FGDC–STD-004-2013 

Second Edition 

Classification of Wetlands and Deepwater Habitats of the 

United States 

Adapted from Cowardin, Carter, Golet and LaRoe (1979)

Wetlands Subcommittee 

Federal Geographic Data Committee 

August 2013 

 
Federal Geographic Data Committee 

Established by Office of Management and Budget Circular A-16, the Federal Geographic Data 

Committee (FGDC) promotes the coordinated development, use, sharing, and dissemination of 

geographic data. 

The FGDC is composed of representatives from the Departments of Agriculture, Commerce, 

Defense, Energy, Housing and Urban Development, the Interior, State, and Transportation; the 

Environmental Protection Agency (EPA); the Federal Emergency Management Agency (FEMA); 

the Library of Congress; the National Aeronautics and Space Administration (NASA); the National 

Archives and Records Administration; and the Tennessee Valley Authority. Additional Federal 

agencies participate on FGDC subcommittees and working groups. The Department of the Interior 

chairs the committee. 

FGDC subcommittees work on issues related to data categories coordinated under the circular. 

Subcommittees establish and implement standards for data content, quality, and transfer; encourage 

the exchange of information and the transfer of data; and organize the collection of geographic data 

to reduce duplication of effort. Working groups are established for issues that transcend data 

categories. 

For more information about the committee, or to be added to the committee’s newsletter mailing 

list, please contact: 

Federal Geographic Data Committee Secretariat 

c/o U.S. Geological Survey 

590 National Center 

Reston, Virginia 22092 

Telephone: (703) 648-5514 

Facsimile: (703) 648-5755 

Internet (electronic mail): gdc@usgs.gov 

Anonymous FTP: ftp://fgdc.er.usgs.gov/pub/gdc/ 

World Wide Web: http://fgdc.er.usgs.gov/fgdc.html

This standard should be cited as: 

Federal Geographic Data Committee. 2013. Classification of wetlands and deepwater habitats of the 

United States. FGDC-STD-004-2013. Second Edition. Wetlands Subcommittee, Federal Geographic 

Data Committee and U.S. Fish and Wildlife Service, Washington, DC. 
Preface

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

was developed to support a detailed inventory and periodic monitoring of the Nation’s wet habitats 

using remote sensing. It became a National Standard in 1996 (FGDC-STD-004), but has been the de 

facto standard for mapping U.S. wetlands and deepwater habitats since 1976. As of February 2013, 

the U.S Fish and Wildlife Service’s (FWS) National Wetlands Inventory (NWI) had produced 

wetland data for nearly the entire country. Digital data were available for 89% of the continental 

United States, 34% of Alaska, 100% of the Hawaiian Islands, 76% of Puerto Rico and the U.S. 

Virgin Islands and 100% of Guam and Saipan in the Pacific Trust Territories. These data have been 

incorporated in five reports to Congress on the Status and Trends of Wetlands and Deepwater 

Habitats of the Conterminous United States and more than a hundred regional, state, local, 

watershed and special interest reports. The classification system (Cowardin et al. 1979) has been 

cited extensively in the scientific literature and applied internationally. 

Shortly after publication of the classification, a National list of hydrophytes and other plants 

occurring in wetlands and deepwater habitats and a National list of hydric soils were released to 

support the classification and inventory work. Maintenance of these lists has been a significant, 

complex task. The U.S. Department of Agriculture's Natural Resources Conservation Service has 

responsibility for managing the hydric soils list (USDA 2010), and the U.S. Army Corps of 

Engineers maintains the plant list (Lichvar and Kartesz 2009). 

Preparation of this second edition of the Wetlands Classification Standard began in the spring of 

2010. Over the last three years, a great number of people reviewed drafts of the revised report and 

submitted edits, questions, and suggestions for improvement. Among the reviewers were present 

and past staff of the National Wetlands Inventory; members of the Wetlands Mapping Standard 

Working Group, which was reconvened specifically to work on this revision; and other Federal and 

private-sector wetland specialists and contractors. Among the most important contributors were: 

Ralph Tiner, National Wetlands Inventory, FWS; Larry Handley, U.S. Geological Survey; and Jane 

Awl, Wetland Mapping Consortium. Thanks also go to Mark Newcastle, Printing and 

Publishing, FWS for his professional help in redrafting the figures. I am indebted to my wife, Carol 

Wilen, for allowing me to spend too many Saturdays, Sundays and holidays focused on this, and 

other, work-related projects. 

Special thanks go to Dr. Frank Golet, Professor Emeritus at the University of Rhode Island and one 

of the authors of the original classification (Cowardin et al. 1979). His detailed, comprehensive 

reviews of numerous drafts helped to assure that all revisions were technically sound and consistent 

with both current science and the structure and intent of the original classification. His careful 

editing also has enhanced the clarity and user-friendliness of this document. 

I look back on a long haul made pleasurable by the opportunity of working again with old friends, 

as well as a new generation of colleagues who will use this classification system going forward. 

Bill Wilen 

National Wetlands Inventory 

U.S. Fish and Wildlife Service 

March 2013 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

______________________________________________________________________________________

i 

CONTENTS 

Page

1. INTRODUCTION ............................................................................................................ 1

1.1 Objectives ........................................................................................................... 2

1.2 Scope ................................................................................................................... 2

1.2.1 Exemptions to the FGDC Wetlands Classification Standard ..................... 2

1.2.2 Coordination with FGDC Coastal and Marine Ecological Classification 

Standard ..................................................................................................... 3

1.3 Applicability ....................................................................................................... 3

1.4 Related Standards ................................................................................................ 4

1.5 Standards Maintenance Procedures .................................................................... 5

1.6 Maintenance Authority ....................................................................................... 5

2. WETLANDS AND DEEPWATER HABITATS ..................................................................... 5

2.1 Concepts and Definitions .................................................................................... 5

2.1.1 Wetlands ..................................................................................................... 6

2.1.2 Deepwater Habitats ..................................................................................... 8

2.2 Limits .................................................................................................................. 8

3. THE CLASSIFICATION SYSTEM ..................................................................................... 8

3.1 Systems and Subsystems .................................................................................. 11

3.1.1 Marine System .......................................................................................... 11

3.1.2 Estuarine System ....................................................................................... 13

3.1.3 Riverine System ........................................................................................ 14

3.1.4 Lacustrine System ..................................................................................... 16

3.1.5 Palustrine System ...................................................................................... 18

3.2 Classes, Subclasses, and Dominance Types ..................................................... 19

3.2.1 Rock Bottom ............................................................................................. 21

3.2.2 Unconsolidated Bottom ............................................................................ 22

3.2.3 Aquatic Bed .............................................................................................. 24

3.2.4 Reef ........................................................................................................... 26

3.2.5 Streambed ................................................................................................. 27

3.2.6 Rocky Shore .............................................................................................. 29

3.2.7 Unconsolidated Shore ............................................................................... 30

3.2.8 Moss-Lichen Wetland ............................................................................... 32

3.2.9 Emergent Wetland .................................................................................... 33

3.2.10 Scrub-Shrub Wetland ................................................................................ 34

3.2.11 Forested Wetland ...................................................................................... 35

3.3 Modifiers ........................................................................................................... 36

3.3.1 Water Regime Modifiers ........................................................................... 37

3.3.2 Water Chemistry Modifiers ...................................................................... 40

3.3.3 Soil Modifiers ........................................................................................... 43

3.3.4 Special Modifiers ...................................................................................... 43

4. USE OF THE CLASSIFICATION SYSTEM ....................................................................... 45

5. REGIONALIZATION FOR THE CLASSIFICATION SYSTEM .............................................. 46

6. APPLICATION OF THE FGDC WETLANDS CLASSIFICATION STANDARD ..................... 46
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

______________________________________________________________________________________

ii 

7. REFERENCES .............................................................................................................. 47

APPENDIX A (INFORMATIVE): GLOSSARY OF TECHNICAL TERMS, ACRONYMS, AND 

ABBREVIATIONS ................................................................................................................ 56

APPENDIX B (INFORMATIVE): ARTIFICIAL KEYS TO THE SYSTEMS AND CLASSES ......... 64

APPENDIX C (INFORMATIVE): SCIENTIFIC AND COMMON NAMES OF PLANTS ............... 67

APPENDIX D (INFORMATIVE): SCIENTIFIC AND COMMON NAMES OF ANIMALS ............. 73

APPENDIX E (NORMATIVE): CRITERIA FOR DIFFERENTIATING BETWEEN MINERAL SOILS 

AND ORGANIC SOILS .......................................................................................................... 77

APPENDIX F (INFORMATIVE): REGIONALIZATION FOR THE CLASSIFICATION SYSTEM .... 82

APPENDIX G (INFORMATIVE): WETLAND IMAGE GALLERY ............................................ 85

FIGURES AND TABLES

Figure 1. Classification hierarchy of wetlands and deepwater habitats, showing Systems, 

Subsystems, and Classes ..................................................................................................... 9

Figure 2. Distinguishing features and examples of habitats in the Marine System. ......... 12

Figure 3. Distinguishing features and examples of habitats in the Estuarine System. ..... 13

Figure 4. Distinguishing features and examples of habitats in the Riverine System. ....... 15

Figure 5. Distinguishing features and examples of habitats in the Lacustrine System. .... 17

Figure 6. Distinguishing features and examples of habitats in the Palustrine System. .... 18

Figure 7. Ecoregions of the United States. ....................................................................... 84

Table 1. Distribution of Subclasses within the classification hierarchy ........................... 10

Table 2. Salinity Modifiers ............................................................................................... 42

Table 3. pH Modifiers ....................................................................................................... 42
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

1 

1. Introduction 

Wetlands and deepwater habitats are essential breeding, rearing, and feeding grounds for 

many species of fish and wildlife. They also perform flood protection, pollution control 

and a variety of other important functions. National and international recognition of the 

beneficial roles of wetlands has intensified the need for reliable information on the status 

and extent of wetland resources. To develop comparable information over large areas, a 

clear definition and classification of wetlands and deepwater habitats are required. 

The United States Fish and Wildlife Service (USFWS) has a long history of involvement 

in wetlands classification and inventory. Conservation and management of migratory 

waterfowl are a responsibility of the USFWS based on migratory bird treaties with 

Canada and Mexico. Thus, conservation of wetland habitats is one of the agency’s 

primary objectives. The USFWS conducted the first quantitative national inventory of 

wetlands in the mid-1950s; the results were summarized in U.S. Fish and Wildlife 

Service Circular 39 (Shaw and Fredine 1956). That inventory was based on a 

classification, developed by Martin et al. (1953), which included 20 classes of wetlands. 

The Martin et al. classification was inconsistently applied among regions primarily 

because of a lack of detail in the definitions of wetland types (Cowardin et al. 1979). By 

the mid-1970s, there was a surge of public and professional interest in wetlands that 

transcended the habitat function for migratory birds. 

In January of 1975, the USFWS convened a small number of interested individuals from 

various agencies and regions to formulate the skeleton of a new classification that could 

serve as the basis for a new National Wetlands Inventory (NWI). Three important points 

were agreed upon: (1) none of the existing classifications met the requirement for 

national uniformity, (2) regional classifications would not suffice because of the 

confusion resulting at regional boundaries, and (3) a new classification should be 

hierarchical in structure. 

Following that meeting, Lewis M. Cowardin, USFWS, and Virginia Carter, U.S. 

Geological Survey (USGS), prepared a tentative classification that was presented at a 

July 1975 national workshop, where 150 Federal, Tribal and state wetlands management 

personnel were invited to comment on the proposed classification (Sather 1976). Input 

from that workshop resulted in major modifications of the Cowardin and Carter paper 

and led to the preparation of a revision, Interim Classification of Wetlands and Aquatic 

Habitats of the United States (Cowardin et al. 1976). Francis C. Golet, University of 

Rhode Island, and Edward T. LaRoe, National Oceanographic and Atmospheric 

Administration (NOAA), joined Cowardin and Carter as co-authors of the 1976 

document and subsequent versions of the classification system. The Interim 

Classification was tested using both high- and low-altitude aerial photographs and fieldchecks at 21 sites scattered across the country. NWI staff worked with the authors to 

resolve practical problems encountered during extensive test mapping. At the same time, 

the authors tested the evolving classification at numerous locations throughout the U.S. 

The final version was published in 1979 as the Classification of Wetlands and Deepwater 

Habitats of the United States (Cowardin et al. 1979). It was reprinted with technical 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

2 

revisions and additional plates in 1985 and reprinted again in larger format in 1992. The 

classification was adopted by the Federal Geographic Data Committee (FGDC) as a 

National Standard (FGDC-STD-004) in 1996. That was the governing document until the 

Second Edition was published in 2013. 

1.1 Objectives 

The primary objective of the Classification of Wetlands and Deepwater Habitats of the 

United States, as originally drafted by Cowardin et al. (1979:3), was “to impose 

boundaries on natural ecosystems for the purposes of inventory, evaluation, and 

management.” The FGDC Wetlands Classification Standard (WCS) provides minimum 

requirements and guidelines for classification of both wetlands and deepwater habitats 

that are consistent with the FGDC Wetlands Mapping Standard (FGDC-STD-015-2009). 

1.2 Scope 

Any new, updated, or revised mapping of wetlands or deepwater habitats shall conform 

to the FGDC Wetlands Classification Standard. More general mapping activities may 

incorporate wetlands data from the National Spatial Data Infrastructure (NSDI), rather 

than conducting new wetlands classification (see further information in the FGDC 

Wetlands Mapping Standard). 

The Classification of Wetlands and Deepwater Habitats of the United States was 

developed by wetland ecologists, with the assistance of many private individuals and 

organizations and local, state, and Federal agencies. It was designed for use over a broad 

geographic area—all U.S. States and Territories—by individuals and organizations with 

varied interests and objectives. The definition of wetland in this classification delimits the 

biological extent of wetland, as influenced by substrate properties and the hydrologic 

characteristics at each site. This robust classification system has been successfully 

applied throughout the United States and its Territories since the mid-1970s, making it a 

truly national system. 

1.2.1 Exemptions to the FGDC Wetlands Classification Standard 

Circumstances under which the FGDC Wetlands Classification Standard is not required 

include the following: 

1. Wetlands inventory mapping activities that are not federally-funded. 

However, such projects are strongly encouraged to comply with the WCS. 

The builders of the NSDI will not incorporate non-compliant wetlands 

inventory data from any source except USFWS wetlands maps created 

prior to implementation of the Wetlands Mapping Standard (FGDC-STD015- 2009). 

2. Mapping designed, or intended, to support legal, regulatory, or 

jurisdictional analyses by Federal, Tribal, state, and local regulatory 

agencies or to differentiate between regulatory and non-regulatory 

wetlands. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

3 

3. Marine and estuarine benthic habitat mapping because it currently 

necessitates the use of definitions and classifications that differ from the 

WCS. 

4. Classification data developed during site-specific wetland studies for 

scientific research, environmental assessments (EA), environmental 

impact statements (EIS), and wetland determinations for regulatory 

purposes when these site-specific activities necessitate the use of 

definitions and classifications that are incompatible with the WCS. 

However, the use of the WCS is strongly encouraged for these types of 

studies, whenever possible, so that the results can be interpolated or 

extrapolated across the country. 

1.2.2 Coordination with FGDC Coastal and Marine Ecological 

Classification Standard 

The FGDC Wetlands Classification Standard (WCS; FGDC-STD-004-2013) will be used 

to map all nontidal deepwater habitats except for the Great Lakes, and all coastal and 

inland wetlands except for permanently flooded tidal freshwater wetlands. The Coastal 

and Marine Ecological Classification Standard (CMECS; FGDC-STD-018-2012) will be 

used to map deepwater habitats in the Great Lakes and in the Marine and Estuarine 

Systems, as well as all permanently flooded tidal freshwater habitats (deepwater and 

wetland). The WCS will use 0.5 parts per thousand (ppt) ocean-derived salinity as the 

upstream boundary for the Estuarine System, and CMECS will use head-of-tide. 

1.3 Applicability 

The FGDC Wetlands Classification Standard is intended for all Federal or federallyfunded wetlands inventory mapping including those activities conducted by Federal 

agencies, states, and federally-recognized tribal entities, non-governmental organizations, 

universities, and others. Specifically, if Federal funding is used in support of wetlands 

inventory mapping activities, then use of this Standard is mandatory. The adoption of this 

Standard for all other wetlands inventory mapping efforts (non-federally funded) is 

strongly encouraged to maintain and expand the wetlands layer of the NSDI. 

The FGDC Wetlands Classification Standard is neither designed, nor intended, to support 

legal, regulatory, or jurisdictional analyses of wetlands mapping products, nor does it 

attempt to differentiate between regulatory and non-regulatory wetlands. Federal, Tribal, 

state, and local regulatory agencies with jurisdiction over wetlands may define and 

describe wetlands in a different manner than the FGDC Wetlands Classification Standard 

and the FGDC Wetlands Mapping Standard. There is no attempt to define the limits of 

proprietary jurisdiction of any Federal, Tribal, state, or local government or to establish 

the geographical scope of the regulatory programs of government agencies. Persons 

intending to engage in activities involving modifications within or adjacent to wetland 

areas should seek the advice of appropriate Federal, Tribal, state, or local agencies 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

4 

concerning specified agency regulatory programs and jurisdictions that may affect such 

activities. 

1.4 Related Standards 

Related FGDC Standards: 

Wetlands Mapping Standard, FGDC-STD-015-2009 

Coastal and Marine Ecological Classification Standard, FGDC-STD-018-2012 

Soil Geographic Data Standard, FGDC-STD-006 

National Vegetation Classification Standard (Version 2), FGDC-STD-005-2008 

Information Technology—Geographic Information Framework Data Content Standard, 

Part 5: Governmental unit and other geographic area boundaries, FGDC-STD014.5-2008 

FGDC Standards are available at: http://www.fgdc.gov/ 

Other Related Practices: 

A System for Mapping Riparian Areas in the Western United States (Dick 2009),

http://www.fws.gov/wetlands/Documents/A-System-for-Mapping-Riparian-AreasIn-The-Western-United-States-2009.pdf See further documentation on riparian area 

standards at http://www.fws.gov/stand/standards/dl_riparian_WWW.html

Primary Indicators Method. Tiner, R. W. 1993. The primary indicators method—a 

practical approach to wetland recognition and delineation in the United States.

Wetlands 13(1): 50-64. (This method is typically used for verifying Service 

Wetland Database wetlands on the ground.) 

http://www.fws.gov/wetlands/Documents/The-Primary-Indicators-Method-APractical-Approach-to-Wetland-Recognition-and-Delineation-in-the-UnitedStates.pdf 

 

National Hydrography Dataset (NHD) maintained by the USGS, http://nhd.usgs.gov/ 

Canadian Wetland Inventory maintained by Agriculture and Agri-Food Canada (AAFC), 

http://www.wetkit.net/modules/1/showtool.php?tool_id=83

RAMSAR Classification for Wetland Type maintained by Convention on Wetlands 

(Ramsar, Iran, 1971), 

http://www.ramsar.org/cda/ramsar/display/main/main.jsp?zn=ramsar&cp=1-26-

76%5E21235_4000_0__ 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

5 

Guidance for Benthic Habitat Mapping: An Aerial Photographic Approach maintained by 

the NOAA Coastal Services Center, 

http://www.csc.noaa.gov/benthic/mapping/pdf/bhmguide.pdf

Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. Kittel, S. Menard, M. 

Pyne, M. Reid, K. Schulz, K. Snow, and J. Teague. 2003. Ecological Systems of the 

United States: A Working Classification of U.S. Terrestrial Systems. NatureServe, 

Arlington, Virginia, http://www.natureserve.org/library/usEcologicalsystems.pdf

1.5 Standards Maintenance Procedures 

The intent of the FGDC Wetlands Subcommittee was to produce a newly edited and 

updated version of the FGDC Wetlands Classification Standard (FGDC-STD-004-1996), 

Classification of Wetlands and Deepwater Habitats of the United States (originally 

authored by Cowardin et al. 1979). This revised Standard has been formatted to be 

consistent with more recently endorsed FGDC Standards. The text has been edited, 

refined, clarified, and rewritten as necessary. Some portions were rewritten because the 

scientific foundation upon which the original classification (Cowardin et al. 1979) was 

developed has advanced. The Wetlands Mapping Standard FGDC-STD-015-2009, also 

developed by the FGDC Wetlands Subcommittee, was endorsed by the FGDC in July of 

2009. NWI’s Data Collection Requirements and Procedures for Mapping Wetland, 

Deepwater, and Related Habitats of the United States (Dahl et al. 2009) will be revised 

as necessary to keep pace with advances in technology. 

1.6 Maintenance Authority 

The maintenance authority resides with the USFWS. Pertinent enabling authority resides 

in the Emergency Wetlands Resources Act of 1986. The USFWS has designated its NWI 

Project to undertake the responsibilities to satisfy the requirements of Circular A-16. In 

carrying out Federal Government-wide leadership in spatial wetlands data coordination, 

the USFWS is directly responsible to the FGDC, and the NWI ensures compliance with 

the objectives and guidance provided by the FGDC. 

2. Wetlands and Deepwater Habitats 

2.1 Concepts and Definitions 

The definitions used in the FGDC Wetlands Classification Standard are neither designed, 

nor intended, to support legal, regulatory, or jurisdictional analyses of wetlands and 

deepwater habitats, nor do they attempt to differentiate between regulatory and nonregulatory wetlands or waters. 

Marshes, swamps, and bogs have been well-known terms for centuries, but only since the 

mid-1970s have attempts been made to group these landscape units under the single term 

“wetlands.” This general term has grown out of a need to understand and describe the 

characteristics and values of all types of land, and to effectively manage wetland habitats. 

There is no single, correct, indisputable, ecologically sound definition for wetlands, 

primarily because of the diversity of wetlands and because the demarcation between dry 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

6 

and wet environments lies along a continuum or gradient. Because reasons or needs for 

defining wetlands also vary, multiple definitions and criteria have been developed for 

different purposes. The primary purpose of this classification is to identify and describe 

wet habitats to aid in their inventory, assessment, and management. The definition used 

in this classification is habitat-based and amenable to remote sensing technology. 

2.1.1 Wetlands 

In general terms, wetlands are lands where saturation with water is the dominant factor 

determining the nature of substrate development and the types of plant and animal 

communities living in the substrate and on its surface. The single feature that most 

wetlands share is a substrate that is at least periodically saturated with or covered by 

water. The water creates severe physiological problems for all plants and animals except 

those that are specially adapted for such conditions. 

Wetland “substrates” consist of unconsolidated mineral material, organic material, or 

rock that is flooded or saturated long enough each year to support wetland organisms (see 

glossary in Appendix A). Most wetland substrates also qualify as “soil.” According to the 

U.S. Department of Agriculture (USDA), Natural Resources Conservation Service 

(NRCS), “soil” is a natural body that occurs at the land surface and has recognizable 

horizons, or layers, or has the ability to support rooted plants (Soil Survey Staff 1999; see 

Appendix A for a more detailed technical definition). As noted, the great majority of 

wetlands have soil; obvious exceptions include bedrock and boulder or cobble shores 

which lack horizons and have too little fine material to support rooted plants. In this 

classification, the term “soil” is only used for wetland substrates that meet the USDA 

definition. The more generic term “substrate” may be applied to any wetland, but is most 

often used in this classification when referring to nonvegetated habitats and when 

defining terms (e.g., individual Water Regimes and Marine and Estuarine Subsystems) 

that apply to, or include, both habitats that have soil and habitats that do not. 

The following definition of wetlands is neither designed, nor intended, to support legal, 

regulatory, or jurisdictional analyses, nor does it attempt to differentiate between 

regulatory and non-regulatory wetlands. 

