluble pollutants. Essential elements of detention basin/retention pond and vegetated systems, pretreatment BMPs are applicable to other BMPs as well. The longevity of pretreatment BMPs is high with frequent maintenance. A sediment trap is an excavated pit or cast structure 1 to 2 m (3 to 6 ft) deep. Typically, sediment traps can accommodate the 2- and 10-year storms. Water quality inlets and catch basins are chambered, underground retention systems. Water quality inlets have multiple chambers with permanent pools of water in the first couple of chambers. Floatable debris and sediments are trapped in the first chamber, oil and grease are trapped in a second chamber, and water is routed out of a third chamber into the storm drain or another BMP. Catch basins operate similarly, but only a single chamber is present. Water quality inlets and catch basins are particularly applicable to parking lots and other areas with substantial vehicular traffic. Detention Basins/Retention Ponds Detention basins capture and hold stormwater for 24 h or more, which permits solids to settle and downstream flooding to be reduced. Typically, a detention basin will have a lower stage capable of detaining smaller storms, and an upper stage capable of detaining larger, less frequent storms. One of the less expensive BMPs ©2001 CRC Press LLC

capable of controlling both stormwater quantity and quality, detention basins remove significant levels of sediment and sorbed pollutants. Detention basins are largely ineffective at removing soluble pollutants. Retention ponds use a deep, permanent pool of water to remove both solid and soluble pollutants (Figure 6). Soluble pollutants, such as nutrients, are removed by the biological activity of algae and fringing wetland. Retention ponds also have additional storage capacity to control peak discharge rates. A pool depth of 0.9 to 1.8 m (3 to 6 ft) is recommended to optimize particle settling.

Figure 6

Retention ponds use a deep, permanent pool of water to remove solid and soluble pollutants.

Both detention basins and retention ponds require a contributing watershed of at least 4 ha (10 acres). Inflow points should have energy dissipaters and a forebay or settling zone to trap course sediments. The original design should account for the gradual accumulation of sediment. A routine inspection should be conducted at least once a year, and sediment should be removed as necessary. Vegetated Treatment Treatment by vegetated BMPs ranges from simple drainage channels to constructed wetlands. Each vegetated BMP, to a degree, controls peak discharges by reducing runoff velocity and promoting infiltration and reduces pollutants by trapping, filtering, and infiltration. Both drainage channels and water quality swales are most effective when the percentage of impervious cover in the contributing area is relatively small and the slope is minimal (0 to 5 percent). Constructed wetlands require relatively large contributing drainage areas to maintain dry weather base flows. All vegetated BMPs benefit from inclusion of a sediment forebay to settle large particles. Drainage channels have grass or some other channel lining so runoff can be conveyed during large storm events without causing erosion. Channels are applicable to residential and other low to moderate density areas and can be used in parking lots. A minimum channel length of 30 m (10 ft) is recommended to optimize pollutant removal. ©2001 CRC Press LLC

Water quality swales are drainage channels enhanced to remove stormwater pollutants and are typically sized to accommodate the 10-year storm. The three major types of water quality swales are dry swales, wet swales, and grassed swales (DEP/CZM, 1987; Claytor and Schueler, 1996). Dry swales allow for filtering or infiltration through the bottom of the swale. Underlying soils should be permeable, and the seasonal high water table should not be within 0.7 to 1.3 m of the swale bottom. Wet swales are useful when the water table is at or near the soil surface, or soils are poorly drained (Figure 7). Sediment accumulation, filtration, and vegetation uptake remove pollutants. Grassed swales resemble dry swales in that underlying soils are relatively permeable, but they are vegetated with moisture-tolerant grass species that produce a fine, uniform, dense cover. Filtration, vegetation uptake, sediment accumulation, and to some extent infiltration are the pollutant removal mechanisms.

Figure 7

Water quality swales remove stormwater pollutants by filtration, vegetation uptake, sediment accumulation, and infiltration.

Constructed wetlands are the most complex, and most expensive, vegetated treatment BMP. Designed to mimic elements of natural wetlands, constructed wetlands reduce peak discharge and reduce the occurrence of downstream flooding, settle particulate pollutants, and facilitate the uptake of pollutants by vegetation. Constructed wetlands require relatively large contributing drainage areas to maintain dry weather base flows, and construction costs are relatively high. Chapter 10 discusses constructed wetlands for the treatment of stormwater and other waste waters. Infiltration Infiltration BMPs are aggregate-filled devices which capture stormwater runoff and gradually exfiltrate the runoff through the bottom of the device into the subsoil ©2001 CRC Press LLC

and groundwater. Examples include dry wells and infiltration trenches and basins. Infiltration BMPs require permeable underlying soils (minimum 1.3 cm/h) and a groundwater level at least 0.7 m (2 ft) below the bottom of the infiltration device. To avoid contaminating groundwater, infiltration BMPs should not be used when runoff is highly contaminated. Infiltration BMPs can be used to manage peak discharges and reduce runoff volume. Regular maintenance is required because infiltration BMPs are susceptible to clogging by sediments. Dry wells are small pits used for infiltrating relatively good quality water such as roof runoff. With a storage time of 48 to 72 h, dry wells typically have a contributing drainage area of less than 0.4 ha (1 acre). Infiltration trenches are applicable to sites with gentle slopes (5 percent or less), groundwater levels at least 1.2 m (4 ft) below the surface, and contributing drainage areas of 2 ha (5 acres) or less. In addition to reducing runoff volume and peak discharge, infiltration trenches remove soluble and particulate pollutants from runoff. Infiltration trenches require pretreatment by inlets, sumps, swales, or forebays to remove sediment and oil, and grease which may clog the trench. Infiltration basins resemble detention/retention ponds but are constructed over permeable soils. The contributing drainage area should be 6 ha (15 acres) or less, depth to seasonal high water table at least 0.7 m (2 ft), and the soil infiltration rate 1.3 to 6 cm (0.5 to 2.4 in.) per hour. A sediment forebay or other pretreatment device is necessary to capture coarse particulate pollutants. Infiltration basins are designed to have a retention time of 48 to 72 h. Filtration Filtration basins consist of sand, peat, or compost underlain by gravel and perforated underdrains. Filter fabrics may be installed at the top of the bed, and between the filter media and gravel bed, to minimize clogging. Pollutant removal is achieved by settling on top of the basin and by straining pollutants through the filtering media. A sedimentation chamber designed to remove coarse pollutants precedes the filter basin. Filter basins are applicable to small drainage areas of 0.2 to 2 ha (0.4 to 4 acres) for most development situations. A design filtration rate of 5 cm (2 in.) per hour is typical, and the filter should drain within 24 h.

REFERENCES Bingham, D., Wetlands for stormwater treatment, in Applied Wetlands Science and Technology, Kent, D. M., Ed., Lewis Publishers, Boca Raton, FL, 1995. Brach, J., Protecting Water Quality in Urban Areas: Best Management Practices for Minnesota, Minnesota Pollution Control Agency, Division of Water Quality, St. Paul, MN, 1989. Brown, K. W., Thomas, J. C., and Duble, R. L., Nitrogen source effect on nitrate and ammonium leaching and runoff losses from greens, J. Agron., 74, 947, 1982. Brown, W. E. and Caraco, D. S., Muddy water in - muddy water out?: a critique of erosion and sediment control plans, Watershed Prot. Tech., 2(3), 393, 1997.

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Canter, L. W. and Knox, R. C., Septic Tank System Effects on Groundwater Quality, Lewis Publishers, Chelsea, MI, 1985. Cape Cod Commission Water Resources Office, Nitrogen Loading, Technical Bulletin 91-001, Barnstable, MA, 1992. Cape Cod Planning and Economic Development Commission, Water Supply Protection Project, final report, Barnstable, Bourne, Brewster, Dennis, and Yarmouth, Barnstable, MA, 1979. Cape Cod Planning and Economic Development Commission and U.S. Environmental Protection Agency, Draft environmental impact statement and proposed 208 water quality management plan for Cape Cod, Barnstable, MA, 1978. Claytor, R. A. and Schueler, T. R., Design of Stormwater Filtering Systems, Center for Watershed Protection, prepared for Chesapeake Research Consortium, Solomons, MD, 1996. Dahl, T. E., Wetland Losses in the United States 1780s to 1980s, U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C., 1990. Eichner, E. M. and Cambareri, T. C., The Cape Cod Golf Course Monitoring Project, Cape Cod Commission, Water Resources Office, Barnstable, MA, 1990. Heimlich, R. and Melanson, J., Wetlands lost, wetlands gained, Natl. Wetlands Newsl., May–June, 17(3), 1, 23, 1995. Hollis, T. and Bedding, J., Can we stop wetlands from drying up?, New Sci., July, 31, 1994. Horner, R. R., Skupien, J. J., Livingston, E. H., and Shaver, H. E., Fundamentals of Urban Runoff Management: Technical and Institutional Issues, Terrene Institute, Washington, D.C., 1994. Horner, R. R., Guedry, J., and Kortenhog, M. H., Improving the Cost Effectiveness of Highway Construction Site Erosion and Pollution Control, Washington State Transportation Center, Federal Highway Administration, Seattle, WA, 1990. IEP, Water Resources Protection Study: Town of Yarmouth, Massachusetts, Sandwich, MA, 1988. Kelly, J. R. and Levin, S. A., A comparison of aquatic and terrestrial nutrient cycling and production processes in natural ecosystems, with reference to ecological concepts of relevance to some waste disposal issues, in The Role of the Oceans as a Waste Disposal Option, Kullenberg, G., Ed., NATO Advanced Research Workshop Series, Reidel, Dordrecht, The Netherlands, 1986, 154. Loehr, R. C., Characteristics and comparative magnitude of nonpoint sources, J. Water Pollut. Control Fed., 46, 1849, 1974. Long Island Regional Planning Board, Special Groundwater Protection Area Project for the Oyster Bay Pilot Area and Brookhaven Pilot Area, 1986. Massachusetts Department of Environmental Protection and Massachusetts Office of Coastal Zone Management, Stormwater management, Vol. 2, Stormwater Technical Handbook, MADEP, 1997. McManus, K., Wetlands avoidance and impact minimization, in Applied Wetlands Science and Technology, Kent, D. M., Ed., Lewis Publishers, Boca Raton, FL, 1994, 105. Mitsch, W., The world’s wetlands and SWS—a call for an international view, Wetlands Bull., September, 1, 4, 1995. Mitsch, W. H. and Knight, R. L., Treatment Wetlands, Lewis Publishers, Boca Raton, FL, 1997. Nassau-Suffolk Regional Planning Board, The Long Island Comprehensive Waste Treatment Management Plan, Hauppauge, NY, 1978. Nelson, K. A., Design considerations for segmental retaining walls in water environments, Land Water, July/August, 22, 1995.

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Nixon, S. W., Nutrients and the productivity of estuarine and coastal marine ecosystems, J. Limnol. Soc. S. Afr., 12, 43, 1986. Paterson, R. G., Luger, M. I., Burby, R. J., Kaiser, E. J., Malcolm, H. R., and Beard, A. C., Costs and benefits of erosion and sediment control: the North Carolina experience, Environ. Manage., 17(2), 167, 1993. Petrovic, A. M., The fate of nitrogenous fertilizers applied to turfgrass, J. Environ. Qual., 19(1), 1, 1990. Robertson, W. D., Cherry, J. D., and Sudicky, E. A., Groundwater contamination from two small septic systems on sand aquifers, Ground Water, 29(1), 82, 1991. Schueler, T. R., Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban BMPs, Metropolitan Washington Council of Governments, Washington, D.C., 1987. Soil Conservation Service, Urban Hydrology for Small Watersheds, 2nd ed., Technical Release 55, U.S. Department of Agriculture, Washington, D.C., 1986. Suffolk County Department of Health Services, Pilot Plant Study: Nitrogen Removal in Modified Residential Subsurface Sewage Disposal System, Phase 2—Additional Investigations, Hauppauge, NY, 1983. U.S. Congress, National Environmental Policy Act, PL 91-190, 42 USC4321, Federal Register, Vol. 43, U.S. Government Printing Office, Washington, D.C. U.S. Environmental Protection Agency, 1990. U.S. Environmental Protection Agency and Massachusetts Executive Office of Environmental Affairs, 1991. U.S. Office of Technology Assessment, Wetlands: Their Use and Regulation, U.S. Congress, Washington, D.C., 1984. Valiela, I., Collins, G., Kremer, J., Lajtha, K., Geist, M., Seely, B., Brawley, J., and Sham, C. H., Nitrogen loading from coastal watersheds to receiving estuaries: new method and application, Ecol. Appl., 7(2), 358, 1997. W&H Pacific and CH2M-Hill, Demonstration project using yard debris compost for erosion control, Portland Metropolitan Service District, Portland, OR, 1993. Woodward, S. E., The Effectiveness of Buffer Strips to Protect Water Quality, Master’s thesis, University of Maine, Orono, ME, 1989.

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Zentner, John “Wetland Enhancement, Restoration, and Creation” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

CHAPTER

6

Wetland Enhancement, Restoration, and Creation John Zentner

CONTENTS Site Selection and Analysis Topography Vegetation Association Mapping Site History and Current Status Hydrological Analysis Soil Analysis Cultural Constraints Adjacent Site Conditions The Use of Template Associations Small-Scale Experimental Construction Goal Setting Elements of a Goal Statement Goal-Setting Process Practicability Construction Design Geography Size and Shape Location Slope Adjacent Uses Hydrology Hydroperiod and Depth Water Supply Soil

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Vegetation Succession Planting Design Plant Selection Stock Selection Planting Density Weed Control Cultural Issues Mosquitoes Water Quality Implementation Construction Sequencing Protective Flagging Weed Removal Salvaging Grading Planting Water Supply Fencing As Builts Maintenance Weed Control Erosion Control Herbivory Plant Care Irrigation System Maintenance Litter Removal General Maintenance Frequency Minimizing Maintenance Efforts Research Needs References

Freshwater wetlands develop at elevations above open water aquatic habitats and below uplands. They are found in a wide range of hydrologic conditions, from permanently flooded (to a depth of 1 m) to seasonally saturated. Freshwater wetlands occur on a wide variety of soil types including both organic and mineral soils, as well as in nonsoil conditions. Most freshwater wetlands are either freshwater marshes or riparian woodlands. Freshwater marshes are dominated by herbaceous emergents and can be divided into three general categories reflective of hydrology (Figure 1). Wet meadows are temporarily or intermittently flooded and dominated by graminoids and Juncaceae. In the United States, seasonal marshes are seasonally flooded or saturated and dominated by Cyperaceae and Juncaceae. Perennial marshes are permanently or

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UPLAND

Hydrology Dominant Plants Figure 1

WET MEADOW

SEASONAL MARSH

PERENNIAL MARSH

Temporarily flooded or intermittently flooded

Seasonally flooded or saturated

Permanently flooded or semi-permanently flooded

Grasses, rushes

Sedges, rushes

Cattail, bulrush, tules

OPEN WATER

Freshwater marshes are dominated by herbaceous emergents and can be divided into three hydrological categories: perennial marsh, seasonal marsh, and wet meadow.

