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Wetlands: Characteristics and Boundaries Wetlands CHARACTERISTICS AND BOUNDARIES Committee on Characterization of Wetlands Water Science and Technology Board Board on Environmental Studies and Toxicology Commission on Geosciences, Environment, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1995
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Wetlands: Characteristics and Boundaries NATIONAL ACADEMY PRESS 2101 Constitution Avenue, N.W. Washington, DC 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. Support for this project was provided by the U.S. Environmental Protection Agency under Agreement No. CX-821125-01-0 and the U.S. Department of Agriculture Natural Resources Conservation Service under Agreement No. SCD-68-3475-3-161. The Director, Grants Administration Division, has approved a deviation from 40 CFR 30.518 of EPA's Assistance Regulations. This approval permits a waiver of EPA's peer review process and submission of the draft final report. The recipient agrees that the following disclaimer will be added to all documents published under this project. "Although the results described in this document have been funded wholly or in part by the United States Environmental Protection Agency under Assistance Agreement X821125010 to the National Academy of Sciences, it has not been subjected to the Agency's peer and administrative review and therefore may not necessarily reflect the views of the Agency and no official endorsement should be inferred." Cover art by Raphael Lopez, San Diego, California Library of Congress Cataloging-in-Publication Data Wetlands: characteristics and boundaries. p. cm William M. Lewis, Jr., chair. Includes bibliographical references and index. ISBN 0-309-05134-7 (cloth) 1. Wetlands. 2. Wetland ecology. 3. Wetland conservation— Government policy—United States. I. Lewis, William M., 1945-. II. National Research Council (U.S.). Committee on Characterization of Wetlands. QH87.3W475 1995 333.91'8'0973—dc 20 95-440 Copyright 1995 by the National Academy of Sciences. All rights reserved. Printed in the United States of America
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Wetlands: Characteristics and Boundaries COMMITTEE ON CHARACTERIZATION OF WETLANDS WILLIAM M. LEWIS, JR., Chair, University of Colorado, Boulder, Colorado BARBARA BEDFORD, Cornell University, Ithaca, New York FRED BOSSELMAN, IIT Chicago Kent College of Law, Chicago, Illinois MARK BRINSON, East Carolina University, Greenville, North Carolina PAUL GARRETT, Federal Highway Administration, Washington, District of Columbia CONSTANCE HUNT, The World Wildlife Fund, Washington, District of Columbia CAROL JOHNSTON, University of Minnesota, Duluth, Minnesota DOUGLAS KANE, University of Alaska, Fairbanks, Alaska A. MICHAEL MACRANDER, Shell Oil Company, Houston, Texas JAMES MCCULLEY, Environmental Consultants, Inc., Christiana, Delaware WILLIAM J. MITSCH, The Ohio State University, Columbus, Ohio WILLIAM PATRICK, JR., Louisiana State University, Baton Rouge, Louisiana ROGER POST, Alaska Department of Fish and Game, Fairbanks, Alaska DON SIEGEL, Syracuse University, Syracuse, New York R. WAYNE SKAGGS, North Carolina State University, Raleigh, North Carolina MARGARET STRAND, Bayh, Connaughton & Malone, P.C., Washington, District of Columbia JOY B. ZEDLER, San Diego State University, San Diego, California BEST Liaison EDWIN H. CLARK, II, Clean Sites, Inc., Alexandria, Virginia WSTB Liaison DAVID L. FREYBERG, Stanford University, Stanford, California Federal Liaisons GREGORY E. PECK, Environmental Protection Agency MICHAEL A. FRITZ, Environmental Protection Agency MICHAEL L. DAVIS, Department of the Army Corps of Engineers KAREN KOCHENBACH, Department of the Army Corps of Engineers BILLY TEELS, Department of Agriculture, Natural Resources Conservation Service MARGE KOLAR, Department of the Interior, Fish and Wildlife Service MIKE LONG, Department of the Interior, Fish and Wildlife Service JOHN R. HALL, Department of Commerce, National Marine Fisheries Service
