"Wetlands" has become a hot word in the current environmental debate. But what does it signify? In 1991, proposed changes in the legal definities of wetlands stirred controversy and focused attention on the scientific and economic aspects of their management.
This volume explores how to define wetlands. The committee—whose members were drawn from academia, government, business, and the environmental community—builds a rational, scientific basis for delineating wetlands in the landscape and offers recommendations for further action.
Wetlands also discusses the diverse hydrological and ecological functions of wetlands, and makes recommendations concerning so-called controversial areas such as permafrost wetlands, riparian ecosystems, irregularly flooded sites, and agricultural wetlands. It presents criteria for identifying wetlands and explores the problems of applying those criteria when there are seasonal changes in water levels.
This comprehensive and practical volume will be of interest to environmental scientists and advocates, hydrologists, policymakers, regulators, faculty, researchers, and students of environmental studies.
- Wetlands
- Copyright
- Acknowledgments
- Preface
- Contents
- Executive Summary
- DEFINITIONS, FACTORS, CRITERIA, AND INDICATORS
- WATER
- SUBSTRATE
- VEGETATION
- COMBINATIONS OF INDICATORS FOR WATER, SOIL, AND VEGETATION
- ESPECIALLY CONTROVERSIAL WETLANDS
- REGIONALIZATION
- MAPS, IMAGES, AND MODELING
- REGULATORY PRACTICE
- FUNCTIONAL ASSESSMENT
- GENERAL CONCLUSIONS
- 1 Introduction and Background
- PURPOSES OF THE NRC REPORT
- Identification and Characterization
- Identification of Functions and Values
- Variations
- Relationships of the Three Themes
- PATH TO REGULATION
- CURRENT CONTEXT FOR REGULATION
- 2 Ecology of Wetland Ecosystems
- INTRODUCTION
- THE NATURE OF WETLANDS
- Hydrology as a Driving Force
- Causes of Variation
- Organic Matter
- Natural Disturbance
- Nutrient Transformation
- WETLAND FUNCTIONS
- Relationship to Value
- Unique Functions
- Landscape Perspective
- Relationship to Biodiversity
- Removal of Nutrients and Sediments
- Wetlands as Hydrologic Features of Watersheds
- NATURE OF BOUNDARIES WITH UPLANDS
- CONCLUSIONS
- RECOMMENDATION
- 3 Wetland Definitions: History and Scientific Basis
- HISTORY OF TERMINOLOGY
- Nineteenth-Century American Legislation
- Swamp and Overflowed Lands Acts
- Wildlife Refuge System
- Rivers and Harbors Act
- New Legal Status
- Water Pollution Control Act Amendments of 1972
- Judicial Interpretation of the 1972 Statute
- EVOLUTION OF THE REGULATORY DEFINITIONS
- 1956 Fish and Wildlife Service Definition
- 1974 Wetland Inventory Project
- 1975 USACE Proposed Definition
- 1976 FWS Interim Classification
- 1977 USACE Definition
- Clean Water Act of 1977
- 1979 Cowardin Report
- Riverside Bayview Decision
- FOOD SECURITY ACT
- STATUS OF DEFINITIONS
- 1977 USACE Definition
- 1985 FSA Definition
- 1979 FWS Definition
- FRAME OF REFERENCE FOR REGULATORY DEFINITIONS
- Reference Definition
- Terminology: Parameters, Criteria, Indicators
- Criteria and Indicators
- APPLICATION OF DEFINITIONS
- RECOMMENDATIONS
- 4 Wetland Delineation: Past and Current Practice
- INTRODUCTION
- WETLAND DELINEATION: MOTIVATION AND PROCEDURE
- Clean Water Act
- The Food Security Act
- FEDERAL AGENCY MANUALS BEFORE 1989
- NFSAM
- Attempts to Revise the Federal Manuals
- COMPARING THE FEDERAL MANUALS
- Hydrology
- Hydrologic Evidence
- Growing Season
- Hydrophytic Vegetation
- Wetland Plant Species
- Determining Prevalence
- Treatment of FAC Species and FACU-Dominated Wetlands
- Hydric Soils
- Special Situations: Disturbed Areas, Problem Areas, Exceptions
- Differences Resulting from Application of the Manuals
- 5 Wetland Characterization: Water, Substrate, and Biota
- INTRODUCTION
- HYDROLOGY
- Nature of Wetland Hydrology
- Need to Evaluate Wetland Hydrology
- Hydrologic Criterion
- Saturation in Relation to Water Table Depth
- Duration of Saturation and the Growing Season
- Effects of Soil Temperature on Development of Anaerobic Conditions
- Definitions of Growing Season and Their Application to Wetlands
- Biological Zero
- Growing Season as Defined by the Frost-Free Period
- Interaction of Duration Threshold with Length of Growing Season
- Resolving the Problem of Growing Season
- Frequency of Saturation
- Critical Depth of Saturation
- Interannual Variation
- Overview of Hydrologic Thresholds
- Direct Methods for Evaluating Hydrology
- Indirect Methods for Evaluating Hydrology
- SOILS
- Concepts of Soil
- Soil-Forming Processes in Wetlands
- Accumulation of Organic Matter
- Development of Anaerobic Conditions
- Redoximorphic Features
- Hydric Soils List