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semipermanently flooded and dominated by tall emergents such as cattails (Typha latifolia) or bulrush (Scirpus acutus). Riparian woodlands are dominated by shrubs and trees and are characterized by impermanent and varying periods of inundation or root zone saturation during the growing season. Compared to freshwater marshes, riparian woodlands occur on relatively permeable and well-oxygenated substrates. As with freshwater marshes, riparian woodlands can be categorized by hydrological regime (Figure 2). High terrace woodlands are temporarily flooded and dominated by a variety of species, especially oaks (Quercus spp.), that are typified by heavy seeds with relatively longer viability. Mid-terrace woodlands are seasonally flooded and generally dominated by green ash (Fraxinus pennsylvanica), sycamore (Platanus occidentalis), and other species with medium weight seeds. And low terrace woodlands are semipermanently flooded and generally dominated by willows (Salix spp.), silver maple (Acer saccharinum), and similar species with relatively light seeds of limited viability. These categories correspond to Categories V (higher hardwood wetlands), IV (medium hardwood wetlands), and III (lower hardwood wetlands), as described by Cowardin et al. (1979), Larson et al. (1981), and Clark and Benforado (1981). Coastal wetlands share many of the characteristics of freshwater wetlands and are generally defined as those wetlands that lie within the realm and effects, however minor, of tidal salt water. As such, coastal wetlands include saltmarsh, fresh and brackish tidal marsh, and, in tropical waters, mangrove. Saltmarsh is the most ubiquitous type of coastal wetland, occurring on all coasts where appropriate substrate and tidal regimes are present (Figure 3). Saltmarshes are distributed over a relatively broad salinity range, from the high intertidal zone to the oligohaline habitats upstream on tidal tributaries where salinity may never exceed 10 parts per thousand. In the United States, various species of cordgrass (Spartina spp.) are dominant, with rushes (Juncus spp.) also common. On the Pacific Coast, Spartina foliosa and pickleweed (Salicornia virginica) are common. On the Gulf Coast and in the southeast, other species of cordgrass (Spartina alterniflora, S. patens), saltgrass (Distichlis spicata), and black needlerush (Juncus roemerianus) are typical. Sawgrass (Cladium jamaicense) marshes, such as the Everglades, occur in more brackish water. On the Atlantic Coast and to the northeast, Spartina cynosuroides, S. alterniflora, J. roemerianus, and some other species are common. Wax myrtle (Myrica cerifera) and groundsel tree (Baccharis halimifolia) are typical shrubs associated with salt marshes from the Gulf Coast to New England. Oligohaline (salinity of 0.5 to 5.0 ppt) and tidal freshwater marshes (salinity is less than 0.5 ppt) are herbaceous wetlands located in tidally influenced rivers or streams. The plant community exhibits a diverse mixture of true marine species and typical freshwater taxa that tolerate low salinities (Cowardin et al., 1979; Lewis, 1990). Mangrove forests are limited in distribution to subtropical and tropical zones (Figure 4). In the United States, they occur predominantly in southern Florida, sparsely along the Gulf Coast to the Laguna Madre of Texas, and extensively in Puerto Rico (Kuenzler, 1974). Many species of trees of different families are called mangroves, with black mangrove (Avicennia germinans), red mangrove (Rhizophora mangle), and white mangrove (Laguncularia racemosa) common to the ©2001 CRC Press LLC

UPLAND

Hydrology Dominant Plants Figure 2

HIGH TERRACE WOODLAND

MID-TERRACE WOODLAND

LOW TERRACE WOODLAND

Temporarily flooded

Seasonally flooded

Semi-Permanently flooded

Oaks

Green Ash, Sycamore

Willows, Silver Maple

Riparian woodlands are dominated by shrubs and trees. As with freshwater marshes, riparian woodlands can be categorized by hydrological regime: semipermanently flooded, seasonally flooded, and temporarily flooded.

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Figure 3

Saltmarshes are the most widely distributed of coastal wetlands. They occur over a relatively broad salinity range from the high intertidal zone to oligohaline habitats on tidal tributaries.

United States. There are an additional 31 species worldwide (Tomlinson, 1986). All mangroves have features in common that are adaptations for survival in the saline conditions of the intertidal zone (Tomlinson, 1986). Morphological adaptations include the aerial roots (pneumatophores) of black mangrove that provide for gas exchange and the viviparous, floating propagules of red mangroves. In fact, nearly all species of mangroves are viviparous, with the white mangrove being an exception. Physiological mechanisms for dealing with salt excretion or exclusion are also characteristic of mangroves. Lewis (1990) recently defined wetland enhancement, restoration, and creation. Enhancement is an increase in values afforded to a specific vegetation association by construction actions. Restoration is the recreation of a specific vegetation association on a site where that association was once known to occur. Creation is the construction of a wetland from an upland or aquatic site. The term construction will be used to encompass enhancement, restoration, and creation in this chapter. The earliest wetland construction projects may have occurred many thousands of years ago with the manipulation and creation of freshwater and coastal wetlands to enhance rice or fish harvests. Waterfowl conservation and hunting organizations have been responsible for numerous wetland construction projects in this century. New York, especially, had numerous small freshwater marshes created in the mid1950s (Dane, 1959). Specific problems associated with wetlands, such as nuisance mosquitoes, have also resulted in a number of useful research and enhancement practices. More recently, interest in wetland construction is a response to regulatory requirements. Nevertheless, there is also a greater public interest and understanding

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Figure 4

Mangrove forests are found throughout the subtropics and tropics. The tree species which comprise mangrove forests have morphological and physiological adaptations for surviving in intertidal saline conditions.

of the environmental values of wetlands and a desire for the recreation of lost or diminished landscapes and values. This chapter discusses the construction of freshwater marshes, riparian woodlands, and coastal wetlands. The construction process is described in five steps inherent to designing, building, and maintaining wetland landscapes. These steps are site analysis, goal setting, construction design, implementation, and maintenance. Implicit in these steps are two tenets. First, specification of a target vegetation association (TVA) is the primary goal. A TVA provides the habitat for any plant or wildlife populations that may be desired on the project site and, because of its structural nature, facilitates maintenance and monitoring efforts. Second, in construction planning there is no substitution for directed observation of the project site and the TVA.

SITE SELECTION AND ANALYSIS The ideal construction site will most closely meet the requirements of the community to be constructed. Therefore, the goals of the project will have substantial bearing on final site selection. Construction projects inherently require understanding the initial cause of habitat differentiation or degradation and determining the probability that the habitat can be constructed and maintained. The question of habitat displacement inevitably needs to be addressed in the site selection process as well. Site analysis is the first tangible step in a wetland construction project. The analysis may be completed during a wetland delineation effort, as the first step in a ©2001 CRC Press LLC

neighborhood restoration program, or from many other perspectives. This step provides the basic framework for goal setting, identification of the TVAs, and development of performance standards. The site analysis typically includes a topographic assessment, wetland vegetation association mapping and analyses, and a review of historic conditions. The analyses will also include an assessment of hydrologic, soil, and cultural conditions, and examination of any nearby templates, or examples, of TVAs. Small-scale experimental wetland construction efforts should be initiated at this time if possible. Generally, the initial site analysis is completed within a period of three weeks to three months, with a relatively intensive effort in defining site topography, vegetation associations, soils, and historic and cultural conditions in the first few weeks. Less extensive effort is expended in monitoring hydrology and constructing and observing experimental wetlands over the remaining period. Topography Elevation and slope are two of the more critical factors in determining the success of wetland construction projects. It is difficult to recommend an absolute planting elevation for a given species because of local and geographic variability. Synergistic effects may also alter growth at given elevations. For example, reduced salinity may permit growth of smooth cordgrass at higher and lower elevations than those typically recommended for the species. The optimum elevation can be determined empirically by observing and measuring the lower and upper elevation limits of a nearby natural wetland. Lewis (1990) recommends that the lowest and highest points should be disregarded, and only the middle range used for planting. If reference information is unavailable, an adequate test program should be conducted prior to initiating construction. Some degree of slope is essential for proper drainage. A gradual slope will increase the area available for planting and will dissipate hydrologic energy over a greater area, thereby reducing the possibility of erosion (Broome, 1990). Slope should be toward water sources to minimize ponding as substrates settle following site preparation. Gentle slopes do not drain as extensively as steeper ones, which is generally beneficial to most wetland vegetation. However, gentle slopes are more susceptible than steeper slopes to ponding, which can be especially problematic for riparian woodland species unless the soils are also relatively permeable. Vegetation Association Mapping Wetland vegetation associations for the construction site and surrounding area can be identified, and their extent determined, by mapping from an aerial photograph. Aerial photographs are usually available as stock or library film from an aerial survey center. These centers fly important regions every two to three years, providing a backlog or library of film that can be reproduced at a variety of scales. Requesting a half-tone mylar as well as a print of the project site is important. The mylar can be used to make blueprints for field use, and blackline prints can be reproduced and included in reports. ©2001 CRC Press LLC

The borders of the vegetation associations are more precisely defined through on-site analysis after initial mapping from an aerial photograph. For marshes, randomly selected 1-m plots representative of each vegetation association can be sampled for species and cover. Randomly selected 0.25 hectare (ha) polygons (defined by tree cover and separation among woodland vegetation associations) are effective in woodlands. Table 1 provides an example of vegetation association mapping from a hypothetical freshwater wetland project site in California characterized by gently sloping hills surrounding a central creek. The result is a table that describes the vegetation associations and the absolute and relative cover of marsh and riparian woodland vegetation. A scan of the table and knowledge of the region reveal that three vegetation associations are present and that the site is dominated by nonnative species and species representative of disturbed areas. It is also appropriate at this time to identify and survey any upland areas that may be considered for wetland construction to ensure that valuable upland habitats are not inadvertently lost. Table 1

Example of Vegetation Association Mapping from a Hypothetical Project Site in California1

Vegetation Association

Plant Species

Wet meadow

Area (ha)

Cover (%)

1.4

80 40

Lolium perenne* Hordeum hystrix* Elymus triticoides Elymus glaucus Seasonal marsh

1.4 Lolium perenne* Juncus balticus Lotus corniculatus* Polypogon monspieliensis*

Perennial marsh

40 30 20 10 0.9

Typha latifolia** Scirpus acutus Low-terrace woodland

0.5 Salix lasiolepis**

30 20 10 50

100 80 20 100 100

* Nonnative species. **Species indicative of disturbance. 1

The table provides absolute and relative information for use in site analysis and target vegetation association selection.

Site History and Current Status Shisler (1990) states that if wetlands are not present there has to be a reason, especially for tidal wetlands. Determining this reason is fundamental to reviewing a site for potential wetland habitat construction. If possible, past functioning of the ©2001 CRC Press LLC

wetland should be evaluated, and all past uses of the site should be reviewed prior to habitat construction. Current and future land use, zoning regulations, and projected sea-level rise may also have a bearing on site selection. Historic aerial and other site photographs, and any available topographic or other maps, are reviewed to define the past conditions and boundaries of the site vegetation associations. Important issues to review with these sources include the location of historic wetland vegetation associations and their relationship to current vegetation associations, water sources, and cultural elements. Historic aerials are often available from the U.S. Geologic Survey (USGS) and local aerial photography sources. Historic maps are also found at USGS as well as local historical societies. Costs for historic aerials are generally less than current aerials, however, reproduction costs for older maps may be significant. Hydrological Analysis The quantity, quality, and timing of water entering the wetland are of critical importance to its survival. If the correct hydrology is not present, or is insufficient, the project will fail (Shisler, 1990). The initial site analysis provides an opportunity to define the hydrologic conditions that create the site or template vegetation associations. Generally, hydroperiod, the duration of inundation or saturation, and water depth best define the vegetation association for freshwater wetlands. Accordingly, hydrology stakes and shallow observation wells are placed in wetland and upland areas to define surface and groundwater conditions. The wells typically consist of 10 cm diameter PVC pipe inserted 1.2 to 2.4 m into the ground, with a surrounding backfill of gravel or other permeable material. Wells and stakes can be observed weekly during the analysis to define the depth of ponding and the surface approach of groundwater. However, short-term monitoring may not reflect typical groundwater levels. Long-term groundwater level data may be available from local water districts or farmers. For coastal wetlands, hydrologic factors that need to be evaluated during the site selection process include drainage features, such as channels and ponds, the tidal regime and range, wave intensity, and salinity. Obviously, some of these can be manipulated through design while others cannot. It is sometimes necessary to base site selection upon the most practical trade-off. In general, coastal wetland construction projects are more likely to be successful in sheltered locations where wave energy and current velocity are minimal. Salinity variation at the site should be monitored so that appropriate plant species can be selected. Adequate drainage is another requirement, because standing water is typically detrimental to the establishment of wetland vegetation. Wide, shallow channels that retain water at low tide maximize flushing and plant health. Water quality (e.g., dissolved oxygen, turbidity) is an especially important factor determining site selection for seagrass restoration projects. Other factors affecting hydrology are precipitation, surface flows, ground water, and evapotranspiration. Each of these factors affects habitat productivity and species diversity.

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Soil Analysis Soil analysis can be one of the most important steps in defining wetland construction opportunities and constraints, especially for the drier freshwater marshes and riparian woodlands. The soil analysis can identify the edaphic requirements of the vegetation, thereby defining the appropriate TVA. Soil analysis will also identify any restrictions to construction activities because of soil permeability or soil chemistry. Generally, the best source of information on freshwater wetland soil characteristics for an area is direct site observations. Direct observations can be supplemented by local, state, or federal information, such as Natural Resource Conservation Service (NRCS, formerly U.S. Soil Conservation Service) soil series maps. The latter are available at no cost from NRCS offices. The NRCS and associated services such as county agricultural offices often have aerial photographs for review as well. Where soil series maps are unavailable, NRCS field personnel may provide on-site assistance. Site observations typically consist of a series of soil pits, 30 to 50 cm in depth, dug by hand throughout the site for the purpose of defining surface conditions. Use of a backhoe to define conditions at depth is generally helpful and is essential if significant excavation is required. Test pits will help identify any significant variation in permeability among soil layers. It is also useful to identify similar soils on proximal, undisturbed sites using the NRCS soil survey so that natural vegetation associations can be observed and used as a template. Soil chemical properties can be analyzed in a laboratory. If the site requires the addition of soil, or if the site has been filled in the past, the possibility of contamination should be investigated. Generally, sandy soils are more amenable to grading and planting than are silt and clay. However, some degree of organic content is recommended as a nutrient source (Broome, 1990). The soil must be of sufficient depth to support planting. Garbisch (1986) recommends a minimum depth of 0.3 m for marshes. Trees for woodland construction will typically require a greater soil depth, depending on the species. Based on a literature review and field inspections of created wetlands in New Jersey, substrate preferences for coastal marshes were ranked as follows: 1. 2. 3. 4.

Natural marsh peat Clay and silty clay Estuarine sediments (dredge and fill) Sand (Shisler, 1990)

For riparian woodlands, however, the list is almost completely reversed. Some anoxic soils can become highly acidic upon exposure to air, such as during earthwork, and may warrant the addition of a calcareous material such as crushed shell as a buffering agent. At sites subject to tidal or riverine inundation, sedimentation processes should be carefully studied. Some degree of sedimentation may be desirable to stabilize initial plantings; however, burial of seedlings should be avoided.

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Cultural Constraints Few sites are unconstrained by human artifacts. Artifacts may range from prehistoric remains to buried sewer lines. Visible artifacts such as roads that affect the project site (e.g., drainage impediment) should be identified. Identification of subsurface artifacts is more difficult. Nevertheless, cultural resources can be preliminarily identified in the United States through record searches with the State Historic Preservation Office (SHPO) or local universities. Buried infrastructure may be identified through interviews and research at local Public Works Departments. Adjacent Site Conditions Conditions near the proposed construction site should also be considered. Sites adjacent to existing functioning wetlands offer the greatest chance for success. Conversely, an increasing wetland area in the watershed may alter hydrologic regimes. The presence of aggressive exotic species close to the proposed site may also be a problem. In many cases, a buffer zone should be included in the project design. A buffer zone may increase the diversity of flora and fauna present (Josselyn et al., 1990) and will protect the site from human and vehicular traffic. The buffer zone must be kept clear of exotics and other nuisance species that may invade the project site. Buffer zones with tall vegetation provide animals, especially birds and mammals, with refuge from cold winds, high temperatures, and high waters. The proximity or attractiveness of the potential construction site to predation should also be considered. Geese (e.g., Branta canadensis), muskrat (Ondatra zibethica), and nutria (Myocastor coypus) have all been identified as voracious consumers of newly planted marsh vegetation (Shisler, 1990; Broome, 1990). Conversely, placement of a well-designed created wetland near a disturbed wetland may offer refuge to dwindling populations of desirable species. Open water near potential sites should be assessed for boat traffic and offshore depth because both can affect wave energy. Shallow offshore water reduces the severity of waves reaching the shore (Broome, 1990). The degree of wave energy can be modified to a certain extent (see below), but sites facing more than 5.5 nautical miles of open water are generally not recommended for planting (Crewz and Lewis, 1991). The Use of Template Associations Recreation of an historic vegetation association will in many instances increase the probability of success. In the event that the TVA is missing or poorly represented on the project site, a proximally located vegetation association can be used as a template. The template association should have hydrology and soils similar to existing or intended conditions for the construction site. In addition to determining species composition, the template vegetation association should be studied to determine species evenness and distribution, and identify potential additions to the planting list and likely successional patterns. The specific TVA to be constructed may be difficult ©2001 CRC Press LLC

to predict at this stage of the project. However, initial review of several different vegetation associations may have a significant effect on goal setting. For example, participants in a riparian woodland construction project for a degraded waterway in Solano County, CA, wished to plant the California sycamore (Platanus racemosa) extensively due to its stature and appearance. However, the sycamore is adapted to alluvial flats with relatively permeable soils and would not do well on the project site's clay soils. Taking the participants to a regional park that included a wellpreserved riparian woodland native to this region and similar to the project site resulted in the selection of several alternative trees, all better adapted to the project site. Small-Scale Experimental Construction When time is available, small-scale experimental projects or pilot studies should be undertaken to identify soil and hydrology constraints and to refine planning alternatives. Appropriate studies include determining the water-holding capacity of unmodified soils, determining germination and salvage survival rates for target vegetation, refining transplanting techniques, and evaluating construction management abilities. The importance of small-scale pilot projects for building confidence and consensus among the planning group should not be underestimated.