The FGDC Wetlands Classification Standard (WCS) defines “wetlands” according to 

Cowardin et al. (1979): 

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 hydrophytes1

; (2) 

 

1 Lichvar, R. W., and J. T. Kartesz. 2009. North American Digital Flora: National Wetland Plant List, version 

2.4.0 U.S. Army Corps of Engineers, Engineer Research and Development Center, Cold Regions Research and 

Engineering Laboratory, Hanover, New Hampshire, and BONAP, Chapel Hill, North Carolina 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

7 

the substrate is predominantly undrained hydric soil2

; and (3) the substrate is nonsoil 

and is saturated with water or covered by shallow water at some time during the growing 

season of each year. 

As noted in this definition, plant community composition, soil morphology, and site 

wetness (hydrology) are the principal indicators of whether a site is a wetland for 

ecological purposes. Site wetness, i.e., the presence of water, while central to the concept 

of wetland, is often the most difficult indicator to assess accurately because it is more 

dynamic (temporally variable) than plant community composition or soil properties. 

Plants and soil tend to reflect the prevailing degree of wetness at a site over time. For this 

reason, they frequently are excellent indicators of relative wetness, and this is why they 

are listed first as indicators of wetlands. 

Cowardin et al. (1979) intended that all available information should be used in making a 

wetland identification, as follows: 

 If plants and soil are present at a site, then both a predominance of hydrophytes 

and a predominance of undrained hydric soil, as well as wetland hydrology, 

should be required for positive wetland identification. 

 If plants are present but soil is absent (e.g., Algal Aquatic Beds on rock 

substrates), then a predominance of hydrophytic vegetation, as well as wetland 

hydrology, should be required for a positive wetland identification. 

 If plants are absent but soil is present, then a predominance of undrained hydric 

soil, as well as wetland hydrology, should be required for positive wetland 

identification. 

 If neither plants nor soil is present, then the wetland identification must be made 

strictly on the basis of hydrology. In this case, the substrate should be “saturated 

with water or covered by shallow water at some time during the growing season 

of each year.” Cowardin et al. (1979) fully realized how vague this hydrologic 

definition was but, given the lack of detailed hydrologic data from the diversity of 

wetland types, geologic regions, and climatic regions of the U.S., there was no 

way they could have been more specific. Even today, these data are not readily 

available across the nation. 

In these examples, three (3) indicators – hydrophytic vegetation, undrained hydric soil, 

and wetland hydrology; two (2) indicators—hydrophytic vegetation and wetland 

hydrology or undrained hydric soil and wetland hydrology; and one (1) indicator—

wetland hydrology, respectively, would be used to make the identification, based on the 

features available at the particular site. 

 

2 U.S. Department of Agriculture, Natural Resources Conservation Service. 2010. Field indicators of hydric soils 

in the United States. Version 7. L.M. Vasilas, G.W. Hunt, and C.V. Noble, eds. USDA, NRCS, in cooperation 

with the National Technical Committee for Hydric Soils.
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

8 

2.1.2 Deepwater Habitats 

DEEPWATER HABITATS are permanently flooded lands lying below the deepwater 

boundary of wetlands (see Section 2.2 for explanation of wetland limits). Deepwater 

habitats include environments where surface water is permanent and often deep, so that 

water, rather than air, is the principal medium within which the dominant organisms live, 

whether or not they are rooted in, or attached to, the substrate. As in wetlands, the 

dominant plants are hydrophytes. 

Wetlands and deepwater habitats are defined separately because traditionally the term 

wetlands has not included deep, permanent water; however, both must be considered in 

an ecological approach to classification. The WCS includes five major Systems: Marine, 

Estuarine, Riverine, Lacustrine, and Palustrine. The first four of these include both 

wetlands and deepwater habitats but the Palustrine includes only wetland habitats. 

2.2 Limits 

The upland limit of wetlands is characterized by (1) the boundary between land with 

predominantly hydrophytic cover and land with predominantly mesophytic or xerophytic 

cover; (2) the boundary between soil that is predominantly hydric and soil that is 

predominantly nonhydric; and (3) the boundary between land that is flooded or saturated 

at some time during the growing season each year and land that is not. 

The boundary between wetlands and deepwater habitats in the Marine and Estuarine 

Systems coincides with the elevation of the extreme low water of spring tide; all 

permanently flooded areas are considered deepwater habitats in these Systems. The 

boundary between wetlands and deepwater habitat in the Riverine and Lacustrine 

Systems lies at a depth of 2.5 m (8.2 ft) below low water; however, if emergents, shrubs, 

or trees grow beyond this depth at any time, their deepwater edge is the boundary. 

The 2.5-m lower limit for inland wetlands was selected because it approximates the 

maximum depth to which emergent plants normally grow (Welch 1952, Zhadin and Gerd 

1963, Sculthorpe 1967) and the depth beyond which soil does not occur, according to the 

USDA Natural Resources Conservation Service (Soil Survey Staff 1999). As 

Daubenmire (1968:138) stated, emergents are not true aquatic plants, but are 

“amphibious,” growing in both permanently flooded and wet, nonflooded soils. 

3. The Classification System 

The structure of this classification is hierarchical, progressing from Systems and 

Subsystems at the most general levels to Classes, Subclasses, and Dominance Types. 

Figure 1 illustrates the classification structure through the Class level. Table 1 lists the 

Subclasses that occur within each System, Subsystem and Class. Modifiers for Water 

Regime, Water Chemistry, and Soil are applied to Classes and Subclasses. Special 

Modifiers describe wetlands and deepwater habitats that have been either created or 

highly modified by humans or beaver. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

9 

Figure 1. Classification hierarchy of wetlands and deepwater habitats, showing Systems, Subsystems, and 

Classes. The Palustrine System does not include deepwater habitats. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

10 

Table 1. Distribution of Subclasses within the classification hierarchy

Systems and Subsystems 

Marine Estuarine Riverine Lacustrine Palustrine 

Classes and Subclasses ST IT ST IT TI LP UP IN LM LT –

Rock Bottom

 Bedrock       

 Rubble       

Unconsolidated Bottom 

 Cobble-Gravel        

 Sand        

 Mud        

 Organic      

Aquatic Bed 

 Algal          

 Aquatic Moss      

 Rooted Vascular          

 Floating Vascular        

Reef

 Coral   

 Mollusk   

 Worm     

Streambed

 Bedrock    

 Rubble    

 Cobble-Gravel    

 Sand    

 Mud    

 Organic    

 Vegetated (pioneer plants)  

Rocky Shore 

 Bedrock      

 Rubble      

Unconsolidated Shore 

 Cobble-Gravel       

 Sand       

 Mud       

 Organic       

 Vegetated (pioneer plants)    

Moss-Lichen Wetland 

 Moss 

 Lichen 

Emergent Wetland 

 Persistent  

 Nonpersistent     

Scrub-Shrub Wetland 

 Broad-leaved Deciduous  

 Needle-leaved Deciduous  

 Broad-leaved Evergreen  

 Needle-leaved Evergreen  

 Dead  

Forested Wetland 

 Broad-leaved Deciduous  

 Needle-leaved Deciduous  

 Broad-leaved Evergreen  

 Needle-leaved Evergreen  

 Dead  

ST = Subtidal, IT = Intertidal, TI = Tidal, LP = Lower Perennial, UP = Upper Perennial, IN = Intermittent, LM = Limnetic, LT = Littoral
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

11 

Artificial keys to the Systems and Classes are given in Appendix B. Scientific and 

common names of plants (Appendix C) are based on Lichvar and Kartesz (2009). 

Scientific and common names of animals (Appendix D) are based on the Integrated 

Taxonomic Information System (http://www.itis.gov); no attempt has been made to 

resolve nomenclatorial problems where there is a taxonomic dispute. Many of the terms 

in this classification have various meanings, even in the scientific literature, and in some 

instances our use of terms is new. Therefore, we have provided a glossary (Appendix A) 

to guide the reader in our usage of terms. 

3.1 Systems and Subsystems 

The term SYSTEM refers here to a complex of wetlands and deepwater habitats that share 

the influence of similar hydrologic, geomorphologic, chemical, or biological factors. We 

further subdivide Systems into more specific categories called SUBSYSTEMS. 

The characteristics of the five major Systems—Marine, Estuarine, Riverine, Lacustrine, 

and Palustrine—have been discussed at length in the scientific literature and the concepts 

are well recognized; however, there is frequent disagreement as to which attributes 

should be used to bound the Systems in space. For example, both the limit of tidal 

influence and the limit of ocean-derived salinity have been proposed for bounding the 

upstream end of the Estuarine System (Caspers 1967). As Bormann and Likens (1969) 

pointed out, boundaries of ecosystems are defined to meet practical needs. 

3.1.1 Marine System 

Definition. The Marine System (Figure 2) consists of the open ocean overlying the 

continental shelf and its associated high-energy coastline. Marine habitats are exposed to 

the waves and currents of the open ocean and the Water Regimes are determined 

primarily by the ebb and flow of oceanic tides. Salinities exceed 30 parts per thousand 

(ppt), with little or no dilution except outside the mouths of estuaries. Shallow coastal 

indentations or bays without appreciable freshwater inflow, and coasts with exposed 

rocky islands that provide the mainland with little or no shelter from wind and waves, are 

also considered part of the Marine System because they generally support typical marine 

biota. 

Limits. The Marine System extends from the outer edge of the continental shelf 

shoreward to one of three lines: (1) the landward limit of tidal inundation (extreme high 

water of spring tides), including the splash zone from breaking waves; (2) the seaward 

limit of wetland emergents, trees, or shrubs; or (3) the seaward limit of the Estuarine 

System, where this limit is determined by factors other than vegetation. Deepwater 

habitats lying beyond the seaward limit of the Marine System are outside the scope of the 

WCS. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

12 

Figure 2. Distinguishing features and examples of habitats in the Marine System. 

EHWS = extreme high water of spring tides; ELWS = extreme low water of spring tides.

Description. The distribution of plants and animals in the Marine System primarily 

reflects differences in four factors: (1) degree of exposure of the site to waves; (2) texture 

and physicochemical nature of the substrate; (3) amplitude of the tides; and (4) latitude, 

which governs water temperature, the intensity and duration of solar radiation, and the 

presence or absence of ice. 

Subsystems. 

Subtidal. The substrate in these habitats is continuously covered with tidal water (i.e., 

located below extreme low water). 

Intertidal. The substrate in these habitats is flooded and exposed by tides; includes the 

associated splash zone. 

Classes. Rock Bottom, Unconsolidated Bottom, Aquatic Bed, Reef, Rocky Shore, and 

Unconsolidated Shore. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

13 

3.1.2 Estuarine System 

Definition. The Estuarine System (Figure 3) consists of deepwater tidal habitats and 

adjacent tidal wetlands that are usually semienclosed by land but have open, partly 

obstructed, or sporadic access to the open ocean, and in which ocean water is at least 

occasionally diluted by freshwater runoff from the land. The salinity may be periodically 

increased above that of the open ocean by evaporation. Along some low-energy 

coastlines there is appreciable dilution of sea water. Offshore areas with typical estuarine 

plants and animals, such as red mangroves (Rhizophora mangle) and eastern oysters 

(Crassostrea virginica), are also included in the Estuarine System.3

Figure 3. Distinguishing features and examples of habitats in the Estuarine System. 

EHWS = extreme high water of spring tides; ELWS = extreme low water of spring tides.

Limits. The Estuarine System extends (1) upstream and landward to where ocean-derived 

salts measure less than 0.5 ppt during the period of average annual low flow; (2) seaward 

to an imaginary line closing the mouth of a river, bay, or sound; and (3) to the seaward 

 

3 The Coastal Zone Management Act of 1972 defines an estuary as “that part of a river or stream or other body 

of water having unimpaired connection with the open sea, where the sea-water is measurably diluted with 

freshwater derived from land drainage." The Act further states that "the term includes estuary-type areas of the 

Great Lakes." However, in the WCS we do not consider areas of the Great Lakes as Estuarine. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

14 

limit of wetland emergents, shrubs, or trees where they are not included in (2). The 

Estuarine System also includes offshore areas of continuously diluted sea water. 

Description. The Estuarine System includes both estuaries and lagoons. It is more 

strongly influenced by its association with land than is the Marine System. In terms of 

wave action, estuaries are generally considered to be low-energy systems (Chapman 

1977). 

Estuarine water regimes and water chemistry are affected by one or more of the following 

forces: oceanic tides, precipitation, freshwater runoff from land areas, evaporation, and 

wind. Estuarine salinities range from hyperhaline to oligohaline (see Section 3.3.2.1 for 

Salinity Modifiers). The salinity may be variable, as in hyperhaline lagoons (e.g., Laguna 

Madre, Texas) and most estuaries (e.g., Chesapeake Bay, Virginia-Maryland); or it may 

be relatively stable, as in sheltered euhaline embayments (e.g., Chincoteague Bay, 

Maryland) or embayments with partly obstructed access or small tidal range (e.g., 

Pamlico Sound, North Carolina). (For an extended discussion of estuaries and lagoons, 

see Lauff 1967.) 

Subsystems. 

Subtidal. The substrate in these habitats is continuously covered with tidal water (i.e., 

located below extreme low water). 

Intertidal. The substrate in these habitats is flooded and exposed by tides; includes the 

associated splash zone. 

Classes. Rock Bottom, Unconsolidated Bottom, Aquatic Bed, Reef, Streambed, Rocky 

Shore, Unconsolidated Shore, Emergent Wetland, Scrub-Shrub Wetland, and Forested 

Wetland. 

3.1.3 Riverine System 

Definition. The Riverine System (Figure 4) includes all wetlands and deepwater habitats 

contained within a channel, with two exceptions: (1) wetlands dominated by trees, 

shrubs, persistent emergents, emergent mosses, or lichens, and (2) habitats with water 

containing ocean-derived salts of 0.5 ppt or greater. A channel is “an open conduit either 

naturally or artificially created which periodically or continuously contains moving 

water, or which forms a connecting link between two bodies of standing water” 

(Langbein and Iseri 1960:5). 

Limits. The Riverine System is bounded on the landward side by upland, by the channel 

bank (including natural and man-made levees), or by wetlands dominated by trees, 

shrubs, persistent emergents, emergent mosses, or lichens. In braided streams, the System 

is bounded by the banks forming the outer limits of the depression within which the 

braiding occurs. 

The Riverine System terminates at the downstream end where the concentration of oceanderived salts in the water equals or exceeds 0.5 ppt during the period of annual average 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

15 

low flow, or where the channel enters a lake. It terminates at the upstream end where 

tributary streams originate, or where the channel leaves a lake. Springs discharging into a 

channel are considered part of the Riverine System. 

Figure 4. Distinguishing features and examples of habitats in the Riverine System.

Description. Water is usually, but not always, flowing in the Riverine System. Upland 

islands or Palustrine wetlands may occur in the channel, but they are not included in the 

Riverine System. Palustrine Moss-Lichen Wetlands, Emergent Wetlands, Scrub-Shrub 

Wetlands, and Forested Wetlands may occur adjacent to the Riverine System, often on a 

floodplain. Many biologists have suggested that all the wetlands occurring on the river 

floodplain should be a part of the Riverine System because they consider their presence 

to be the result of river flooding. However, this classification follows Reid and Wood 

(1976:72,84) who stated, “The floodplain is a flat expanse of land bordering an old 

river.... Often the floodplain may take the form of a very level plain occupied by the 

present stream channel, and it may never, or only occasionally, be flooded.... It is this 

subsurface water (the groundwater) that controls to a great extent the level of lake 

surfaces, the flow of streams, and the extent of swamps and marshes.” 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

16 

Subsystems. The Riverine System is divided into four Subsystems: the Tidal, the Lower 

Perennial, the Upper Perennial, and the Intermittent. Each is defined in terms of water 

permanence, gradient, substrate, and the extent of floodplain development. The 

Subsystems have characteristic flora and fauna (see Illies and Botosaneau 1963; Hynes 

1970; Reid and Wood 1976). All four Subsystems are not necessarily present in all rivers, 

and the order of occurrence may be other than that given below. 

Tidal. This Subsystem extends from the upstream limit of tidal fluctuations down to the 

upper boundary of the Estuarine System, where the concentration of ocean-derived salts 

reaches 0.5 ppt during the period of average annual low flow. The gradient is low and 

water velocity fluctuates under tidal influence. The stream bottom is mainly mud with 

occasional patches of sand. Oxygen deficits may sometimes occur and the fauna is 

similar to that in the Lower Perennial Subsystem. The floodplain is typically well 

developed. 

Lower Perennial. This Subsystem is characterized by a low gradient. There is no tidal 

influence, and some water flows all year, except during years of extreme drought. The 

substrate consists mainly of sand and mud. Oxygen deficits may sometimes occur. The 

fauna is composed mostly of species that reach their maximum abundance in still water, 

and true planktonic organisms are common. The gradient is lower than that of the Upper 

Perennial Subsystem and the floodplain is well developed.

Upper Perennial. This Subsystem is characterized by a high gradient. There is no tidal 

influence, and some water flows all year, except during years of extreme drought. The 

substrate consists of rock, cobbles, or gravel with occasional patches of sand. The natural 

dissolved oxygen concentration is normally near saturation. The fauna is characteristic of 

running water, and there are few or no planktonic forms. The gradient is high compared 

with that of the Lower Perennial Subsystem, and there is very little floodplain 

development. 

Intermittent. This Subsystem includes channels that contain flowing water only part of 

the year. When the water is not flowing, it may remain in isolated pools or surface water 

may be absent. 

Classes: Rock Bottom, Unconsolidated Bottom, Aquatic Bed, Streambed, Rocky Shore, 

Unconsolidated Shore, and Emergent Wetland (nonpersistent). 

3.1.4 Lacustrine System 

Definition. The Lacustrine System (Figure 5) includes wetlands and deepwater habitats 

with all of the following characteristics: (1) situated in a topographic depression or a 

dammed river channel; (2) lacking trees, shrubs, persistent emergents, emergent mosses 

or lichens with 30 percent or greater areal coverage; and (3) total area of at least 8 

hectares (ha) (20 acres). Similar wetlands and deepwater habitats totaling less than 8 ha 

are also included in the Lacustrine System if an active wave-formed or bedrock shoreline 

feature makes up all or part of the boundary, or if the water depth in the deepest part of 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

17 

the basin equals or exceeds 2.5 m (8.2 ft) at low water. Lacustrine waters may be tidal or 

nontidal, but ocean-derived salinity is always less than 0.5 ppt. 

Figure 5. Distinguishing features and examples of habitats in the Lacustrine System.

Limits. The Lacustrine System is bounded by upland or by wetlands dominated by trees, 

shrubs, persistent emergents, emergent mosses, or lichens. Lacustrine Systems formed by 

damming a river channel are bounded by a contour approximating the normal spillway 

elevation or normal pool elevation, except where Palustrine wetlands extend lakeward of 

that boundary. Where a river enters a lake, the extension of the Lacustrine shoreline 

forms the Riverine-Lacustrine boundary. 

Description. The Lacustrine System includes permanently flooded lakes and reservoirs 

(e.g., Lake Superior), intermittent lakes (e.g., playa lakes), and tidal lakes with oceanderived salinities below 0.5 ppt (e.g., Grand Lake, Louisiana). Typically, there are 

extensive areas of deep water and there is considerable wave action. Islands of Palustrine 

wetlands may lie within the boundaries of the Lacustrine System. 

Subsystems. 

Limnetic. This subsystem includes all deepwater habitats (i.e., areas > 2.5 m [8.2 ft] deep 

below low water) in the Lacustrine System. Many small Lacustrine Systems have no 

Limnetic Subsystem. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

18 

Littoral. This subsystem includes all wetland habitats in the Lacustrine System. It extends 

from the shoreward boundary of the System to a depth of 2.5 m (8.2 ft) below low water, 

or to the maximum extent of nonpersistent emergents if these grow at depths greater than 

2.5 m. 

Classes: Rock Bottom, Unconsolidated Bottom, Aquatic Bed, Rocky Shore, 

Unconsolidated Shore, and Emergent Wetland (nonpersistent). 

3.1.5 Palustrine System 

Definition. The Palustrine System (Figure 6) includes all nontidal wetlands dominated by 

trees, shrubs, persistent emergents, emergent mosses or lichens, and all such wetlands 

that occur in tidal areas where salinity due to ocean-derived salts is below 0.5 ppt. It also 

includes wetlands lacking such vegetation, but with all of the following four 

characteristics: (1) area less than 8 ha (20 acres); (2) active wave-formed or bedrock 

shoreline features lacking; (3) water depth in the deepest part of basin less than 2.5 m (8.2 

ft) at low water; and (4) salinity due to ocean-derived salts less than 0.5 ppt. 

Figure 6. Distinguishing features and examples of habitats in the Palustrine System.

Limits. The Palustrine System is bounded by upland or by any of the other four Systems. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

19 

Description. The Palustrine System was developed to group the vegetated wetlands 

traditionally called by such names as marsh, swamp, bog, fen, and prairie, which are 

found throughout the U.S. It also includes the small, shallow, permanent or intermittent 

water bodies often called ponds. Palustrine wetlands may be situated shoreward of lakes, 

river channels, or estuaries; on river floodplains; in isolated catchments; or on slopes. 

They may also occur as islands in lakes or rivers. The erosive forces of wind and water 

are of minor importance except during severe floods. 

The emergent vegetation adjacent to rivers and lakes is often referred to as “the shore 

zone” or the “zone of emergent vegetation” (Reid and Wood 1976), and is generally 

considered separately from the river or lake. As an example, Hynes (1970:85) wrote in 

reference to riverine habitats, “We will not here consider the long list of emergent plants 

which may occur along the banks out of the current, as they do not belong, strictly 

speaking, to the running water habitat.” There are often great similarities between 

wetlands lying adjacent to lakes or rivers and isolated wetlands of the same Class in 

basins without open water. 

Subsystems. None. 

Classes: Rock Bottom, Unconsolidated Bottom, Aquatic Bed, Unconsolidated Shore, 

Moss-Lichen Wetland, Emergent Wetland, Scrub-Shrub Wetland, and Forested Wetland. 

3.2 Classes, Subclasses, and Dominance Types 

The CLASS is the highest taxonomic unit below the Subsystem level. It describes the 

general appearance of the habitat in terms of either the dominant life form of the 

vegetation or the physiography and composition of the substrate—features that can be 

recognized without the aid of detailed environmental measurements. Vegetation is used at 

two different levels in the classification. The basic life form layers, from highest to 

lowest—trees, shrubs, emergents, emergent mosses or lichens, and surface plants or 

submergents—are used to define Classes because they are relatively easy to distinguish, 

do not change distribution rapidly, and have traditionally been used for classification of 

wetlands and habitat assessment.4 Pioneer plants that colonize wetlands during dry 

periods, but disappear when surface water returns, are treated at the Subclass level 

because they are transient and may be mesophytes or xerophytes. Use of life forms at the 

Class level has two major advantages: (1) extensive biological knowledge is not required 

to distinguish between various life forms, and (2) many life forms can be readily 

identified on a variety of remote sensing products (e.g., Radforth 1962; Anderson et al. 

1976). 

 

4 The initial attempts to use familiar terms such as marsh, swamp, bog, and meadow at the Class level were 

unsuccessful primarily because of wide discrepancies in the use of these terms in various regions of the United 

States. In an effort to resolve that difficulty, we based the Classes on the fundamental components (life form, 

water regime, substrate type, water chemistry) that give rise to such terms. This approach has greatly reduced the 

misunderstandings and confusion that result from the use of the familiar terms.
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

20 

If living vegetation (except pioneer species) covers 30 percent or more of the substrate, 

we distinguish Classes on the basis of the life form of the plants that constitute the 

uppermost layer of vegetation and that possess an areal coverage 30 percent or greater. 