- Use of Hydric Soils in Delineation
- Use of Soil Surveys
- Field Indicators of Hydric Soils
- VEGETATION
- Hydrophyte List
- Definition of Hydrophyte
- Development of the Hydrophyte List
- Facultative Species and the Concept of Wetland Ecotypes
- Determining Predominance Of Hydrophytic Vegetation
- Measure of Dominance: The 50% Rule
- Prevalence Index
- Evaluation of Thresholds
- Visible Adaptations as Indicators of Hydrophytic Vegetation
- Treatment of Facultative Species
- Vegetation and Hydrology
- Vegetation and Soil Type
- Use of Vegetation to Set Boundaries
- OTHER INDICATORS OF THE SUBSTRATE AND BIOLOGICAL CRITERIA
- COMBINING THE FACTORS
- Necessity for Three Factors
- Coincidence of Characteristic Hydrology, Soils, and Vegetation
- Modified Approach to Evaluating Evidence
- Primary Indicators
- Hierarchical Approach
- Future Delineation Manuals
- RECOMMENDATIONS
- 6 Especially Controversial Wetlands
- INTRODUCTION
- PERMAFROST WETLANDS
- Relevance of Permafrost to Wetland Formation
- Dynamics of Permafrost Wetlands
- Regulation of Permafrost Wetlands
- RIPARIAN ECOSYSTEMS
- Support of Biodiversity
- Current Regulation of Riparian Ecosystems
- ISOLATED WETLANDS AND HEADWATERS
- ESPECIALLY SHALLOW OR INTERMITTENTLY FLOODED WETLANDS
- AGRICULTURAL WETLANDS
- Functions of Agricultural Wetlands
- Differential Regulation of Agricultural Wetlands
- SITES ALTERED FOR NONAGRICULTURAL PURPOSES
- Types of Alterations
- Identification of Normal Conditions
- Assessment of Altered Lands
- Limitations of assessment Methods for Altered Sites
- TRANSITIONAL ZONES
- RECOMMENDATIONS
- 7 Regionalization
- INTRODUCTION
- HIERARCHY OF REGIONAL VARIATION
- Regional Variation in Hydrology
- Regional Variation of Soils
- Regional Variation of Plants
- Regional Variation in Abundance of Wetlands
- REGIONALIZATION SCHEMES
- Regional Classification Systems
- CURRENT APPROACHES
- Regionalization of Federal Agencies
- Regional Lists of Hydrophytes and Soils
- Hydrology and Growing Season
- Regional Applicability of Current Delineation Methods
- ADVANTAGES AND DISADVANTAGES OF REGIONALIZATION
- RESEARCH TO SUPPORT REGIONALIZATION
- Benchmark Wetlands
- Validation of Modeling Experiments
- Field Experiments on the Reliability of Wetland Indicators
- IMPLEMENTATION OF REGIONALIZATION
- RECOMMENDATIONS
- 8 Maps, Images, and Modeling in the Assessment of Wetlands
- INTRODUCTION
- AERIAL PHOTOGRAPHY AND SATELLITE IMAGING
- Detection of Standing Water
- Other Factors
- WETLAND DELINEATION UNDER THE FOOD SECURITY ACT
- Determinations Before 1994
- Determinations After 1994
- NWI MAPPING
- GEOGRAPHIC INFORMATION SYSTEMS
- HYDROLOGIC MODELING
- Mathematical Models to Assess Wetland Hydrology
- Types of Mathematical Models
- Model Selection and Application
- Advantages and Disadvantages of Hydrologic Modeling
- QUANTITATIVE ANALYSIS OF BOUNDARIES
- Transect Data for Boundary Determination
- Detection of Boundaries with Image Analysis
- Scientific vs. Legal Boundaries
- RECOMMENDATIONS
- 9 Regulation of Wetlands: Administrative Issues
- INTRODUCTION
- CONSISTENCY AND RELIABILITY OF WETLAND DELINEATIONS
- Multiple Agencies
- Standards for Expertise, Training, and Certification
- Verification of Delineations
- Uniformity and the Exercise of Professional Judgment
- Resource Regulation and Private Rights
- Use of Flow Diagrams and Charts
- CONCLUSIONS
- RECOMMENDATIONS
- 10 Functional Assessment of Wetlands
- INTRODUCTION
- FUNCTION AND VALUES OF WETLANDS
- GENERAL REQUIREMENTS FOR FUNCTIONAL ASSESSMENT
- METHODS OF FUNCTIONAL ASSESSMENT
- FUTURE METHODS OF FUNCTIONAL ASSESSMENT
- Assessment Based on Hydrogeomorphic Classification and Reference Wetlands
- Wetland Evaluation Under the National Food Security Act Manual
- Relevance of Hydrologic Factors to Functional Assessment
- RELEVANCE OF WETLAND ASSESSMENT TO 404 PERMIT APPLICATIONS
- USE OF FUNCTIONAL ASSESSMENT IN WATERSHED PLANNING
- Advanced Identification (ADID)
- Special Area Management Plans
- CONCLUSION
- RECOMMENDATIONS
- References
- APPENDIXES
- APPENDIX A Soil Taxonomy
- SOIL NOMENCLATURE 101
- SOIL MOISTURE REGIME
- AQUIC CONDITIONS
- Elements of Aquic Conditions
- OTHER TERMS RELATED TO SOIL WETNESS
- Natural Drainage Classes
- Soil Inundation
- REFERENCES
- APPENDIX B Case Histories
- CASE HISTORY 1
- CASE HISTORY 2
- REFERENCES
- CASE HISTORY 3
- CASE HISTORY 4
- CASE STUDY 5
- APPENDIX C Glossary
- APPENDIX D Committee on Wetlands Characterization Biographical Sketches
- Index
- OTHER RECENT REPORTS OF THE WATER SCIENCE AND TECHNOLOGY BOARD
- OTHER RECENT REPORTS OF THE BOARD ON ENVIRONMENTAL STUDIES AND TOXICOLOGY
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