GOAL SETTING The setting of specific goals is crucial to wetland construction projects. Goals help define monitoring elements and protocols, and establish standards for judging success. The latter allows others to objectively evaluate the project and serves as a basis for practitioner and general public educational efforts. Elements of a Goal Statement Goal statements are typically comprised of a substantive objective, for example, construct 1.3 ha of coastal salt marsh. Specification of a TVA may be the most appropriate substantive goal as noted in the introduction to this chapter. A TVA can be related to wetland functions (e.g., provision of wildlife or fisheries habitat), facilitates clear performance standards and monitoring, and can be readily measured. This is most easily accomplished through comparison with an existing or historically well-described vegetation association from the project site or a nearby site. One of the more difficult tasks is to keep the TVA general enough to be realizable, yet specific enough that the goal is meaningful. Typically, selection of a species type association, for example a rush-dominated wet meadow, is an effective approach. Other commonly used options for the substantive element of the goal statement include a specific wildlife or plant population. In this case, the measurement parameter would identify a particular population level as the target. Wildlife goals are generally less useful than TVAs because wildlife populations vary so greatly year to year as a result of regional conditions. Regional climate changes can have a much greater effect on wildlife populations, for example, than the maturation of the ©2001 CRC Press LLC

construction site. Moreover, the construction project will build a specific type of habitat or assemblage of habitats to produce the desired change in wildlife populations. Therefore, designation of the TVA(s) makes as much sense as designation of the wildlife goal and is more readily measured. A wetland function, such as water quality improvement, is also often used as the substantive element of the goal and the measurement parameter defined to include an indicator such as percent reduction in target pollutants. Again, functional goals are still dependent on a specific TVA. Equally important, and often overlooked or unstated, is the procedural element. The procedural element of a goal statement refers to the method by which the goal statement is completed. Too often, goals are developed without discussion with, or consensus among, all interested parties. Conversely, a large committee may develop goals that are nonspecific, thereby negating effective evaluation at any point. Goal-Setting Process Several points should be considered in the development of goals. Construction goals should address the concerns of all those meaningfully affected by the project. Affected parties will include landowners on or adjacent to the project site, regulating agencies, and operation and maintenance entities such as mosquito abatement and flood control districts. Table 2 lists parties potentially affected by wetland construction activities, and goals common to these parties. All parties should be contacted and their comments solicited on initial goal statements. For smaller-scale projects where the affected party’s interests are relatively similar (e.g., neighborhood groups reconstructing a local creek), comments should be used to develop a consensus on project goals. For most projects this is not practicable, and the consultative process will involve reviewing each comment and incorporating a response into the construction plan. Experience suggests that a flexible, two-step goal development process is most effective. The initial goals are developed following the initial site analysis and discussions with the affected parties. Final goals are selected at the conclusion of the construction design process. Even then, the goals may require modification during the construction, or even post-construction monitoring phase, as new opportunities and constraints arise. Practicability A substantial body of literature exists on the design and goals of wetland construction projects (Kusler and Kentula, 1989). However, a significant gap exists between those who develop the goals and write the plans and those who construct wetlands. This gap mirrors a similar chasm found between landscape architects and landscape contractors and is likely to exist because of education dissimilarities, professional practices, and even insurance requirements. This gap poses a significant danger to the development of ecological construction because it may ensure that important knowledge gained during construction is not incorporated into subsequent designs. ©2001 CRC Press LLC

Table 2

Parties Potentially Affected by Wetland Construction Projects and Goals Common to These Parties Affected Parties

Landowners Site landowner Adjacent landowners Adjacent residents

Permitting and commenting agencies Corps of Engineers Wildlife agencies Public land agencies

Operation and maintenance entities Flood control districts Park districts Mosquito abatement

Goals Minimize costs Increase aesthetics Eliminate off-site issues (e.g., mosquitos, odors, floods) Increase access Reduce vandalism Provide appropriate data Respond to all concerns Restore single species habitat Provide appropriate public access Ensure success Minimize maintenance costs Provide adequate flood conveyance Ensure compatibility with park needs Minimize mosquito production

Building a wetland shares many basic elements with any landscape construction project, whether it is gardening or reforestation. The most important issue in any such project is to determine what conditions create the TVA. Subsequent issues may arise that threaten vegetation association growth, whether one is planting corn, taro, or rushes. Wetlands are among the wettest landscapes and, accordingly, the quantity and quality of the water, as well as the use of soil types which ensure water retention, are extremely important. Also important are those conditions that result from the application of significant amounts of water to the soil such as erosion and salt buildup, which reduce the viability of the TVA. Wetland construction strives to achieve ecological function and presumes that the project, once constructed, will evolve in a natural fashion. Ideally, no maintenance will occur following an initial establishment period making an understanding of the successional aspects of the TVA very important. On the other hand, many wetland construction projects, especially those specifically for waterfowl habitat, will use sources of water that require continued operation and maintenance (Payne, 1992). Unless the project is built in an extremely remote area, human actions will influence the project. Conversely, the project may influence humans. For these reasons, wetland construction must consider the role of people in the design and, in some cases, identify methods for ensuring that potential interactions between the constructed habitat and people are mutually beneficial. These elements are considered in more detail in the Construction Design section of this chapter. However, they must also be considered in the goal setting stage. Ignoring these issues and proceeding without consideration of the practicability of the project may shorten the planning phase of the project but will likely decrease the probability of success.

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CONSTRUCTION DESIGN Geography Size and Shape Market or regulatory forces well in advance of any design analysis often determine the size and configuration of the construction site. Even when strict limitations exist, the designer must consider the appropriate extent and shape for the different vegetation associations to be constructed. Recent work stemming from MacArthur and Wilson’s (1967) research on island biogeography suggests that areas of at least 16 ha contain significantly greater numbers of species of birds, mammals, and invertebrates than do smaller areas (Tilghman, 1987; Faeth and Kane, 1978). Species richness is also positively correlated with edge length and habitat diversity (O’Meara, 1984). Location Exposure to wave energy is particularly important for coastal wetland construction projects. The relationship between wave energy and effects on cordgrass planting can be related to fetch (the distance traveled by waves). At less than one nautical mile of fetch, plantings will be unaffected. Between 1 and 3.5 nautical miles, some replanting is necessary, and over 3.5 nautical miles, some kind of wave-barrier structure is necessary to protect plantings (Crewz and Lewis, 1991). Orientation of the site with respect to colonizing (or invading) plants and animals is another factor influencing design. Exposure to desirable flora and fauna should be provided. Conversely, exposure to exotic and nuisance species should be restricted. Prevailing winds and currents may enhance or deter establishment of volunteers. The presence and condition of adjacent wetlands may also affect design specifics. For example, preserving isolated patches of desirable vegetation may inhibit water circulation by creating berms. Sound ecological judgment must be used in assessing whether existing vegetation impairs or contributes to developing desired functional attributes at the site (Crewz and Lewis, 1991). Slope Perhaps the most critical aspect in successful wetland construction design is grading the soil surface to the elevation that provides the optimal hydrologic regime for the TVA (Broome, 1990). It would not be an overstatement to consider accurate topographic surveys and grading the keystone to meeting wetland construction goals. Slopes should be as gradual as possible, while still allowing good surface drainage at low water conditions. Gentle slopes at the perimeters of the project site are recommended to reduce erosion and filter runoff reaching the site. If steep slopes are necessary, they should be stabilized to serve as a deterrent to exotic or nuisance species invasion. Gradual slopes at the perimeter of construction sites also serve to

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prevent compression of vegetative zones owing to sea-level rise, the rate of which is predicted to increase rapidly after the year 2025 (Crewz and Lewis, 1991). Adjacent Uses Significant opportunities exist for a larger native landscape or a corridor when adjacent uses include natural or restored lands. Whereas a great deal of information has been developed on the value of larger sites, the case for creating corridors is more intuitive. MacClintock et al. (1977), Fahrig and Merriam (1985), and Wegner and Merriam (1979) all provide study results that suggest that birds and small mammals actively use natural corridors, and that patches of native landscape connected by such corridors to larger habitats receive greater wildlife use than isolated patches. Construction projects should consider potential use of the wetland by people and the effects of the human landscape on the natural system. Adams and Dove (1989) document widespread interest in viewing and interacting with wildlife within suburban and urban settings. Providing a trail that offers views and interaction with the wetland is often the best means to ensure visitors do not impact sensitive areas. Leaving the edge of the wetland open so that views of the wetland are created may be the best means to ensure that the wetland is not used for trash and debris dumping. Glare is best treated with tall, rapidly growing trees as a buffer. Off-road vehicle access should be eliminated through the use of post and cable barriers between any public roadways and the wetland, unless steep vertical barriers or moats are provided. Domestic and feral cats and dogs are significant predators on ground-nesting wetland birds. Both can be restrained with fences, and open water is an effective barrier to cats. Hydrology Wetland hydroperiod, including the duration and frequency of inundation or saturation, and depth of inundation, are generally the major determinants of wetland vegetation associations. However, the manner in which the water is supplied to the construction site may be equally crucial. Artificial supply systems, such as drip or spray irrigation and pumps, require a significant amount of maintenance and reduce the naturalness of the wetland. However, these systems eliminate much of the uncertainty involved in water supply planning. Natural water supply systems such as open channels are less manageable but can result in a self-maintaining system that mimics natural systems. Use of natural water supply systems requires a good understanding of ecology and engineering and will require more effort in the investigation and planning stages. Hydroperiod and Depth Two models are useful in estimating wetland hydroperiod and depth of inundation in freshwater wetlands. Slope models are used to define the hydroperiod and depth of inundation for wetlands abutting a river or lake. Basin models are used to model wetlands isolated from riverine or lacustrine systems. For tidal wetlands, a variety of models have been used to describe tidal flows. In any case, tidal ranges ©2001 CRC Press LLC

and important elevations (mean high water, etc.) must be identified; these are generally derived from local tidal gauges and other records. Slope wetlands are characterized by seasonally varying water levels with no implied storage. The relationship between wetland vegetation associations and water surface elevations is well described (Dickson et al., 1965; Harris et al., 1975). However, water surface elevation analyses of streamflows for storms of various intensity or duration are complex. Channelized streamflow equations have been developed for flood control analyses. These equations consider the amount of flow, the crosssectional area and slope of the channel, and a friction element that defines channel roughness. The latter reflects the capability of channel vegetation to reduce flow velocity. The HEC-1 model developed by the Corps of Engineers (1981) is an example of this type of model. Used in conjunction with an accurate topographic map of a site, these models can predict the depth of water and duration of flooding at a specific elevation for a specific storm event. However, these models require accurate data that are typically very expensive to generate. Slope wetland hydrology can often be more simply defined by directed observations of the vegetation associations and of the channel during specific storm events. The locations of wetland vegetation associations in a slope environment relate to water level, which is related to topographic position. Identifying the elevation of a TVA relative to the channel and then predicting the creation of a new and similar association based on a similar channel position is crude but relatively effective (Figure 5). Observations during storm conditions are crucial for determining channel behavior during high flows. Widening it to pre-alteration conditions and thus reestablishing the TVA might easily restore a channelized stream. However, other factors may also be critical. For example, soil or underlying bedrock may be radically different on adjacent reaches. Greater or lesser permeability in the construction reach might result in less or more water than predicted. Other factors such as channel roughness in the form of dense vegetation or in-channel morphological features may slow flows and significantly reduce peak flows. A comparison of stormflow peak and duration in the template and construction reaches can eliminate most sources of error. Basin wetland hydrology is best defined by a water budget. That is, the water available to support the wetland is a function of water inflow minus water outflow. This is illustrated by S = P + SI + GI – ET – SO – GO where S equals the storage in the wetland basin. P equals the precipitation. SI equals the surface inflow. GI equals the groundwater inflow. ET equals the evapotranspiration. SO equals the surface outflow. GO equals the groundwater outflow or infiltration. ©2001 CRC Press LLC

Figure 5

Determining the appropriate elevation of a constructed slope wetland can sometimes be accomplished through observation of existing vegetation associations and the elevations at which the associations occur.

Water sources for wetlands include precipitation falling directly on the wetland, surface inflow, and groundwater inflow. Precipitation amounts should be identified on at least a monthly basis. Data are usually available from local weather stations or airports. In the United States, National Oceanic and Atmospheric Administration (NOAA) handbooks are also a good source of information. Surface inflow is the product of precipitation within the watershed less the amount lost to evapotranspiration and infiltration or inflow from adjacent lacustrine or riverine sources. For inflow from adjacent sources, a stage-discharge model may be used to determine surface inflow or the elevation of the flood flow can be estimated based upon corresponding vegetation association boundaries. Groundwater inflow is often extremely difficult to determine and is best accomplished through the use of piezometers. ©2001 CRC Press LLC

Water is lost from the wetland (and its watershed) through evapotranspiration, surface outflow, and groundwater outflow. Evapotranspiration is often described on a monthly basis in NRCS soil surveys, NOAA handbooks, and other sources. The low point in the basin will control the basin water surface elevations and surface outflow. The average storage capacity is then the remaining volume of water in the basin. Some water flowing into the basin will be lost to outflow through the soil, with the amount of outflow determined by the height of groundwater and the type of soil. Where groundwater levels are high or the soil underneath the basin is at field capacity, no or little loss will occur. Where groundwater levels are low or the soils beneath the basin are not at field capacity, water loss to the soil will be more significant. The amount of loss during these conditions is dependent upon soil type, with clay soils generally appropriating less water than sandy soils. The factors used in a water budget calculation are often dependent upon each other and interaction between the surface and groundwater components can confound the results of the budget analysis (Brown and Stark, 1987). Additionally, many other factors may affect the parameters or their measurement. In all cases, the models should be verified, validated, and calibrated through direct observation of existing or experimental wetlands. Water Supply Providing a relatively natural water supply system, or designing a wetland within a system such as a channel also used for flood conveyance, is relatively simple in tidal conditions but increasingly problematic with greater freshwater inflow. Much experience, often not positive, has been gained from the design of flood channels that also host wetland creation efforts. Concrete or earth-lined trapezoidal channels have been extremely popular in flood control design because they require little land, are relatively inexpensive to build, keep flood flows below existing ground levels, and are easy to maintain. As these systems were expanded to provide for wetland construction, however, the inherent problems associated with this channel design have become apparent. The substantive problem is the perennial saturation of the flat bottom of the channel, which encourages the development of a low-terrace riparian woodland. Woody species tend to grow densely and rapidly, creating a significant impedance to flood flows. One resolution of these maintenance conflicts would be the establishment of a wetland vegetation association with relatively low channel impedance. Riparian woodland associations vary tremendously in their effect on channel impedance but generally follow a pattern of greater impedance with greater affinity for water. That is, a low-terrace woodland impedes flood flows more than a mid-terrace association, which in turn impedes flow more than a high-terrace association. In a study of riparian woodland establishment patterns at several wetland creation projects in the Central Valley of California, Zentner and Zentner (1992) observed that the low-terrace woodland in this region occurs from the upper edge of the summer water level to approximately the mean annual flood line. The mid-terrace zone occurs from the mean annual flood line to about the 10- to 15-year storm line, and the high-terrace woodland

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occurs from the mid-terrace zone to the 100-year flood line. Therefore, to circumvent blockage of flood waters by dense low-terrace riparian growth while still providing for wetlands, broad low terraces could be designed that can accommodate flood flows despite the dense nature of the vegetation. Alternatively, the low-terrace zone could be restricted, and terraces would be constructed just above the mean annual flood line where mid-terrace riparian woodland, in friable soils, or marshes in indurated soils can be maintained (Figures 6 and 7). Additional hydrological factors, including water velocity, sediment loading, and erosion potential, will also be important. Table 3 is a checklist for reviewing channel design issues. The checklist can be used to review both upstream and downstream preconstruction and postconstruction conditions. In the western United States, and most likely for other regions as well, seasonal low water, mean annual flood level, and the 100-year flood level are the most pertinent water surface elevations. Seasonal low water level defines the upper limit of perennial marsh and the lower limit of low-terrace riparian woodland. Mean annual flow approximates the upper limit of seasonal marsh and low-terrace woodland. The 100-year flood level is an important cultural limit, and flows above that level resulting from a wetland construction project will require special consideration. The relevant tidal wetland elevations include mean tide level, mean higher water (MHW), and mean higher high water (MHHW), all important boundaries for vegetation associations (Lewis, 1994). Impedance associated with the vegetation association has an important effect on channel flow, as does channel bottom slope microtopography. Each of these factors, as well as channel soil characteristics, are important factors in erosion and sedimentation. Sandy soils erode more easily than clays under most conditions, and impediments to channel flow such as bridges increase scouring through local increases in flow velocity. Decreases in flow velocity, especially when there is a high sediment load, will result in silting-in of channel bottom basins. For coastal wetlands, some kind of proximal offshore structure may be needed for many sites exposed to moderate wave energy. The protection offered by berms or breakwaters can be substantial and are a critical factor in successful establishment of newly planted vegetation. At some sites, construction of a breakwater may be all that is necessary to stabilize a site, both subtidally and intertidally, and consequently facilitates significant habitat improvement. For example, a small spoil island in Clearwater Harbor, FL, that provided good wildlife habitat for local populations (especially birds) was experiencing severe shoreline erosion. Offshore seagrass beds were also showing signs of stress related to excess wave energy. In 1989, a 140-mlong breakwater of large rocks was constructed approximately 25 m offshore of the island, seaward of the grass beds. Following breakwater placement, the shoreline stabilized through formation of a small beach and the seagrass beds appear healthy and may be expanding in area. Large rocks and rubble are the material recommended for construction of breakwaters in most circumstances. Smaller material may be less stable, or can consolidate excessively, prohibiting adequate tidal flushing. Constructed properly, rock berms used in conjunction with mangrove restoration projects aid in trapping propagules, thereby reducing or eliminating the need for planting.

