Description: FW 1, National Wetlands Inventory

FWM#:      328 (replaces 660 FW 3, FWM 220, 10/5/95)
Date:         April 6, 1998
Series:       Special Programs
Part 905:   Habitat Mapping
Originating Office: Division of Habitat Conservation

1.1 Purpose. This chapter provides guidance for conducting habitat mapping by the National Wetlands Inventory.

1.2 Objectives. The objectives of the NWI are to:

A. Produce detailed maps of the characteristics and extent of the Nation's wetlands.

B. Construct a national digital wetlands map data base.

C. Archive and make available for dissemination all maps and digital wetlands data.

D. Prepare reports (with outside funding) summarizing results of State wetlands inventories.

E. Report to Congress statistically accurate national data on wetland status and trends.

F. Assemble and distribute information, such as wetland maps, digital data, lists of plants that occur in wetlands, and other wetland topics.

1.3 Background.

A. NWI Overview. The operational phase of the NWI, initiated on October 1, 1979, involves wetland mapping and status and trends analysis.

(1) Mapping.

(a) The primary products of the NWI are large-scale (1:24,000) maps that show the location, shape, and characteristics of wetlands and deepwater habitats on U.S. Geological Survey base topographic maps. Smaller scale maps are sometimes prepared in tundra regions of Alaska and in desert regions of the arid west. Maps are used by local, State, and Federal agencies; private industry; and organizations in numerous applications including comprehensive resource management plans, impact assessments, facility and corridor siting, oil spill contingency plans, natural resource inventories, and habitat surveys.

(b) Mapping priorities depend on the availability of funds and high quality aerial photography.

(2) Status and Trends

(a) National estimates of the wetland status and trends (i.e., losses and gains), developed through statistical sampling, are made at approximately 10-year intervals contingent on funding. These estimates are used to evaluate the effectiveness of Federal programs and policies, identify national or regional problems, and increase public awareness.

B. Relationship to Wetland Regulation. Federal, State, and local regulatory agencies with jurisdiction over wetlands may define and describe wetlands in different manners and extent for regulatory purposes than that used in the NWI. There is no attempt, in either design or products of this inventory, to define the limits of proprietary jurisdiction of any Federal, State, or local government or to establish the geographic 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, State, or local agencies concerning specific agency regulatory programs and proprietary jurisdictions that may affect such activities.

1.4 Authority. Authority for NWI activities is contained in the Emergency Wetlands Resources Act of 1986; the Wild Bird Conservation Act; the Coastal Wetlands Planning, Protection, and Restoration Act; and the Clean Water Act. Associated NWI ongoing activities are as follows:

A. Section 401(a) of the Emergency Wetlands Resources Act of 1986 (EWRA) (Public Law 99-645). Title IV - Wetlands Inventory and Trend Analysis as amended by Section 305 of the Wild Bird Conservation Act (WBCA) of 1992 (Public Law 102-440).

(1) Section 401(a) of the EWRA. Requires the Secretary of the Interior, acting through the Director of the Service, to continue the NWI project and:

(a) Produce by September 30, 1998, NWI maps for those portions of the contiguous United States for which final maps have not been produced earlier; and

(b) Produce by September 30, 1990, and at 10-year intervals thereafter, reports to update and improve the information on national wetlands trends.

(2) Section 305 of the WBCA. Amends Section 401(a) of the EWRA to require that NWI:

(a) Produce, by September 30, 2000, NWI maps for Alaska and other noncontiguous portions of the United States; and

(b) Produce, by September 30, 2004, a digital wetlands data base for the United States based on the final wetlands maps produced under this section; and

(c) Archive and make available for dissemination wetlands data and maps digitized under this section as such data and maps become available.

B. Additional Authorizations.

(1) Coastal Wetlands Planning, Protection and Restoration Act, Section 305, National Coastal Wetlands Conservation, Grants Program. Wetlands Assessment section requires that the Director of the Service, with funds made available in accordance with Section 306 of the Act, direct the NWI to:

(a) Update and digitize wetlands maps in the State of Texas.