For example, an area with 50 percent areal coverage of trees over a shrub layer with a 60 

percent areal coverage would be classified as Forested Wetland; an area with 20 percent 

areal coverage of trees over the same (60 percent) shrub layer would be classified as 

Scrub-Shrub Wetland. When trees or shrubs alone cover less than 30 percent of an area 

but in combination cover 30 percent or more, the wetland is assigned to the Class ScrubShrub. When trees and shrubs cover less than 30 percent of the area but the total cover of 

vegetation (except pioneer species) is 30 percent or greater, the wetland is assigned to the 

appropriate Class for the predominant life form below the shrub layer. 

When the height of two or more plant life forms in an area is equal, and each covers 30 

percent or more of the area, the Class is based on the life form that has the greater cover. 

If the cover of the life forms is equal, then the Class is based on the life form that is more 

persistent. If the life forms are equally persistent, then the Class is based on the life form 

that would normally be considered to be more advanced from a successional standpoint 

(e.g., shrub > emergent plant > emergent moss or lichen). 

Finer distinctions in life forms are recognized at the SUBCLASS level. Subclasses are 

named on the basis of the specific life form with the greatest areal coverage. In ScrubShrub and Forested Wetlands, for example, most Subclasses are distinguished by leaf 

type (broad-leaved deciduous, needle-leaved deciduous, broad-leaved evergreen, and 

needle-leaved evergreen). 

When an area is covered more or less uniformly by dead trees or dead shrubs—regardless 

of their abundance—and living vegetation covers less than 30 percent of that area, the 

site would be placed in either the Dead Forested Wetland Subclass or the Dead ScrubShrub Wetland Subclass, depending on whether dead trees or dead shrubs predominate. 

However, if living vegetation covers 30 percent or more of a stand of dead trees or 

shrubs, then the dominant life form, Class, and Subclass would be based on the living 

vegetation, using the rules outlined above. 

If living vegetation covers less than 30 percent of the substrate, the physiography and 

composition of the substrate are the principal characteristics used to distinguish Classes. 

Substrate particle sizes include boulders, stones, cobbles, gravel, sand, silt, and clay (see 

Appendix A for definitions). Cowardin et al. (1979) employed these, alone or in 

combination, along with the term ‘bedrock,’ as Subclasses for nonvegetated wetlands and 

deepwater habitats.

The nature of the substrate reflects regional and local variations in geology and the 

influence of wind, waves, and currents on erosion and deposition of substrate materials. 

Bottoms, Shores, and Streambeds are separated on the basis of duration of inundation. In 

the Riverine, Lacustrine, and Palustrine Systems, Bottoms are submerged all or most of 

the time, whereas Streambeds and Shores are exposed much of the time. In the Marine 

and Estuarine Systems, Bottoms are Subtidal, whereas Streambeds and Shores are 

Intertidal. Bottoms, Shores, and Streambeds are further divided at the Class level on the 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

21 

basis of the important characteristic of rock versus unconsolidated substrate. Subclasses 

are based on finer distinctions in substrate material unless, as with Streambeds and 

Shores, pioneer plants (often mesophytes or xerophytes) cover 30 percent or more of the 

substrate; the Subclass then is simply “vegetated.” Further detail as to the type of 

vegetation must be obtained at the level of Dominance Type. Reefs are a unique Class in 

which the substrate itself is composed primarily of living and dead animals. Subclasses of 

Reefs are designated on the basis of the type of organism that formed the reef. 

The DOMINANCE TYPE is the taxonomic category subordinate to Subclass. Dominance 

Types are determined on the basis of dominant plant species (e.g., Jeglum et al. 1974), 

dominant sedentary or sessile animal species (e.g., Thorson 1957), or dominant plant and 

animal species (e.g., Stephenson and Stephenson 1972). A dominant plant species has 

traditionally meant one that has control over the community (Weaver and Clements 

1938), and this plant is also usually the predominant species (Cain and Castro 1959). 

When the Subclass is based on life form, the Dominance Type is named for the dominant 

species or combination of species (codominants) in the same layer of vegetation used to 

determine the Subclass.5 For example, a Needle-leaved Evergreen Forested Wetland with 

70 percent areal cover of black spruce (Picea mariana) and 30 percent areal cover of 

American larch (Larix laricina) would be designated as a Picea mariana Dominance 

Type. When the relative abundance of codominant species is nearly equal, the 

Dominance Type consists of a combination of species names. For example, an Emergent 

Wetland with about equal areal cover of broad-leaf cattail (Typha latifolia) and hardstem 

bulrush (Scirpus acutus) would be designated a Typha latifolia-Scirpus acutus

Dominance Type. 

When the Subclass is based on substrate material, the Dominance Type is named for the 

predominant plant or sedentary or sessile macroinvertebrate species, without regard for 

life form. In the Marine and Estuarine Systems, sponges, alcyonarians, mollusks, 

crustaceans, worms, ascidians, and echinoderms may all be part of the community 

represented by the Macoma balthica Dominance Type. Sometimes it is necessary to 

designate two or more codominant species as a Dominance Type. Thorson (1957) 

recommended guidelines and suggested definitions for establishing community types and 

dominants on level bottoms. 

3.2.1 Rock Bottom 

Definition. The Class Rock Bottom includes all wetlands and deepwater habitats with 

substrates having an areal cover of stones, boulders, or bedrock 75 percent or greater and 

vegetative cover of less than 30 percent. Water Regimes are restricted to Subtidal, 

Permanently Flooded, Intermittently Exposed, Semipermanently Flooded, Permanently 

Flooded-Tidal Fresh, and Semipermanently Flooded-Tidal Fresh. 

 

5 Percent areal cover is seldom measured in the application of the WCS, but the term must be defined in terms of 

area. We suggest 2 m2

 for herbaceous and moss layers, 16 m2 for shrub layers, and 100 m2 for tree layers 

(Mueller-Dombois and Ellenberg 1974). When percent areal cover is the key for establishing boundaries between 

units of the classification, it may occasionally be necessary to measure cover on plots, in order to maintain 

uniformity of ocular estimates made in the field or interpretations made from aerial imagery. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

22 

Description. The rock substrate of the rocky benthic or bottom zone is one of the most 

important factors in determining the abundance, variety, and distribution of organisms. 

The stability of the bottom allows a rich assemblage of plants and animals to develop. 

Rock Bottoms are usually high-energy habitats with well-aerated waters. Temperature, 

salinity, current, and light penetration are also important factors in determining the 

composition of the benthic community. Animals that live on the rocky surface are 

generally firmly attached by hooking or sucking devices, although they may occasionally 

move about over the substrate. Some may be permanently attached by cement. A few 

animals hide in rocky crevices and under rocks, some move rapidly enough to avoid 

being swept away, and others burrow into the finer substrates between boulders. Plants 

are also firmly attached (e.g., by hold-fasts), and in the Riverine System both plants and 

animals are commonly streamlined or flattened in response to high water velocities. 

Subclasses and Dominance Types. 

Bedrock. Bottoms in which bedrock covers 75 percent or more of the surface. 

Rubble. Bottoms with less than 75 percent areal cover of bedrock, but stones and 

boulders alone, or in combination with bedrock, cover 75 percent or more of the surface. 

Examples of Dominance Types for these two Subclasses in the Marine and Estuarine 

Systems are the encrusting sponges Hippospongia, the tunicate Cnemidocarpa, the sea 

urchin Strongylocentrotus, the sea star Pisaster, the sea whip Muricea, and the American 

lobster Homarus americanus. Examples of Lacustrine, Palustrine, and Riverine 

Dominance Types are the freshwater sponges Spongilla and Heteromeyenia, the pond 

snail Lymnaea, the mayfly Ephemerella, various midges of the Chironomidae, the 

caddisfly Hydropsyche, the leech Helobdella, the riffle beetle Psephenus, the chironomid 

midge Eukiefferiella, the crayfish Procambarus, and the black fly Simulium. 

Dominance Types for Rock Bottoms in the Marine and Estuarine Systems were taken 

primarily from Smith (1964) and Ricketts and Calvin (1968), and those for Rock Bottoms 

in the Lacustrine, Riverine, and Palustrine Systems from Krecker and Lancaster (1933), 

Stehr and Branson (1938), Ward and Whipple (1959), Clarke (1973), Hart and Fuller 

(1974), Ward (1975), Slack et al. (1977), and Pennak (1978). 

3.2.2 Unconsolidated Bottom 

Definition. The Class Unconsolidated Bottom includes all wetlands and deepwater 

habitats with at least 25 percent cover of particles smaller than stones and a vegetative 

cover less than 30 percent. Water Regimes are restricted to Subtidal, Permanently 

Flooded, Intermittently Exposed, Semipermanently Flooded, Permanently Flooded-Tidal 

Fresh, and Semipermanently Flooded-Tidal Fresh. 

Description. Unconsolidated Bottoms are characterized by the lack of large stable 

surfaces for plant and animal attachment. They are usually found in areas with lower 

energy than Rock Bottoms, and may be very unstable. Exposure to wave and current 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

23 

action, temperature, salinity, and light penetration determines the composition and 

distribution of organisms. 

Most macroalgae attach to the substrate by means of basal hold-fast cells or discs; in sand 

and mud, however, algae penetrate the substrate and higher plants can successfully root if 

wave action and currents are not too strong. Most animals in unconsolidated sediments 

live within the substrate, e.g., Macoma and the amphipod Melita. Some, such as the 

polychaete worm Chaetopterus, maintain permanent burrows, and others may live on the 

surface, especially in coarse-grained sediments. 

In the Marine and Estuarine Systems, Unconsolidated Bottom communities are relatively 

stable. They vary from the Arctic to the tropics, depending largely on temperature, and 

from the open ocean to the upper end of the estuary, depending on salinity. Thorson 

(1957) summarized and described characteristic types of level-bottom communities in 

detail. 

In the Riverine System, the substrate type is largely determined by current velocity, and 

plants and animals exhibit a high degree of morphologic and behavioral adaptation to 

flowing water. Certain species are confined to specific substrates and some are at least 

more abundant in one type of substrate than in others. According to Hynes (1970:208), 

“The larger the stones, and hence the more complex the substratum, the more diverse is 

the invertebrate fauna.” In the Lacustrine and Palustrine Systems, there is usually a high 

correlation, within a given water body, between the nature of the substrate and the 

number of species and individuals. For example, in the profundal bottom of eutrophic 

lakes where light is absent, oxygen content is low, and carbon dioxide concentration is 

high, the sediments are ooze-like organic materials and species diversity is low. Each 

substrate type typically supports a relatively distinct community of organisms (Reid and 

Wood 1976). 

Subclasses and Dominance Types. 

Cobble-Gravel. The unconsolidated particles smaller than stones are predominantly 

cobbles and gravel, although finer sediments may be intermixed. Examples of 

Dominance Types for the Marine and Estuarine Systems are the mussels Modiolus and 

Mytilus, the brittle star Amphipholis, the soft-shell clam Mya, and the Venus clam 

Saxidomus. Examples for the Lacustrine, Palustrine, and Riverine Systems are the midge 

Diamesa, stonefly-midge Nemoura-Eukiefferiella (Slack et al. 1977), chironomid midgecaddisfly-snail Chironomus-Hydropsyche-Physa (Krecker and Lancaster 1933), the pond 

snail Lymnaea, the mayfly Baetis, the freshwater sponge Eunapius, the oligochaete worm 

Lumbriculus, the scud Gammarus, and the freshwater mollusks Anodonta, Elliptio, and 

Lampsilis. 

Sand. The unconsolidated particles smaller than stones are predominantly sand, although 

finer or coarser sediments may be intermixed. Examples of Dominance Types in the 

Marine and Estuarine Systems are the wedge shell Donax, the scallop Pecten, the tellin 

shell Tellina, the heart urchin Echinocardium, the lugworm Arenicola, the sand dollar 

Dendraster, and the sea pansy Renilla. Examples for the Lacustrine, Palustrine, and 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

24 

Riverine Systems are the snail Physa, the scud Gammarus, the oligochaete worm 

Limnodrilus, the mayfly Ephemerella, the freshwater mollusks Elliptio and Anodonta, 

and the fingernail clam Sphaerium. 

Mud. The unconsolidated particles smaller than stones are predominantly silt and clay, 

although coarser sediments or organic material may be intermixed. Organisms living in 

mud must be able to adapt to low oxygen concentrations. Examples of Dominance Types 

for the Marine and Estuarine Systems include the terebellid worm Amphitrite, the boring 

clam Platyodon, the deep-sea scallop Placopecten, the quahog Mercenaria, the macoma 

Macoma, the echiurid worm Urechis, the mud snail Nassarius, and the sea cucumber 

Thyone. Examples of Dominance Types for the Lacustrine, Palustrine, and Riverine 

Systems are the sewage worm Tubifex, freshwater mollusks Anodonta, Anodontoides, and 

Elliptio, the fingernail clams Pisidium and Sphaerium, and the midge Chironomus. 

Organic. The unconsolidated material smaller than stones is predominantly organic; there 

is no minimum depth requirement. The organic material is dead plant tissue in varying 

stages of decomposition. The number of species is limited and faunal productivity is very 

low (Welch 1952). Examples of Dominance Types for Estuarine and Marine Systems are 

the soft-shell clam Mya, the false angel wing Petricola pholadiformis, the clam worm 

Nereis, and the mud snail Nassarius. Examples for the Lacustrine, Palustrine, and 

Riverine Systems are the sewage worm Tubifex, the snail Physa, the harpacticoid 

copepod Canthocamptus, and the oligochaete worm Limnodrilus. Dominance Types for 

Unconsolidated Bottoms in the Marine and Estuarine Systems were taken predominantly 

from Miner (1950), Smith (1964), Abbott (1968), and Ricketts and Calvin (1968). 

Dominance Types for Unconsolidated Bottoms in the Lacustrine, Riverine, and Palustrine 

Systems were taken predominantly from Krecker and Lancaster (1933), Stehr and 

Branson (1938), Johnson (1970), Brinkhurst and Jamieson (1972), Clarke (1973), Hart 

and Fuller (1974), Ward (1975), and Pennak (1978). 

3.2.3 Aquatic Bed 

Definition. The Class Aquatic Bed includes wetlands and deepwater habitats where 

plants that grow principally on or below the surface of the water (i.e., surface plants or 

submergents) are the uppermost life form layer with at least 30 percent areal coverage. 

Water Regimes include Subtidal, Irregularly Exposed, Regularly Flooded, Permanently 

Flooded, Intermittently Exposed, Semipermanently Flooded, Seasonally Flooded, 

Permanently Flooded-Tidal Fresh, Semipermanently Flooded-Tidal Fresh, Regularly 

Flooded-Tidal Fresh, and Seasonally Flooded-Tidal Fresh. Not all Water Regimes apply 

to all subclasses. 

Description. Aquatic Beds represent a diverse group of plant communities that require 

surface water for optimum growth and reproduction. They include submerged or floatingleaved rooted vascular plants, free-floating vascular plants, submergent mosses, and 

algae. They are best developed in relatively permanent water or under conditions of 

repeated flooding. The plants are either attached to the substrate or float freely on, or 

beneath, the water surface. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

25 

Subclasses and Dominance Types. 

Algal. In these Aquatic Beds, algae have the greatest areal coverage. Algal Beds are 

widespread and diverse in the Marine and Estuarine Systems, where they occupy 

substrates characterized by a wide range of sediment depths and textures. They occur in 

both the Subtidal and Intertidal Subsystems and may grow to depths of 30 m (98 ft). 

Coastal Algal Beds are most luxuriant along the rocky shores of the Northeast and West. 

Kelp (Macrocystis) beds are especially well developed on the rocky substrates of the 

Pacific Coast. Dominance Types such as the rockweeds Fucus and Ascophyllum and the 

kelp Laminaria are common along both coasts. In tropical regions, green algae, including 

forms containing calcareous particles, are more characteristic; Halimeda and Penicillus

are common examples. The red alga Laurencia, and the green algae Caulerpa, 

Enteromorpha, and Ulva are also common Estuarine and Marine Dominance Types; 

Enteromorpha and Ulva are tolerant of fresh water and flourish near the upper end of 

some estuaries. The stonewort Chara also is found in estuaries. 

Inland, the stoneworts Chara, Nitella, and Tolypella are examples of algae that look 

much like vascular plants and may grow in similar situations. However, meadows of 

Chara may be found in Lacustrine water as deep as 40 m (131 ft) (Zhadin and Gerd 

1963), where hydrostatic pressure limits the survival of vascular submergents 

(phanaerogams) (Welch 1952). Other algae bearing less resemblance to vascular plants 

are also common. Mats of filamentous algae may cover the bottom in dense blankets, 

may rise to the surface under certain conditions, or may become stranded on 

Unconsolidated or Rocky Shores. 

Aquatic Moss. In this Subclass, aquatic mosses have the greatest areal coverage. Aquatic 

mosses are far less common than algae or vascular plants. Aquatic Moss Beds occur 

primarily in the Riverine System and in Permanently Flooded and Intermittently Exposed 

parts of some Lacustrine systems. The most important Dominance Types include genera 

such as Fissidens, Drepanocladus, and Fontinalis. Fontinalis may grow to depths as 

great as 120 m (394 ft) (Hutchinson 1975). For simplicity, aquatic liverworts of the genus 

Marsupella are included in this Subclass. 

Rooted Vascular. In this Subclass, rooted vascular plants have the greatest areal 

coverage. In the Marine and Estuarine Systems, Rooted Vascular Beds include a large 

array of species that grow primarily below water. They have been referred to by others as 

temperate grass flats (Phillips 1974); tropical marine meadows (Odum 1974); and 

eelgrass beds, turtlegrass beds, and seagrass beds (Akins and Jefferson 1973; Eleuterius 

1973; Phillips 1974). The greatest number of species occurs in shallow, clear tropical, or 

subtropical waters of moderate current strength in the Caribbean and along the Florida 

and Gulf Coasts. Principal Dominance Types in these areas include turtlegrass (Thalassia 

testudinum), shoalgrass (Halodule writghtii), manatee grass (Cymodocea filiformis), 

widgeon grass (Ruppia martima), sea grasses (Halophila spp.), and wild celery

(Vallisneria americana). 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

26 

Five major vascular species dominate along the temperate coasts of North America: 

shoalgrass, surf grasses (Phyllospadix scoulleri, P. torreyi), widgeon grass, and eelgrass 

(Zostera marina). Eelgrass beds have the most extensive distribution, but they are limited 

primarily to the more sheltered estuarine environment. In the lower salinity zones of 

estuaries, stands of widgeon grass, pondweed (Potamogeton), and wild celery often 

occur, along with naiads (Najas) and water milfoil (Myriophyllum). 

In the Riverine, Lacustrine, and Palustrine Systems, rooted vascular submergent plants 

occur at all depths within the photic zone. They often occur in sheltered areas where there 

is little water movement (Wetzel 1975); however, they also occur in the flowing water of 

the Riverine System, where they may be streamlined or flattened in response to high 

water velocities. Typical inland genera include pondweeds, horned pondweed 

(Zannichellia palustris), ditch grasses (Ruppia), wild celery, and waterweed (Elodea). 

The riverweed (Podostemum ceratophyllum) is included in this Class despite its lack of 

truly recognizable roots (Sculthorpe l967). 

Some rooted vascular aquatic plants have floating leaves. Typical dominants include 

water lilies (Nymphaea, Nuphar), floating-leaf pondweed (Potamogeton natans), and 

water shield (Brasenia schreberi). Plants such as yellow water lily (Nuphar luteum) and 

water smartweed (Polygonum amphibium), which may stand erect above the water 

surface or substrate, may be considered either emergents or rooted vascular aquatic 

plants, depending on the life form adopted at a particular site. 

Floating Vascular. In this Subclass, vascular plants that float freely on or below the 

water surface have the greatest areal coverage. Floating Vascular Beds occur mainly in 

the Lacustrine, Palustrine, and Riverine Systems and in the less saline waters of the 

Estuarine System. Dominant plants that float on the surface include the duckweeds 

(Lemna, Spirodela), water lettuce (Pistia stratiotes), common water hyacinth (Eichhornia 

crassipes), water chestnut (Trapa natans), water mosses (Salvinia spp.), and mosquito 

ferns (Azolla spp.). These plants are found primarily in protected portions of slowflowing rivers and in the Lacustrine and Palustrine Systems. They are easily moved about 

by wind or water currents and cover a large area of water in some parts of the country, 

particularly the Southeast. Dominance Types for beds floating below the surface include 

bladderworts (Utricularia), coontails (Ceratophyllum), and watermeals (Wolffia) 

(Sculthorpe 1967; Hutchinson 1975). 

3.2.4 Reef 

Definition. The Class Reef includes ridge-like or mound-like structures formed by the 

colonization and growth of sedentary invertebrates. Water Regimes are restricted to 

Subtidal, Irregularly Exposed, and Regularly Flooded 

Description. Reefs are characterized by their elevation above the surrounding substrate 

and their interference with normal wave flow; they are primarily subtidal, but parts of 

some reefs may be intertidal as well. Although corals, oysters, and tube worms are the 

most visible organisms and are mainly responsible for reef formation, other mollusks, 

foraminifera, coralline algae, and other forms of life also contribute substantially to reef 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

27 

growth. Frequently, reefs contain far more dead skeletal material and shell fragments than 

living matter. 

Subclasses and Dominance Types. 

Coral. Coral Reefs are widely distributed in shallow waters of warm seas, in Hawaii, 

Puerto Rico, the Virgin Islands, and southern Florida. They were characterized by Odum 

(1971) as stable, well-adapted, highly diverse, and highly productive ecosystems with a 

great degree of internal symbiosis. Coral Reefs lie almost entirely within the Subtidal 

Subsystem of the Marine System, although the upper part of certain Reefs may be 

Intertidal. Examples of Dominance Types are the corals Porites, Acropora, and 

Montipora. The distribution of these types reflects primarily their elevation, wave 

exposure, the age of the Reef, and its exposure to waves. 

Mollusk. This Subclass occurs in both the Intertidal and Subtidal Subsystems of the 

Estuarine System. These Reefs are found on the Pacific, Atlantic, and Gulf Coasts and in 

Hawaii and the Caribbean. Mollusk Reefs may become extensive, affording a substrate 

for sedentary and boring organisms and a shelter for many others. Reef mollusks are 

adapted to great variations in water level, salinity, and temperature, and these same 

factors control their distribution. Examples of Dominance Types for this Subclass are the 

oysters Ostrea and Crassostrea (Smith 1964; Abbott 1968; Ricketts and Calvin 1968). 

Worm. Worm Reefs are constructed by large colonies of Sabellariid worms living in 

individual tubes constructed from cemented sand grains. Although they do not support as 

diverse a biota as do Coral and Mollusk Reefs, they provide a distinct habitat which may 

cover large areas. Worm Reefs are generally confined to tropical waters, and are most 

common along the coasts of Florida, Puerto Rico, and the Virgin Islands. They occur in 

both the Intertidal and Subtidal Systems of the Marine and Estuarine Systems where the 

salinity approximates that of sea water. The reef worm Sabellaria is an example of a 

Dominance Type for this Subclass (Ricketts and Calvin 1968). 

3.2.5 Streambed 

Definition. The Class Streambed includes all wetlands contained within the Intermittent 

Subsystem of the Riverine System and all channels of the Estuarine System or of the 

Tidal Subsystem of the Riverine System that are completely dewatered at low tide. Water 

Regimes are restricted to Irregularly Exposed, Regularly Flooded, Irregularly Flooded, 

Seasonally Flooded, Temporarily Flooded, Intermittently Flooded, and Regularly 

Flooded-Tidal Fresh. Not all Water Regimes apply to all subclasses.