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Figure 6

To avoid blockage of flood waters by dense, low riparian growth, the low-terrace zone can be restricted and terraces can be constructed above the mean annual flood line.

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Figure 7

Another method for avoiding blockage of flood waters while providing for wetlands is to construct seasonal marsh in low-terrace areas.

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Table 3

A Design Checklist for Addressing Critical Hydrological Design Components of Channel Wetland Construction

Water surface elevations Seasonal low water level Mean annual flood level 100-year storm level Vegetation association High impedance Moderate impedance Low impedance Channel bottom slope On-site Upstream Downstream Erosion and erosion potential On-site Upstream Downstream Sedimentation and sedimentation potential On-site Upstream Downstream

Soil Soil properties have generally received little consideration in the design and construction of wetlands. Exceptions include wetlands where soil characteristics determine the wetland form, such as western vernal pools and bogs. In large part, this historic inattention to soils is due to the predominance of tidal and perennial marsh construction which can be supported to some extent on almost any soil as long as an appropriate hydroperiod and water depth are provided. However, constructing the drier freshwater wetland types, such as seasonal wetlands or wet meadows, has made soil considerations more important. Soil texture and its corollary soil permeability often strongly influence the type of marsh or the development of a woodland in place of a marsh. Hydroperiod and inundation depth being equal, fine textured, less permeable soils support a wetter vegetation association and a generally larger wetland than do course textured, more permeable soils. More permeable and well oxygenated soils (including various grades of rock) will support woodlands in addition to, or instead of, marshes. As noted above, tidal and perennial freshwater marshes can be established on almost any soil type. Soil depth is also an insignificant factor in many instances. Areas with indurated soil layers at the surface have established perennial marsh within three months of inundation as have areas of cobble (Zentner and Zentner, 1989). Nevertheless, wetland vegetation establishment is easier where significant levels of organic material are present to increase soil water retention capacity. In

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several cases, peat or other organic mulches have been added to the substrate and have increased the growth of perennial marsh species (Brown et al., 1984). Seasonal marshes generally require a surface horizon of 10 to 45 cm depth and a soil with some water holding capacity. This is particularly true when root zone saturation is infrequent. However, if the soil is extremely permeable, seasonal marshes can still be established where water levels are periodically within 15 to 45 cm of the soil surface. Generally, these conditions must exist for two weeks per month during the growing season. Seasonal marshes can even be established on cobble but to a lesser extent than perennial marshes. Wet meadows are greatly affected by soil type. Typically, wet meadows occur on clay or clay loam soil which is saturated for 4 to 8 weeks in an average year. Generally, inundation is infrequent but may be long-standing when it does occur due to the dense nature of the soil. Soil depth may also be important for many of the wet meadow species. Some rushes, for example, have a root depth to 1.8 m. Riparian woodlands may establish on a broad array of substrates, but, as with marshes, wetter vegetation associations are less affected by soil type than drier vegetation associations. Accordingly, low-terrace woodland species may establish on thin cobble layers above mud soils, a useful technique for stabilizing rock weirs in wetlands. However, mid- and high-terrace woodland species require a greater depth of permeable soil as noted above. In some instances, soil analyses of a potential construction site may show that wetland establishment is not feasible under natural conditions. Godley and Callahan (1984) document the construction of marsh and riparian woodlands in sandhills of Florida using a combination of a clay liner and organic soils to retain water. Pond wetlands with marsh and woodland components have been constructed in the xeric foothills of central California in cobble piles with extreme permeability using a mixture of clay and bentonite to retain water (Zentner and Zentner, 1990). Despite the apparent success of these examples, all sites must be examined with an understanding that wetland construction on such sites may best be conducted elsewhere. One of the primary functional objectives of any ecological construction is to minimize or eliminate maintenance after an initial establishment period. Projects that depend on continual maintenance are at best unnatural, and often unsuccessful in the long term. Vegetation At its most basic, plant ecology is the study of plants and plant associations and the relationship of plants and plant associations to various edaphic and landscape factors. Because wetland construction seeks to place a specific vegetation association in a specific location, it is basically applied plant ecology. Plant ecology encompasses an extremely broad range of subjects. It can be argued that a multitude of factors affect the landscape position of a plant or vegetation association and, therefore, affect construction design. Primary among these factors are soil and hydrology. Other factors having a significant effect on the establishment and persistence of the TVA are plant succession, planting design, and ruderal invasion.

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Succession Succession refers to the changes that a vegetation association may go through in response to autogenic or allogenic factors. Two forms of succession are recognized: phase and type. Phase succession is said to occur when the soil and hydrology conditions do not change, but the vegetation association changes, usually from a seral to a mature stage. Generally, most vegetation associations have seral and mature phases. The variation between seral and mature phases of marshes is relatively noticeable. Typically, readily seeded species such as cattails dominate the seral stage of a perennial marsh while species more adapted to vegetative propagation dominate the mature phase. Seed viability for these mature marsh species is often low or noncompetitive on bare ground compared with the more adventitious species. As such, plug planting may be the only practicable means of assuring growth of the mature phase during the early years of a construction project. Conversely, identifying the seral stage species of the TVA allows the ecologist the option of not planting these species but instead simply ensuring a seed source. Understanding this phase of the TVA is important and is best accomplished through observation of template sites or experimental plots. Seral and mature stages of woodland vegetation associations are often extremely difficult to identify. Successional models for woodlands suggest that the low-terrace woodland association is the seral stage for the drier vegetation associations. This may be due to the historic predominance of autogenic succession in woodlands that once assured episodic or periodic pulses of sediment through the system. Once these successional forces have been eliminated through flood control, relatively static vegetation associations may result. However, phase succession is still observable in the response of species to canopy openings and, in the propagule stage, to varying degrees of light intensity. Species that do well in full sun when planted in the field or in nursery conditions generally represent the seral stage of the TVA. Conversely, species that require some shade typically comprise the mature stage. A common problem in woodland construction involves the planting of a full complement of woodland species in a newly constructed site, that is, a site exposed to full sun, without consideration of the successional status of each species. Type succession is said to occur when the soil, hydrology, and vegetation association change. Classical models of succession provide for the eventual disappearance of a freshwater wetland as substrate surface elevations increase due to peat or sediment buildup and its replacement by an upland forest community (Clements, 1934). Similarly, riparian woodlands would shift from the low-terrace stage through the high-terrace stage and into an upland woodland or forest. More recent work suggests that succession in many wetlands is a combination of autogenic forces such as peat buildup, which direct it in a linear, Clementsian development pattern, and allogenic forces that may disrupt or reverse this pattern. To some extent, allogenic forces are more familiar to wetland scientists and are revealed by relatively persistent zonation which when disturbed exhibits a predictable series of changes (Mitsch and Gosselink, 1986). In wetland construction design, succession and the external forces that often seem to control wetland change are both important parameters. Succession in ©2001 CRC Press LLC

wetlands often follows the classical autogenic model. Under more or less natural conditions, riparian woodlands become isolated from waterways, or sediment buildup provides for drier conditions, and the wetter association is gradually (or rapidly in some cases) replaced with a less hydric association (McBride and Strahan, 1984). Similarly, perennial marshes may gradually increase in surface elevation to become seasonal marshes or wet meadows. However, the allogenic model also often holds true. Marshes may not transition through woodlands. For example, soil conditions adverse to woodlands, especially duripans or heavy clay layers, favor dense mats of marsh plants. The construction design should also be sensitive to those forces that may be periodic or episodic such as beavers, floods, fires, or debris flows. Cultural factors are also increasingly important in succession. When floods are controlled and the waterway form remains constant, or sediment inputs have otherwise been significantly reduced, wetland associations may remain in place without succeeding to more xeric associations. For example, Klimas (1989) found that highterrace, oak-dominated riparian woodlands were significantly underrepresented in the lower Mississippi River valley compared to the more mesic woodland associations. Typically, riparian woodland associations vary in seed size and weight in direct relationship to their successional stage and location relative to seasonal low water levels. Low-terrace woodland species have the lightest seeds and are the first of the woodland vegetation associations to establish, while the high-terrace species have heavy seeds and are a much later successional stage. Klimas theorized that levees acted as barriers to the dispersal of the heavier seeds, which were not transported by flood waters as easily as the lighter seeds. Similarly, aggregate-rich lands adjacent to the San Joaquin River, CA, were mined over an 80-year period resulting in a series of ponds supported by groundwater in a matrix soil of gravely loam. The soils are very permeable and little to no flooding occurs. A low-terrace willow-cottonwood association, a typical early sere, dominates all the ponds regardless of age (Zentner and Zentner, 1989). Without this broad understanding, a designer reviewing the woodland stands in both regions would tend to underrepresent the upper elevation woodlands (dominated by oaks in both cases) in the planting plan, thereby mimicking an altered vegetation association. The construction design must analyze which set of conditions will govern the construction site and then plan for these accordingly. Planting Design If a site is ideally suited to a particular type of habitat improvement, the decision of whether or not to install plants may present itself. Suitable tidal freshwater sites can rapidly become vegetated in as little as six months (Broome, 1990). On the north-central Gulf Coast, two general types of marsh habitat improvement projects are common. The first is the use of dredged material which may be confined by temporary or permanent dikes. Alternatively, dredged material may be deposited unrestricted in open water. Such projects are rarely or only experimentally planted and are usually allowed to vegetate naturally. The second less common approach to unplanted marsh construction is diversion of river flow. This process provides substrate and the introduction of fresh water counteracts the effects of saltwater intrusion ©2001 CRC Press LLC

and rising sea level. Again, natural colonization is allowed to occur in projects of this type (Chabrek, 1990). The major benefit of natural colonization is the automatic use of local gene stock. However, the time required for natural colonization varies considerably. Good plant establishment can occur within several months in freshwater tidal wetlands but may require several years in more saline conditions (Shisler, 1990). The presence of an adequate seed or propagule source should be verified if natural colonization is anticipated. Another option is the use of wetland soils salvaged from another site. The topsoil (sometimes referred to as mulch) removed from a wetland scheduled for destruction can be stockpiled and later used as a top layer in a wetland improvement project. The effectiveness of this soil as a seed bank depends on the plant species present (exotics and nuisance species may be excessive) and the viability of the seeds. The latter depends on the species, the length of time the topsoil has been stockpiled, and the conditions under which the topsoil was stockpiled. This technique is most effective if the soil is in place at the beginning of the growing season. Salvaged soils appear to be most useful for construction of seasonal marshes, probably due to their relatively high species diversity. At least 20 to 25 cm of soil and plants should be transplanted into the seasonal marsh zone and immediately supplied with the appropriate hydrologic regime. Plant Selection If planting is elected, the species selected will depend on the type of wetland desired. In Florida, one or two species are commonly used for coastal marsh habitat projects with the emphasis on smooth cordgrass. However, with the increasing emphasis on wetland function, complex plantings of multiple species may become more common. For regional guidelines on plant species selection, refer to the reviews in Kusler and Kentula (1989). Crewz and Lewis (1991) provide specific guidelines for species in Florida. As suggested above, construction of a freshwater perennial marsh in a riparian situation may require only inflow water and at least a thin, preferably organic, soil layer. A more complex task is ensuring that the marsh is not overwhelmed by weedy species such as cattails. Planting marsh species representative of the mature perennial marsh in the proposed establishment zone is cost-effective and provides for rapid establishment of a diverse flora. Marsh species should be salvaged in the form of plugs from nearby sites to supplement on-site salvage. Wet meadows may be established using common agricultural practices such as preparation of the seed bed and sowing of seed, or direct planting of small, container species (plugs) into unamended soil. Seed bed preparation (outside of the necessary hydrologic modifications) will consist of weed removal, disking or otherwise cultivating the soil, seeding, and harrowing to cover the seed. For species that do not produce highly viable seed, plugging rooted plants or hydromulching with stolons should be considered.

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Similarly, although it is often neglected in forested wetland construction work, the herb stratum is an important component of the riparian woodland. One to two month old plugs of native species should be planted at one to two plugs per square meter. Additionally, spreading detritus from an existing forest floor may be very helpful as is planting stock inoculated with the appropriate mycorrhizal fungi. Stock Selection The species to be planted and the form of the propagule need to be specified. Depending on the species and the location, seeds, seedlings, vegetative shoots, or transplants may be the most desirable planting unit. In the case of mangroves, propagules are recommended for red mangroves, but seedlings of black and white mangroves are recommended. Smooth cordgrass can be grown from seed but not throughout its range. However, plugs and bare-root culms are easily transplanted, and nursery-grown units from field-harvested stock are easy to cultivate, handle, and install. Seedlings grown from seeds of cordgrass and black needlerush are used in the southeast (Broome, 1990), although transplants of black needlerush are generally unsuccessful. Saltgrass can be grown from transplants, rhizomes, seeds, or plugs. In general, plants grown locally should be used because adaptations to local conditions may create ecotypes. This is especially important with regard to species with wide geographic ranges such as smooth cordgrass. Planting Density Installation on 1-m centers is the standard for most coastal marsh, mangrove, and seagrass restoration projects. However, this is probably not a realistic specification. Naturally colonizing species, mangroves for example, tend to initially occur at much higher initial densities. Density decreases over time, with differential survival of the hardiest plants. Crewz and Lewis (1991) recommend 25-cm centers for red mangrove propagules and 50-cm centers for 1-year-old seedlings. As increasing planting density also increases the cost of a project, there should be a distinction made for mitigation vs. restoration. The importance of obtaining functional equivalency in mitigation should require higher planting density, while restoration can be more economical, relying on natural colonization and a longer period of time allowed to achieve stated objectives. Planting density should be determined according to the desired rate of plant coverage which should be rapid in the case of mitigation for short-term wetland losses. The size of the site may also affect planting density because large sites are often planted at a lower density than a smaller one of the same wetland type, simply for reasons of economics. Reviews of riparian woodland plantings have found average densities of mature stands to vary from 200 to 300 trees per hectare, roughly equivalent to plantings on 2.5- to 3-m centers. Under natural conditions of course, the initial establishment rate is often much greater, especially for the low-terrace woodland species. A sparser planting rate assumes some maintenance or other care in planting that will result in a significantly higher survival rate than under natural conditions.

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Weed Control Weeds are nonnative, adventitious plants that replace desired components of the TVA. The term nonnative is used here to describe a species that occurs outside its historic range or landscape position. Weeds include species such as common reed (Phragmites communis), which has replaced native species in the New Jersey Meadowlands, or melaleuca (Melaleuca quinquenervia), which has invaded south Florida wetlands. Weeds do not include native species, such as cattails, whose growth and spread are promoted by disturbance but which are typically the natural, seral phase of a TVA. In some instances, weed control or elimination can be the sole action taken in a wetland construction project. The spread of adventitious nonnatives throughout the environment threatens many native vegetation associations. However, simply eliminating the exotics will not suffice to restore a TVA. Weed management should identify and address the conditions that allowed or encouraged the exotics to become established, remove the exotic, replace the exotic with the appropriate native plant, and maintain the TVA such that further opportunities for the exotic to become reestablished are limited. For example, a noxious pest in California, bristly ox-tongue (Picris echiodes) has very light seed that does well in heavily grazed, dense, annual grasslands. Grazing leaves small openings in the turf that allow the plant to germinate. Mulching bare soil or ensuring a dense carpet of native groundcover, and then reducing soil disturbance, can effectively eliminate this species. Cultural Issues Mosquitoes Marshes and mosquitoes, as well as the problems caused by mosquitoes, have been synonymous for millennia. The increase in wetland construction projects has been a cause of some alarm for mosquito abatement officials. Mosquito abatement officials will eventually modify marshes that generate mosquitoes that act as vectors for diseases or that annoy nearby residents. Mosquito abatement officials operate under a public health and safety mandate and are generally immune to wetland protection regulations. Mosquito abatement officials are, therefore, particularly interested in influencing wetland construction design so that postconstruction control is unnecessary. Mosquitoes have relatively short growth periods (generally 20 to 30 days) and can fly 2 to 3 km. Those mosquitoes that bite people do not breed in turbid waters, in waters that are too cold or hot, or rapidly flowing waters. Also, insect and fish predators can significantly reduce mosquito populations. Generally, optimal conditions for mosquitoes consist of well-vegetated, shallow (less than 20 cm) still water that is isolated from deeper water that would contain predators. Wetlands can be designed to limit mosquito production (Figure 8). Wet meadow and seasonal marsh areas can be designed to dry by the onset of warm weather. This can be accomplished using the basin model described above to compare evapotranspiration rates with the hydrologic requirements of the TVAs to define weir height. ©2001 CRC Press LLC

This, in turn, determines the water depth. Perennial marshes can be designed as a series of isolated stands adjacent to open water areas that contain mosquito predators. Ponded water areas would include a slide-gated culvert to allow drainage and maintenance of the site should a major outbreak occur. In general, designs should include significant amounts of wet meadow, seasonal marsh, and open water habitat but limited perennial marsh. Large expanses of perennial marsh, as are created for duck clubs, generally also need active annual drainage and intensive management to limit mosquito production if they are near residential areas.