(b) Conduct an assessment of the status, condition, and trends of wetlands in that State.

(2) Clean Water Act (33 U.S.C. Section 1288). Requires the Secretary of the Interior ". . . to complete the National Wetlands Inventory of the United States. . . and to provide information. . . to States. . . ."

C. OMB Circular A-16, Coordination of Surveying, Mapping, and Related Spatial Data. Implements the development of a national digital spatial information resource, with the involvement of Federal, State, and local governments and the private sector. In accordance with the Circular, an interagency wetlands subcommittee was established. The lead agency responsible for the coordination, management, and dissemination of wetland related data is the Department of the Interior, which delegated the authority to the Service. The Service designated the NWI to undertake the responsibilities to satisfy the requirements of Circular A-16.

1.5 Responsibility. Responsibility for NWI operations lies with Headquarters, the NWI Center in St. Petersburg, Florida, and seven Regional Offices.

A. Headquarters.

(1) The NWI Project Leader is supervised by the Chief, Division of Habitat Conservation in the Service's Ecological Services program, and coordinates budget, annual work plans, and strategic planning. The Project Leader acts as Chair of the Federal Geographic Data Committee's Wetlands Subcommittee under the authority of revised OMB Circular A-16.

(2) The NWI Center, reports to the NWI Project Leader in Headquarters and is the focal point for operational activities. The NWI Center will:

(a) Acquire all materials necessary to perform the inventory.

(b) Provide technical assistance and work materials to the Regional Wetland Coordinators.

(c) Provide oversight of the private sector support contractors responsible for map production.

(d) Investigate methods to update wetland maps in areas of rapid change; maintain standard procedures for classifying and inventorying wetlands; make information available for decision making; and evaluate NWI product use.

(e) Conduct wetland status and trends activities including updating the national study, maintaining and enhancing wetland change detection, and determining areas of wetland losses and gains to assess policy or management effectiveness.

(f) Cooperate with other Federal agencies on monitoring changes in wetland status and trends.

B. Regional Offices. NWI Regional Wetland Coordinators work under the direction of the Ecological Services program in each Service Regional Office. The Coordinators:

(1) Inventory wetlands in their Region and ensure that all NWI products meet Regional needs.

(2) Negotiate mapping contracts for wetlands photo-interpretation.

(3) Perform quality control on all photointerpretation and draft NWI mapping products.

(4) Coordinate interagency review of draft maps.

(5) Initiate regional wetlands status and trends studies to meet Regional and Agency needs.

(6) Secure funding from other agencies and develop necessary cooperative agreements.

(7) Produce Regional wetlands reports.

(8) Develop localized wetland studies.

(9) Provide technical assistance in wetlands classification, mapping, and digital data bases.

(10) Provide training in wetland classification and use of NWI products.

1.6 Standards. Standards for NWI operations are defined in five documents considered handbooks to this chapter. These standards may not be changed without approval of the Director.

A. The Service's wetlands classification system, "Classification of wetlands and deepwater habitats of the United States" by L.M. Cowardin, V. Carter, F.C. Golet, and E.T. LaRoe (1979) FWS/OBS-79/31. This system is the Federal wetlands standard.

B. "Cartographic conventions for the National Wetlands Inventory".

C. "Photointerpretation conventions for the National Wetlands Inventory."

D. "Digitizing conventions for the National Wetlands Inventory."

E. "Continuous wetland trend analysis project specifications."

1.7 Procedures for Map Production. NWI map production includes many quality control steps prior to releasing the final product:

A. Review of aerial photography or other documentation to identify obvious wetland types and problematic areas.

B. Selection of sites for possible field checking.

C. Field investigations and site-specific data collection to resolve photointerpretation questions.

D. Review of field sites on aerial photos using stereoscopic imaging.

E. Stereoscopic photointerpretation of high-altitude aerial photographs, delineation of wetland boundaries on overlays, classification of the delineated wetlands, and review of wetland information on the site.

F. Follow up field trips, if necessary.

G. Performance of Regional and national quality control of interpreted photos. National quality control is performed at the NWI Center.