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Wetlands: Characteristics and Boundaries Staff SHEILA D. DAVID, Study Director, WSTB DAVID POLICANSKY, Study Director, BEST TANIA L. WILLIAMS, Research Associate, BEST GREGORY K. NYCE, Senior Project Assistant, WSTB
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Wetlands: Characteristics and Boundaries WATER SCIENCE AND TECHNOLOGY BOARD DAVID L. FREYBERG, Chair, Stanford University, Stanford, California BRUCE E. RITTMANN, Vice Chair, Northwestern University, Evanston, Illinois LINDA M. ABRIOLA, University of Michigan, Ann Arbor, Michigan J. DAN ALLEN, Chevron USA, Inc., New Orleans, Louisiana PATRICK BREZONIK, Water Resources Research Center, St. Paul, Minnesota WILLIAM M. EICHBAUM, The World Wildlife Fund, Washington, District of Columbia WILFORD R. GARDNER, University of California, Berkeley, California WILLIAM GRAF, Arizona State University, Tempe, Arizona THOMAS M. HELLMAN, Bristol-Myers Squibb Company, New York, New York CHARLES C. JOHNSON, Jr., U.S. Public Health Service, Washington, District of Columbia (Retired) CAROL A. JOHNSTON, University of Minnesota, Duluth, Minnesota WILLIAM M. LEWIS, JR., University of Colorado, Boulder, Colorado CAROLYN H. OLSEN, Brown and Caldwell, Pleasant Hill, California CHARLES R. O'MELIA, The John Hopkins University, Baltimore, Maryland IGNACIO RODRIGUEZ-ITURBE, Texas A&M University, College Station, Texas HENRY J. VAUX, JR., University of California, Riverside, California Staff STEPHEN D. PARKER, Director JEANNE AQUILINO, Administrative Specialist ANGELA BRUBAKER, Senior Project Assistant SHEILA D. DAVID, Senior Staff Officer CHRIS ELFRING, Senior Staff Officer ETAN GUMERMAN, Research Associate ANITA A. HALL, Administrative Assistant GARY KRAUSS, Staff Officer JACQUELINE MACDONALD, Senior Staff Officer MARY BETH MORRIS, Senior Project Assistant GREGORY NYCE, Senior Project Assistant
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Wetlands: Characteristics and Boundaries BOARD ON ENVIRONMENTAL STUDIES AND TOXICOLOGY PAUL G. PASSER, Chair, Miami University, Oxford, Ohio MICHAEL J. BEAN, Environmental Defense Fund, Washington, District of Columbia EULA BINGHAM, University of Cincinnati, Cincinnati, Ohio EDWIN H. CLARK II, Clean Sites, Inc., Alexandria, Virginia ALLAN H. CONNEY, Rutgers University, Piscataway, New Jersey ELLIS COWLING, North Carolina State University, Raleigh, North Carolina JOHN L. EMMERSON, Portland, Oregon ROBERT C. FORNEY, Unionville, Pennsylvania ROBERT A. FROSCH, Harvard University, Cambridge, Massachusetts KAI LEE, Williams College, Williamstown, Massachusetts JANE LUBCHENCO, Oregon State University, Corvallis, Oregon GORDON ORIANS, University of Washington, Seattle, Washington FRANK L. PARKER, Vanderbilt University, Nashville, Tennessee GEOFFREY PLACE, Hilton Head, South Carolina DAVID P. RALL, Washington, District of Columbia LESLIE A. REAL, Indiana University, Bloomington, Indiana KRISTIN SHRADER-FRECHETTE, University of South Florida, Tampa, Florida BURTON H. SINGER, Princeton University, Princeton, New Jersey MARGARET STRAND, Bayh, Connaughton & Malone, P.C., Washington, District of Columbia GERALD VAN BELLE, University of Washington, Seattle, Washington BAILUS WALKER, JR., Howard University, Washington, District of Columbia Staff JAMES J. REISA, Director DAVID J. POLICANSKY, Associate Director and Program Director for Natural Resources and Applied Ecology KULBIR BAKSHI, Program Director for Committee on Toxicology CAROL MACZKA, Program Director for Human Toxicology and Risk Assessment LEE R. PAULSON, Program Director for Information Systems and Statistics RAYMOND A. WASSEL, Program Director for Environmental Sciences and Engineering