Wet Meadow Seasonal Marsh Perennial Marsh Open Water

Berm/Dam

Berm/Dam

Winter Water Level Summer Water Level

SM WM

Figure 8

Slide Gate

OW PM

KEY KEY: Wet Medow (WM) Seasonal Marsh (SM) Perennial Marsh (PM) Open Water (OW)

Mosquito production can be limited by designing wet meadow and seasonal marsh areas to periodically dry out, by limiting perennial marsh, and by providing a permanent open water refuge for mosquito predators.

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Water Quality Untreated stormwater from urban areas is likely to contain pollutants, especially metals, in such concentrations that water quality objectives are exceeded in downstream receiving waters. Many, though not all, pollutants contained in urban runoff are sediment associated. Controls to remove sediments, such as settling or infiltration basins and filtration devices, are recommended in design manuals as the most practical manner to control discharges of pollutants in urban runoff (Stahre and Urbonas, 1989). Settling basins should be designed to retain a specific level of storm event in the basin for a 24- to 48-h period. Storms between the mean annual and 10–year storm levels are often used to define the basin size. Infiltration basins should be underlain by a soil that allows percolation at a rate sufficient to trap sediments in the interstitial area for the same storm level. Inflow structures for these basins should be designed so that erosion and short circuiting through the basin are minimized. Outflow structures should be dual low flow and high flow, allowing the passage of extreme events while ensuring that first flush waters receive the extended detention or infiltration time needed to allow settling. Low flow structures used in these basins should include trash racks to prevent clogging.

IMPLEMENTATION The project designer and the contractors should meet and agree upon a specific order of operations and responsibilities prior to beginning any construction project. The order of operations set forth in Table 4 is believed to be the most efficient method of constructing a woodland or marsh project. However, changes in the order of operations may be necessary to allow for weather conditions or other factors. It is imperative that the constructed wetlands, as well as any wetlands to be preserved, are not disturbed by construction activities. This includes using wetlands as right of ways to transport equipment or as equipment storage areas. Communication and coordination between wetland construction operations and any other construction operations are essential. Access, turning on or off utilities, stockpiling materials on project sites, or any situation that might affect either operation should be resolved in advance. Table 4

Recommended Sequence of Construction Events for Wetlands Construction

Install protective flagging and stakes to preserve or salvage areas Remove all invasive exotic plants and on-site garbage Salvage all specified plants Grade construction site to specifications Dispose of excavated materials at designated fill sites Prepare woodland planting basins, seed beds, and otherplanting areas Install water supply or irrigation system and test Plant in designated zones Provide protection of construction area Prepare as-builts and construction report

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An Ecological Monitor (EM) should be designated to ensure that the wetland is constructed in accordance with the approved construction plan. The EM should be responsible for certifying that the project has been built in accordance with the approved construction plan and permits, and should monitor all operations occurring in the wetland areas. The EM should also attend any preconstruction conferences and meetings during construction which are pertinent to the wetland. Among the factors that expedite project implementation is obtaining all necessary permits issued prior to scheduled site preparation and planting. There can be several regulatory agencies involved in the wetland construction project and the specific requirements of each must be met. These obligations typically include assurance that nearby habitats will not be disturbed and provision of means to control siltation during construction. The planting schedule needs to be coordinated with plant availability, regardless of whether plants are field-collected or nursery-grown. This also needs to be scheduled for the optimal time of the year for planting the species involved. Construction and final grading should take place well in advance of the optimum planting dates because several weeks are required for the settling of fill material (Broome, 1990). Generally, planting should occur when temperature, rainfall, and salinity are moderate. For example, in the southeast, planting should occur between the first of April and mid-June (Broome, 1990). In central and south Florida, this period can be extended to mid-March through September. Predicted tides and other hydrologic conditions should be checked to avoid excessively high or low water conditions. Construction should also be timed to avoid disturbance to seasonally nesting or migratory wildlife. Construction Sequencing Construction should proceed in an orderly sequence for most projects (Table 4). This sequence begins with the installation of protective flagging for any areas to be preserved and includes removing invasive species, salvaging desired species, grading, planting, and fencing. Production of as-built plans is the final operation. Construction of a water supply may be necessary some instances. Protective Flagging All existing habitats that will remain undisturbed, those which will be salvaged within the general work area, and all travel ways should be staked and flagged prior to any grading activities. Flagging should be highly visible and replaced as necessary so as to be continuously in place during construction activities. Stakes should be at least 1 m tall and painted an easily observable color such as fluorescent orange. Flagging should extend around the protected area perimeters or along their entire lengths to prevent any unwanted intrusions or damage. Accidentally damaged plants or areas should be repaired. All fencing and flagging should be removed at the end of the construction project.

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Weed Removal Mowing or scraping requirements for weed removal will vary from site to site depending on the amount and type of weeds and the amount of grading. Typically, areas of noxious weeds should be excavated and the infested soil deposited elsewhere. Alternatively, the weeds should be disked, watered to encourage seed growth, and disked again. The latter should be repeated until weed growth is extremely sparse. Chemical controls may also be used. Areas with little or no grading will require at least a thorough mowing so that debris will not hamper construction. A flail-type mower should be used and all debris thoroughly mulched. Salvaging All appropriate plants and soil on site should be salvaged for replanting. Salvaging of wetland soil, and hence the seed bank, can be extremely important for construction success. Dunn and Best (1983) found that a representation of plants from all successional stages may only occur where a seed bank has been placed in the marsh. Erwin et al. (1985) found much higher species richness and cover in marshes created with salvaged topsoil than with subsoil. However, seeds of woody species may be absent or underrepresented in seed banks (Leck 1989). The collection and broadcasting of woody seeds or the planting of propagules can effect timely development of riparian woodland associations. Salvaged plants should be kept in the shade and watered if excavation has not proceeded to the point where they can be planted immediately (within 48 h of excavation). The viability of salvaged plants declines significantly after 45 days. Additionally, marsh plants may be salvaged from selected locations outside the project site. Salvaging should occur manually or with a trenching or similar narrowbucket backhoe, and should remove no more than 20 percent of any one stand. Grading Studies of wetland construction projects completed between 1960 and 1980 show that improper grading and grading management are two of the most important factors contributing to failure (Garbisch, 1977; Zentner, 1989). The EM is most useful during this stage and will often be required to make quick decisions when unanticipated issues develop. For example, while excavating a basin for wetland construction in Folsom, CA, the EM noticed a slightly discolored soil area. The discoloration proved to be an unobserved sand lens which, if left untreated, would have resulted in complete drainage of the proposed marsh after inundation. Similarly, large organic debris may be encountered during excavation and should be incorporated by the EM into the project. The EM should recognize that few preconstruction soil surveys are sufficient to precisely define subsurface conditions. Grading requirements are defined almost entirely by measurement of elevation change. These measurements require reference to established benchmarks. Nearby structures may have recorded elevations that can be obtained from local government agencies. At least two benchmarks should be used when establishing a site-reference ©2001 CRC Press LLC

elevation. As an alternative, local plant populations can be used as a guide to proper elevations. Juveniles or seedlings of the desired species provide the most accurate information because they are more sensitive to elevation differences than adult specimens. The site should be surveyed after grading and prior to plant installation to ensure that the specified characteristics have been attained. Topographic surveys should be completed and reviewed before construction equipment is removed from the site, so that slope and elevation can be efficiently adjusted. Shisler (1990) recommends preparing a bathymetric or topographic contour map on 15 cm (0.5 ft) contours after fill has settled but prior to planting. The map also provides a base for as built surveys and monitoring efforts. If the site has been filled or excavated, sufficient time for the substrate to settle should be allowed prior to determining and adjusting final elevations. This is especially important for tidal sites. The site may be susceptible to ponding and resuspension (turbidity), and the substrate will not provide adequate support to young plants, if planting occurs too soon after earthwork. Planting As noted previously, plant material may be installed as container stock, bare root seedlings, cuttings, canes, plugs, or seed. The first four are typical for woodland plantings, plugs are most often used in marsh projects, while seed is common for both woodland and marsh. Container plants generally range in size from small seedlings to 3.75 l (1 gal) or similar-sized stock. Smaller stock is less expensive to grow and plant while larger material can provide an immediate presence to increase buffer capabilities and aesthetics. Wetland or wetland buffer conditions are rarely as protected as nurseries, and larger stock will require additional care during the first year after planting to reach its potential. All plant material used should be collected from within the immediate region. Considerations as to the proximity of the gene pools and planted species vary greatly from one plant species to another. Plant material should be free from disease, insects, and weeds, not be rootbound, and identified correctly as to genus and species. All plant species and quantities should correspond to the planting plan and should be inspected prior to planting. Container plants should be collected, propagated, and grown for at least one growing season prior to planting. Stock should be planted in a hole twice as deep and wide as the root ball (Figure 9). The hole should be backfilled with good quality soil so that the root collar of the plant is level with the surrounding soil level. Slowrelease fertilizer may be added to each planting hole prior to planting the seedling. A water-conserving polymer may also be useful in arid regions. The root ball should be covered with at least 1 cm of soil to prevent a wicking effect from drying out of the root ball. In many irrigated cases, construction of a basin will help hold water near the plant and ensure adequate irrigation. The basin typically consists of a 0.6 m diameter (or larger) water ring 5 cm deep with a surrounding berm 5 cm above grade centered around the plant. Shredded bark or similar mulch should be placed on watering basins to a depth of 5 cm making sure not to cover the crown of the rootball. A weed mat may be used to further reduce weed growth but should then be covered ©2001 CRC Press LLC

with mulch to prevent overheating of the near-surface soil. Weed mats generally reduce weed growth but increase construction costs significantly. In addition, the weed mats trap moisture and facilitate fungal growth that can lead to reduced plant viability. Where planting basins are eroded, dirt can settle on top of the weed mat and form a substrate for weed growth. When drip irrigation is used, a plant emitter should be placed directly on top of the root ball. The plant should be watered thoroughly after installation and checked 2 to 3 days later for settling and stress.

Figure 9

Survival of planted stock can be maximized through careful attention to planting, watering, and fertilizing.

Most container plants will benefit from an augured planting hole when riparian woodland planting occurs in low permeability soils. For example, 3.75 I propagules with deep tap roots generally require holes augured to a depth of 1.2 m using a 23 cm diameter auger. Holes should be responsive to the plant form. For example, deep tap root species will use deeper and narrower holes than shallow-rooted species. ©2001 CRC Press LLC

All holes should be backfilled by the end of the same workday and should be completely saturated to promote settling of excavated soil. Bare-root seedlings have been a staple of the fruit tree industry for some time and are now commonplace in constructed wetlands. Bare-root seedlings are essentially large container stock without the containers. Instructions for container stock are applicable to bare-root material. Special care should be taken that the material is planted in a hole deep enough and wide enough to prevent recurving or J-rooting the tap root. The use of dormant cuttings in low-terrace woodland construction is wellrecognized. Cuttings should be at least 2 to 5 cm in diameter and 1 m in length, although these dimensions will vary somewhat by region. At one extreme, construction work in the xeric southwest may involve auguring deep beneath the surface and the planting of poles up to 6 m long in attempts to reach subsurface water (Anderson et al., 1984). At the other extreme, planting the same species in the more mesic Pacific Northwest, which is characterized by less permeable soil, may require a pole cutting 30 cm in length or less. All cuttings should be taken from young wood, be free of disease, 2/3 of the cutting should be pounded into the ground, and the soil should be tamped around the cutting. The top should be cut off at a 45 degree angle to facilitate growth. Cuttings must be kept moist and either can be planted the same day they were cut or left in water for 4 to 5 days to harden off. Cuttings are probably the most inexpensive way to quickly establish riparian woodland cover. Canes are effective planting stock for many vines. They resemble cuttings in that they should be nearly dormant and leafless, 60 to 75 cm long, and in healthy condition. A shallow trench 3/4 of the cane length should be made and the cane laid in the trench and largely covered with one end exposed above the soil. The trenches should be oriented on the contour, that is, perpendicular to the slope. Plugs are small clumps of herbaceous plant material and associated soil. Plugs are easiest to salvage with backhoes and excavators, although they are also grown in containers. Each salvaged plug should be about 30 by 30 cm, and should retain as much substrate as possible (at least 10 to 20 cm deep). Containerized plugs are generally much smaller, 3 cm across and 6 to 8 cm deep. Plugs should be planted so that the bases of the stems are level with the ground surface in inundated to saturated soil. All seed used on the site should be certified as to germination percentage and should be weed and disease free. Seeding rates and ratios should follow specifications developed by the grower. The EM should inspect all seed, soil preparation, calibration ratios, and phases of seeding operations. Specific soil preparation and seeding techniques should be adopted for each site and outlined in each site’s planting plan. Generally, seeding will work best when it follows local agricultural practices. Extensive seed bed preparation (disking, cross-disking, harrowing, and cultipacking) may not be applicable on all sites but will provide good germination at relatively low cost. Hydroseeding or hydromulching with stolons may be applicable where dense plantings or site conditions make tractor or hand seeding and seedbed preparation impracticable. Hydroseeding is more costly and good access to the planting site is required.

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The optimal time for seeding operations is during the dormant period. Seed broadcast early in the dormant season generally results in greater seed emergence than seed broadcast later in the dormant season. In arid regions, one key to success is to establish healthy, growing roots prior to the summer drought, so that the roots may follow the subsurface moisture level downward through the soil as summer progresses. The actual means of plant installation depends on the habitat type, the planting units used, and the substrate. On intertidal sandy substrates, mechanical means (e.g., tobacco planter pulled by a tractor) can be used, while on soft or muddy substrates, planting must often be conducted by hand working off of wooden mats or rafts. Transplanted material should be removed from the donor site so conditions conducive to invasion by exotics or attractive to potentially destructive fauna are not created. For example, large open patches are attractive to Canada geese and invite root predation by avian and mammal populations (Shisler, 1990). The use of fertilizer varies by species. The use of a slow-release fertilizer for riparian woodlands has been noted above. The effects of fertilizer on mangroves are unclear, but fertilizer has been shown to accelerate the growth of cordgrass (Broome, 1990). Fertilizer and lime can be used to provide short-term adjustments to substrate nutrient status and pH. Although plants may respond positively to small amounts of fertilizer at planting, accommodation to predominant long-term substrate conditions is probably desirable (Crewz and Lewis, 1991). When used, a time-release fertilizer incorporated into the substrate at the time of planting is recommended. Broadcasting fertilizer over the site is expensive, often increases weed cover, and only delays the achievement of nutritional equilibrium. Some coastal projects will require temporary protection of newly installed plants from excessive wave action during a preliminary establishment period. This can be accomplished by using floating tire breakwaters, earthen dikes, sandbags, and erosion control fabric. Although unattractive, floating tire breakwaters have the advantage of being reusable once plant establishment has occurred. The Riley encased methodology (Riley et al., 1999) is a promising technique for establishing mangroves in moderate to high energy environments. The method places seedlings in slotted PVC pipes inserted into the substrate in the intertidal zone. Water Supply Construction and placement of water control structures are relatively simple provided certain issues are resolved. First, review the placement of the structure prior to emplacement. Design analyses are important, and care should be taken to ensure that the location and design make sense in the field before blindly following construction plans. Second, ensure that the structure is firmly sealed into the surrounding soil. Water will tend to erode soil around the structure if proper contact is not provided. Third, check the structure during daily, seasonal, and episodic flows. Finally, remember that any structure placed in a waterway will require continual maintenance. Plan ahead to provide the appropriate financing and maintenance reminders. Enclosed supply systems (drip irrigation) may be required during the initial establishment period to assure the success of new plantings. Spray irrigation is not ©2001 CRC Press LLC

recommended owing to its propensity to encourage weeds. Systems connected to a potable water supply will require a reduced pressure backflow assembly inspected and tested by a certified backflow technician. Nonpotable supplies will require filtering, usually several large filters in sequence. All irrigation lines should include a tracer line (#14 UF direct burial for easy identification of line location). Generally, drip irrigation systems consist of a main line of polyvinyl chloride (PVC) tubing 5 to 15 cm in diameter running to valves that control the flow. From the valves, secondary or PVC lateral lines, 2.5 to 5 cm in diameter, transport water to local points where polyethylene (poly) tubing (2.5 cm in diameter) provides water directly to the plants. Before passing into the poly tubing, all water should be filtered and the pressure reduced. Smaller poly tubing, known as spaghetti tubing, may be hooked into the larger poly lines for further movement of water. However, spaghetti tubing is difficult to maintain and not recommended for most construction projects. In buffer strips along streets and other visible areas, irrigation should be below grade. In more secluded areas, mainlines and valves should be below grade, but poly lines may be installed above grade. The latter reduces trenching costs and eases maintenance. Jute hooks or 15 cm staples should be used to secure poly tubing in place. Staples should be placed every 3 m on a run and 30 cm on either side of each planting. All lines should be thoroughly flushed before inserting emitters, and each planting receives an emitter. Emitters should be placed directly over the root ball because the density of the root ball and indigenous soil may be quite different. Pressure testing upon completion of the main line and valves should be required; lateral lines should be left on for a period of at least 2 h to visually inspect all leaks. Upon completing the irrigation system, the EM should make a final walkthrough to verify the system is operating correctly. Fencing All habitat areas adjacent to streets should be separated from the roadways by a post and cable or similar barrier. In areas where maintenance access for vehicles is necessary, locking bullards should be installed in accordance with local specifications. Fencing during the construction period may also be necessary. As-Builts The EM should be responsible for overseeing preparation of grading, planting, and irrigation as-builts when the project is completed. The planting of as-builts should include the location, genus and species, and container size of each propagule. The EM should also certify that the project has been built in accordance with the plan and transmit the as-builts and certification to the appropriate parties.