Description. Streambeds vary greatly in substrate and form depending on the gradient of 

the channel, the velocity of the water, and the sediment load. The substrate material 

frequently changes abruptly between riffles and pools, and complex patterns of bars may 

form on the convex side of single channels or be included as islands within the bed of 

braided streams (Crickmay 1974). In mountainous areas the entire channel may be cut 

through bedrock. In most cases streambeds are not vegetated because of the scouring 

effect of moving water, but, like Unconsolidated Shores, they may be colonized by 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

28 

“pioneer” annuals or perennials during periods of low flow or they may have perennial 

emergents and shrubs that are too scattered to qualify the area for classification as 

Emergent Wetland or Scrub-Shrub Wetland. 

Subclasses and Dominance Types. 

Bedrock. This Subclass is characterized by a bedrock substrate covering 75 percent or 

more of the stream channel. It occurs most commonly in the Riverine System in high 

mountain areas or in glaciated areas where bedrock is exposed. Examples of Dominance 

Types are the mollusk Ancylus, the oligochaete worm Limnodrilus, the snail Physa, the 

fingernail clam Pisidium, and the mayflies Caenis and Ephemerella. 

Rubble. This Subclass is characterized by stones, boulders, and bedrock that, combined, 

cover 75 percent or more of the channel; however, bedrock alone covers less than 75 

percent. Like Bedrock Streambeds, Rubble Streambeds are most common in mountainous 

areas and the dominant organisms are similar to those of Bedrock and are often forms 

capable of attachment to rocks in flowing water. 

Cobble-Gravel. In this Subclass at least 25 percent of the substrate is covered by 

unconsolidated particles smaller than stones; cobbles or gravel predominate. The 

Subclass occurs in riffle areas or in the channels of braided streams. Examples of 

Dominance Types in the Intermittent Subsystem of the Riverine System are the snail 

Physa, the oligochaete worm Limnodrilus, the mayfly Caenis, the midge Chironomus, 

and the mosquito Anopheles. Examples of Dominance Types in the Estuarine System or 

Tidal Subsystem of the Riverine System are the mussels Modiolus and Mytilus. 

Sand. In this Subclass, sand-sized particles predominate among the particles smaller than 

stones. Sand Streambed often contains bars and beaches interspersed with Mud 

Streambed or it may be interspersed with Cobble-Gravel Streambed in areas of fast flow 

or heavy sediment load. Examples of Dominance Types in the Riverine System are the 

scud Gammarus, the snails Physa and Lymnaea, and the midge Chironomus; in the 

Estuarine System the ghost shrimp Callianassa is a common Dominance Type. 

Mud. In this Subclass, the particles smaller than stones are chiefly silt or clay. Mud 

Streambeds are common in arid areas where intermittent flow is characteristic of streams 

of low gradient. Such species as tamarisk (Tamarix gallica) may occur, but are not dense 

enough to qualify the area for classification as Scrub-Shrub Wetland. Mud Streambeds 

are also common in the Estuarine System and the Tidal Subsystem of the Riverine 

System. Examples of Dominance Types for Mud Streambeds include the crayfish 

Procambarus, the pouch snail Aplexa, the fly Tabanus, the snail Lymnaea, the fingernail 

clam Sphaerium, and (in the Estuarine System) the mud snail Nassarius. 

Organic. This Subclass is characterized by channels formed in peat or muck. Organic 

Streambeds are common in the small creeks draining Estuarine Emergent Wetlands with 

organic soils. Examples of Dominance Types are the mussel Modiolus in the Estuarine 

System and the oligochaete worm Limnodrilus in the Riverine System. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

29 

Vegetated. These Streambeds are exposed long enough to be colonized by pioneer plants 

that, unlike Emergent Wetland plants or Scrub-Shrub Wetland plants, are usually killed 

by rising water levels. Many of the pioneer species are weedy mesophytes or xerophytes. 

At least 30 percent cover of pioneer plants is required. Common panic grass (Panicum 

capillare) is a typical Dominance Type in the Riverine System. 

Dominance Types for Streambeds in the Estuarine System were taken primarily from 

Smith (1964), Abbott (1968), and Ricketts and Calvin (1968) and those for streambeds in 

the Riverine System from Krecker and Lancaster (1933), Stehr and Branson (1938), van 

der Schalie (1948), Kenk (1949), Cummins et al. (1964), Clarke (1973), and Ward 

(1975). 

3.2.6 Rocky Shore 

Definition. The Class Rocky Shore includes wetland habitats characterized by bedrock, 

stones, or boulders, which singly or in combination have an areal cover of 75 percent or 

more, and an areal coverage by vegetation of less than 30 percent. Water Regimes are 

restricted to Irregularly Exposed, Regularly Flooded, Irregularly Flooded, Seasonally 

Flooded, Temporarily Flooded, Intermittently Flooded, and Regularly Flooded-Tidal 

Fresh

Description. In Marine and Estuarine Systems, Rocky Shores are generally high-energy 

habitats that lie exposed as a result of continuous erosion by wind-driven waves or strong 

currents. The substrate is stable enough to permit the attachment and growth of sessile or 

sedentary invertebrates and attached algae or lichens. Rocky Shores usually display a 

vertical zonation that is a function of tidal range, wave action, and degree of exposure to 

the sun. In the Lacustrine and Riverine Systems, Rocky Shores support sparse plant and 

animal communities. 

Subclasses and Dominance Types. 

Bedrock. These wetlands have bedrock covering 75 percent or more of the surface and 

less than 30 percent areal coverage of macrophytes. 

Rubble. These wetlands have less than 75 percent areal cover of bedrock, but stones and 

boulders alone or in combination with bedrock cover 75 percent or more of the area. The 

areal coverage of macrophytes is less than 30 percent. 

Communities or zones of Marine and Estuarine Rocky Shores have been widely studied 

(Lewis 1964; Ricketts and Calvin 1968; Stephenson and Stephenson 1972). Each zone 

supports a rich assemblage of invertebrates and algae or lichens or both. Dominance 

Types of the Rocky Shores often can be characterized by one or two dominant genera 

from these zones. 

The uppermost zone (here termed the littorine-lichen zone) is dominated by periwinkles 

(Littorina and Nerita) and lichens. This zone frequently takes on a dark, or even black 

appearance, although abundant lichens may lend a colorful tone. These organisms are 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

30 

rarely submerged, but are kept moist by sea spray. Frequently this habitat is invaded from 

the landward side by semimarine genera such as the slater Ligia. 

The next lower zone (the balanoid zone) is commonly dominated by mollusks, green 

algae, and barnacles of the balanoid group. The zone appears white. Dominance Types 

such as the barnacles Balanus, Chthamalus, and Tetraclita may form an almost pure 

sheet, or these animals may be interspersed with mollusks, tube worms, and algae such as 

Pelvetia, Enteromorpha, and Ulva. 

The transition between the littorine-lichen and balanoid zones is frequently marked by the 

replacement of the periwinkles with limpets such as Acmaea and Siphonaria. The limpet 

band approximates the upper limit of the regularly flooded intertidal zone. 

In the middle and lower intertidal areas, which are flooded and exposed by tides at least 

once daily, lie a number of other communities which can be characterized by dominant 

genera. Mytilus and gooseneck barnacles (Pollicipes) form communities exposed to 

strong wave action. Aquatic Beds dominated by Fucus and Laminaria lie slightly lower, 

just above those dominated by coralline algae (Lithothamnion). The Laminaria

Dominance Type approximates the lower end of the Intertidal Subsystem; it is generally 

exposed at least once daily. The Lithothamnion Dominance Type forms the transition to 

the Subtidal Subsystem and is exposed only irregularly. 

In the Palustrine, Riverine, and Lacustrine Systems, various species of lichens such as 

Verrucaria spp. and Dermatocarpon fluviatile, as well as blue-green algae, frequently 

form characteristic zones on Rocky Shores. The distribution of these species depends on 

the duration of flooding or wetting by spray and is similar to the zonation of species in 

the Marine and Estuarine Systems (Hutchinson 1975). Though less abundant than 

lichens, aquatic liverworts such as Marsupella emarginata var. aquatica or mosses such 

as Fissidens julianus are found on the Rocky Shores of lakes and rivers. If aquatic 

liverworts or mosses cover 30 percent or more of the substrate, they should be placed in 

the Class Aquatic Bed. Other examples of Rocky Shore Dominance Types are the 

caddisfly Hydropsyche and the fingernail clam Pisidium. 

3.2.7 Unconsolidated Shore 

Definition. The Class Unconsolidated Shore includes all wetland habitats having three 

characteristics: (1) unconsolidated substrates with less than 75 percent areal cover of 

stones, boulders, or bedrock; (2) less than 30 percent areal cover of vegetation other than 

pioneer plants; and (3) any of the following Water Regimes: Irregularly Exposed, 

Regularly Flooded, Irregularly Flooded, Seasonally Flooded, Seasonally FloodedSaturated, Temporarily Flooded, Intermittently Flooded, Regularly Flooded-Tidal Fresh, 

Seasonally Flooded-Tidal Fresh, and Temporarily Flooded-Tidal Fresh. Intermittent or 

intertidal channels of the Riverine System and intertidal channels of the Estuarine System 

are classified as Streambed. Not all Water Regimes apply to all subclasses.

Description. Unconsolidated Shores are characterized by substrates lacking vegetation 

except for pioneer plants that become established during brief periods when growing 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

31 

conditions are favorable. Erosion and deposition by waves and currents produce a 

number of landforms such as beaches, bars, and flats, all of which are included in this 

Class. Unconsolidated Shores are commonly found adjacent to Unconsolidated Bottoms 

in all Systems; in the Palustrine and Lacustrine Systems, the Class may occupy the entire 

basin. As in Unconsolidated Bottoms, the particle size of the substrate and the water 

regime are the important factors determining the types of plant and animal communities 

present. Different substrates usually support characteristic invertebrate fauna. Faunal 

distribution is controlled by waves, currents, interstitial moisture, salinity, and grain size 

(Hedgpeth 1957; Ranwell 1972; Riedl and McMahan 1974). 

Subclasses and Dominance Types. 

Cobble-Gravel. The unconsolidated particles smaller than stones are predominantly 

cobbles and gravel. Shell fragments, sand, and silt often fill the spaces between the larger 

particles. Stones and boulders may be found scattered on some Cobble-Gravel Shores. In 

areas of strong wave and current action these shores take the form of beaches or bars, but 

occasionally they form extensive flats. Examples of Dominance Types in the Marine and 

Estuarine Systems are: the acorn barnacle Balanus, the limpet Patella, the periwinkle 

Littorina, the rock shell Thais, the mussels Mytilus and Modiolus, and the Venus clam 

Saxidomus. In the Lacustrine, Palustrine, and Riverine Systems examples of Dominance 

Types are the freshwater mollusk Elliptio, the snails Lymnaea and Physa, the toad bug 

Gelastocoris, the leech Erpodella, and the springtail Agrenia. 

Sand. The unconsolidated particles smaller than stones are predominantly sand, although 

finer or coarser sediments may be intermixed. Sand may be either calcareous or 

terrigenous in origin. Sand shores are a prominent feature of the Marine, Estuarine, 

Riverine, and Lacustrine Systems where the substrate material is exposed to the sorting 

and washing action of waves. Examples of Dominance Types in the Marine and Estuarine 

Systems are the wedge shell Donax, the soft-shell clam Mya, the quahog Mercenaria, the 

olive shell Oliva, the blood worm Euzonus, the beach hopper Orchestia, the pismo clam 

Tivela stultorum, the mole crab Emerita, and the lugworm Arenicola. Examples of 

Dominance Types in the Riverine, Lacustrine, and Palustrine Systems are the copepods 

Parastenocaris and Phyllognathopus, the oligochaete worm Pristina, the freshwater 

mollusks Anodonta and Elliptio, and the fingernail clams Pisidium and Sphaerium. 

Mud. The unconsolidated particles smaller than stones are predominantly silt and clay, 

although coarser sediments or organic material may be intermixed. Anaerobic conditions 

often exist below the surface. Mud Shores have a higher organic content than CobbleGravel or Sand Shores. They are typically found in areas of minor wave action. They 

tend to have little slope and are frequently called flats. Mud Shores support diverse 

populations of tube-dwelling and burrowing invertebrates that include worms, clams, and 

crustaceans (Gray 1974). They are commonly colonized by algae and diatoms which may 

form a crust or mat. 

Irregularly flooded Mud Shores in the Estuarine System have been called salt flats, pans, 

or pannes. They are typically high in salinity and are usually surrounded by, or lie on the 

landward side of, Emergent Wetland (Martin et al. 1953, Type 15). In many arid areas, 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

32 

Palustrine and Lacustrine Mud Shores are encrusted or saturated with salt. Martin et al. 

(1953) called these habitats inland saline flats (Type 9); they are also called alkali flats, 

salt flats, and salt pans. Mud Shores may also result from removal of vegetation by man, 

animals, or fire, or from the discharge of thermal waters or pollutants. 

Examples of Dominance Types in the Marine and Estuarine Systems include the fiddler 

crab Uca, the ghost shrimp Callianassa, the mud snails Nassarius and Macoma, the clam 

worm Nereis, the sea anemone Cerianthus, and the sea cucumber Thyone. In the 

Lacustrine, Palustrine, and Riverine Systems, examples of Dominance Types are the 

fingernail clam Pisidium, the snails Aplexa and Lymaea, the crayfish Procambarus, the 

harpacticoid copepods Canthocamptus and Bryocamptus, the fingernail clam Sphaerium, 

the freshwater mollusk Elliptio, the shore bug Saldula, the isopod Asellus, the crayfish 

Cambarus, and the mayfly Tortopus. 

Organic. The unconsolidated material smaller than stones is predominantly organic; there 

is no minimum depth requirement. The organic material is dead plant tissue in varying 

stages of decomposition. In the Marine and Estuarine Systems, Organic Shores are often 

dominated by microinvertebrates such as foraminifera, and by Nassarius, Littorina, Uca, 

Modiolus, Mya, Nereis, and the false angel wing Petricola pholadiformis. In the 

Lacustrine, Palustrine, and Riverine Systems, examples of Dominance Types are 

Canthocamptus, Bryocamptus, Chironomus, and the backswimmer Notonecta. 

Vegetated. Some nontidal Shores are exposed for a sufficient period to be colonized by 

pioneer plants that, unlike Emergent Wetland plants or Scrub-Shrub Wetland plants, are 

usually killed by rising water levels. Many of the pioneer species are weedy mesophytes 

or xerophytes. At least 30 percent cover of pioneer plants is required. Examples of 

Dominance Types are rough cocklebur (Xanthium strumarium) and large barnyard grass 

(Echinochloa crusgalli). 

Dominance Types for Unconsolidated Shores in the Marine and Estuarine Systems were 

taken primarily from Smith (1964), Morris (1966), Abbott (1968), Ricketts and Calvin 

(1968), and Gosner (1971). Dominance Types for Unconsolidated Shores in the 

Lacustrine, Riverine, and Palustrine Systems were taken primarily from Stehr and 

Branson (1938), Kenk (1949), Ward and Whipple (1959), Cummins et al. (1964), 

Johnson (1970), Ingram (1971), Clarke (1973), and Hart and Fuller (1974). 

3.2.8 Moss-Lichen Wetland

Definition. The Moss-Lichen Wetland Class includes areas where mosses or lichens 

cover at least 30 percent of substrates other than rock and where emergents, shrubs, or 

trees alone or in combination cover less than 30 percent. Water Regimes include 

Seasonally Flooded, Seasonally Flooded-Saturated, Continuously Saturated and 

Seasonally Saturated.

Description. Mosses and lichens are important components of the flora in many 

wetlands, especially in the North, but these plants usually form a ground cover under a 

dominant layer of trees, shrubs, or emergents. In some instances higher plants are 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

33 

uncommon and mosses or lichens dominate the flora. Such Moss-Lichen Wetlands are 

not common, even in the northern U.S. where they occur most frequently. 

Subclasses and Dominance Types. 

Moss. In this Subclass, the areal coverage of mosses exceeds that of lichens. Moss 

dominated wetlands are most abundant in the far northern boreal forests and Arctic 

tundra, where they are dominated by peat mosses such as Sphagnum fuscum and S. 

warnstorfii. These wetlands are typically called bogs (Golet and Larson 1974; Jeglum et 

al. 1974; Zoltai et al. 1975), whether Sphagnum or higher plants dominate. In Alaska, 

Drepanocladus revolvans, D. lycodiodes, and the liverwort Chiloscyphus fragilis may 

dominate shallow pools with semipermanent water. Other mosses, including Campylium 

stellatum, Aulacomnium palustre, A. turgidum and Oncophorus wahlenbergii, are typical 

of wet, saturated soils in these regions (Britton 1957, Drury 1962). 

Lichen. In this Subclass, the areal coverage of lichens exceeds that of mosses. Lichen 

Wetlands also are a Northern Subclass. Reindeer moss (Cladina and Cladonia), the 

principal Dominance Type, occurs primarily in boreal and Arctic regions. Lichen cover is 

generally elevated above moss, sedge-moss, or dwarf shrub-sedge-moss layers. Pollett 

and Bridgewater (1973) described areas with mosses and lichens as bogs or fens, the 

distinction being based on the availability of nutrients and the particular plant species 

present. The presence of Lichen Wetlands has been noted in the Hudson Bay Lowlands 

(Sjörs 1959) and in Ontario (Jeglum et al. 1974). 

3.2.9 Emergent Wetland 

Definition. In this wetland Class, emergent plants—i.e., erect, rooted, herbaceous 

hydrophytes, excluding mosses and lichens—are the tallest life form with at least 30% 

areal coverage. This vegetation is present for most of the growing season in most years. 

These wetlands are usually dominated by perennial plants. All Water Regimes are 

included except Subtidal and Irregularly Exposed. Not all Water Regimes apply to all 

subclasses.

Description. In areas with relatively stable climatic conditions, Emergent Wetlands 

maintain the same appearance year after year. In other areas, such as the prairies of the 

central U.S., violent climatic fluctuations cause them to revert to an open water phase in 

some years (Stewart and Kantrud 1972). Emergent Wetlands are found throughout the 

U.S. and occur in all Systems except the Marine. Emergent Wetlands are known by many 

names, including marsh, wet meadow, fen, prairie pothole, and slough. Areas that are 

dominated by pioneer plants, which become established during periods of low water, are 

not Emergent Wetlands and should be classified as Vegetated Unconsolidated Shores or 

Vegetated Streambeds. 

Subclasses and Dominance Types. 

Persistent. In this Subclass, the areal coverage of persistent emergents exceeds that of 

nonpersistent emergents. Persistent emergents are emergent hydrophytes whose stems 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

34 

and leaves are evident all year above the surface of the water, or above the soil surface if 

water is absent. Persistent Emergent Wetlands occur only in the Estuarine and Palustrine 

Systems. 

Persistent Emergent Wetlands dominated by saltmarsh cordgrass (Spartina alterniflora), 

saltmeadow cordgrass (S. patens), big cordgrass (S. cynosuroides), Roemer's rush 

(Juncus roemerianus), narrow-leaved cattail (Typha angustifolia), and mash-millet 

(Zizaniopsis miliacea) are major components of the Estuarine Systems of the Atlantic and 

Gulf Coasts of the U.S. On the Pacific Coast, woody saltwort (Salicornia virginica), 

broom seepweed (Suaeda californica), seaside arrow-grass (Triglochin maritimum), and 

California cordgrass (Spartina foliosa) are common dominants. 

Palustrine Persistent Emergent Wetlands contain a vast array of grasslike plants such as 

cattails (Typha spp.), bulrushes (Scirpus spp.), saw grass (Cladium jamaicense), sedges 

(Carex spp.); and true grasses such as manna grasses (Glyceria spp.), slough grass 

(Beckmannia syzigachne), and common river grass (Scolochloa festucacea). There is also 

a variety of broad-leaved persistent emergents such as purple loosestrife (Lythrum 

salicaria), Mexican dock (Rumex mexicanus), swamp loosestrife (Decodon verticillatus), 

and some species of smartweeds (Polygonum). 

Nonpersistent. In this Subclass, the areal coverage of nonpersistent emergents exceeds 

that of persistent emergents. Nonpersistent emergents are emergent hydrophytes whose 

stems and leaves are evident above the water surface, or above the soil surface if surface 

water is absent, only during the growing season or shortly thereafter. During the dormant 

season, there is no obvious sign of emergent vegetation. Nonpersistent Emergent 

Wetlands occur in all Systems except the Marine. Nonpersistent emergents also include 

species such as green arrow-arum (Peltandra virginica), pickerelweed (Pontederia 

cordata), and arrowheads (Sagittaria spp.). Movement of ice in Estuarine, Riverine, or 

Lacustrine Systems often removes all traces of emergent vegetation during the winter. 

Where this occurs, the area should be classified as Nonpersistent Emergent Wetland.

3.2.10 Scrub-Shrub Wetland 

Definition. In Scrub-Shrub Wetlands, woody plants less than 6 m (20 ft) tall are the 

dominant life form—i.e., the tallest life form with at least 30 percent areal coverage. The 

“shrub” life form actually includes true shrubs, young specimens of tree species that have 

not yet reached 6 m in height, and woody plants (including tree species) that are stunted 

because of adverse environmental conditions. All Water Regimes except Subtidal and 

Regularly Flooded-Tidal Fresh are included. Not all Water Regimes apply to all 

subclasses. 

Description. Scrub-Shrub Wetlands may represent a successional stage leading to 

Forested Wetland, or they may be relatively stable communities. They occur only in the 

Estuarine and Palustrine Systems, but are one of the most widespread Classes in the U.S. 

(Shaw and Fredine 1956). Scrub-Shrub Wetlands are known by many names, such as 

shrub swamp (Shaw and Fredine 1956), shrub carr (Curtis 1959), bog (Heinselman 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

35 

1970), fen (Jeglum 1974), and pocosin (Kologiski 1977). For practical reasons we have 

also included stands of young trees less than 6 m tall. 

Subclasses and Dominance Types. 

Broad-leaved Deciduous. In this Subclass, broad-leaved deciduous species have the 

greatest areal coverage within the shrub layer. In the Estuarine System, Dominance Types 

include species such as sea-myrtle (Baccharis halimifolia) and high-tide bush (Iva 

frutescens). In the Palustrine System, typical Dominance Types are alders (Alnus spp.), 

willows (Salix spp.), buttonbush (Cephalanthus occidentalis), red osier dogwood (Cornus 

stolonifera), honeycup (Zenobia pulverulenta), Douglas' meadowsweet (Spiraea 

douglasii), bog birch (Betula pumila), and young red maple (Acer rubrum). 

Needle-leaved Deciduous. In this Subclass, needle-leaved deciduous species have the 

greatest areal coverage within the shrub layer. Dominance Types include young or 

stunted tamarack and southern bald-cypress (Taxodium distichum). 

Broad-leaved Evergreen. In this Subclass, broad-leaved evergreen species have the 

greatest areal coverage within the shrub layer. In the Estuarine System, vast wetland 

acreages are dominated by mangroves (Rhizophora mangle, Languncularia racemosa, 

Conocarpus erectus, and Avicennia germinans). In the Palustrine System, the broadleaved evergreen species are typically found on organic soils. Northern representatives 

are labrador tea (Ledum groenlandicum), bog rosemary (Andromeda polifolia L.), bog 

laurel (Kalmia polifolia), and the semi-evergreen, leatherleaf (Chamaedaphne 

calyculata). In the South, shinyleaf (Lyonia lucida), coastal dogbobble (Leucothoe 

axillaris), inkberry (Ilex glabra), and the semi-evergreen, swamp titi (Cyrilla 

racemiflora), are characteristic broad-leaved evergreen species. 

Needle-leaved Evergreen. In this Subclass, needle-leaved evergreen species have the 

greatest areal coverage within the shrub layer. Examples of Dominance Types include 

young or stunted black spruce (Picea mariana) and pond pine (Pinus serotina). 