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Wetlands: Characteristics and Boundaries COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES M. GORDON WOLMAN, Chairman, The Johns Hopkins University, Baltimore, Maryland PATRICK R. ATKINS, Aluminum Company of America, Pittsburgh, Pennsylvania EDITH BROWN WEISS, Georgetown University Law Center, Washington, District of Columbia JAMES P. BRUCE, Canadian Climate Program Board, Ottawa, Ontario, Canada WILLIAM L. FISHER, University of Texas, Austin, Texas EDWARD A. FRIEMAN, Scripps Institution of Oceanography, La Jolla, California GEORGE M. HORNBERGER, University of Virginia, Charlottesville, Virginia W. BARCLAY KAMB, California Institute of Technology, Pasadena, California PERRY L. MCCARTY, Stanford University, California S. GEORGE PHILANDER, Princeton University, Princeton, New Jersey RAYMOND A. PRICE, Queen's University at Kingston, Ontario, Canada THOMAS A. SCHELLING, University of Maryland, College Park, Maryland ELLEN SILBERGELD, Environmental Defense Fund, Washington, District of Columbia STEVEN M. STANLEY, The Johns Hopkins University, Baltimore, Maryland VICTORIA J. TSCHINKEL, Landers and Parsons, Tallahassee, Florida Staff STEPHEN RATTIEN, Executive Director STEPHEN D. PARKER, Associate Executive Director MORGAN GOPNIK, Assistant Executive Director JAMES MALLORY, Administrative Officer SANDI FITZPATRICK, Administrative Associate
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Wetlands: Characteristics and Boundaries The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Harold Liebowitz is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. Harold Liebowitz are chairman and vice chairman, respectively, of the National Research Council.
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Wetlands: Characteristics and Boundaries Acknowledgments Many individuals assisted the committee in its task by participating in committee meetings, helping to plan field trips, and providing background information. The committee is especially thankful for the generous assistance provided by Mike Fritz, EPA; Mike Long, FWS; Billy Teels, NRCS; and Russell Theriot and Karen Kochenbach of USACE. The committee received valuable advice and assistance from Greg Peck, EPA; Marge Kohlar, FWS; and Mike Davis, USACE. Field trips held in conjunction with committee meetings helped the committee better understand the problems of wetlands delineation. We would like to express our appreciation to the following people who assisted the committee and NRC staff during these field trips. Kent Island, Maryland Leander Brown, USACE Woody Francis, USACE Alex Dolgos, USACE Tom Filip, USACE Charlie Rhodes, Jr., EPA Norman Melvin, NRCS Vicksburg, Mississippi James Gosselink, Louisiana State University Randy Pearson, Space Remote Sensing Center, Stennis Space Center, MS Larry Harper, USACE
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Wetlands: Characteristics and Boundaries David Lofton, USACE Harvey Huffstatler, USACE Tom Welborn, EPA David Jones, NRCS Raymond Callahan, NRCS David Pettry, Mississippi State University Sedona, Arizona Kevin Martin, Soil and Environmental Consultants, Inc., Raleigh, NC Robert Pierce, Wetlands Science Applications, Inc., Poolesville, MD Duncan Patten, University of Arizona Tom Yocum, EPA Wendy Melgin, EPA Kathy Kunz, USACE Fred Weinman, EPA Mary Butterwick, EPA David Cooper, Colorado State University Marie Sullivan, FWS Ft. Myers, Florida Maurice Mausbach, NRCS Kevin Reush, consultant, Lakeland, FL Kevin Erwin, consultant, Ft. Myers, FL Robin Lewis, Lewis Environmental Services, Tampa, FL Public Session in Ft Myers: Jim Shepard, National Council of the Paper Industry for Air and Stream Improvement Susan Asmus, National Association of Home Builders Jamestown, North Dakota Ned Euliss, FWS Porter Reed, FWS Arnold van der Valk, Iowa State University Dan Smith, USACE Lewis Cowardin, FWS Jimmie Richardson, North Dakota State University Harold Kantrud, FWS Public session in Jamestown: Don Parrish, American Farm Bureau Don Etler, Iowa Drainage District Association Vic Legler, Landowners Association of North Dakota
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Wetlands: Characteristics and Boundaries Gerald Eid, North Dakota Home Builders Association Kenneth Dierks, Lanley and McDonald Consultants, Virginia Beach, VA Greg Larson, Minnesota Board of Water and Soil Resources Jay Leitch, North Dakota State University Others Gary Jellick, Greenhorne & O'Mara, Inc. Ralph Tiner, FWS Kim Santos, FWS Dennis Tressel, NRCS