MAINTENANCE Popular thought would have it that native plants are pre-adapted to the growing conditions of a site and should not require substantial maintenance to reach maturity. ©2001 CRC Press LLC

However, site conditions in the United States and much of the rest of the world have changed so radically over the past two centuries that site conditions often no longer reflect the conditions under which native species developed. Good examples are the wet meadows of the Southwest. Prior to European settlement, these meadows were dominated by perennial graminoids. With the arrival of Europeans came an invasion of annuals that almost extirpated the native perennials. Over the past 200 years, invading annuals and introduced livestock have succeeded in producing a substantial seed bed of annuals, formed thick thatch-dominated near-surface conditions, and fostered the growth of small and large mammal populations. These changes in the western environment have made construction of native meadows much more difficult than simply clearing a patch of ground and spreading some seed. Vigorous maintenance efforts must be carried out to keep the annuals from re-invading the native meadow. Additionally, construction is not a natural process, but rather it entails artificially inseminating a site with plant material. Under natural conditions, the plants that reach 10 cm are the few survivors of several thousands of seeds in a favorable microsite at a time when conditions are relatively optimal for their growth. The project proponent rarely has the luxury to wait or the knowledge to define these conditions. Consequently, the species to be planted are unlikely to be propagated naturally and may not even be planted in a site for which they are now adapted. Maintenance activities will be needed to ensure that the vegetation association develops as a native vegetation association, without invasion by harmful exotic species. The array of tasks required for any one project may not match the list provided in Table 5, but each project is likely to require some form of maintenance. Although maintenance is required, it should be viewed as a short-term measure, not only owing to its costs but because long-term maintenance suggests that the TVA is ill-suited for site conditions. Consequently, effective wetland construction will entail a good design to ensure the best possible match between the selected species and a site, and manipulation of the site to improve planting and growth conditions. Maintenance, even intensive maintenance activities, should generally be limited to the first three years after the cessation of planting. If a site is not relatively self-sufficient after this time, either additional construction work will be required or the design must be reconsidered. Weed Control In most cases, careful design and preplanting weed control procedures will reduce the burden of weed abatement considerably. However, a freshly graded construction site is a haven for weeds that may be carried in from off site. The ecologist must make a distinction between ruderal species that are part of natural succession and those species that will impede development of the TVA. The latter, particularly nonnative, aggressive species can be addressed using manual or chemical controls. The ecologist must also ensure that the appropriate native species replaces the weed, and the conditions that resulted in weed growth will not reoccur. Manual controls include hand removal of the entire plant or cutting the plant above ground. Hand removal of the entire weed is labor intensive and is best suited ©2001 CRC Press LLC

Table 5

Wetland Construction Maintenance is an Essential Step for Ensuring Project Success Problem

Weeds Annual Perennial Woody Erosion Sheet Scour Slump replant Herbivory Post-planting Grazing Plant care Nutrients Form Water supply Pest/diseases Irrigation Mortality Litter Trash

Tools

Survey Frequency

Manual Chemical Hand removal

1 to 3 times per year

Redirect flow Regrade

Post-storm and annually

Screens

Once

Fertilizer Staking Basin rework IPM/spray

As needed

Replacement

Monthly

Patrol

Monthly

* Each project should be assessed for the problems listed and appropriate remediation should be initiated.

for woody plants. The advantage of hand removal is that the area of impact is usually quite small. Less specific weed control activities can create the type of disturbance which results in more weed growth. It is often much less expensive to cut the weed and then spot spray the stump with an herbicide. However, for conditions that militate against the use of chemical controls, an array of tools are available from suppliers that can be used to selectively remove even mid-sized trees without disturbing the adjacent land or plants. Cutting can include hand-pruning or chopping, weed whips or similar hand-held but gas-powered tools, and tractor-driven or floating mowers. Selection of a manual control method will depend on the type and extent of the weed and the project design. Hand pruning or chopping is labor intensive and costly unless the personnel consist of volunteers. Prior to selecting this method, the ecologist should personally weed a specific area for at least 2 h and develop an estimate of the amount of personhours required, multiplying this by the cost of the labor. Where weeding will occur in dense growth, or where only a few plants among many are to be eliminated, this method is the most productive. Weed whips and similar tools are very useful for clearing annual or soft perennial growth over large or small areas where tractors cannot be driven (e.g., slopes, marshes). However, these should not be used near planted trees and shrubs or aboveground irrigation lines as even an experienced practitioner can mistakenly girdle a plant or cut a poly line. Mechanical mowers are the most efficient means of cutting large areas of vegetation. However, they cannot run on steep slopes (although some have mowing booms that can reach out and cut limited areas) and require a certain distance between trees and shrubs to be preserved. ©2001 CRC Press LLC

These issues should be considered during the design phase. An easily maintained project is generally subject to less disturbance and may prove to be more successful. Timing is often crucial in manually controlling weeds, especially annuals. Because cutting does not remove the root systems, it is generally important to cut the plant just prior to seed set to maximize the likelihood of complete control. Even this technique may not always work. Mowing of the annual yellow star thistle (Centaurea solstitialis) on clay soils just before seed set almost eliminated this noxious weed on one site. By contrast, mowing of another population on rocky soils (where this species thrives) resulted in a second flowering several weeks later. Chemical controls are often the least expensive means of eradicating or reducing weed growth. However, very few chemicals are licensed for use in wetlands and a licensed technician is often required by local regulations. Further, environmental conditions (e.g., wind speeds) never seem to be as optimal as required and spraying often inflicts damage outside the target area. Chemical controls include pre-emergents that are applied to the ground prior to the emergence of the weeds in the spring and post-emergents that kill or stunt plants during their active growth stages. Preemergents are most useful when applied adjacent to newly planted propagules because they limit the growth of competing weeds. Post-emergent controls are most useful for broad areas completely dominated by weeds, areas where no plants are proposed (e.g., firebreaks), or spot-spraying of individual weeds. Surveys for weed control needs should start at the beginning of the first growing season following construction. Weeding frequency will depend on the weed species and seasonal growth cycles. Annuals may need controls applied as much as three times in a year, whereas woody plants can generally be removed once per year. Erosion Control Erosion control is best effected by good design. However, one of the truisms of any construction project is that site conditions are not completely predictable. Unseen channel irregularities, inclusions of different soil types, and similar events will require modifications to the design during construction in order to minimize subsequent maintenance efforts. Erosion in marshes or the channel banks of riparian woodlands often occurs as sheet erosion, scouring, or slumping. Sheet erosion takes place on relatively flat slopes and generally results in the loss of all or most of the new plantings. This typically is due to poor seed bed preparation, inadequate root penetration prior to the storm, a subsurface soil layer that inhibits root growth, or a combination of these factors. The remedy is to try again. If possible, channel the flowing water into a swale rather than across the slope. Scouring occurs on moderate to steep slopes where higher velocities rapidly remove soil to some depth. Scouring is usually the result of modifications that have increased velocities through the site or re-oriented high velocity flows. Remedies are cause specific, but look for forces that have increased upstream flows or reduced downstream elevations. Slumping occurs when the surface soil on a channel bank moves downward as a relatively intact unit, often because it has been undercut. The movement will take ©2001 CRC Press LLC

anything on top of the soil unit with it including plantings or irrigation lines. Remedies are, again, site specific, but may be corrected by light grading and replanting after the erosive stimulus has been corrected. It is not unusual for the design to underestimate the flow velocities at specific points in a channel. Water supply structures, especially those perpendicular to the channel, can be undermined or the adjacent side slopes eroded. Heavy rock interplanted with fast-growing trees may eliminate future erosion when only a few centimeter of soil are lost between the structure and the soil. More significant erosion will require replacing the structure or identifying and rectifying the cause of the erosion. Reviewing the project site for erosion should occur immediately after the first three typical storms and each time thereafter for storms of greater intensity. Erosion controls are best applied annually, either immediately following the storm event that caused the erosion or during the appropriate planting or grading period. Herbivory Grazing has been and may be used to manage a TVA. However, the effect of herbivores on target plants is not always beneficial. The most common remedy for deer, rabbit, or beaver grazing is to provide wire screens around the plants or planting area. These screens can be relatively costly to provide, adding as much as US $1.00 to the cost of each plant. Consequently, screening most efficiently might be applied after a problem has surfaced. Screens in or adjacent to waterways should be removed prior to high water levels or floating material will catch in the screen. This may create enough mass that the screen, debris, and the plant will wash away. Monitoring for herbivory should occur weekly during the spring of the first year after planting, and less frequently thereafter. Plant Care Container-grown trees and shrubs in woodland construction sites may be fertilized once in the spring of the first and second year after planting if nutrient levels are low on the site. Fertilizer should be dribbled into the basin around the propagule. Trees may also need to be staked if wind or other forces are warping or bending the trees unnaturally. To stake a tree, place two 2.5 m pressure-treated stakes, 5 cm in diameter, 60 cm into the ground, 30 cm on either side of the tree. The tree should be bound to the stakes using tree tie tape fastened in a figure-eight pattern, 30 cm below the top of the stake. Basins around propagules should also be maintained to supply sufficient irrigation water. Insect or disease infestations are common on habitat construction projects. Generally, all infestations should be treated using Integrated Pest Management (IPM) techniques. Plantings of a single species are especially susceptible to massive outbreaks that are not well treated by IPM, however, and commercial sprays may be required. Monitoring for these problems should be completed weekly during the first year of the project with remedial action taken immediately.

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Irrigation System Maintenance The irrigation system should be checked regularly and frequently (e.g., weekly) immediately following planting for malfunction and vandalism. All drip lines and filters should be flushed as needed. Emitters must be checked regularly for malfunctions, position of emitter over root ball, and vandalism. Flushing end caps must also be checked regularly. In colder climates, backflow devices and mainline systems should be completely drained at the end of the growing season to prevent rupture due to freezing. Irrigation for plantings is a temporary tool to help establish the constructed vegetation association. Water should be decreased every year, and ideally should not be needed by the fourth year. Caution should be exercised not to create lush plants that would become dependent on regular watering. Deep watering should be spaced at the longest time possible before plants show signs of stress. This type of watering will encourage plant roots to travel downward into the appropriate water zones in the soil. Litter Removal Wetlands are usually depressions in the landscape and seem to collect litter. Litter can impede the growth of propagules or seedlings and increase the cost of plant care maintenance efforts. Therefore, each site is thoroughly policed and all litter and debris removed from the site at least annually. Construction projects that are near or within residential areas generally collect the most trash. Over 181 kg of litter was collected from one project in central California in 2 months time, at a cost of 42 labor h and US $350 in dump fees. Experience suggests that projects in residential areas will require at least 1 to 2 h per week for litter collection. General Maintenance Frequency Most projects will require a walk through by an ecologist or maintenance technician every 1 to 3 weeks for the first 1 to 2 years. The precise number of visits depends on the size of the site, its proximity to disturbance, and the time of year. Visits reasonably may be required every week for the first year and twice monthly for the next 2 years. Smaller sites, for example those less than 4 ha, can reasonably be visited once every 2 to 3 weeks during the first year, and monthly in subsequent years. Minimizing Maintenance Efforts Local education can effectively reduce maintenance efforts associated with vandalism and litter. Efforts should be aimed at informing neighbors as to the project goals, values, and needs, and in enlisting their support for the long-term protection of the site. Conducting a replanting project for local third through sixth graders at least once every 2 years has proven helpful. Small brochures for each project that are mailed to local residents can also be beneficial. Preparation of a maintenance ©2001 CRC Press LLC

manual in the last year of monitoring for long-term maintenance of the project area also is effective.

RESEARCH NEEDS Many issues related to the enhancement, restoration, and creation of wetlands would benefit from the conduct of basic and applied research. This is especially true for coastal wetlands. These include an increased knowledge about species’ life requisites. The physical and chemical properties of wetlands, including topography, soils properties, subsidence rates (which vary locally), and hydraulic circulation, are often poorly understood. For wetlands designed to improve local water quality, information is needed on the effects of treatment on other wetland functions.

REFERENCES Adams, L. W. and Dove, L. E., Wildlife Reserves and Corridors in the Urban Environment. National Institute for Urban Wildlife, Columbia, MD, 1989. Anderson, B.W., Disano, J., Brooks, D. L., and Ohmart, R. D., Mortality and growth of cottonwood on dredge-spoil, in California Riparian Systems: Ecology, Conservation and Productive Management, Warner, R. E. and Hendrix, K. M., Eds., University of California Press, Berkeley, 1984. Broome, S. W., Creation and restoration of tidal wetlands of the southeastern United States, in Wetland Creation and Restoration: The Status of the Science, Kusler, J. A. and Kentula, M. E., Eds., Island Press, Washington, D.C., 1990, 37. Brown, M. T., Gross, F., and Higman, J., Studies of a method of wetland reconstruction following phosphate mining, in Proceedings of the Eleventh Annual Conference on Wetland Restoration and Creation, Webb, F. J., Ed., Hillsborough Community College, Tampa, FL, 1984. Brown, R. G. and Stark, J. R., Comparison of ground-water and surface-water interactions in two wetlands, in Wetland and Riparian Ecosystems of the American West, Mutz, K. M. and Lee, L .C., Eds., Proceedings of the Eighth Annual Meeting of the Society of Wetland Scientists, Society of Wetland Scientists, Wilmington, NC, 1987. Chabrek, R. H., Creation, restoration, and enhancement of marshes of the north central Gulf Coast, in Wetland Creation and Restoration: The Status of the Science, Kusler, J. A. and Kentula, M. E., Eds., Island Press, Washington, D.C., 1990, 125. Clark J. R. and Benforado, J., Eds., Wetlands of Bottomland Hardwood Forests, Elsevier, Amsterdam, 1981. Clements, F. E., The relict method of dynamic ecology, Ecology, 2, 39, 1934. Cowardin, L. M., Carter, V., Golet, F. C., and LaRoe, E. T., Classification of Wetlands and Deepwater Habitats of the United States, FWS/OBS-79/31, U.S. Fish and Wildlife Service, Washington, D.C., 1979. Crewz, D. W. and Lewis, R. R., An evaluation of historical attempts to establish emergent vegetation in marine wetlands in Florida, Florida Sea Grant College Technical Paper No. 60, Florida Sea Grant College, University of Florida, Gainesville, FL, 1991. Dane, C. W., Succession of aquatic marsh plants in small artificial marshes in New York State, NY Fish Game, 6(1), 57, 1959. ©2001 CRC Press LLC