Dead. This Subclass includes stands of dead woody plants less than 6 m tall, regardless 

of their density, with less than 30 percent cover of living vegetation. If living vegetation 

equals or exceeds 30 percent in such stands, the Class and Subclass are based on the 

dominant life form of the living plants. Dead Scrub-Shrub Wetlands usually are produced 

by a prolonged rise in the water level resulting from impoundment by humans or beavers. 

In tidal areas, hurricanes, coastal subsidence, and sea level rise also may be responsible. 

3.2.11 Forested Wetland 

Definition. In Forested Wetlands, trees are the dominant life form—i.e., the tallest life 

form with at least 30 percent areal coverage. Trees are defined as woody plants at least 6 

m (20 ft) in height. All Water Regimes except Subtidal and Regularly Flooded-Tidal 

Fresh are included. Not all Water Regimes apply to all subclasses. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

36 

Description. Forested Wetlands are most common in the eastern U.S. and in those 

sections of the West where moisture is relatively abundant, particularly along rivers and 

in the mountains. They occur only in the Palustrine and Estuarine Systems and normally 

possess an overstory of trees, an understory of young trees or shrubs, and an herbaceous 

layer. Forested Wetlands in the Estuarine System, which include the mangrove forests of 

Florida, Puerto Rico, and the Virgin Islands, are known by such names as swamps, 

hammocks, heads, and bottoms. Such common names are often applied, in combination 

with species names or plant association names, in Palustrine forests as well (e.g., cedar 

swamp, bottomland hardwoods). 

Subclasses and Dominance Types. 

Broad-leaved Deciduous. In this Subclass, broad-leaved deciduous species have the 

greatest areal coverage in the tree layer. Broad-leaved Deciduous Forested Wetlands, 

which are represented throughout the United States, are most common in the South and 

East. Common Dominance Types include red maple, American elm (Ulmus americana), 

ashes (Fraxinus pennsylvanica and F. nigra), black gum (Nyssa sylvatica), tupelo gum 

(N. aquatica), swamp white oak (Quercus bicolor), overcup oak (Q. lyrata), and swamp 

chestnut oak (Q. michauxii). Wetlands in this Subclass generally occur on mineral soils 

or highly decomposed organic soils. 

Needle-leaved Deciduous. In this Subclass, needle-leaved deciduous species have the 

greatest areal coverage in the tree layer. The southern representative of the Needle-leaved 

Deciduous Subclass is bald cypress, which is noted for its ability to tolerate long periods 

of surface inundation. Tamarack is characteristic of the Boreal Forest Region, where it 

occurs as a dominant on organic soils. Relatively few other species are included in this 

Subclass. 

Broad-Leaved Evergreen. In this Subclass, broad-leaved evergreen species have the 

greatest areal coverage in the tree layer. In the Southeast, Broad-leaved Evergreen 

Forested Wetlands reach their greatest development. Red bay (Persea borbonia), loblolly 

bay (Gordonia lasianthus), and sweet bay (Magnolia virginiana) are prevalent, especially 

on organic soils. Other Dominance Types include red mangrove (Rhizophora mangle), 

black mangrove (Avicennia germinans), and white mangrove (Languncularia racemosa), 

which are adapted to varying levels of salinity. 

Needle-leaved Evergreen. In this Subclass, needle-leaved evergreen species have the 

greatest areal coverage in the tree layer. Black spruce, growing on nutrient-poor organic 

soils, represents a major dominant of the Needle-leaved Evergreen Subclass in the North. 

Eastern arborvitae (Thuja occidentalis) dominates northern wetlands on more nutrientrich sites. Along the Atlantic Coast, Atlantic white cedar (Chamaecyparis thyoides) is 

one of the most common dominants on organic soils. Pond pine is a common needleleaved evergreen found in the Southeast in association with dense stands of broad-leaved 

evergreen and deciduous shrubs. 

Dead. This Subclass includes stands of dead woody plants at least 6 m tall, regardless of 

their density, with less than 30 percent cover of living vegetation. If living vegetation 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

37 

equals or exceeds 30 percent in such stands, the Class and Subclass are based on the 

dominant life form of the living plants. Dead Forested Wetlands usually are produced by 

a prolonged rise in the water level resulting from impoundment by humans or beavers. In 

tidal areas, hurricanes, coastal subsidence, and sea level rise also may be responsible. 

3.3 Modifiers 

To fully describe wetlands and deepwater habitats, one must apply certain Modifiers to 

the classification hierarchy. The Modifiers described were adapted from existing 

classifications or were developed specifically for this classification system. 

3.3.1 Water Regime Modifiers 

Description of hydrologic characteristics requires detailed knowledge of the duration and 

timing of surface inundation, both yearly and long-term, as well as an understanding of 

groundwater fluctuations. Because such information is seldom available, the Water 

Regimes that, in part, determine characteristic wetland and deepwater plant and animal 

communities are described here in only general terms. Water Regimes are grouped under 

three major headings, Tidal Salt, Nontidal, and Tidal Fresh. 

Tidal Salt. 

Tidal Salt Water Regime Modifiers are used for wetlands and deepwater habitats in the 

Marine and Estuarine Systems, where ocean-derived salinity equals or exceeds 0.5 ppt. 

These Water Regimes are primarily a function of oceanic tides.

Subtidal. Tidal salt water continuously covers the substrate. 

Irregularly Exposed. Tides expose the substrate less often than daily. 

Regularly Flooded. Tides alternately flood and expose the substrate at least once daily. 

Irregularly Flooded. Tides flood the substrate less often than daily. 

The periodicity and amplitude of tides vary in different parts of the U.S., mainly because 

of differences in latitude and geomorphology. On the Atlantic Coast, two nearly equal 

high tides are the rule (semidiurnal); on the Gulf Coast, there is frequently only one high 

tide and one low tide each day (diurnal); and on the Pacific Coast there are usually two 

unequal high tides and two unequal low tides (mixed semidiurnal). 

Tides range in height from about 9.5 m (31 ft) at St. John, New Brunswick (NOAA 1973) 

to less than 1 m (3.3 ft) along the Louisiana coast (Chabreck 1972). Tides of only 10 cm 

(4.0 inches) are not uncommon in Louisiana. Therefore, although no hard and fast rules 

apply, the division between Regularly Flooded and Irregularly Flooded Water Regimes 

would probably occur approximately at mean high water on the Atlantic Coast, at the 

lowest level of the higher high tide on the Pacific Coast, and just above mean tide level of 

the Gulf Coast. The width of the intertidal zone is determined by the tidal range, the slope 

of the shoreline, and the degree of exposure of the site to wind and waves. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

38 

Nontidal. 

Nontidal Water Regime Modifiers are used for all nontidal parts of the Palustrine, 

Lacustrine, and Riverine Systems. Although not influenced by oceanic tides, Nontidal 

Water Regimes may be affected by wind or seiches in lakes. Nontidal Water Regimes are 

defined in terms of the growing season which, for the purposes of this classification, 

begins with green-up and bud-break of native plants in the spring and ends with plant 

dieback and leaf-drop in the fall due to the onset of cold weather. During the rest of the 

year, which is defined as the dormant season, even extended periods of flooding may 

have little influence on the development or survival of plant communities. 

Permanently Flooded. Water covers the substrate throughout the year in all years. 

Intermittently Exposed. Water covers the substrate throughout the year except in years of 

extreme drought. 

Semipermanently Flooded. Surface water persists throughout the growing season in most 

years. When surface water is absent, the water table is usually at or very near the land 

surface. 

Seasonally Flooded. Surface water is present for extended periods (generally for more 

than a month) during the growing season, but is absent by the end of the season in most 

years. When surface water is absent, the depth to substrate saturation may vary 

considerably among sites and among years. 

Seasonally Flooded-Saturated. Surface water is present for extended periods (generally 

for more than a month) during the growing season, but is absent by the end of the season 

in most years. When surface water is absent, the substrate typically remains saturated at 

or near the surface. 

Seasonally Saturated. The substrate is saturated at or near the surface for extended 

periods during the growing season, but unsaturated conditions prevail by the end of the 

season in most years. Surface water is typically absent, but may occur for a few days after 

heavy rain and upland runoff. 

Continuously Saturated. The substrate is saturated at or near the surface throughout the 

year in all, or most, years. Widespread surface inundation is rare, but water may be 

present in shallow depressions that intersect the groundwater table, particularly on a 

floating peat mat. 

Temporarily Flooded. Surface water is present for brief periods (from a few days to a 

few weeks) during the growing season, but the water table usually lies well below the 

ground surface for the most of the season. 

Intermittently Flooded. The substrate is usually exposed, but surface water is present for 

variable periods without detectable seasonal periodicity. Weeks, months, or even years 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

39 

may intervene between periods of inundation. The dominant plant communities under 

this Water Regime may change as soil moisture conditions change. Some areas exhibiting 

this Water Regime do not fall within our definition of wetland because they do not have 

hydric soils or support hydrophytes. This Water Regime is generally limited to the arid 

West. 

Artificially Flooded. The amount and duration of flooding are controlled by means of 

pumps or siphons in combination with dikes, berms, or dams. The vegetation growing on 

these areas cannot be considered a reliable indicator of Water Regime. Examples of 

Artificially Flooded wetlands are some agricultural lands managed under a rice-soybean 

rotation, and wildlife management areas where forests, crops, or pioneer plants may be 

flooded or dewatered to attract wetland wildlife. Neither wetlands within or resulting 

from leakage from man-made impoundments, nor irrigated pasture lands supplied by 

diversion ditches or artesian wells, are included under this Modifier. The Artificially 

Flooded Water Regime Modifier should not be used for impoundments or excavated 

wetlands unless both water inputs and outputs are controlled to achieve a specific depth 

and duration of flooding. 

Tidal Fresh.

The Tidal Subsystem of the Riverine System and tidally influenced parts of the Palustrine 

and Lacustrine Systems are unique because the hydrology of their habitats is driven 

primarily by nontidal inputs and outputs, but influenced by tides as well. In these 

habitats, ocean-derived salts measure less than 0.5 ppt. The hydrologic regimes of Tidal 

Fresh habitats are described through the use of four Nontidal Water Regime Modifiers, 

coupled with the suffix ‘-Tidal Fresh’, as in Seasonally Flooded-Tidal Fresh, and an 

additional Modifier based on tidal action. Each of the first four Modifiers reflects the 

relative duration of substrate inundation during the growing season. It also indicates that, 

in response to oceanic tides, the water level at each site rises and falls daily. The fifth 

Modifier focuses specifically on the daily flooding and exposure of the substrate by tides 

at the water’s edge. Use of certain Modifiers is limited to certain Systems. 

Permanently Flooded-Tidal Fresh. Tidal fresh water covers the substrate throughout the 

year in all years. This Modifier is used for Riverine, Lacustrine, and Palustrine habitats. 

Semipermanently Flooded-Tidal Fresh. Tidal fresh surface water persists throughout the 

growing season in most years. When surface water is absent, the water table is usually at 

or very near the land surface. This Modifier is used for Riverine, Lacustrine, and 

Palustrine habitats. 

Seasonally Flooded-Tidal Fresh. Tidal fresh surface water is present for extended 

periods (generally for more than a month) during the growing season, but is absent by the 

end of the season in most years. When surface water is absent, the depth to substrate 

saturation may vary considerably among sites and among years. This Modifier is used for 

Palustrine habitats only. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

40 

Temporarily Flooded-Tidal Fresh. Tidal fresh surface water is present for brief periods 

(from a few days to a few weeks) during the growing season, but the water table usually 

lies well below the ground surface for the most of the season. This Modifier is used for 

Palustrine habitats only. 

Regularly Flooded-Tidal Fresh. Tides alternately flood and expose the substrate daily 

for variable periods (from a few weeks to several months) during the growing season. 

This Modifier is used for Riverine and Lacustrine habitats. 

3.3.2 Water Chemistry Modifiers 

The accurate characterization of water chemistry in wetlands and deepwater habitats is 

difficult, both because of problems in measurement and because values tend to vary with 

changes in the season, weather, time of day, and other factors. Yet, very subtle changes in 

water chemistry, which occur over short distances, may have a marked influence on the 

types of plants or animals that inhabit an area. A description of water chemistry, 

therefore, must be an essential part of this classification system. 

Two kinds of Water Chemistry Modifiers are employed in this classification: Salinity 

Modifiers and pH (hydrogen-ion) Modifiers. All habitats are classified according to 

salinity, and freshwater habitats are further classified by pH levels. 

3.3.2.1 Salinity Modifiers 

Differences in salinity are reflected in the species composition of plants and animals. 

Many authors have suggested using biological changes as the basis for subdividing the 

salinity range between sea water and fresh water (Remane and Schlieper 1971). Others 

have suggested a similar subdivision for salinity in inland wetlands (Moyle 1946; Bayly 

1967; Stewart and Kantrud 1971). Since the gradation between fresh and hypersaline or 

hyperhaline waters is continuous, any boundary is artificial, and few classification 

systems agree completely. The salinity classification adopted here for both coastal and 

inland waters is a modified version of the Venice System (1959), which was originally 

proposed at an international “Symposium on the Classification of Brackish Waters.” 

Estuarine and Marine waters are a complex solution of salts, dominated by sodium 

chloride (NaCl). The term haline is used to indicate the dominance of ocean salt. The 

relative proportions of the various major ions are usually similar to those found in sea 

water, even if the water is diluted below sea water strength. Dilution of sea water with 

fresh water and concentration of sea water by evaporation result in a wide range of 

recorded salinities in both surface water and interstitial water within the substrate. 

The salinity of inland water is dominated by four major cations, calcium (Ca), 

magnesium (Mg), sodium (Na), and potassium (K); and three major anions, carbonate 

(C03), sulfate (SO4), and chloride (Cl) (Wetzel 1975). Salinity is governed by the 

interactions between precipitation, surface runoff, groundwater flow, evaporation, and 

sometimes evapotranspiration by plants. The ionic ratios of inland waters usually differ 

appreciably from those in the sea, although there are exceptions (Bayly 1967). The great 

chemical diversity of these waters, the wide variation in physical conditions such as 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

41 

temperature, and often the relative impermanence of surface water, make it extremely 

difficult to subdivide the inland salinity range in a meaningful way. Bayly (l967) 

attempted a subdivision on the basis of animal life; Moyle (1945) and Stewart and 

Kantrud (1971) have suggested two very different divisions on the basis of plant life. 

The term saline is used to indicate that any of a number of ions may be dominant or 

codominant. These salinities are expressed in units of specific conductance as well as 

percent salt (Ungar 1974) and they are also covered by the salinity ranges in Table 2. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

42 

Table 2. Salinity Modifiers

Coastal 

Modifiersa

Inland Modifiersb Salinity (ppt) Approximate Specific Conductance 

(μMhos at 25°C) 

Hyperhaline Hypersaline >40 >60,000 

Euhaline Eusaline 30.0-40 45,000-60,000 

Mixohaline Mixosaline 0.5-30 800-45,000 

Polyhaline Polysaline 18.0-30 30,000-45,000 

Mesohaline Mesosaline 5.0-18 8,000-30,000 

Oligohaline Oligosaline 0.5-5 800-8,000 

Fresh Fresh <0.5 <800 

a Coastal Modifiers are used in the Marine and Estuarine Systems. 

b Inland Modifiers are used in the Riverine, Lacustrine, and Palustrine Systems. 

3.3.2.2 pH Modifiers 

Acid waters are, almost by definition, poor in calcium and often generally low in other 

ions, but some very soft waters may have a neutral pH (Hynes 1970). It is difficult to 

separate the effects of high concentrations of hydrogen ions from low base content, and 

many studies suggest that acidity may never be the major factor controlling the presence 

or absence of particular plants and animals. Nevertheless, some researchers have 

demonstrated a good correlation between pH levels and plant distribution (Sjörs 1950; 

Jeglum 1971). Jeglum (1971) showed that plants can be used to predict the pH of moist 

peat. 

There seems to be little doubt that, where a peat layer isolates plant roots from the 

underlying mineral substrate, the scarcity of minerals in the root zone strongly influences 

the types of plants that occupy the site. For this reason, many authors subdivide 

freshwater, organic wetlands into mineral-rich and mineral-poor categories (Sjörs 1950; 

Heinselman 1970; Jeglum 1971; Moore and Bellamy 1974). We have instituted pH 

Modifiers for freshwater wetlands (Table 3) because pH has been widely used to indicate 

the difference between mineral-rich and mineral-poor sites, and because it is relatively 

easy to determine. The ranges presented here are similar to those of Jeglum (1971), 

except that the upper limit of the circumneutral level (Jeglum’s mesotrophic) was raised 

to bring it into agreement with usage of the term in the U.S. The ranges given apply to the 

pH of water. They were converted from Jeglum’s moist-peat equivalents by adding 0.5 

pH units. 

 Table 3. pH Modifiers

Modifier pH of Water 

Acid <5.5 

Circumneutral 5.5-7.4 

Alkaline >7.4 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

43 

3.3.3 Soil Modifiers 

Soil is one of the most important physical components of wetlands. Through its depth, 

mineral composition, organic matter content, moisture regime, temperature regime, and 

chemistry, it exercises a strong influence over the types of plants that live on its surface 

and the kinds of organisms that dwell within it. In addition, the nature of soil in a 

wetland, particularly the thickness of organic soil, is of critical importance to engineers 

planning construction of highways or buildings. For these and other reasons, it is 

essential that soil be considered in the classification of wetlands. 

As noted in Section 2.2, we have placed the boundary between wetlands and deepwater 

habitats in the Riverine and Lacustrine Systems at a depth of 2.5 m (8.2 ft) below low 

water because this represents the approximate limit of soil as defined in Soil Taxonomy 

(Soil Survey Staff 1999) and the approximate maximum depth to which emergent plants 

normally grow (Welch 1952, Zhadin and Gerd 1963, Sculthorpe 1967). Thus, according 

to our definitions, inland wetlands may have soil, but inland deepwater habitats do not. 

All Palustrine waters are less than 2.5 m deep; therefore, potentially all Palustrine 

habitats have soil. In the Marine and Estuarine Systems, the deep limit of soil lies at a 

depth of 2.5 m below extreme low water; however, we separate wetlands from deepwater 

habitats precisely at the extreme low water mark in those Systems. So, according to our 

definitions, Marine and Estuarine wetlands may have soil, and deepwater habitats also 

may have soil out to the 2.5-m depth limit. 

The most basic distinction in soil classification in the U.S. is between mineral soil and 

organic soil (Soil Survey Staff 1999). In general“a soil is classified as an organic soil 

(Histosols) if more than half of the upper 80 cm (32 inches) of the soil is organic or if 

organic soil material of any thickness rests on rock or on fragmental material having 

interstices filled with organic matter.” Soil that does not meet this criterion is considered 

mineral soil. Organic soil material is soil material that contains at least 12-18 percent 

organic carbon by weight, the required amount depending on the clay content in the 

mineral fraction (Soil Survey Staff 1999). See Appendix E for additional details on the 

differences between mineral and organic soils. 

The U.S. soil classification is hierarchical and permits the description of soils at several 

levels of detail. For example, suborders of the order Histosols are recognized according 

to the degree of decomposition of the organic matter. In the WCS, we use the Soil 

Modifiers Organic and Mineral, based on the criteria presented above. If a more detailed 

soil classification is desired, the latest edition of Keys to Soil Taxonomy (Soil Survey 

Staff 2010) should be used. 

3.3.4 Special Modifiers 

Many wetland and deepwater habitats are man-made, and natural ones have been 

modified to some degree by the activities of humans or beaver. With the exception of 

Beaver, all of the Special Modifiers describe human alterations to wetlands. Since the 

nature of these modifications often greatly influences the character of such habitats, 

special modifying terms have been included here to emphasize their importance. The 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

44 

following Modifiers should be used singly. It may be difficult, in some instances, to 

choose the single Special Modifier that best describes the landscape modification. 

Because the Diked/Impounded Modifier is crucial for use in coastal watersheds as 

denoting wetland modifications for sea level rise models, it will be given priority over 

any other Modifiers (e.g., spoil areas that have been diked or impounded should be 

classified using the Diked/Impounded Modifier, not the Spoil Modifier.) 

Beaver— These wetlands have been created or modified by beaver (Castor canadensis). 

Dam building by beaver may increase the size of existing wetlands or create small 

impoundments that are easily identified on aerial imagery. Such flooding frequently 

creates Dead Forested or Dead Scrub-Shrub Wetland initially, followed in a few years by 

Aquatic Bed and Emergent Wetland. 

Partly Drained/Ditched—A partly drained wetland has been altered hydrologically, but 

soil moisture is still sufficient to support hydrophytes. Drained areas that can no longer 

support hydrophytes are not considered wetland. This Modifier is also used to identify 

wetlands containing, or connected to, ditches. The Partly Drained/Ditched Modifier can 

be applied even if the ditches are too small to delineate. The Excavated Modifier should 

be used to identify ditches that are large enough to delineate as separate features; 

however, the Partly Drained/Ditched Modifier also should be applied to the wetland area 

affected by the ditching. 

Farmed—Farmed wetlands occur where the soil surface has been mechanically or 

physically altered for production of crops, but where hydrophytes would become 

reestablished if the farming were discontinued. Farmed wetlands should be classified as 

Palustrine-Farmed. Cultivated cranberry bogs may be classified Palustrine-Farmed or 

Palustrine Scrub-Shrub Wetland-Farmed. 

Managed — This modifier is used to identify wetlands where water inputs are controlled 

to achieve a specific water regime or habitat type. Water control structures in 

combination with dikes and impoundments are common. 

Excavated—This Modifier is used to identify wetland basins or channels that were 

excavated by humans. 

Diked/Impounded—These wetlands have been created or modified by a man-made 

barrier or dam that obstructs the inflow or outflow of water. 

Artificial Substrate—This Modifier describes concrete-lined drainageways, as well as 

Rock Bottom, Unconsolidated Bottom, Rocky Shore and Unconsolidated Shore where 

the substrate material has been emplaced by humans. Jetties and breakwaters are 

examples of Artificial Rocky Shores. 

Spoil— The Spoil Modifier is used to describe wetlands where deposition of spoil 

material forms the primary substrate type. By definition, spoil is material that has been 

excavated and emplaced by humans. Ancillary data may be needed to accurately identify 

spoil in areas such as reclaimed strip mines that have become revegetated. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

45 

4. Use of the Classification System 

We have designed the various levels of this classification for specific purposes, and the 

relative importance of each will vary among users. The Systems and Subsystems are most 

important in applications involving large regions or the entire country. They serve to 

organize the Classes into meaningful assemblages of information for data storage and 

retrieval. 

The Classes and Subclasses are the most important part of the classification for many 

users and are basic to habitat mapping. Most Classes should be easily recognizable by 

users in a wide variety of disciplines. However, the Class designations apply to average 

conditions over a period of years and, since many habitats are dynamic and subject to 

rapid changes in appearance, the proper classification will frequently require data that 

span a period of years and several seasons in each of those years. 

The Dominance Type is most important to users interested in detailed regional studies. It 

may be necessary to identify Dominance Types in order to determine which modifying 

terms are appropriate, because plants and animals present in an area tend to reflect 

environmental conditions over a period of time. Water Regime can be determined from 

long-term hydrologic studies where these are available. The more common procedure is 

to estimate this characteristic from the Dominance Types. Several studies have related 

water regimes to the presence and distribution of plants or animals (e.g., Stephenson and 

Stephenson 1972; Stewart and Kantrud 1972; Chapman 1974). 

Similarly, we do not intend that salinity measurements be made for all wetlands or 

deepwater habitats except where these data are required; often plant species or 

associations can be used to indicate broad salinity ranges. Lists of halophytes have been 

prepared for both coastal and inland areas (e.g., Duncan 1974; MacDonald and Barbour 

1974; Ungar 1974), and a number of floristic and ecological studies have described plants 

that are indicators of salinity (e.g., Penfound and Hathaway 1938; Moyle 1945; Kurz and 

Wagner 1957; Dillon 1966; Anderson et al. 1968; Chabreck 1972; Stewart and Kantrud 

1972; Ungar 1974; Odum et al. 1984). 

