Information Resources and Technology Management

Data Layer: WETLANDS

You are invited to read the definitions of terms used in this data standard.

Wetlands Data

Hard copy and digital wetland maps created by the U.S. Fish and Wildlife Service, Division of Habitat and Resource Conservation, Branch of Habitat Assessment, National Wetlands Inventory Project.

NOTE: The FGDC endorsed the Wetlands Mapping Standard in July 2009. The purpose of this standard is to support accurate mapping and classification of wetlands, while ensuring mechanisms for their revisions and update as directed under OMB Circular A-16, Revised. It is designed to direct the current and future digital mapping of wetlands. This mapping standard will be used for all wetland mapping nationally including Federal Agencies, States, Tribes, especially if that mapping data will be uploaded into NWI/The National Map as a data layer. Specifically, if Federal funding is involved, then use of the proposed Standard is required. For all other efforts, use of the standard is strongly encouraged. More information about the Wetlands Mapping Standard is available here.

National Standards and Quality Components For Wetlands, Deepwater and Related Habitat Mapping. 2004. U.S. Fish and Wildlife Service, Division of Habitat and Resource Conservation, Branch of Habitat Assessment, Arlington, VA. 18 pp.
Historical Data For information on past versions of this standard, contact the National Data Administrator, Geospatial and Data Services, Division of Information Resources and Technology Management.

Classification of Wetlands and Deepwater Habitats of the United States - U.S. Fish and Wildlife Service Data Standard.

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, D.C. 131 pp.

Coordination of Wetlands Data Collection:
• National Wetlands Inventory:  A Strategy for the 21st Century. 2001.  U.S. Fish and Wildlife Service, Branch of Habitat Assessment, Arlington, VA. 13 pp.
• National Standards and Quality Components For Wetlands, Deepwater and Related Habitat Mapping.  2004. U.S. Fish and Wildlife Service, Branch of Habitat Assessment, Arlington, VA. 18 pp.
• Technical Procedures for Wetland and Deepwater Habitat Mapping. 2004.  In Manuscript. U.S. Fish and Wildlife Service, Branch of Habitat Assessment, Arlington, VA. 46 pp.

National Wetlands Inventory Home Page - online maps, map information, wetland information, and more!

Use Instructions

The Service’s topical wetland maps are graphic representations of the type, size and location of wetlands and deepwater habitats in the United States. These maps, produced from the analysis of high altitude imagery, collateral data sources and field work, represent reconnaissance level information on the location, type, and size of wetlands habitats. Published wetland maps, at the nominal scale of 1:24,000 for the conterminous U.S. and 1:63,360 for Alaska, comply with National Map Accuracy Standards. Due to the margin of error inherent in the use of imagery, detailed on-the-ground inspection of any particular site may result in revision of the wetland boundaries or classification established through image analysis.

The accuracy of image interpretation depends on the quality of the imagery, experience of the image analysts, amount and quality of the collateral data, and extent of ground truth verification conducted in the field. Metadata should be consulted to determine the date of the source imagery and any problems that may have occurred during the mapping process.

Wetlands or other mapped features may have changed since the date of the imagery and/or field work. There may be occasional differences in polygon boundaries or classifications between the information depicted on the map and the actual conditions on site. 

Wetlands Master Geodatabase (MGD):  Development of a MGD stems from the Service’s need to expand and improve the availability of digital wetlands data. With the advent of computer technologies that allow the integration of large relational databases with spatial information, the MGD provides an opportunity to capitalize on years of data collection by developing scientifically sound, technologically relevant tools for analyzing, distributing, archiving and updating aquatic resource information. The MGD provides a seamless layer of digital wetlands and deepwater habitat data in a geodatabase format, i.e., a single standard projection (Albers Equal-Area Conic Projection) with horizontal planar units in meters, the North American Datum of 1983 (NAD83), and minimum coordinate precision of one centimeter. The MGD also accommodates upland(s), riparian habitats and hydrogeomorphic coding of features within the data set and provides technologically advanced mechanisms to edit, store, distribute and archive resource inventory data.
Wetland Resource Attribution and Verification Tools:  In cooperation with the U.S. Geological Survey (USGS), customized tools have been developed for resource mapping using geodatabases in ArcMap. These customized Attribution and Verification tools, installation instructions, and user information are available for download at

For the purpose of adapting the wetland classification system to map form, a series of alphanumeric codes has been developed to correspond with the classification nomenclature that best describes the habitat. The customized Attribution Tools are extensions to the Environmental Systems Research Institute, Inc. (ESRI) ArcMap desktop application for all map-based tasks including cartography, map analysis, and editing.  To run these tools, any workstation must be capable of running the ArcGIS family of software, including ArcDesktop and ArcWorkstation. 

The Attribution tools are ‘resource mapping’ tools designed to attribute map features that may depict wetlands, riparian areas, uplands or other natural resource features. These tools can also serve as a reference for uncommon or rarely used codes or to assist users who are not familiar with the alphanumeric wetland mapping codes. The main Attribution Tool contains the entire hierarchal scheme for the classification of wetlands and deepwater habitats (Cowardin et al. 1979).

The Verification tools automate (to the extent possible) the quality control functions necessary to ensure an accurate geodatabase by addressing geopositional errors, digital anomalies, and some logic checks that make use of the geographic information system.

Wetlands Mapper:  This new version of the wetlands mapping application, developed in collaboration with the USGS, promotes a greater awareness of wetlands map data applications and delivers easy-to-use, map-like views of America's wetland resources in a digital format. For ease of viewing the map information, wetland types are displayed in aggregation with similar classifications (e.g., all freshwater emergent wetlands are displayed as a single color category). The web site currently serves wetland data for 26,000 USGS quadrangles (approximately 42 percent of the conterminous U.S.) in a seamless ArcSDE geodatabase. Additional data for the entire state of Hawaii, 13 percent of Alaska, and portions of Puerto Rico and the U.S. Trust Territories will be available soon. 

FWS Created & Adopted
Approval Date
June 26, 2006
Validation Date
February 14, 2011
Data Steward
Thomas E. Dahl, Chief, National Standards and Support Team (NSST), Division of Habitat and Resource Conservation.


Last updated: August 12, 2014