Dickson, R. E., Hosner, J. F., and Hosley, N. A., The effects of four water regimes upon the growth of four bottomland tree species, For. Sci., 11(3), 299, 1965. Dunn, W. J. and Best, G. R., Enhancing ecological succession: seed bank survey of some Florida marshes and role of seed banks in marsh reclamation, in Proceedings of the 1983 Symposium on Surface Mining, Hydrology, Sedimentology, and Reclamation, University of Kentucky, Lexington, 1983. Erwin, K. L., Best, G. R., Dunn, W. J., and Wallace, P. M., Marsh and forested wetland reclamation of a central Florida phosphate mine, Wetlands, 4, 87, 1985. Faeth, S. H. and Kane, T. C., Urban biogeography: city parks as islands for Diptera and Coleoptera, Oecologia, 32, 127, 1978. Fahrig, L. and Merriam, G., Habitat patch connectivity and population survival, Ecology, 66, 1762, 1985. Garbisch, E. W., Recent and planned marsh establishment work throughout the contiguous United States: a survey and basic guidelines, U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS, 1977. Garbisch, E. W., Highway and wetlands: compensating wetland losses, Federal Highway Administration Report No. FHWA-IP-86–22, U.S. Department of Transportation, 1986. Godley, J. S. and Callahan, R. J., Creation of wetlands in a xeric community, in Proceedings of the 10th Annual Conference on Wetland Restoration and Creation, Webb, F. J., Ed., Hillsborough Community College, Tampa, FL, 1984. Harris, R. W., Leiser, A. T., and Fissell, A. T., Plant tolerance to flooding, University of California at Davis, Department of Environmental Horticulture, Davis, CA, 1975. Josselyn, M., Zedler, J., and Griswold, T., Wetland mitigation along the Pacific coast of the United States, in Wetland Creation and Restoration: The Status of the Science, Kusler, J. A. and Kentula, M. E., Eds., Island Press, Washington, D.C., 1990, 3. Klimas, C. V., Limitations on ecosystem function in the forested corridor along the lower Mississippi River, in Wetlands and River Corridor Management, Kusler, J. A. and Daly, S., Eds., Proceedings of a symposium presented by the Association of Wetland Managers, Charleston, SC, July 5–9, 1989. Kuenzler, E. J., Mangrove swamp systems, in Coastal Ecosystems of the United States, Vol. I, Odum, H. T., Copeland, B. J., and McMahan, E. A., Eds., The Conservation Foundation, Washington, D.C., 1974, 346. Kusler, J. A. and Kentula, M. E., Eds., Wetland Creation and Restoration: The Status of the Science, EPA/600/3–98/0, EPA, Corvallis, OR, 1989. Larson, J. S., Bedinger, M. S., Bryan, C. F., Brown, S., Huffman, R. T., Miller, E. L., Rhodes, D. G., and Touchet, B. A., Transition from wetlands to uplands in southeastern bottomland hardwood forests, in Wetlands of Bottomland Hardwood Forests, Clark, J. R. and Benforado, J., Eds., Elsevier, Amsterdam, 1981. Leck, M. A., Wetland seed banks, in Ecology of Soil Seed Banks, Leck, M. A., Parker, V. T., and Simpson, R. L., Eds., Academic Press, San Diego, CA, 1989. Lewis, R. R., Mangrove forests, in Creation and Restoration of Coastal Plant Communities, Lewis, R. R., Ed., CRC Press, Boca Raton, FL, 1982, 153. Lewis, R. R., The restoration and creation of seagrass meadows in the southeastern United States, in Proceedings of the Symposium on Subtropical Seagrasses of the Southeastern United States, Durako, M. J., Phillips, R. C., and Lewis, R. R., Eds., Florida Department of Natural Resources Mar. Res. Pub. No. 42, St. Petersburg, FL, 1987, 174. Lewis, R. R., Wetlands restoration/creation/enhancement terminology: suggestions for standardization, in Wetland Creation and Restoration: The Status of the Science, Kusler, J. A. and Kentula, M. E., Eds., Island Press, Washington, D.C., 1990, 417.

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Lewis, R. R., Enhancement, restoration, and creation of coastal wetlands, in Applied Wetland Science and Technology, Kent, D. M., Ed., Lewis Publishers, Boca Raton, FL, 1994. MacArthur, R. H. and Wilson, E. O., The Theory of Island Biogeography, Princeton University Press, Princeton, NJ, 1967. MacClintock, L., Whitcomb, R. F., and Whitcomb, B. L., Evidence for the value of corridors and the minimization of isolation in preservation of biotic diversity, Am. Birds, 31, 6, 1977. McBride, J. R. and Strahan, J., Establishment and survival of woody riparian species on gravel bars of an intermittent stream, Am. Midland Nat., 112(2), 235, 1984. Mitsch, W. J. and Gosselink, J. G., Wetlands, Van Nostrand Reinhold, New York, 1986. National Research Council, Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy, National Academy Press, Washington, D.C., 1992. O’Meara, T. E., Habitat island effects on the avian community in cypress ponds, Proc. Am. Conf. SE Assoc. Fish and Wildlife Agencies, 38, 97, 1984. Payne, N. F., Techniques for Wildlife Habitat Management of Wetlands, McGraw-Hill, New York, 1992. Riley, R., Kent, D. M., Salgado, C., and DeBusk, T., The Riley encased methodology for establishing mangroves, Land Water, May/June, 48, 1999. Shisler, J. K., Creation and restoration of coastal wetlands of the northeastern United States, in Wetland Creation and Restoration: The Status of the Science, Kusler, J. A. and Kentula, M. E., Eds., Island Press, Washington, D.C., 1990, 143. Stahre, P. and Urbonas, B., Stormwater Detention, Prentice-Hall, Englewood Cliffs, NJ, 1989. Tilghman, N. G., Characteristics of urban woodlands affecting breeding bird diversity and abundance, Land. Urban Plan., 14, 481, 1987. Tomlinson, P. B., The Botany of Mangroves, Cambridge University Press, Cambridge, U.K., 1986. U.S. Army Corps of Engineers, HEC-1 Flood Hydrograph Package: User’s Manual, Water Resources Support Center, Hydrologic Engineering Center, Davis, CA, 1981. Wegner, J. F. and Merriam, G., Movements by birds and small mammals between wood and adjoining farmland habitats, Appl. Ecol., 16, 349, 1979. Zentner and Zentner, Ball Ranch mitigation program, Report prepared for the Sienna Corporation, Walnut Creek, CA, 1989. Zentner and Zentner, Natoma Station monitoring report, Report prepared for the U.S. Army Corps of Engineers, Sacramento District, Walnut Creek, CA, 1990. Zentner and Zentner, Lower Laguna Creek drainage master plan: mitigation program, Report prepared for Sacramento County, Walnut Creek, CA, 1992.

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Rolband, Michael S. et al “Wetland Mitigation Banking” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001

CHAPTER

7

Wetland Mitigation Banking Michael S. Rolband, Ann Redmond, and Tom Kelsch

CONTENTS Background Regulatory Context The Banking Process Types of Wetland Mitigation Banks Perspectives on Mitigation Banking Ecological Perspective Regulatory Management Perspective User Perspective Economics Demand for the Product Service Area Regulatory Climate Service Area Size Mitigation Ratios Performance Requirements Monitoring and Maintenance Requirements Permitting Difficulty Attitudes about Mitigation Alternatives Regulatory Stability User Requirements Competitive Supply of the Product and Product Alternatives On-Site Opportunity for Wetland Mitigation Off-Site Opportunities for Wetland Mitigation Other Wetland Banks In Lieu Fee Alternatives

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Risk Assessment and Presale of the Product Revenue Projections Costs of Mitigation Bank Development Land Costs Hard Costs Soft Costs Long-Term Stewardship Economic Projections References

Mitigating the environmental impacts of necessary development actions on wetlands and other aquatic resources is a central premise of wetland regulatory programs. Offsetting losses through the restoration or creation of replacement wetlands has been promoted as a way to achieve a goal of no net loss of remaining wetland resources while still permitting unavoidable impacts to occur. As evidenced by recent studies, however, the effectiveness of on-site compensatory mitigation efforts has produced mixed results. Success rates range from 27 to 50 percent, due in part to 22 to 34 percent of the mitigation projects never being built (Redmond, 1991; Gallihugh, 1998; DeWeese, 1994; Brown and Veneman, 1998). In response to problems associated with individual mitigation efforts, there has been growing interest in the concept of mitigation banking. Mitigation banking refers to the restoration, creation, enhancement, and, in certain circumstances, the preservation of wetlands, for the purpose of compensating for multiple wetland losses in advance of development actions. It typically involves the consolidation of small, fragmented wetland mitigation projects into one large contiguous site. Units of restored, created, enhanced, or preserved wetlands are expressed as credits which may subsequently be withdrawn to offset debits incurred at a project development site. Mitigation banks provide greater flexibility to landowners needing to comply with mitigation requirements and can have several advantages over individual mitigation projects. To the advantage of permit applicants, mitigation banks may reduce permit processing times and provide more cost-effective compensatory mitigation. Most permit applicants do not wish to become wetland experts, but rather they are simply seeking authorization to move forward with their development projects. Through the purchase of credits from an approved mitigation bank, these applicants can transfer the responsibility for providing mitigation to an entity who has the expertise, resources, and incentive to ensure that the mitigation is ultimately successful. Mitigation banking also enhances the effectiveness of wetland protection programs. The environment benefits from consolidation of compensatory mitigation into a single large parcel, or contiguous parcels, that maximize the opportunity to successfully restore important wetland functions. Establishment of a mitigation bank often involves financial resources, planning, and scientific expertise not practicable to many project-specific compensatory mitigation proposals. Consolidation of resources can increase the potential for the establishment and long-term management ©2001 CRC Press LLC

of successful mitigation. Also, mitigation banking typically ensures that compensatory mitigation is implemented and functioning in advance of project impacts. This reduces temporal losses of aquatic functions and uncertainty over whether the mitigation will be successful in offsetting project impacts. Finally, consolidation of compensatory mitigation within a mitigation bank increases the efficiency of limited regulatory agency resources. The review and compliance monitoring of mitigation projects is improved and, thus, agency ability to ensure the success of efforts to restore, create, or enhance wetlands for mitigation purposes is improved.

BACKGROUND The concept of mitigation banking in the United States dates back to the early 1980s when resource agencies, and some in the regulated community, were looking for ways to mitigate wetland impacts more efficiently and effectively. A 1988 U.S. Fish and Wildlife (USFWS) report profiled 13 mitigation banks that were in existence at the time (Short, 1988). Many of these banks were established by enterprising individuals who saw the opportunity to establish joint partnerships to protect and restore priority wetlands using funds from ports, transportation agencies, and others who needed to offset unavoidable impacts. These early efforts were initiated in the absence of any federal or state policies on how to establish mitigation banks. In 1991, in response to a request by Congress, the Corps of Engineers Institute for Water Resources, in collaboration with the Environmental Law Institute and others, initiated a comprehensive study of mitigation banking. The purpose of the study was to determine the potential of mitigation banking for achieving established wetland goals and to determine the applicability of mitigation banking to the U.S. Clean Water Act Section 404 regulatory program. The study included a critical review and evaluation of existing mitigation banks and an analysis of the economic, policy, and other institutional issues affecting banking (Reppert, 1992). The study identified 40 mitigation banks in existence, and another 60 banks that were under development or being considered for approval. An increase in the development of mitigation banks from 1988 to 1992 was the result of state departments of transportation recognizing the ecological, economic, and administrative benefits of consolidating mitigation efforts. The increase in banks was also instigated in part because the 1991 Intermodal Surface Transportation Efficiency Act specifically authorized the use of federal funds for such purposes. Virtually all of the existing banks identified in the Institute for Water Resources study were single-user banks—banks established by a public agency or private company to satisfy their own mitigation needs. Of those banks under development, however, the survey identified several commercial banks whose intent was to offer mitigation credits for sale to the general public. Local agencies, private entrepreneurs, and joint ventures between government agencies and private entities sponsored the commercial bank proposals. The Environmental Law Institute in a 1994 study also noted the trend toward commercial banks.

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Another important finding of the mitigation banking study was the need for a specific policy providing ecological, economic, and legal standards for the establishment and use of banks. A policy would reduce uncertainty, and in so doing, encourage further investment. At the federal level, the Army Corps of Engineers (Corps) and the U.S. Environmental Protection Agency (USEPA) first acknowledged the potential role for mitigation banks in the Section 404 regulatory program in their 1990 Memorandum of Agreement (MOA). In discussing options for providing compensatory mitigation, the memorandum indicates that use of mitigation banks may be acceptable where a bank has been approved by the agencies. In November 1995, the Corps, USEPA, USFWS, National Marine Fisheries Service, and Natural Resources Conservation Service issued the Federal Guidance for the Establishment, Use and Operation of Mitigation Banks. This policy statement details the terms and conditions under which the agencies may approve a mitigation bank for use as compensatory mitigation within the Section 404 regulatory program and the Swampbuster provisions of the Farm Bill. Mitigation banking has been endorsed by both the Bush and Clinton administrations within their comprehensive plans for reforming federal wetland programs. Moreover, Congress has entertained several legislation proposals to promote the use of mitigation banks. In 1998, Congress passed a new transportation bill (TEA-21) that provides further support for the use of mitigation banks to offset wetland impacts that result from transportation projects. In addition to the federal policy, approximately 20 states have established, or are in the process of establishing, policies on mitigation banking. While many of these policies are generally consistent with the federal policy, each is tailored to the unique regulatory requirements of state wetland legislation and is responsive to particular regional conditions. The interest in establishing mitigation banks appears to be increasing, owing in part to the release of federal and state policies. In 1994, the Institute for Wetland Resources identified 46 existing wetland banks in the United States. Only 1 of these 46 was a privately owned bank offering credits to the general public (Environmental Law Institute, 1994). By 1998, the Corps identified over 200 mitigation banks that were either approved or under agency review. Of these 200, approximately 40 existing banks and 75 proposed banks were private commercial banks (unpublished Institute for Wetland Resources survey). Other banking trends include the increased use of mitigation banks as a watershed management tool and the use of mitigation credits for other environmental programs such as endangered species and water quality programs.

REGULATORY CONTEXT In the United States, Section 404 of the Clean Water Act establishes a program to regulate the discharge of dredged or fill material into waters of the United States, including wetlands. Activities typically regulated under this program include fills for development, water resource projects such as dams and levees, infrastructure

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development including highway and airport construction, and conversions of wetlands to uplands for farming or forestry. In 1990, the Bush Administration implemented the Memorandum of Agreement between the Department of the Army and the Environmental Protection Agency Concerning Determination of Mitigation under the Clean Water Act Section 404(b)(1) Guidelines (USEPA, 1990). The Mitigation MOA establishes criteria that must be satisfied before a dredge and fill permit can be obtained from the Corps. First, all practicable steps to avoid wetland impacts must be undertaken by evaluating less damaging project alternatives. Second, applicants must minimize potential impacts to wetlands. And finally, all remaining, unavoidable impacts must be offset through compensatory mitigation. Compensatory mitigation includes the restoration of historic or degraded wetlands, the enhancement of functions of existing wetlands, the creation of new wetlands from uplands, or, in exceptional circumstances, the protection of existing wetlands through acquisition or conservation easement. As clarified in the Mitigation MOA, there is a preference for compensatory mitigation to be located on-site or as close to the impact site as possible. In this way, environmental impacts to local flooding, water quality, fish and wildlife habitat, and other public interests are minimized. In addition, there is a preference that mitigation be in kind, that is, of the same habitat type as the wetlands to be impacted to ensure the mitigation provides similar functions and values. These preferences notwithstanding, the Mitigation MOA also identifies mitigation banking as an option for offsetting unavoidable impacts. On August 24, 1993, the White House Office on Environmental Policy issued a comprehensive plan for reforming federal wetland programs. Regarding mitigation, the plan acknowledges that the aforementioned sequential criteria constitute a logical, predictable, and reasonable framework and that mitigation banking is appropriate in some circumstances. The plan suggests Congress should endorse banking as a compensatory mitigation option under the Section 404 regulatory program. As an outgrowth of the interagency wetland plan, on November 28, 1995, the Corps, the USEPA, the Natural Resource Conservation Service, the USFWS, and the National Marine Fisheries Service issued a Memorandum to the Field titled “Federal Guidance for the Establishment, Use and Operation of Mitigation Banks” (U.S. Army Corps of Engineers et al., 1995). The “Guidance” encourages mitigation banking as an alternative under the Mitigation MOA. The “Guidance” states that mitigation banking is appropriate when compensation for permitted impacts cannot be achieved at the development site or would not be as environmentally beneficial. Under the terms and conditions of the Guidance, applicants for a Section 404 dredge and fill permit may seek approval from the Corps to compensate for unavoidable impacts through the purchase of credits from an operational mitigation bank. In such circumstances, the Corps may approve use of the mitigation credits where onsite mitigation is not practicable (i.e., available and capable of being done) or use of the bank is environmentally preferable to other mitigation options. Moreover, the agencies have established a general preference for using mitigation bank credits to offset minor impacts associated with activities authorized under nationwide and other general permits. Nationwide and general permits are designed to facilitate decision making on relatively small-scale projects and for impacts typically associated with ©2001 CRC Press LLC

linear projects such as road development or utility line installation. Upon authorization by the Corps, the legal responsibility for providing mitigation is transferred to the mitigation bank sponsor through the sale of mitigation credits. In addition to regulation at the federal level, some states have promulgated regulations on mitigation banking (Table 1). Regulation by states has the effect of applying the philosophy and needs of the region to the practice. There are no cases (as of April 1999) where state law alters the existing federal regulations. In all cases, mitigation banking is one tool in the mitigation toolbox. The Banking Process A bank sponsor, who proposes to establish and operate a mitigation bank, initiates mitigation banking. Pertinent regulatory agencies form a mitigation bank review team (MBRT) to work with the bank sponsor. In the United States, the mitigation bank review team typically consists of an interagency group of federal, state, tribal, and/or local regulatory and resource agency representatives. The sponsor will discuss the concept with the MBRT in a pre-application meeting, thereby providing early feedback for the banker as to whether the concept appears viable. The MBRT members may also have knowledge of the project area that will assist the banker in its decision to move forward with the concept. For example, there may be a proposal to build a wellfield proximal to the proposed bank site that would likely affect hydrologic restoration. Alternatively, there may be a recent or pending designation of the area as being of significant conservation interest, to which the bank can then contribute. A prospectus describes the proposed project, and in permitting parlance would constitute a permit application. In the early stages, the prospectus will normally be presented at a conceptual to moderate level of detail, depending on the region or project. Once the proposed bank has been deemed appropriate, then the final details are developed and provided to the MBRT. An accepted prospectus becomes a Mitigation Banking Instrument (MBI). The MBI is developed by the bank sponsor, in consultation with the MBRT, and submitted to the MBRT for review and approval. The role of the instrument is to authorize the mitigation bank project. The instrument includes a preamble describing the project and sections regarding the establishment, operation, maintenance, and monitoring of the project. If a Section 404 permit is also required, the permit is issued as a separate authorization. Because of the importance of these projects, all MBIs must be publicly noticed. The Institute for Water Resources (1996) has developed a model MBI. The MBRT continues to oversee the project once the mitigation bank has been approved and implemented. The operational phase of the project will continue for years, until the project has been declared ecologically successful and transitions to the long-term management phase. During this phase, the sponsor preserves the project site, completes the physical site work, markets, sells, or uses the credits, and monitors and maintains the site. The MBRT reviews the monitoring reports, performs compliance inspections, approves the release of credits, and approves the use of credits for the offset of permitted impacts. The mitigation bank is then debited an ©2001 CRC Press LLC