In areas where the Dominance Types to be expected under different Water Regimes and 

types of Water Chemistry Modifiers have not been identified, detailed regional studies 

will be required before the classification can be applied in detail. In areas where detailed 

soil maps are available, it is also possible to infer Water Regime and Water Chemistry 

from soil map units. 

Some of the Modifiers are an integral part of this classification and their use is essential; 

others are used only for detailed applications or for special cases. The minimum standard 

for wetland classification is: System, Subsystem (with the exception of Palustrine), Class, 

Subclass (only required for Forested, Scrub-Shrub, and Emergent Wetland Classes), 

Water Regime Modifier, and Special Modifier (only required where applicable). The 

minimum standard for deepwater habitat classification is: System, Subsystem, Class, and 

Water Regime Modifier. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

46 

Water Chemistry Modifiers and Soil Modifiers generally are not used when classification 

data are obtained using remote sensing. These Modifiers should be applied only when 

detailed, supporting data have been gathered in the field or from reliable sources such as 

soil surveys. 

The user is urged not to rely on single observations of Water Regime or Water 

Chemistry. Such measurements give misleading results in all but the most stable habitats. 

If a more detailed Soil Modifier, such as soil order or suborder (Soil Survey Staff, 2010) 

can be obtained, it should be used in place of the Modifiers, Mineral and Organic. 

5. Regionalization for the Classification System 

In 1977 the USFWS adopted Bailey’s (1976) ecoregions to give the inland wetlands and 

deepwater habitats of the United States an ecological address (see Cowardin et al. 1979). 

For the WCS, the 1995 version of Bailey’s ecoregions is to be used wherever there is a 

need for regionalization in the U.S. interior 

(see http://www.fs.fed.us/rm/ecoregions/products/map-ecoregions-united-states/.) 

See further information in Appendix F. 

6. Application of the FGDC Wetlands Classification 

Standard 

Before attempting to apply the WCS, the user should be aware of the following: 

(1) Some information about the area to be classified must be available before the WCS 

can be applied. This information may be in the form of historical data, aerial 

photographs or digital images, brief on-site inspection, or detailed and intensive 

studies. 

(2) The classification is designed for use at varying levels of detail. There are few areas 

for which sufficient information is currently available to allow the most detailed 

level of classification. If the level of detail provided by the data is not sufficient to 

meet the classification needs of the user, additional data gathering should be 

undertaken. In order for projects to conform to the Mapping Standard (FGDC-STD015-2009), additional data gathering will be required whenever the detail is 

insufficient to meet the classification requirements of the Standard. 

(3) When used in mapping projects, this classification is scale-specific, both for the 

minimum size of units mapped and for the degree of detail attainable. 

(4) This classification provides examples of common Dominance Types for various 

wetland and deepwater habitats. Users should feel free to add to this list as other 

dominant species are encountered during regional and local applications of the 

classification system throughout the United States. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

47 

(5) One of the main purposes of the FGDC Wetlands Classification Standard is to 

ensure uniformity in wetland classification throughout the U.S. It is important that 

the user pay particular attention to the definitions in this classification. Any 

deviation from, or modification of, these definitions in the application of this 

classification system will lead to a lack of uniformity and defeat the purpose of the 

Standard. 

(6) One of the principal uses of the WCS is for inventory and mapping. In order to 

maintain national consistency, the mapping conventions developed and refined by 

the USFWS over the first 30 years of NWI mapping were used as the basis for the 

FGDC Wetlands Mapping Standard (FGDC-STD-015-2009). The Mapping 

Standard was endorsed by the FGDC in July 2009. It specifies the minimum data 

quality components for wetlands inventory mapping needed to support inclusion of 

the data into the National Spatial Data Infrastructure (NSDI), which is mandatory 

when these activities are fully or partially funded or conducted by the Federal 

Government. The Mapping Standard balances the burden on the end-user 

community with the need for consistency and documented quality of digital 

mapping products. Additionally, the FGDC Wetlands Mapping Standard is created 

to coordinate wetlands mapping with the National Hydrography Dataset, a national 

geospatial framework recognized by the FGDC. Although the FGDC Wetlands 

Mapping Standard is structured to be extensible over time, it is deliberately 

developed with a forward-looking perspective to accommodate technology and 

map-scale enhancements to assure its long-term usability, and minimize the need 

for revisions and updates. 

7. References 

Abbott, R. T. 1968. Seashells of North America. Golden Press, New York. 

Akins, G. J., and C. Q. Jefferson. 1973. Coastal wetlands of Oregon. Oregon Coastal 

Conservation and Development Commission, Florence, Oregon. 

Anderson, J. R., E. E. Hardy, J. T. Roach, and R. E. Witmer. 1976. A land use and land 

cover classification system for use with remote sensor data. U.S. Geol. Surv. Prof. 

Pap. 964. 

Anderson, R. R., R. G. Brown, and R. D. Rappleye. 1968. Water quality and plant 

distribution along the upper Patuxent River, Maryland. Chesapeake Sci. 9:145-

156. 

Bailey, R. G. 1976. Ecoregions of the United States. 1:7,500,000-scale map. U.S. 

Department of Agriculture, Forest Service, Intermountain Region, Ogden, Utah. 

Bailey, R. G. 1995. Description of the ecosystems of the United States. 2nd edition. U.S. 

Dep. Agric., For. Serv., Misc. Publ. 1391, including 1:7,500,000-scale map. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

48 

Bailey, R. G. 2005. Identifying ecoregion boundaries. Environmental Management. 34, 

Suppl.1: S14-S26. 

Bailey, R. G., P. E. Avers, T. King, and W. H. McNab, eds. 1994. Ecoregions and 

subregions of the United States. 1:7,500,000-scale map with table of map unit 

descriptions compiled and edited by W. H. McNab and R. G. Bailey. U.S. 

Department of Agriculture, Forest Service, Washington, DC. 

Bayly, I. A. E. 1967. The general biological classification of aquatic environments with 

special reference to those of Australia. Pages 78-104 in A. H. Weatherley, ed. 

Australian inland waters and their fauna. Australian National University Press, 

Canberra. 

Black, C. A. 1968. Soil plant relationships. John Wiley & Sons, Inc., New York. 

Bormann, F. H., and G. E. Likens, 1969. The watershed-ecosystem concept and studies 

of nutrient cycles. Pages 49-76 in G. M. VanDyne, ed. The ecosystem concept in 

natural resource management. Academic Press, New York. 

Brinkhurst, R. O., and B. G. M. Jamieson. 1972. Aquatic oligochaetes of the world. 

University of Toronto Press, Toronto. 

Britton, M. E. 1957. Vegetation of the Arctic tundra. Oregon State Univ. Biol. Colloq. 

18:26-61. 

Cain, S. A. and G. M. de Oliveira Castro. 1959. Manual of vegetation analysis. Harper & 

Brothers, New York. 

Caspers, H. 1967. Estuaries: analysis of definitions and biological considerations. Pages 

6-8 in G. H. Lauff, ed. Estuaries. Am. Assoc. Adv. Sci. Publ. 83. 

Chabreck, R. H. 1972. Vegetation, water and soil characteristics of the Louisiana coastal 

region. La. Agric. Exp. Stn. Bull. 664. 

Chapman, V. J. 1974. Salt marshes and salt deserts of the world. 2nd supplemented 

edition. J. Cramer, Lehre. 

Chapman, V. J. 1977. Introduction. Pages 1-30 in V. J. Chapman, ed. Wet coastal 

ecosystems. Ecosystems of the world 1. Elsevier Scientific Publishing Co., New 

York. 

Clarke, A. H. 1973. The freshwater mollusks of the Canadian Interior Basin. Malacologia 

13(1-2):1-509. 

Cleland, D.T., J.A. Freeouf, J.E. Keys, G.J. Nowacki, C.A. Carpenter, and W.H. 

McNab. 2005. Ecological subregions: sections and subsections of the 

conterminous United States. 1:3,500,000-scale map; CD-ROM. U.S. Department 

of Agriculture, Forest Service, Washington, DC. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

49 

Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. Kittel, S. Menard, M. 

Pyne, M. Reid, K. Schulz, K. Snow, and J. Teague. 2003. Ecological systems of 

the United States: a working classification of U.S. terrestrial systems. 

NatureServe, Arlington, Virginia. 

Cowardin, L. M., V. Carter, F. C. Golet and E. T. LaRoe. 1976. Interim classification of 

wetlands and aquatic habitats of the United States. U.S. Fish and Wildlife Service, 

Office of Biological Services, Washington, DC. 

Cowardin, L. M., V. Carter, F. C. Golet, and E. T. LaRoe. 1979. Classification of 

wetlands and deepwater habitats of the United States. U.S. Fish and Wildlife 

Service. FWS/OBS-79/31. Washington, DC. 

Crickmay, C. H. 1974. The work of the river. The MacMillan Press, Ltd., London. 

Cummins, K. W., C. A. Tryon, Jr., and R. T. Hartman, eds. 1964. Organism-substrate 

relationships in streams. Pymatuning Lab. Ecol., Univ. Pittsburg Spec. Publ. 4. 

Curtis, J. T. 1959. The vegetation of Wisconsin. The University of Wisconsin Press, 

Madison. 

Dahl, T. E., J. Dick, J. Swords, and B. O. Wilen. 2009. Data collection requirements and 

procedures for mapping wetland, deepwater and related habitats of the United 

States. U.S. Fish and Wildlife Service, Division of Habitat and Resource 

Conservation, National Standards and Support Team, Madison, Wisconsin. 

(Available at http://www.fws.gov/wetlands/) 

Daubenmire, R. 1968. Plant communities. Harper & Row, New York. 

Dick, J. 2009. A system for mapping riparian areas in the western United States, U.S. 

Fish and Wildlife Service, Division of Habitat and Resource Conservation. 

(Available at http://www.fws.gov/wetlands/) 

Dillon, O. W. 1966. Gulf coast marsh handbook. U. S. Soil Conservation Service, 

Alexandria, Louisiana. 

Drury, W. H., Jr. 1962. Patterned ground and vegetation on southern Bylot Island, 

Northwest Territories, Canada. Harvard Univ. Gray Herb. Contrib. 190. 

Duncan, W. H. 1974. Vascular halophytes of the Atlantic and Gulf coasts of North 

America north of Mexico. Pages 23-50 in R. J. Reimold and W. H. Queen, eds. 

Ecology of halophytes. Academic Press, Inc., New York. 

Eleuterius, L. M. 1973. The distribution of certain submerged plants in Mississippi Sound 

and adjacent waters. Pages 191-197 in J. L. Christmas, ed. Cooperative Gulf of 

Mexico estuarine inventory and study. Mississippi Gulf Coast Research 

Laboratory, Ocean Springs. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

50 

Golet, F. C., and J. S. Larson. 1974. Classification of freshwater wetlands in the glaciated 

Northeast. U.S. Fish Wildl. Serv., Resour. Publ. 116. 

Gosner, K. L. 1971. Guide to identification of marine and estuarine invertebrates: Cape 

Hatteras to the Bay of Fundy. John Wiley & Sons, Inc., New York. 

Gray, I. E. 1974. Worm and clam flats. Pages 204-243 in H. T. Odum, B. J. Copeland, 

and E. A. McMahan, eds. Coastal ecological systems of the United States. Vol. 2. 

The Conservation Foundation, Washington, DC. 

Hart, C. W., Jr., and S. L. H. Fuller, eds. 1974. Pollution ecology of freshwater 

invertebrates. Academic Press, Inc., New York. 

Hedgpeth, J. W. 1957. Classification of marine environments. Pages 17-28 in J. W. 

Hedgpeth, ed. Treatise on marine ecology and paleoecology; Vol. l-Ecology. 

Geol. Soc. Am. Mem. 67. 

Heinselman, M. L. 1970. Landscape evolution, peatland types, and the environment in 

the Lake Agassiz Peatlands Natural Area, Minnesota. Ecol. Monogr. 40(2):235-

261. 

Hutchinson, G. E. 1975. A treatise on limnology. Vol. 3. Limnological botany. John 

Wiley & Sons, New York. 

Hynes, H. B. N. 1970. The ecology of running waters. University of Toronto Press, 

Toronto. 

Illies, J., and L. Botosaneau. 1963. Problems et methodes de la classification et de la 

zonation ecologique des aux courantes, considerees surtout du point de vue 

faunistique. Int. Assoc. Theor. Appl. Limnol. Commun. 12. 

Ingram, W. M. 1971. Survival of fresh-water mollusks during periods of dryness. Nautilis 

54(3):84-87. 

Integrated Taxonomic Information System. 2012. Scientific and common names of 

animals. (Available at http://www.itis.gov/) 

Jeglum, J. K. 1971. Plant indicators of pH and water level in peatlands at Candle Lake, 

Saskatchewan. Can. J. Bot. 49:1661-1676. 

Jeglum, J. K., A. N. Boissonneau, and V. G. Haavisto. 1974. Toward a wetland 

classification for Ontario. Can. For. Serv. Inf. Rep. 0-X-215. 

Johnson, R. I. 1970. The systematics and zoogeography of the Unionidae (Mollusca: 

Bivalvia) of the Southern Atlantic Slope Region. Harvard Univ. Mus. Comp. 

Zool. Bull. 140(6):263-450. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

51 

Kenk, R. 1949. The animal life of temporary and permanent ponds in southern Michigan. 

Univ. Mich. Mus. Zool. Misc. Publ. 71. 

Kologiski, R. L. 1977. The phytosociology of the Green Swamp, North Carolina. North 

Carolina Agric. Exp. Stn. Tech. Bull. 250. 

Köppen, W. 1931. Grundriss der Klimakunde. Walter de Gruyter & Co., Berlin. 

Krecker, F. H., and L. Y. Lancaster. 1933. Bottom shore fauna of western Lake Erie: a 

population study to a depth of six feet. Ecology 14:79-83. 

Kurz, H., and K. Wagner. 1957. Tidal marshes of the Gulf and Atlantic coasts of northern 

Florida and Charleston, South Carolina. Fla. State Univ. Stud. 24. 

Langbein, W. B., and K. T. Iseri. 1960. General introduction and hydrologic definitions 

manual of hydrology. Part 1. General surface-water techniques. U.S. Geol. Surv. 

Water-Supply Pap. 1541-A. 

Lauff, G. H., ed. 1967. Estuaries. Am. Assoc. Adv. Sci. Publ. 83. 

Lewis, J. R. 1964. The ecology of rocky shores. English Universities Press Ltd., London. 

Lichvar, R. W., and J. T. Kartesz. 2009. North American Digital Flora: National Wetland 

Plant List, version 2.4.0 (http://wetland_plants.usace.army.mil). U.S. Army Corps 

of Engineers, Engineer Research and Development Center, Cold Regions 

Research and Engineering Laboratory, Hanover, New Hampshire, and BONAP, 

Chapel Hill, North Carolina. 

Liu, T. K. 1970. A review of engineering soil classification systems. Pages 362-382 in

Special procedures for testing soil and rock for engineering purposes. Am. Soc. 

Test. Mater. Spec. Tech. Publ. 479. 

MacDonald, K. B., and M. B. Barbour. 1974. Beach and salt marsh vegetation of the 

North American Pacific coast. Pages 175-233 in R. J. Reimold and W. H. Queen, 

eds. Ecology of halophytes. Academic Press, Inc., New York. 

Martin, A. C., N. Hotchkiss, F. M. Uhler, and W. S. Bourn. 1953. Classification of 

wetlands of the United States. U.S. Fish Wildl. Serv., Spec. Sci. Rep.--Wildl. 20. 

McNab, W. H., D. T. Cleland, J. A. Freeouf, J. E. Keys, G. J. Nowacki, and C. A. 

Carpenter, compilers. 2005. Description of ecological subregions: sections of the 

conterminous United States. CD-ROM. U.S. Department of Agriculture, Forest 

Service, Washington, DC. 

Miner, R. W. 1950. Field book of seashore life. G. P Putnam’s Sons, New York. 

Moore, P. D., and D. J. Bellamy. 1974. Peatlands. Springer-Verlag, Inc., New York. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

52 

Morris, P. A. 1966. A field guide to shells of the Pacific Coast and Hawaii. Houghton 

Mifflin Company, Boston. 

Moyle, J. B. 1945. Some chemical factors influencing the distribution of aquatic plants in 

Minnesota. Am. Midl. Nat. 34(2):402-420. 

Moyle, J. B. 1946. Some indices of lake productivity. Trans. Am. Fish. Soc. 76:322-334. 

Mueller-Dombois, D., and H. Ellenberg. 1974. Aims and methods of vegetation ecology. 

John Wiley & Sons, New York. 

Nowacki, G., and T. Brock. 1995. Ecoregions and subregions of Alaska. ECOMAP 

Version 2.0; 1:7,500,000-scale map. U.S. Department of Agriculture, Forest 

Service, Alaska Region, Juneau. 

Odum, E. P. 1971. Fundamentals of ecology. W. B. Saunders Co., Philadelphia. 

Odum, H. T. 1974. Tropical marine meadows. Pages 442-487 in H. T. Odum, B. J. 

Copeland, and E. A. McMahan, eds. Coastal ecological systems of the United 

States. Vol. 1. The Conservation Foundation, Washington, DC. 

Odum, W. E., T. J. Smith, III, J. K. Hoover, and C. C. McIvor. 1984. The ecology of tidal 

freshwater marshes of the United States East Coast: a community profile. U.S. 

Fish and Wildlife Service. FWS/OBS-83/17. Washington, DC. 

Penfound, W. T., and E. S. Hathaway. 1938. Plant communities in the marshlands of 

southeastern Louisiana. Ecol. Monogr. 8:1-56. 

Pennak, R. W. 1978. Fresh-water invertebrates of the United States. 2nd Edition. John 

Wiley & Sons, New York. 

Phillips, R. C. 1974. Temperate grass flats. Pages 244-314 in H. T. Odum, B. J. 

Copeland, and E. A. McMahan, eds. Coastal ecological systems of the United 

States. Vol. 2. The Conservation Foundation, Washington, DC. 

Pollett, F. C., and P. B. Bridgewater. 1973. Phytosociology of peatlands in central 

Newfoundland. Can. J. For. Res. 3(3):433-442. 

Radforth, N. W. 1962. Organic terrain and geomorphology. Can. Geogr. 6(3-4):166-171. 

Ranwell, D. S. 1972. Ecology of salt marshes and sand dunes. Chapman and Hall, 

London. 

Reid, G. K., and R. D. Wood. 1976. Ecology of inland waters and estuaries. D. Van 

Nostrand and Co., New York. 

Remane, A., and C. Schlieper. 1971. Biology of brackish water. Wiley Interscience 

Division, John Wiley & Sons, New York. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

53 

Ricketts, E. F., and J. Calvin. 1968. Between Pacific tides, 4th edition. Revised by J. W. 

Hedgpeth. Stanford University Press, Stanford, California. 

Riedl, R., and E. A. McMahan. 1974. High energy beaches. Pages 180-251 in H. T. 

Odum, B. J. Copeland, and E. A. McMahan, eds. Coastal ecological systems of 

the United States. Vol. 1. The Conservation Foundation, Washington, DC. 

Sather, J. H., ed. 1976. Proceedings of the National Wetland Classification and Inventory 

Workshop. U.S. Fish and Wildlife Service. FWS/OBS – 76/09. Washington, DC. 

Sculthorpe, C. D. 1967. The biology of aquatic vascular plants. Edward Arnold Ltd., 

London. 

Shaw, S. P., and C. G. Fredine. 1956. Wetlands of the United States. U.S. Fish Wildl. 

Serv., Circ. 39. 

Sjörs, H. 1950. On the relation between vegetation and electrolytes in north Swedish mire 

waters. Oikos 2:241-258. 

Sjörs, H. 1959. Bogs and fens in the Hudson Bay lowlands. J. Arctic Inst. Am. 12(1):2-

19. 

Slack, K. V., J. W. Nauman, and L. J. Tilley. 1977. Benthic invertebrates in an arctic 

mountain stream, Brooks Range, Alaska. J. Res. U.S. Geol. Surv. 5:519- 527. 

Smith, R. I. 1964. Key to marine invertebrates of the Woods Hole Region. Contribution 

No. 11 of the Systematic-Ecology Program, Marine Biological Laboratory, 

Woods Hole, Massachusetts. 

Soil Survey Staff. 1999. Soil taxonomy: a basic system of soil classification for making 

and interpreting soil surveys. 2nd edition. U.S. Dep. Agric., Nat. Resour. Cons. 

Serv., Agric. Handb. 436. 

Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of 

Agriculture, Natural Resources Conservation Service. 

Stehr, W. C., and J. W. Branson. 1938. An ecological study of an intermittent stream. 

Ecology 19(1):294-354. 

Stephenson, T. A., and A. Stephenson. 1972. Life between tidemarks on rocky shores. W. 

H. Freeman and Co., San Francisco. 

Stewart, R. E., and H. A. Kantrud. 1971. Classification of natural ponds and lakes in the 

glaciated prairie region. U.S. Fish. Wildl. Serv., Resour. Publ. 92. 

Stewart, R. E., and H. A. Kantrud. 1972. Vegetation of prairie potholes, North Dakota, in 

relation to quality of water and other environmental factors. U.S. Geol. Surv. Prof. 

Pap. 585-D. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

54 

Tiner, R. W. 1993. The primary indicators method—a practical approach to wetland 

recognition and delineation in the United States. Wetlands 13(1): 50-64. 

Thorson. G. 1957. Bottom communities. Pages 461-534 in J. W. Hedgpeth, ed. Treatise 

on marine ecology and paleoecology. Geol. Soc. Am. Mem. 67. Vol. 1. 

Ungar, I. A. 1974. Inland halophytes of the United States. Pages 235-305 in R. J. 

Reimold and W. H. Queen, eds. Ecology of halophytes. Academic Press, New 

York. 

U.S. Department of Agriculture, Natural Resources Conservation Service. 2010. Field 

indicators of hydric soils in the United States. Version 7. L.M. Vasilas, G. W. 

Hunt and C.V. Nobel, eds. USDA, NRCS, in cooperation with the National 

Technical Committee for Hydric Soils. 

U.S. Department of Interior. 1970. National atlas of the United States. U.S. Geological 

Survey, Washington, DC. 

U.S. National Oceanic and Atmospheric Administration. 1973. Tide tables-high and low 

predictions 1974: East coast of North and South America. U.S. Government 

Printing Office, Washington, DC. 

van der Schalie, H. 1948. The land and freshwater mollusks of Puerto Rico. Univ. Mich. 

Mus. Zool. Misc. Publ. 70. 

Venice System. 1959. The Venice system for the classification of marine waters 

according to salinity. Final resolution of the Symposium on the Classification of 

Brackish Waters. Archo Oceanography and Limnology 11 (suppl.): 243-248. 

Ward, H. B., and G. C. Whipple. 1959. Freshwater biology. John Wiley and Sons, Inc., 

New York. 

Ward, J. V. 1975. Bottom fauna-substrate relationships in a northern Colorado trout 

stream: 1945 and 1974. Ecology 56:1429-1434. 

Weaver, J. E., and F. E. Clements. 1938. Plant ecology. 2nd edition. McGraw-Hill Book 

Company, Inc., New York. 

Weber, C. I., ed. 1973. Biological field and laboratory methods for measuring the quality 

of surface waters and effluents. U.S. Environmental Protection Agency, Office of 

Research and Development, Environmental Monitoring Series. EPA 670/4-73-

001. 

Welch, P. S. 1952. Limnology, 2nd edition. McGraw-Hill, New York. 