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Wetlands: Characteristics and Boundaries Preface Principles for federal regulation of wetlands have been fundamentally challenged several times over the past 20 years. One legacy of these challenges has been a reduction in the credibility of all regulatory practice related to wetlands. For this reason, the U.S. Congress requested that the Environmental Protection Agency ask the National Research Council (NRC) to create a committee that would study the scientific basis for characterization of wetlands. This committee was formed in 1993 through the NRC's Water Science and Technology Board and its Board on Environmental Studies and Toxicology. The committee was asked to review and evaluate the consequences of alternative methods for wetland delineation and to summarize the scientific understanding of wetland functions. Specifically mentioned in the committee's charge are the issues of wetland definition, the structure and functioning of wetlands, and regional differences among wetlands. Members of the committee were drawn from a broad range of expertise, regional perspectives, and professional experience. After its first meeting in Washington, D.C., the committee met in eastern Maryland, the lower Mississippi River valley, Arizona, southwest Florida, and the prairie pothole region of North Dakota. At each of these locations, the committee spent some of its time on field investigations organized under the direction of federal agency personnel and private consultants familiar with regional problems of delineation. This field experience assisted the committee members in their discussion of regional issues. The meetings also included two special sessions for public commentary (in Florida and in North Dakota) and presentations by nongovernment specialists in delineation. The NRC committee has reached broad consensus on the issues related to its
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Wetlands: Characteristics and Boundaries charge. In this report, the committee presents a reference definition of wetlands that sets the stage for a fresh look at existing regulatory definitions and for reconsideration of the confusion surrounding parameters, criteria, and indicators. In addition, the committee offers an overview of wetland functions as they relate to the protection of wetlands. Finally, the committee provides many recommendations and conclusions related to criteria and indicators. Although these recommendations and conclusions do not in themselves constitute a new delineation manual, they specify the essential framework and principles around which a new universal federal manual can be prepared by federal agency personnel. Many of the conclusions and recommendations underscore the committee's confidence in the fundamental soundness of current regulatory practice for characterizing and delineating wetlands. Changes that have been suggested by the committee typically involve refinements of practice rather than drastic change. The committee's report will be scrutinized carefully for bias favoring or opposing the protection of wetlands. The committee members hold a range of personal viewpoints on the degree of rigor with which wetlands should be protected and on the uniformity with which protection should extend across wetlands, but the committee leaves these matters for resolution through law and administrative policy. The committee's task has been to analyze present regulatory practice in relation to wetland delineation and to recommend changes that might bolster the objectivity and scientific validity of wetland delineation and identification. In general, the committee has been impressed with the professionalism and scientific credibility that make up the foundation of federal expertise in characterization and delineation of wetlands. This foundation, when combined with a federal commitment to the use of scientific principles applied with regional realism, should steadily improve public confidence in the national system for characterization of wetlands. The Committee on wetlands Characterization has placed