Table 1

Examples of State Wetland Banking Regulations

State

Wetland Banking

Mitigation Bankers

Florida

Department of Environmental Protection and the 5 regional water management districts (Chapter 62342, Florida Administrative Code)

Private or public

Hackensack Meadowlands District, New Jersey

Interagency Compensatory Wetland Mitigation Agreement (Corps, EPA, NJDEP, Hackensack Meadowlands commission, NMFS and FWS)

Private or public

Louisiana

State’s Coastal Zone

Private or public

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Use of Credits

Mitigation Type

Credits

Management

Land

Some advance credits may be available; credit releases are made with increasing function at the site; some credits are withheld until success Possible to obtain umbrella agreement for establishment and operation of multiple bank sites; some advance use of credits may be approved; preservation credits available once site is preserved Preservation and financial assurances are required for advance credits; preservation is for 20 yr for marshes and 50 yr for forested wetlands

Restoration of native, pre-existing habitats is preferred

Credit assessments are made using a functional assessment methodology

Perpetual management is required and must be endowed prior to the sale of credits

State lands are prohibited for use as mitigation banks

Wetland restoration, creation or enhancement may be used; uplands within the bank site may be assigned credit

Compensation amounts for the offset of impacts is decided on a case by case basis

Endowed perpetual management is required

Public or private lands may be used

Wetland restoration, creation, enhancement, and protection may be used

Credits are assessed using a functional assessment procedure; compensation amounts for the offset of impacts is decided on a case by case basis

Public or private lands may be used

Table 1 (continued) State

Examples of State Wetland Banking Regulations

Wetland Banking

Maryland (nontidal)

Title 26, Subtitle 23, Code of Maryland Regulations (COMAR 26.23.04.06). Nontidal Wetlands Mitigation Banking Act

Maryland (tidal)

Department of the Environment (COMAR 26.24.05.01.B(9) in consultation with local, state, and federal agencies Federal guidance; state provides its assent by signing the Mitigation Banking Instrument

North Carolina

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Mitigation Bankers

Use of Credits

Mitigation Type

Credits

Private or public

Up to 50% of the credits may be available for use in the first two years after construction when the site has been preserved in perpetuity, construction is completed, and the bonding requirements (private banks only) are met; subsequent credit releases are made based on demonstrated increases in function at the site No specific regulations on mitigation banks

Based on rations with a 50% increase in the ratio currently required of the mitigation, uses a wetlands bank; ratios vary by Cowardin Classification and wetlands location

Private

Mitigation via payment to a trust fund for those permit applicants requiring a 401 water quality certification

No specific state provisions governing credit release, perpetual management, financial assurances, service areas, or credit assessments for impacts

Management

Land State lands may be used

The state regulations require “adequate, dedicated financial surety” exists for the perpetual land management

Public or private lands may be used

Table 1 (continued)

Examples of State Wetland Banking Regulations

State

Wetland Banking

Virginia (nontidal)

Does not specifically regulate wetlands banking; regulations establish maximum service area size for banks approved in accordance with applicable federal and state guidance, laws, or regulations Virginia Marine Resource Center (VMRC) and Virginia Institute of Marine Science (VIMS)

Virginia (tidal)

Washington

Federal guidance, state rules expected by December 1999

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Mitigation Bankers

Use of Credits

Mitigation Type

Credits

Department of Environmental Quality (DEQ) authorizes permits to use nontidal wetland banks

Uplands within the bank site may be assigned credit; wetland restoration, creation, enhancement, and protection may be used

Private or public

Sequencing is required prior to authorizing the use of an approved bank as compensation from permitted wetland losses

Generally habitat restoration or creation; also enhancement or in exceptional circumstances, preservation

Private or public

Use of credits prior to meeting all performance standards is allowed

Wetland restoration, creation, enhancement, and preservation may be used, though restoration is preferred

No specific state provisions governing credit release, perpetual management, financial assurances, service areas, or credit assessments for impacts Credit assessments are made using the Function Specific Credit Calculation methodology; performance standards are used to determine credit availability and bank success Long-term management and financial assurances are required

Management

Land Public or private lands may be used

Provisions for longterm management and maintenance are required

The state Department of Ecology and local governments will be signatories to the banking instruments

Public or private lands may be used

amount representing the loss of wetland functions at the impact site. The permit applicant financially compensates the bank sponsor in exchange for allowing its bank to be debited. The bank should be protected and managed over the long term after it has been declared successful. The bank must be legally protected from other future land uses through a conservation easement or similar mechanism. The sponsor is responsible for assuring the financial stability of the bank project over the long term. This necessitates appointment of a long-term manager. This may be the sponsor or another entity, such as a public land manager or environmental organization. Types of Wetland Mitigation Banks The type of sponsor and the operational use can characterize wetland mitigation banks. Sponsors include governmental or quasi-governmental agencies, nonprofit organizations, conservation groups, and private for profit companies. Operational uses include single user and open market sales. The two major types of banks are dedicated banks and commercial banks. Dedicated banks are typically created to compensate for a specific type of activity by a single entity. Dedicated banks include industrial banks—banks created by agreement or permit to mitigate for a specific user impact in a geographic area by a private company. An example of an industrial bank in the United States is the Tenneco LaTerre (Reppert, 1992), a bank sponsored by a private corporation, Tenneco LaTerre, for the purpose of mitigating wetland losses occurring from its oil and gas exploration activities in Louisiana coastal marshes. Another example is the Sunrise Valley Nature Park, a bank that consolidates mitigation for impacts on various separate parcels owned by Mobil Land Development Company in Reston, VA. Another type of dedicated bank is a public works bank. State highway departments, port authorities, or local governments for the purpose of providing mitigation for public works projects sponsored 75 percent of the 46 banks identified by the Corps Institute for Water Resources in 1994. Commercial banks are established by entities whose wetlands credits are available for purchase on the open market by unrelated entities who need wetlands compensation for permitted wetlands impacts. Several types of commercial banks exist. Private entrepreneurial banks create wetland credits and sell them at a profit sufficient to produce an economic return commensurate with the risk undertaken. Nonprofit banks provide mitigation for various activities to achieve a particular ecological and/or economic objective. Credit prices are set so that the sponsor can recover only the costs of the mitigation. For example, the Ohio Wetlands Foundation, a nonprofit group formed by members of the Ohio Homebuilders Association, created a mitigation bank so that builders could have a source of wetland credits and solve an industry problem in a specific geographic area. Governmental banks are banks established by a governmental agency (typically a local government agency) to create mitigation and cover its costs from sales to mitigate for impacts by other governmental or private entities.

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PERSPECTIVES ON MITIGATION BANKING Ecological Perspective Mitigation banking offers several ecological advantages compared to other mitigation vehicles. Many of the regulations governing mitigation banking require that sites be managed over the long term. Therefore, an important evaluation criterion of the mitigation bank planning and approval process is the long-term viability of the site. Long-term viability must be assessed within the context of expected changes in the site's landscape setting. An assessment of this type typically receives less attention in other mitigation planning. Mitigation banking typically consolidates many smaller mitigation obligations into one moderate to large site. Larger sites are more likely to provide significant wetland functions and values than smaller sites. Because banks are typically larger projects than project-specific mitigation, they often include adjacent upland communities. This results in a natural mosaic of upland and wetland in the landscape, increasing the function and value of the wetland and adjacent areas. Also, the relatively large size of mitigation banks facilitates their contribution to watershedbased planning efforts. Mitigation banks typically provide compensation in advance of impacts, meaning that there is little temporal loss in function and value. By contrast, traditional onsite or off-site mitigation is typically implemented or functioning after project impacts occur. This is particularly true of in lieu fee programs, wherein impacts are offset by payment to a management program or conservation organization. As a consequence, temporal losses of functions and values routinely occur. In cases when mitigation fails, function and value losses may be permanent. One disadvantage of mitigation banks is that they do not replace lost functions and values at the point of impact. As such, in cases where on-site mitigation would be viable, that option should be given strong consideration in advance to reduce the local ecosystem impacts. Certain wetland functions, such as flood storage and attenuation and water quality, may not be transferable off site. In some states, such as Florida, nontransferable functions and values are handled separately to ensure their appropriate resolution. Regulatory Management Perspective Mitigation banks can also enhance the effectiveness of wetlands protection programs. U.S. federal guidance mandates a team approach to the assessment of mitigation banking proposals. This approach brings the regulatory and commenting agencies to the same table, with the result that all agencies can contribute their expertise and perspective to the project review. This results in a more meaningful review of the bank proposal and can act to shorten the processing time. The review of one large mitigation proposal is more efficient than the review of numerous, project-specific mitigation proposals. A potential disadvantage of this process is the ability of the team to meet. Limited budgets can limit travel, and coordinating

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multiple schedules can be difficult. Reaching consensus on the terms and conditions of the MBI, as is encouraged by the Federal Guidance, can also be a difficult and time-consuming process. Establishment of a mitigation bank involves financial resources, planning, and scientific expertise at a level not practicable to many project-specific mitigation proposals. Consolidation of resources increases the potential for the successful establishment and long-term management of the mitigation project. Finally, consolidation of mitigation within a bank increases the efficiency of limited agency resources for inspection and compliance monitoring. This improves the agency’s ability to ensure the success of efforts to restore, create, or enhance wetlands for mitigation purposes. User Perspective Most permit applicants do not wish to become wetland experts but are seeking authorization to move forward with their development projects. Mitigation projects may be implemented by people whose main expertise and incentive lies in an unrelated area, such as housing development or highway construction. By contrast, mitigation banks are typically sponsored by organizations whose staff is devoted to implementing successful mitigation projects. A successful banking team provides the permit applicant with the talent and expertise necessary to ensure that the environmental goals set forth in a permit will be achieved. Mitigation banking offers several other advantages to the user. The mitigation plan already has been approved by the agencies, so the time required reviewing and approving a permit is substantially reduced. Purchasing credits from an approved mitigation bank transfers the liability for mitigation success from the user to the banker. The use of credits from a mitigation bank is generally cost competitive with on-site mitigation. By contrast, the costs of implementing successful on-site mitigation may be considerable and open-ended.

ECONOMICS The primary economic issues faced by the sponsor of a mitigation bank resemble those of any business with a product for sale, particularly the real estate development industry. The product a bank sponsor offers is not necessarily a functioning and valuable wetland, but a mechanism that allows a bank user to impact wetlands elsewhere. The goal of the user is more likely to be houses, highways, utility corridors, or some other development or development-related activity. However, mitigation banks are somewhat unique in that the sale of credits produces parks and greenways that provide societal benefits to people other than the bank user. Several factors must be assessed in order to determine the viability of a mitigation bank (Table 2). Each of the factors that contribute to the economic viability of a wetland mitigation bank can be quantified. However, these factors are extremely variable and volatile, which is why the wetland mitigation banking industry, in its current state of development, is extremely risky. One major element of risk is that ©2001 CRC Press LLC

bank demand, product quality, product alternatives, and sometimes price are established or strongly influenced by regulations and policies. These regulations and policies may change frequently and often vary from project to project and user to user. Table 2

Factors That Should Be Assessed in Order to Determine the Viability of a Mitigation Bank

Competitive supply of the product and product alternatives Risk assessment and presale of the product Capital and operating costs of product development Long-term stewardship of the product

Demand for the Product The demand for mitigation credits is driven by three primary factors: service area, regulatory climate, and user requirements (Figure 1). Service Area The service area is the geographic area in which a particular mitigation bank can compensate impacts to wetlands. Ecological concerns (e.g., mitigating in the same watershed where the impact occurred) tend to constrain the appropriate size of a wetland mitigation bank's service area. Economic concerns dictate that the larger the service area, the more likely it is that the bank will experience a sufficient level of demand to be economically practicable. This is because the larger the service area, all other factors being equal, the greater the number of expected wetland impacts. Regulatory Climate Regulatory climate is a term often used to describe how businesses perceive the difficulty of conducting business in a particular location because of local, state, and federal government regulatory agencies. If the regulatory climate is so restrictive that no user in a service area can obtain a permit to impact wetlands, there will be little demand for wetland mitigation credits (Figure 2). Similarly, the regulatory climate may impose mitigation conditions so burdensome (e.g., wetland replacement ratios, performance monitoring, etc.) that impacting wetlands is not cost-effective. Conversely, mitigation requirements may be so minimal that users can satisfy requirements without purchasing credits from a mitigation bank. Thus, the regulatory climate strongly influences the demand for credits generated by economic activity users within a service area. Regulatory decisions in several key areas determine the perception of regulatory climate (Table 3). Service Area Size Free-market advocates suggest that service areas should be unlimited, or at least very large, to encourage maximum levels of competition. This competition could ©2001 CRC Press LLC

Figure 1

Demand for mitigation credits vs. service area size, regulatory climate for obtaining permits to impact wetlands, and the level of prospective user impact to wetlands in the service area.

lead to lower prices, and if the quality of created wetland credits was linked to mitigation ratio requirements, to higher quality wetland compensation. However, the current regulatory climate appears to be focusing on limiting service areas to relatively small areas. If the service areas are too small, the economic practicability of wetland banks will be eliminated. For example, the state of Maryland has recently (1993 to 1998) averaged about 15 hectares (ha) of wetland impacts per year and has established 20 service areas. A mitigation bank is unlikely to be economically viable. Mitigation Ratios Mitigation ratios are established by regulators to compare functions and values of the impacted wetland to the mitigated wetland. The expected likelihood of success

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Figure 2

Regulatory climate factors vs. demand for mitigation credits.

Table 3

Regulatory Decisions in These Key Areas Determine the Perception of Regulatory Climate for Mitigation Banking

Service area size Mitigation ratios Performance requirements Monitoring and maintenance requirements Permitting difficulty Attitudes toward compensatory mitigation alternatives and determinations of the practicability of avoidance of impacts Regulatory stability

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(i.e., a safety factor) and the temporal loss of functions and values (i.e., the time lag between impact and successful mitigation site completion and maturity) are also considered. In other words, the appropriate (mitigation) compensation ratio is based on the level of functional replacement provided, the speed at which functional replacement is achieved, and the risk that the compensation wetland will not perform as expected (King et al., 1993). Some regulators grant lower mitigation ratios to mitigation banks in recognition of their reduced temporal loss, reduced risk of failure, and greater function and value relative to smaller, discontiguous sites. Other regulators grant the same mitigation ratio to mitigation banks as to other types of mitigation. In at least one instance (Maryland), the mitigation ratio is greater for banks than for other types of mitigation. The latter has the effect of discouraging the development of a mitigation banking industry. Another aspect of risk involves the predictability of the mitigation ratios. Some regulators are moving toward specific ratio standards for particular types of impacts. Others are moving toward function and value assessment methodologies that are repeatable, predictable, and useful for all mitigation efforts. This minimizes staff demands, maximizes predictability, and ensures fairness for both users and mitigation providers. However, other regulators seem to be moving in the opposite direction by relying on the best professional judgment of the permit project manager for each specific project. This can lead to unpredictable or biased decisions and consume more staff and banker resources. Regulatory decisions to penalize or reward mitigation banks with higher or lower mitigation ratios are a key indicator of the regulatory climate and are the key determinants of the demand for credits