Wetzel, R. G. 1975. Limnology. W. B. Saunders Co., Philadelphia. 
Federal Geographic Data Committee FGDC–STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

 ____________________________________________________________________________________ 

55 

Zhadin, V. I., and S. V. Gerd. 1963. Fauna and flora of the rivers, lakes and reservoirs of 

the U.S.S.R. Oldbourne Press, London. 

Zoltai, S. C., F. C. Pollett, J. K. Jeglum, and G. D. Adams. 1975. Developing a wetland 

classification for Canada. Proc. N. Am. For. Soils Conf. 4:497-511. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

56 

APPENDIX A (Informative): Glossary of Technical Terms, 

Acronyms, and Abbreviations 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

57 

Technical Terms 

Definitions provided here come from a variety of sources, including some of the 

references in Section 7 of this document. Where definitions have been taken verbatim 

from a source, that source has been cited. In other cases, definitions have been modified 

or drafted specifically for this classification. 

Term Definition 

Acid Term applied to water with a pH less than 5.5. 

Alkaline Term applied to water with a pH greater than 7.4. 

Bar Elongated landform generated by waves and currents, usually running 

parallel to the shore, composed predominantly of unconsolidated sand, 

gravel, stones, cobbles, or rubble and with water on two sides. 

Bay Wide, curving open indentation, recess, or arm of a sea or lake into the 

land or between two capes or headlands; larger than a cove. 

Beach Sloping landform of unconsolidated material on the shore of larger water 

bodies, generated by washing waves, tides or currents and extending from 

the water to a distinct break in landform, substrate type (e.g., a foredune, 

cliff, or bank), or to the line of continuous vegetation, usually the effective 

limit of the highest storm waves. 

Bedrock Solid rock layer exposed at the land surface (outcrop) or underlying 

unconsolidated surface materials such as soil, alluvium, gravel or rock 

fragments. 

Boulder Rock fragment larger than 60.4 cm (24 inches) in diameter. 

Brackish Marine and Estuarine waters with Mixohaline salinity. 

Broad-leaved 

deciduous 

Woody angiosperms (trees or shrubs) with relatively wide, flat leaves that 

are shed during the cold or dry season; e.g., black ash (Fraxinus nigra). 

Broad-leaved 

evergreen 

Woody angiosperms (trees or shrubs) with relatively wide, flat leaves that 

generally remain green and are usually persistent for a year or more; e.g., 

red mangrove (Rhizophora mangle). 

Calcareous Formed of calcium carbonate or magnesium carbonate by biological 

deposition or inorganic precipitation in sufficient quantities to effervesce 

carbon dioxide visibly when treated with cold 0.1 normal hydrochloric acid. 

Calcareous sands are usually formed of a mixture of fragments of mollusk 

shell, echinoderm spines and skeletal material, coral, foraminifera, and 

algal platelets (e.g., Halimeda). 

Channel “An open conduit either naturally or artificially created which periodically or 

continuously contains moving water, or which forms a connecting link 

between two bodies of standing water” (Langbein and Iseri 1960:5). 

Channel bank The sloping land bordering a channel. The bank has steeper slope than the 

bottom of the channel and is usually steeper than the land surrounding the 

channel. 

Circumneutral Term applied to water with a pH of 5.5 to 7.4. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

58 

Term Definition 

Clay Mineral particles smaller than 0.002 mm composed of naturally occurring 

aluminum silicate. 

Cliff High, very steep or overhanging geologic face usually produced by erosion. 

Codominant Two or more species providing about equal areal cover which, in 

combination, control the environment. 

Cobble Rock fragment 7.6 cm (3 inches) to 25.4 cm (10 inches) in diameter. 

Continental Shelf Part of the continental margin that is between the shoreline and the 

continental slope. 

Dam Obstruction across a hydrologic flow impounding water to produce a lake, 

pond, wetland, or other widened aquatic feature. 

Deciduous stand Plant community where deciduous trees or shrubs represent more than 50 

percent of the total areal coverage of trees or shrubs. 

Dike Artificial wall, embankment, ridge, or mound, usually of earth or rock fill, 

built around a relatively flat, low-lying area to protect it from flooding; a 

levee. A dike may also be constructed on the shore or border of a lake or 

estuary to prevent inflow of water to bordering lands. 

Dominant Species that are most numerous, or form the bulk of the biomass, and 

therefore have the greatest effect or influence on the ecological community, 

generally controlling the presence, abundance, or type of other species. 

Dominant life form That life form of plants (e.g., tree, shrub, moss) that constitutes the 

uppermost layer of vegetation at a site and possesses at least 30 percent 

areal cover. The dominant life form determines the Class of vegetated 

wetlands in this classification. 

Dormant season That part of the year that falls outside the growing season. 

Embayment Deep indentation or recess of a shoreline that forms a bay, which may be 

entirely or partially cut-off from the main water body by intervening features 

such as roads, railroad beds, culverts, or dams. 

Emergent 

hydrophytes 

Rooted herbaceous angiosperms, ferns, and fern allies (e.g., Equisetum

spp.) that grow in wet soil, stand erect during most or all of the growing 

season, and may be periodically to permanently flooded at the base, but do 

not tolerate prolonged inundation of the entire plant. Examples include 

bulrushes (Scirpus spp.), grasses, and sedges. 

Emergent mosses Mosses occurring in wetlands, but generally not covered by water. 

Euhaline Characterizes water with a concentration of ocean-derived salts measuring 

30 to 40 parts per thousand (ppt). 

Eutrophic lake Lake that has a high concentration of nutrients such as nitrogen and 

phosphorus which stimulate the growth of plants or algae such that the 

oxygen content is depleted and carbon sequestered. 

Evergreen stand Plant community where evergreen trees or shrubs represent more than 50 

percent of the total areal coverage of trees and shrubs. The canopy is 

never without foliage; however, individual trees or shrubs may shed their 

leaves (Mueller-Dombois and Ellenberg 1974). 

Extreme high water 

of spring tides 

Highest tide occurring during a lunar month, usually near the new or full 

moon. This is equivalent to extreme higher high water of mixed semidiurnal 

tides. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

59 

Term Definition 

Extreme low water 

of spring tides 

Lowest tide occurring during a lunar month, usually near the new or full 

moon. This is equivalent to extreme lower low water of mixed semidiurnal

tides. 

Flat Level landform composed of unconsolidated sediments—usually mud or 

sand. Flats may be irregularly shaped or elongate and continuous with the 

shore, whereas bars are generally elongate, parallel to the shore, and 

separated from the shore by water. 

Floating plant Non-anchored plant that floats freely in the water or on the surface; e.g., 

water hyacinth (Eichhornia crassipes) or common duckweed (Lemna 

minor). 

Floating-leaved 

plant 

Rooted, herbaceous hydrophyte with some leaves floating on the water 

surface; e.g., white water lily (Nymphaea odorata), floating-leaved 

pondweed (Potamogeton natans). Plants such as yellow water lily (Nuphar 

luteum) which sometimes have leaves raised above the surface are 

considered floating-leaved plants or emergents, depending on their growth 

habit at a particular site. 

Floodplain “flat expanse of land bordering an old river . . .“ (Reid and Wood 1976:72, 

84). 

Fresh water Water with a dissolved salt concentration measuring less than 0.5 ppt. 

Gravel Mixture composed primarily of rock fragments 2 mm (0.08 inch) to 7.6 cm 

(3 inches) in diameter. Usually contains much sand. 

Growing season That part of the year that begins with green-up and bud-break of native 

plants in the spring and ends with plant dieback and leaf-drop in the fall due 

to the onset of cold weather. 

Haline Indicates dominance of ocean salt (see also Saline). 

Herbaceous With the characteristics of an herb; a plant with no persistent woody stem 

above ground. 

Histosols The order of organic soils, as defined by USDA Natural Resources 

Conservation Service in Soil Taxonomy (Soil Survey Staff 1999); soils 

consisting primarily of organic soil material such as peat or muck (see also 

Organic soil and Appendix E). 

Hydric soil Soil that formed under conditions of saturation, flooding or ponding long 

enough during the growing season to develop anaerobic conditions in the 

upper part. The concept of hydric soils includes soils developed under 

sufficiently wet conditions to support the growth and regeneration of 

hydrophytic vegetation. (From http://soils.usda.gov/use/hydric/intro.html) 

Hydrophytes, 

hydrophytic 

Any plant growing in water or on a substrate that is at least periodically 

deficient in oxygen as a result of excessive water content. 

Hyperhaline Water with a concentration of ocean-derived salts measuring greater than 

40 ppt. 

Hypersaline Water with a concentration of land-derived salts measuring greater than 40 

ppt. 

Kelp Any of numerous large seaweeds found in colder seas and belonging to the 

order Laminariales, brown algae. 

Lagoon A mostly-enclosed, shallow, saline water body with little freshwater input 

and damped tidal fluxes. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

60 

Term Definition 

Levee An embankment of sediment, bordering one or both sides of natural or 

artificial channels. 

Macrophytic algae Algal plants large enough either as individuals or communities to be readily 

visible without the aid of optical magnification. 

Mangrove Tidally-influenced, tropical or subtropical shrub or forest dominated by true 

mangroves and associates. 

Mean high water Average height of the high water over 19 years. 

Mean higher high 

tide 

Average height of the higher of two unequal daily high tides over 19 years. 

Mean low water Average height of the low water over 19 years. 

Mean lower low 

water 

Average height of the lower of two unequal daily low tides over 19 years. 

Mean tide level A plane midway between mean high water and mean low water. 

Mesohaline Water with a concentration of ocean-derived salts measuring of 5 to 18 ppt. 

Mesophye, 

mesophytic 

Any plant growing where moisture and aeration conditions lie between 

extremes; plants typically found in habitats with average moisture 

conditions, not unusually dry or wet. 

Mesosaline Water with a concentration of land-derived salts measuring 5 to 18 ppt. 

Mineral soil Soil composed of predominantly mineral, rather than organic, material (see 

Appendix E). 

Mixohaline Water with a concentration of ocean-derived salts measuring 0.5 to 30 ppt. 

The term is roughly equivalent to the term brackish. 

Mixosaline Waters with a concentration of land-derived salts measuring 0.5 to 30 ppt. 

Muck Soil consisting primarily of highly decomposed organic matter (sapric soil 

material). 

Mud Wet soft earth composed predominantly of clay- and silt-sized mineral 

particles less than 0.074 mm in diameter (Black 1968; Liu 1970). 

Needle-leaved 

deciduous 

Woody gymnosperms (trees or shrubs) with needle-shaped or scale-like 

leaves that are shed during the cold or dry season; e.g., bald cypress 

(Taxodium distichum). 

Needle-leaved 

evergreen 

Woody gymnosperms with green, needle-shaped, or scale-like leaves that 

are retained by plants throughout the year; e.g., black spruce (Picea 

mariana). 

Nonpersistent 

emergents 

Emergent hydrophytes whose stems and leaves are evident above the 

surface of the water, or above the soil surface if surface water is absent, 

only during the growing season or shortly thereafter. Typically, plant leaves 

and stems break down soon after the growing season or drop beneath the 

water surface (e.g., arrow arum, Peltandra virginica; burreed, Sparganium

spp.; bayonet rush, Juncus militaris). Many nonpersistent emergents have 

fleshy or spongy tissues. 

Obligate hydrophyte Plant that under natural conditions occurs almost always (estimated 

probability 99 percent) in wetlands, e.g., cattail (Typha latifolia), as opposed 

to species that grow in both wetlands and upland, e.g., red maple (Acer 

rubrum). 

Oligohaline Water with a concentration of ocean-derived salts measuring 0.5 to 5.0 ppt. 

Oligosaline Water with a concentration of land-derived salts measuring 0.5 to 5.0 ppt. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

61 

Term Definition 

Organic matter Organic fraction of the soil exclusive of undecayed plant and animal 

residues. 

Organic soil Soil composed of predominantly organic rather than mineral material (see 

Appendix E). 

Peat Soil consisting primarily of poorly to moderately decomposed organic 

matter (fibric to hemic soil material) 

Persistent 

emergents 

Emergent hydrophytes whose stems and leaves are evident throughout the 

year above the surface of the water, or above the soil surface if surface 

water is absent. In some species, such as cattails (Typha spp.), stems may 

remain erect all year; in others, stems and leaves may lie prostrate on the 

soil surface after the peak of the growing season due to tidal action, wind, 

heavy rain, or snow cover. Plants such as saltmarsh cordgrass (Spartina 

alterniflora), whose stems may be severed during Northern winters by ice, 

in combination with tidal action, along the edges of tidal creeks or other 

open water bodies, are considered persistent. 

Photic zone Upper water layer down to the depth of effective light penetration where 

photosynthesis balances respiration. This level (the compensation level) 

usually occurs at the depth of 1 percent light penetration and forms the 

lower boundary of the zone of net metabolic production. 

Pioneer plants Herbaceous annual and seedling perennial plants that colonize bare areas 

as a first stage in secondary succession. 

Polyhaline Water with a concentration of ocean-derived salts measuring18 to 30 ppt. 

Polysaline Water with a concentration of land-derived salts measuring 18 to 30 ppt. 

Reef Ridge or mound-like structure formed by the colonization and growth of 

sedentary invertebrates such as corals, mollusks, or tubeworms. 

Saline Water containing various dissolved salts. We restrict the term to inland 

waters where the ratios of the salts often vary; the term haline is applied to 

coastal waters where the salts are roughly in the same proportion as found 

in undiluted sea water. 

Salinity Total amount of solid material in grams contained in 1 kg of water when all 

the carbonate has been converted to oxide, the bromine and iodine 

replaced by chlorine, and all the organic matter completely oxidized. 

Salt water Water with a dissolved salt concentration measuring at least 0.5 ppt. 

Sand Unconsolidated mineral sediment composed predominantly of particles with 

diameters larger than 0.074 mm (Black 1968) and smaller than 2 mm (Liu 

1970; Weber 1973). 

Shrub Woody plant that at maturity is less than 6 m (20 ft) tall and generally 

exhibits several erect, spreading, or prostrate stems and has a bushy 

appearance; e.g., speckled alder (Alnus rugosa) or buttonbush 

(Cephalanthus occidentalis). 

Silt Mineral particles smaller than a very fine sand grain (0.05 mm) and larger 

than coarse clay (0.002 mm). 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

62 

Term Definition 

Soil “Natural body comprised of solids (minerals and organic matter), liquid, and 

gases that occurs on the land surface, occupies space, and is 

characterized by one or both of the following: horizons, or layers, that are 

distinguishable from the initial material as a result of additions, losses, 

transfers, and transformations of energy and matter or the ability to support 

rooted plants in a natural environment” (Soil Survey Staff 1999:9). Areas 

covered by surface water more than 2.5 m (8.2 ft) deep at low water are not 

considered to have soil. 

Sound Body of water that is usually broad, elongate, and parallel to the shore 

between the mainland and one or more islands. 

Spring tide Highest high and lowest low tides during the lunar month. 

Stone Rock fragment larger than 25.4 cm (10 inches) but less than 60.4 cm (24 

inches). 

Submergent plant Vascular or nonvascular hygrophyte, either rooted or nonrooted, which lies 

entirely beneath the water surface, except for flowering parts in some 

species; e.g., wild celery (Vallisneria americana) or the stoneworts (Chara 

spp.). 

Substrate Any material at the land surface upon which, or within which, organisms 

may live. In this document, substrates consist primarily of unconsolidated 

mineral material, organic material, or rock that is flooded or saturated long 

enough each year to support wetland flora and fauna. Individual substrates 

may or may not qualify as Soil (see definition above). 

Terrigenous Derived from or originating on the land (usually referring to sediments) as 

opposed to material or sediments produced in the ocean (marine) or as a 

result of biologic activity (biogenous). 

Tree Woody plant which, at maturity, is 6 m (20 ft) or more in height and 

generally has a single trunk, unbranched for 1 m or more above the 

ground, and a more or less definite crown; e.g., red maple (Acer rubrum), 

northern white cedar (Thuja occidentalis). 

Water table Upper surface of a zone of saturation. No water table exists where that 

surface is formed by an impermeable body (Langbein and Iseri 1960:21). 

Woody plant Seed plant (gymnosperm or angiosperm) that develops persistent, hard, 

fibrous tissues, basically xylem; e.g., trees and shrubs. 

Xerophyte, 

xerophytic 

Any plant growing in a habitat in which an appreciable portion of the rooting 

medium dries to the wilting coefficient at frequent intervals; plants typically 

found in very dry habitats. 

 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix A (Informative): Glossary of Technical Terms, Acronyms, and Abbreviations 

 _____________________________________________________________________________________ 

63 

Acronyms and Abbreviations 

Acronym Definition 

AASHTO American Association of State Highway and Transportation Officials 

BBC Benthic Biotic Component 

CMECS Coastal and Marine Ecological Classification Standard 

EAs environmental assessments 

EHWS extreme high water of spring tides 

EIS environmental impact statements 

ELWS extreme low water of spring tides 

FGDC Federal Geographic Data Committee 

ha hectare 

m meter 

MIT Massachusetts Institute of Technology 

NHD National Hydrography Dataset 

NRCS Natural Resources Conservation Service; formerly named Soil Conservation 

Service 

NSDI National Spatial Data Infrastructure 

NWI National Wetlands Inventory 

ppt parts per thousand 

U.S. United States 

USDA United States Department of Agriculture 

USFWS United States Fish and Wildlife Service 

USGS United States Geological Survey 

NOAA National Oceanographic and Atmospheric Administration 

WCS Wetlands Classification Standard, also known as the FGDC Wetlands 

Classification Standard (FGDC-STD-004), “Classification of Wetlands and 

Deepwater Habitats of the United States” 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix B (Informative): Artificial Keys to the Systems and Classes 

 _____________________________________________________________________________________ 

64 

APPENDIX B (Informative): Artificial Keys to the 

Systems and Classes 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix B (Informative): Artificial Keys to the Systems and Classes 

 _____________________________________________________________________________________ 

65 

Artificial Key to the Systems 

1. Water Regime influenced by ocean tides, and salinity due to ocean-derived salts 0.5 

ppt or greater. 

2. Semi-enclosed by land, but with open, partly obstructed or sporadic access to the 

ocean. Halinity wide-ranging because of evaporation or mixing of seawater with 

runoff from land .................................................................................. ESTUARINE 

2. Little or no obstruction to open ocean present. Halinity usually euhaline; little 

mixing of water with runoff from land ....................................................................3 

3. Emergents, trees, or shrubs present ............................................... ESTUARINE 

3. Emergents, trees, or shrubs absent ....................................................... MARINE 

1. Water Regime not influenced by ocean tides, or if influenced by ocean tides, salinity 

less than 0.5 ppt. 

4. Persistent emergents, trees, shrubs, or emergent mosses or lichens cover 30 

percent or more of the area ............................................................... PALUSTRINE 

4. Persistent emergents, trees, shrubs, or emergent mosses or lichens cover less than 

30 percent of substrate but nonpersistent emergents may be widespread during 

some seasons of year ................................................................................................5 

5. Situated in a channel; water, when present, usually flowing ............ RIVERINE 

5. Situated in a basin, catchment, or on level or sloping ground; water usually 

not flowing .........................................................................................................6 

6. Area 8 ha (20 acres) or greater .............................................. LACUSTRINE 

6. Area less than 8 ha .......................................................................................7 

7. Wave-formed or bedrock shoreline feature present or water depth 2.5 

m (8.2 ft) or more ............................................................ LACUSTRINE 

7. No wave-formed or bedrock shoreline feature present and water less 

than 2.5-m deep ............................................................... PALUSTRINE 

Artificial Key to the Classes 

1. During the growing season of most years, areal cover by vegetation is less than 30 

percent. 

2. Substrate a ridge or mound formed by colonization of sedentary invertebrates 

(corals, mollusks, tube worms) ........................................................................ REEF 

2. Substrate of rock or various-sized sediments often occupied by invertebrates but 

not formed by colonization of sedentary invertebrates ............................................3 

3. Water Regime Subtidal, Permanently Flooded, Intermittently Exposed, 

Semipermanently Flooded, Permanently Flooded-Tidal Fresh, or 

Semipermanently Flooded-Tidal Fresh. .............................................................4 

4. Substrate of bedrock, boulders, or stones occurring singly or in 

combination covers 75 percent or more of the area ..........ROCK BOTTOM 

4. Substrate of organic material, mud, sand, gravel, or cobbles with less than 

75 percent areal cover of stones, boulders, or bedrock 

................................................................. UNCONSOLIDATED BOTTOM 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix B (Informative): Artificial Keys to the Systems and Classes 

 _____________________________________________________________________________________ 

66 

3. Water Regime Irregularly Exposed, Regularly Flooded, Irregularly Flooded, 

Seasonally Flooded, Seasonally Flooded-Saturated, Temporarily Flooded, 

Intermittently Flooded, Artificially Flooded, Regularly Flooded-Tidal Fresh, 

Seasonally Flooded-Tidal Fresh, or Temporarily Flooded-Tidal Fresh. ...........5 

5. Contained in a channel that does not have continuously flowing water (i.e., 

Intermittent Subsystem of Riverine System or Intertidal Subsystem of 

Estuarine System) ................................................................. STREAMBED 

5. Contained in a channel with continuously flowing water or not contained 

in a channel .................................................................................................6 

6. Substrate of bedrock, boulders, or stones occurring singly or in 

combination covers 75 percent or more of the area .... ROCKY SHORE 

6. Substrate of organic material, mud, sand, gravel, or cobbles; less than 

75 percent areal cover of stones, boulders, or bedrock 

............................................................... UNCONSOLIDATED SHORE 

1. During the growing season of most years, percentage of area covered by vegetation 

30 percent or greater. 