extraordinary demands on members of the NRC staff. The rapid pace of work, extensive logistical arrangements, and coordination of two NRC boards required experience and great dedication from the staff. The committee is indebted particularly to Sheila David, David Policansky, Tania Williams, and Greg Nyce of the National Research Council, and to David Greene of the University of Colorado's Center for Limnology, for extensive staff work on this project. In addition, the committee greatly appreciates the many briefings and assistance with field trips provided by the staff of the U.S. Environmental Protection Agency, the U.S. Army Corps of Engineers, the U.S. Natural Resources Conservation Service, the U.S. Fish and Wildlife Service, and others. William M. Lewis, Jr., Chairman
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Wetlands: Characteristics and Boundaries Contents EXECUTIVE SUMMARY 1 1 INTRODUCTION AND BACKGROUND 13 Purposes of the NRC Report 14 Path To Regulation 16 Current Context for Regulation 18 2 ECOLOGY OF WETLAND ECOSYSTEMS 20 Introduction 20 The Nature of Wetlands 21 Wetland Functions 34 Nature of Boundaries with Uplands 41 Conclusions 42 Recommendation 42 3 WETLAND DEFINITIONS: HISTORY AND SCIENTIFIC BASIS 43 History of Terminology 43 Evolution of the Regulatory Definitions 47 Food Security Act 56 Status of Definitions 57 Frame of Reference for Regulatory Definitions 58 Application of Definitions 63 Recommendations 64 4 WETLAND DELINEATION: PAST AND CURRENT PRACTICE 65 Introduction 65
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Wetlands: Characteristics and Boundaries Wetland Delineation: Motivation and Procedure 66 Federal Agency Manuals Before 1989 70 Comparing the Federal Manuals 74 5 WETLAND CHARACTERIZATION: WATER, SUBSTRATE, AND BIOTA 90 Introduction 90 Hydrology 90 Soils 109 Vegetation 121 Other Indicators of the Substrate and Biological Criteria 136 Combining the Factors 137 Recommendations 144 6 ESPECIALLY CONTROVERSIAL WETLANDS 149 Introduction 149 Permafrost Wetlands 149 Riparian Ecosystems 152 Isolated Wetlands and Headwaters 155 Especially Shallow or Intermittently Flooded Wetlands 156 Agricultural Wetlands 158 Sites Altered for Nonagricultural Purposes 162 Transitional Zones 166 Recommendations 166 7 REGIONALIZATION 168 Introduction 168 Hierarchy of Regional Variation 169 Regionalization Schemes 174 Current Approaches 179 Advantages and Disadvantages of Regionalization 185 Research to Support Regionalization 186 Implementation of Regionalization 187 Recommendations 188 8 MAPS, IMAGES, AND MODELING IN THE ASSESSMENT OF WETLANDS 190 Introduction 190 Aerial Photography and Satellite Imaging 190 Wetland Delineation Under the Food Security Act 192 NWI Mapping 195 Geographic Information Systems 199 Hydrologic Modeling 201 Quantitative Analysis of Boundaries 204 Recommendations 206
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Wetlands: Characteristics and Boundaries 9 REGULATION OF WETLANDS: ADMINISTRATIVE ISSUES 207 Introduction 207 Consistency and Reliability of Wetland Delineations 207 Conclusions 214 Recommendations 214 10 FUNCTIONAL ASSESSMENT OF WETLANDS 215 Introduction 215 Functions and Values of Wetlands 215 General Requirements for Functional Assessment 216 Methods of Functional Assessment 217 Future Methods of Functional Assessment 220 Relevance of Wetland Assessment to 404 Permit Applications 223 Use of Functional Assessment in Watershed Planning 223 Conclusion 225 Recommendations 226 REFERENCES 227 APPENDIXES A SOIL TAXONOMY 253 Soils Nomenclature 101 253 Soil Moisture Regime 254 Aquic Conditions 254 Other Terms Related to Soil Wetness 256 References 257 B CASE HISTORIES 258 Kirkham Wetlands 258 Yazoo National Wildlife Refuge 263 Verde River Wetlands 271 Hydric Pine Flatwoods of Southwest Florida 275 Prairie Pothole Region 278 C GLOSSARY 284 D COMMITTEE ON WETLANDS CHARACTERIZATION BIOGRAPHICAL SKETCHES 291 INDEX 297 LIST OF PUBLICATIONS 307
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Wetlands: Characteristics and Boundaries Wetlands
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