7. Vegetation composed of pioneer annuals or seedling perennials, often not 

hydrophytes, occurring only at time of substrate exposure .....................................8 

8. Contained in a channel that does not have continuously flowing water 

.......................................................................... STREAMBED (VEGETATED) 

8. Contained in a channel with continuously flowing water, or not contained in a 

channel .................................. UNCONSOLIDATED SHORE (VEGETATED) 

7. Vegetation composed of algae, mosses, lichens, or vascular plants that are usually 

hydrophytic perennials .............................................................................................9 

9. Vegetation composed predominantly of nonvascular species .........................10 

10. Vegetation macrophytic algae, mosses, or lichens growing in water or the 

splash zone of shores ..........................................................AQUATIC BED 

10. Vegetation mosses or lichens usually growing on organic soils and always 

outside the splash zone of shores ................... MOSS-LICHEN WETLAND 

9. Vegetation composed predominantly of vascular species ...............................11 

11. Vegetation herbaceous ...............................................................................12 

12. Vegetation emergents .................................... EMERGENT WETLAND 

12. Vegetation submergent, floating-leaved, or floating ....AQUATIC BED 

11. Vegetation trees or shrubs ..........................................................................13 

13. Dominants less than 6 m (20 ft) tall ........ SCRUB-SHRUB WETLAND 

13. Dominants 6 m tall or taller ............................ FORESTED WETLAND
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix C (Informative): Scientific and Common Names of Plants 

 _____________________________________________________________________________________ 

67 

APPENDIX C (Informative): Scientific and Common 

Names of Plants 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix C (Informative): Scientific and Common Names of Plants 

 _____________________________________________________________________________________ 

68 

Scientific and Common Names of Plants1

Scientific Name Common Name 

Acer rubrum L. Red maple 

Alnus spp. Alders 

Andromeda polifolia L. Bog rosemary 

Ascophyllum spp. Rockweeds 

Avicennia germinans (L.) L. Black mangrove 

Azolla spp. Mosquito ferns 

Baccharis halimifolia L. Groundsel tree 

Beckmannia syzigachne (Steud.) Fernald American slough grass 

Betula nana L. Swamp birch 

B. pumila L. Bog birch 

Brasenia schreberi J. F. Gmel. Water shield 

Campylium stellatum (Hedw.) C. Jens Moss 

Carex spp. Sedges 

Caulerpa spp. Green algae 

Cephalanthus occidentalis L. Common buttonbush 

Ceratophyllum muricatum Prickly hornwort 

Chamaecyparis thyoides (L.) B.S.P. Atlantic white cedar 

Chamaedaphne calyculata (L.) Moench Leatherleaf 

Chara spp. Stoneworts 

Chenopodium glaucum L. Oak-leaf goosefoot 

Chiloscyphus fragilis (Roth) Schiffn. Liverwort 

Cladina spp. Reindeer mosses 

Cladium mariscus (L.) Pohl. Swamp saw-grass 

Conocarpus erectus L. Button mangrove 

Cornus alba L. Red osier dogwood 

Cymodocea filiformis (Kuetz) Correll Manatee grass 

Cyrilla racemiflora L. Swamp titi 

 

1 Lichvar, R. W., and J. T. Kartesz. 2009. North American Digital Flora: National Wetland Plant List, version 

2.4.0 (http://wetland_plants.usace.army.mil). U.S. Army Corps of Engineers, Engineer Research and 

Development Center, Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, and 

BONAP, Chapel Hill, North Carolina.
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix C (Informative): Scientific and Common Names of Plants 

 _____________________________________________________________________________________ 

69 

Scientific Name Common Name 

Decodon verticillatus (L.) Elliott Swamp loosestrife 

Dermatocarpon fluviatile (G. H. Web) Th. Fr. Lichen 

Drepanocladus spp. Mosses 

Echinochloa crusgalli (L.) Beauv. Large barnyard grass 

Eichhornia crassipes (Mart.) Solms Common water hyacinth 

Eleocharis spp. Spike rushes 

Elodea spp. Water weeds 

Fissidens spp. Mosses 

F. julianus (Mont.) Schimper Moss 

Fontinalis spp. Mosses 

Fraxinus nigra Marshall Black ash 

F. pennsylvanica Marshall Green ash 

Fucus spp. Rockweeds 

F. spiralis L. Rockweed 

Glyceria spp. Manna grasses 

Gordonia lasianthus (L.) J. Ellis Loblolly bay 

Halimeda spp. Green algae 

Halodule wrightii Aschers. Shoal grass 

Halophila spp. Sea grasses 

Iva frutescens L. High-tide bush 

Juncus spp. Rushes 

J. militaris Bigel. Bayonet rush 

J. roemerianus Scheele Roemer's rush 

Kalmia polifolia Wangenh. Bog laurel 

Laminaria spp. Kelps 

Languncularia racemosa (L.) C. F. Gaertn. White mangrove 

Larix laricina (DuRoi) K. Koch American larch 

Laurencia spp. Red algae 

Ledum groenlandicum Oeder Rusty Labrador-tea 

Lemna spp. Duckweeds 

L. minor L. Common duckweed 

Leucothoe axillaris (Lam.) D. Don Coastal doghobble 

Lithothamnion spp. Coralline algae 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix C (Informative): Scientific and Common Names of Plants 

 _____________________________________________________________________________________ 

70 

Scientific Name Common Name 

Lyonia lucida (Lam.) K. Koch Shinyleaf 

Lythrum salicaria L. Purple loosestrife 

Macrocystis spp. Kelps 

Magnolia virginiana L. Sweet bay 

Marsupella spp. Liverworts 

M. emarginata (Ehrenberg) Dumortier Liverwort 

Myriophyllum spp. Water milfoils 

Najas spp. Naiads 

Nitella spp. Stoneworts 

Nuphar lutea (L.) Sibth. & J. E. Smith Yellow water lily 

Nymphaea spp. Water lilies 

N. odorata Soland. in Ait. White water lily 

Nyssa sylvatica Marshall Black tupelo 

Oncophorus wahlenbergii Brid. Moss 

Panicum capillare L. Common panic grass 

Peltandra virginica (L.) Schott Green arrow-arum 

Pelvetia spp. Rockweeds 

Penicillus spp. Green algae 

Persea borbonia (L.) Spreng. Red bay 

Persicaria amphibia (L.) S. F. Gray Water smartweed 

Phyllospadix scouleri Hook. Scouler's surf-grass 

P. torreyi S. Wats. Torrey's surf-grass 

Picea mariana (Mill.) B.S.P. Black spruce 

Pistia stratiotes L. Water lettuce 

Polygonum spp. Smartweeds 

Pontederia cordata L. Pickerelweed 

Potamogeton spp. Pondweeds 

Quercus bicolor Willd. Swamp white oak 

Q. lyrata Walter Overcup oak 

Q. michauxii Nutt. Swamp chestnut oak 

Rumex mexicanus Meisn. Mexican dock 

Ruppia spp. Ditch grasses 

R. maritima L. Widgeon grass 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix C (Informative): Scientific and Common Names of Plants 

 _____________________________________________________________________________________ 

71 

Scientific Name Common Name 

Sagittaria spp. Arrowheads 

Salicornia spp. Glassworts 

S. depressa Standl. Woody saltwort 

Salix spp. Willows 

Salvinia spp. Water mosses 

Schoenoplectus acutus (Muhl. ex Bigelow) A. & D.

Love Hardstem club-rush 

Scirpus spp. Bulrushes 

Scolochloa festucacea (Willd.) Link Common river grass 

Sparganium hyperboreum Beurling ex Laestad. Bur-reed 

Spartina alterniflora Loiseleur Saltmarsh cordgrass 

S. cynosuroides (L.) Roth Big cordgrass 

S. foliosa Trin. California cordgrass 

S. patens (Ait.) Muhl. Saltmeadow cordgrass 

Sphagnum spp. Peat mosses 

Spiraea douglasii Hook. Douglas' meadowsweet 

Spirodela spp. Big duckweeds 

Suaeda californica S. Wats. Broom seepweed 

Tamarix gallica L. French tamarisk 

Taxodium distichum (L.) L. C. Rich. Southern bald-cypress 

Thalassia testudinum Banks & Soland. ex Koenig Turtle grass 

Thuja occidentalis L. Eastern arborvitae 

Tolypella spp. Stoneworts 

Trapa natans L. Water chestnut 

Triglochin maritima L. Seaside arrow-grass 

Typha spp. Cattails 

T. angustifolia L. Narrow-leaved cattail 

T. latifolia L. Broad-leaved cattail 

Ulmus americana L. American elm 

Ulva spp. Sea lettuces 

Utricularia spp. Bladderworts 

Vaccinium oxycoccos L. Small cranberry 

Vallisneria americana Michx. Wild celery 

Verrucaria spp. Lichens 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix C (Informative): Scientific and Common Names of Plants 

 _____________________________________________________________________________________ 

72 

Scientific Name Common Name 

Wolffia spp. Watermeals 

Xanthium strumarium L. Rough cocklebur 

Zannichellia palustris L. Horned pondweed 

Zenobia pulverulenta (W. Bartram) Pollard Honeycup 

Zizaniopsis miliacea (Michx.) Doell & Aschers. Marsh-millet 

Zostera marina L. Eelgrass 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix D (Informative): Scientific and Common Names of Animals 

_____________________________________________________________________________________ 

73 

APPENDIX D (Informative): Scientific and Common 

Names of Animals 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix D (Informative): Scientific and Common Names of Animals 

_____________________________________________________________________________________ 

74 

Scientific and Common Names of Animals1

Scientific Name Common Name 

Acmaea spp. Limpets 

Acropora spp. Staghorn corals 

Agrenia spp. Springtails 

Amphipholis spp. Brittle stars 

Amphitrite spp. Terebellid worms 

Ancylus spp. Freshwater limpets 

Anodonta spp. Freshwater mussels 

Anodontoides spp. Freshwater mussels 

Anopheles spp. Mosquitoes 

Aplexa spp. Pouch snails 

Arenicola spp. Lugworms 

Asellus spp. Aquatic sowbugs 

Baetis spp. Mayflies 

Balanus spp. Acorn barnacles 

Bryocamptus spp. Harpacticoid copepods 

Caenis spp. Mayflies 

Callianassa spp. Ghost shrimp 

Crassostrea spp. Oysters 

C. virginica (Geml.) Eastern oyster 

Dendraster spp. Sand dollars 

Diamesa spp. Midges 

Donax spp. Wedge bean clams 

Echinocardium spp. Heart urchins 

Elliptio spp. Freshwater mussels 

Emerita spp. Mole crabs 

Ephemerella spp. Mayflies 

Erpobdella spp. Leeches 

Eukiefferiella spp. Midges 

Eunapius spp. Freshwater sponges 

Euzonus spp. Blood worms 

Gammarus spp. Scuds 

Gelastocoris spp. Toad bugs 

Gordonia ventalina L. Common sea fans 

 

1

 Scientific names validated against the Integrated Taxonomic Information System (ITIS) on 2/17/2012 at 

http://www.itis.gov/. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix D (Informative): Scientific and Common Names of Animals 

_____________________________________________________________________________________ 

75 

Scientific Name Common Name 

Helobdella spp. Leeches 

Heteromeyenia spp. Horse sponges 

Hippospongia spp. Encrusting sponges 

Homarus americanus Milne-Edwards American lobster 

Hydropsyche spp. Caddisflies 

Lampsilis spp. Freshwater mussel 

Ligia spp. Sea slaters 

Limnodrilus spp. Oligochaete black worms 

Littorina spp. Periwinkles 

Lumbriculus spp. Oligochaete worms 

Lymnaea spp. Pond snails 

Macoma spp. Macomas 

M. balthica (Linne) Baltic macoma 

Melita spp. Amphipods 

Mercenaria spp. Quahogs 

Modiolus spp. Horse mussels 

Montipora spp. Corals 

Muricea spp. Sea whips 

Mya spp. Soft-shell clams 

Mytilus spp. Mussels 

Nassarius spp. Sand snails 

Nemoura spp. Stone flies 

Nereis spp. Clam worms 

Nerita spp. Black nerites 

Notonecta spp. Common backswimmers 

Oliva spp. Olive shells 

Orchestia spp. Beach sand fleas 

Ostrea spp. Oysters 

Parastenocaris spp. Copepods 

Patella spp. Limpets 

Pecten spp. Scallops 

Petricola pholadiformis Lam. False angel wings 

Phyllognathopus viguieri Maryek Copepod 

Physa spp. Bladder snail 

Pisaster spp. Sea stars 

Pisidium spp. Fingernail clams 

Placopecten spp. Deep-sea scallops 

Platyodon spp. Boring clams 

Pollicipes spp. Gooseneck barnacles 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix D (Informative): Scientific and Common Names of Animals 

_____________________________________________________________________________________ 

76 

Scientific Name Common Name 

Porites spp. Finger corals 

Pristina spp. Oligochaete worms 

Procambarus spp. Crayfish 

Psephenus spp. Water penny beetles 

Renilla spp. Sea pansies 

Sabellaria spp. Encrusted sand tubeworms 

Saldula spp. Shore bugs 

Saxidomus spp. Venus clams 

Simulium spp. Black flies 

Siphonaria spp. False limpets 

Sphaerium spp. Fingernail clams 

Spongilla spp. Freshwater sponges 

Strongylocentrotus spp. Sea urchins 

Tabanus spp. Flies 

Tellina spp. Tellin shells 

Tetraclita spp. Thatched barnacles 

Thais spp. Rock snails 

Thyone spp. Sea cucumbers 

Tivela stultorum (Mawe) Pismo clams 

Tortopus spp. Mayflies 

Tubifex spp. Sewage worms 

Uca spp. Fiddler crabs 

Urechis spp. Echiurid worms 

 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix E (Normative): Criteria for Differentiating between Mineral Soils and Organic Soils 

_____________________________________________________________________________________ 

77 

APPENDIX E (Normative): Criteria for Differentiating between 

Mineral Soils and Organic Soils 

 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix E (Normative): Criteria for Differentiating between Mineral Soils and Organic Soils 

_____________________________________________________________________________________ 

78 

Criteria for Differentiating between Mineral Soils1 and Organic Soils 

Note: We use the Soil Modifiers, Mineral and Organic, in this classification. Mineral 

soils and organic soils are differentiated based on specific criteria that are enumerated 

in Soil Taxonomy (Soil Survey Staff 1999:19-20). These criteria are restated below for 

ready reference. If a more detailed classification is desired, the latest edition of Keys to 

Soil Taxonomy (Soil Survey Staff 2010) should be used. 

Soil taxonomy differentiates between mineral soils and organic soils. To do this, it is 

necessary to distinguish mineral soil material from organic soil material. Second, it is 

necessary to define the minimum part of a soil that should be mineral if a soil is to be 

classified as a mineral soil and the minimum part that should be organic if the soil is to be 

classified as an organic soil. 

Nearly all soils contain more than traces of both mineral and organic components in some 

horizons, but most soils are dominantly one or the other. The horizons that are less than 

about 20 to 35 percent organic matter, by weight, have properties that are more nearly 

those of mineral than of organic soils. Even with this separation, the volume of organic 

matter at the upper limit exceeds that of the mineral material in the fine-earth fraction. 

Mineral Soil Material 

Mineral soil material (less than 2.0 mm in diameter) either: 

1. Is saturated with water for less than 30 days (cumulative) per year in normal years 

and contains less than 20 percent (by weight) organic carbon; or 

2. Is saturated with water for 30 days or more cumulative in normal years (or is 

artificially drained) and, excluding live roots, has an organic carbon content (by 

weight) of: 

a. Less than 18 percent if the mineral fraction contains 60 percent or more clay; or 

b. Less than 12 percent if the mineral fraction contains no clay; or 

c. Less than 12 + (clay percentage multiplied by 0.1) percent if the mineral fraction 

contains less than 60 percent clay. 

Organic Soil Material 

Soil material that contains more than the amounts of organic carbon described above for 

mineral soil material is considered organic soil material. 

 

1

 Mineral soils include all soil except the suborder Histels and the order Histosols. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix E (Normative): Criteria for Differentiating between Mineral Soils and Organic Soils 

_____________________________________________________________________________________ 

79 

In the definition of mineral soil material above, material that has more organic carbon 

than in item 1 is intended to include what has been called litter or an O horizon. Material 

that has more organic carbon than in item 2 has been called peat or muck. Not all organic 

soil material accumulates in or under water. Leaf litter may rest on a lithic contact and 

support forest vegetation. The soil in this situation is organic only in the sense that the 

mineral fraction is appreciably less than half the weight and is only a small percentage of 

the volume of the soil. 

Distinction between Mineral Soils and Organic Soils 

Most soils are dominantly mineral material, but many mineral soils have horizons of 

organic material. For simplicity in writing definitions of taxa, a distinction between what 

is meant by a mineral soil and an organic soil is useful. To apply the definitions of many 

taxa, one must first decide whether the soil is mineral or organic. An exception is the 

Andisols (defined later). These generally are considered to consist of mineral soils, but 

some may be organic if they meet other criteria for Andisols. Those that exceed the 

organic carbon limit defined for mineral soils have a colloidal fraction dominated by 

short-range-order minerals or aluminum-humus complexes. The mineral fraction in these 

soils is believed to give more control to the soil properties than the organic fraction. 

Therefore, the soils are included with the Andisols rather than the organic soils defined 

later as Histosols. 

If a soil has both organic and mineral horizons, the relative thickness of the organic and 

mineral soil materials must be considered. At some point one must decide that the 

mineral horizons are more important. This point is arbitrary and depends in part on the 

nature of the materials. A thick layer of sphagnum has a very low bulk density and 

contains less organic matter than a thinner layer of well-decomposed muck. It is much 

easier to measure the thickness of layers in the field than it is to determine tons of organic 

matter per hectare. The definition of a mineral soil, therefore, is based on thickness of the 

horizons, or layers, but the limits of thickness must vary with the kinds of materials. The 

definition that follows is intended to classify as mineral soils those that have both thick 

mineral soils layers and no more organic material than the amount permitted in the histic 

epipedon, which is defined in chapter 4. 

In the determination of whether a soil is organic or mineral, the thickness of horizons is 

measured from the surface of the soil whether that is the surface of a mineral or an 

organic horizon, unless the soil is buried as defined in chapter 1. Thus, any O horizon at 

the surface is considered an organic horizon if it meets the requirements of organic soil 

material as defined later, and its thickness is added to that of any other organic horizons 

to determine the total thickness of organic soil materials. 

Definition of Mineral Soils 

Mineral soils are soils that have either of the following: 

1. Mineral soil materials that meet one or more of the following: 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix E (Normative): Criteria for Differentiating between Mineral Soils and Organic Soils 

_____________________________________________________________________________________ 

80 

a. Overlie cindery, fragmental, or pumiceous materials and/or have voids2

 that are 

filled with 10 percent or less organic materials and directly below these materials 

have either a densic, lithic, or paralithic contact; or 

b. When added with underlying cindery, fragmental, or pumiceous materials, total 

more than 10 cm between the soil surface and a depth of 50 cm; or 

c. Constitute more than one-third of the total thickness of the soil to a densic, lithic, 

or paralithic contact or have a total thickness of more than 10 cm; or 

d. If they are saturated with water for 30 days or more per year in normal years (or 

are artificially drained) and have organic materials with an upper boundary within 

40 cm of the soil surface, have a total thickness of either: 

(1) Less than 60 cm if three-fourths or more of their volume consists of moss 

fibers or if their bulk density, moist, is less than 0.1 g/cm3 or 

(2) Less than 40 cm if they consist either of sapric or hemic materials, or of fibric 

materials with less than three-fourths (by volume) moss fibers and a bulk density, 

moist, of 0.1 g/cm3 or more; or 

2. More than 20 percent, by volume, mineral soil materials from the soil surface to a 

depth of 50 cm or to a glacic layer or a densic, lithic, or paralithic contact, 

whichever is shallowest; and 

a. Permafrost within 100 cm of the soil surface; or 

b. Gelic materials within 100 cm of the soil surface and permafrost within 200 cm 

of the soil surface. 

 

 

2

 Materials that meet the definition of cindery, fragmental, or pumiceous but have more than 10 percent, by 

volume, voids that are filled with organic soil materials are considered to be organic soil materials. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix E (Normative): Criteria for Differentiating between Mineral Soils and Organic Soils 

_____________________________________________________________________________________ 

81 

Definition of Organic Soils 

Organic soils have organic soil materials that: 

1. Do not have andic soil properties in 60 percent or more of the thickness between the 

soil surface and either a depth of 60 cm or a densic, lithic, or paralithic contact or 

duripan if shallower; and

2. Meet one or more of the following: 

a. Overlie cindery, fragmental, or pumiceous materials and/or fill their interstices 

and directly below these materials have a densic, lithic, or paralithic contact; or

b. When added with the underlying cindery, fragmental, or pumiceous materials, 

total 40 cm or more between the soil surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of the soil to a densic, lithic, 

or paralithic contact and have no mineral horizons or have mineral horizons with a 

total thickness of 10 cm or less; or 

d. Are saturated with water for 30 days or more per year in normal years (or are 

artificially drained), have an upper boundary within 40 cm of the soil surface, and 

have a total thickness of either: 

(1) 60 cm or more if three-fourths or more of their volume consists of moss fibers 

or if their bulk density, moist, is less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or hemic materials, or of fibric 

materials with less than three-fourths (by volume) moss fibers and a bulk density, 

moist, of 0.1 g/cm3 or more; or

e. Are 80 percent or more, by volume, from the soil surface to a depth of 50 cm or 

to a glacic layer or a densic, lithic, or paralithic contact, whichever is shallowest. 

It is a general rule that a soil is classified as an organic soil (Histosol) if more than half of 

the upper 80 cm (32 in) of the soil is organic or if organic soil material of any thickness 

rests on rock or on fragmental material having interstices filled with organic materials.
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix F (Informative): Regionalization for the Classification System 

_____________________________________________________________________________________ 

82 

APPENDIX F (Informative): Regionalization for 

the Classification System 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix F (Informative): Regionalization for the Classification System 

_____________________________________________________________________________________ 

83 

Regionalization for the Classification System 

In this wetlands and deepwater classification, a given taxon has no particular regional 

alliance; its representatives may be found in one or many parts of the U.S. However, 

regional variations in climate, geology, soils, and vegetation are important in the 

development of different habitats, and management problems often differ greatly among 

regions. For these reasons, there is a need to recognize regional differences. 

Regionalization is designed to facilitate three activities: (1) planning, where it is 

necessary to study management problems and potential solutions on a regional basis; (2) 

organization and retrieval of data gathered in a resource inventory; and (3) interpretation 

of inventory data, including differences in indicator plants and animals among the 

regions. 

In 1977 the USFWS adopted Bailey’s (1976) ecoregions to give the inland wetlands and 

deepwater habitats of the United States an ecological address (see Cowardin et al. 1979). 

In this Standard, the 1995 version of Bailey’s system is to be used wherever there is a 

need for regionalization in the U.S. interior (see 

http://www.fs.fed.us/rm/ecoregions/products/map-ecoregions-united-states#). 

Bailey's approach is based on understanding the role of climate in ecosystem 

differentiation. To a considerable extent, climatic factors determine the boundaries of 

ecosystems at all scales. This will be more important going forward. The most important 

of these is climatic regime, defined as the diurnal and seasonal fluxes of energy and 

moisture. As these fluxes change, the kinds and patterns of dominant life forms of plants 

and animals change and, over the course of centuries, the kinds of soils and water bodies. 

As a result, ecosystems of different climates differ significantly. The areas they occupy 

are not terrestrial or aquatic, but geographical, ecosystem units. Controls over the 

climatic effect change with scale. Understanding these controlling factors on a scalerelated basis is key to setting ecosystem boundaries. 

As with the wetlands and deepwater classification system, Bailey’s classification of 

ecoregions is hierarchical. The upper four levels are domain (defined as including 

subcontinental areas of related climates), division (defined as including regional climate 

at the level of Köppen’s [1931] types), province (defined as including broad plant 

formations), and section (defined on the basis of physiography by Bailey et al. [1994] and 

revised by Cleland et al. [2005] for the conterminous U.S. and Nowacki and Brock 

[1995] for Alaska). Mountainous provinces and sections exhibiting altitudinal zonation 

and having the climatic regime of the adjacent lowlands are distinguished according to 

the character of the zonation. On the map, ecoregion sections within each ecoregion 

province are shown in the same color and the sections are numbered with an 

alphanumeric code; numbers 1 through 3 represent the first three levels in the hierarchy. 

The numbers are followed by a capital letter representing the fourth level. The codes for 

mountains are preceded by the letter “M.” The reader is referred to Bailey (1995, 2005) 

and McNab et al. (2005) for detailed discussion and description of the units appearing on 

this map, reproduced in Figure 7. 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix F (Informative): Regionalization for the Classification System 

_____________________________________________________________________________________ 

84 

Figure 7. Ecoregions of the United States.
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix G (Informative): Wetland Image Gallery 

_____________________________________________________________________________________ 

85 

APPENDIX G (Informative): Wetland Image Gallery 
Federal Geographic Data Committee FGDC-STD-004-2013 

Classification of Wetlands and Deepwater Habitats 

Appendix G (Informative): Wetland Image Gallery 

_____________________________________________________________________________________ 

86 

Wetland Image Gallery

http://www.wetlandgallery.cnlworld.org 

The Wetland Image Gallery is a compilation of images that illustrate the types of 

wetlands and deepwater habitats in the United States. Established in 2010, it helps users 

to visualize, and better understand, the great diversity of wet habitats in this country. The 

general public, government personnel, wetland scientists, geographers, environmentalists, 

and other interested parties may contribute to the Wetland Image Gallery. This is a 

crowd-sourcing source effort, with all of its inherent advantages and disadvantages. The 

intent is to continuously update and add new images to complement the Wetlands 

Classification Standard (FGDC-STD-004-2013), the Wetlands Mapping Standard 

(FGDC-STD-015-2009) and the National Wetlands Inventory’s Data Collection 

Requirements and Procedures document (Dahl et al. 2009).