H. Production of draft maps (using a standard USGS topographic map as the base) and distribution to cooperators.

I. Conduct Federal and State interagency draft map review including field checks to validate accuracy.

J. Preparation of edited draft maps.

K. Recording of metadata in the Maps Data Base. Metadata describe the content, quality, and condition of other data and are used for cataloging and data transfer. All USGS Earth Science Information Centers (ESIC) are linked to the NWI wetland maps metadata data base.

L. Production of final map.

M. Sale of maps and digital wetland data through a three-tiered system ranging from State-run distribution centers to regional centers to a national toll free number (1-800-USA-MAPS).

N. Free distribution of digital wetland maps through the NWI Home Page at

O. Provision of copies of maps to the Library of Congress.

P. Distribution of microfiche copies of NWI maps produced at the National Archives and Records Center in Seattle, Washington, to participating Map Depository Libraries.

Q. Archiving of Mylar copies of maps with the National Archives in Washington, D.C., to be kept for perpetuity.

1.8 Procedures for Map Digitizing. NWI wetland maps are digitized on a 100-percent user-pay basis by cooperators. Digital wetland file production includes several quality control checks:

A. Visual inspection of hard copy NWI maps to ensure satisfactory line work, valid wetland attributes, and edge matches between adjacent quads.

B. Determination of the appropriate digitizing method:

(1) Board digitizing method: technician performs map set-up on digitizing board, digitizes nodes and segments of each wetland feature, enters wetland attributes and adjacent features.

(2) Scanner method: scan wetlands line work overlay, convert scanned raster file (the scanning lines that form the image or the graphic output on a computer display) to vector file, edit vector file, perform edge matching between adjacent quads, add attributes to wetland features.

C. Post-processing quality control, which involves software verification of correct data structure and computer checks of data quality, generation of plot of data, and visual inspection against the hard copy NWI map, and review of attribute summary to ensure that only legal attributes are present.

D. Preparation of documentation.

E. Digital quality control, which includes identification of data structure, review of attributes, and validation of ability to convert data to other formats.

F. Archival of data to the national digital wetlands data base. Metadata are entered in the maps data base to alert USGS/ESIC offices of data availability.

G. Distribution of data including conversion to user-requested computer format, preparation of documentation, shipment to user; serving digital data on the NWI Home Page.

1.9 Procedures for Determining Status and Trends

A. Aerial photographs are delineated with a stereoscope. USGS topographic base maps (1:24,000 scale), NWI maps, soil survey maps, NOAA navigation charts, and regional/local wetland surveys are used for reference.

B. Quality control of delineated photographs is performed and selected sites are field verified.

C. Four-square-mile sample plots are produced on Mylar to overlay on USGS 1:24,000 scale base maps.

D. Plots are quality controlled to eliminate false change.

E. Wetland acreage and change data are captured.

F. Raw acreage data are added to status and trends data base.

G. Quality control checks of data entry and data structure are conducted.

H. Acreage summaries are produced.

I. A Geographic Information System may be used for further analysis and graphics display.

J. Reports are written.

K. Data are archived and updated periodically.

1.10 Reports

A. Regional and State Wetlands Reports. Wetland and deepwater habitat acreage data are compiled at the completion of wetlands mapping as funding permits. These data are used to prepare status and trends reports in specific geographic areas. The reports include descriptions of the inventory methods, wetland and deepwater habitat acreage summaries in the area (e.g., State, county, or watershed), and discussions of wetland plant communities, hydric soils, and related topics. All State, regional, or local trends studies and all wetland inventory updates are funded on a 100-percent user-pay basis by a cooperator.

B. National Reports. Statistically-based national wetlands status and trends reports are produced every 10 years as required by the EWRA (i.e., 1990, 2000, 2010 etc.). The first report was published in 1990 (Wetland Losses in the United States, 1780s to 1980s). Supplemental interpretive or analysis reports may be produced in the interim. Reports on specialized study areas may also be released as results warrant.

C. Wetland Plant List. This is a list of plant species that occur in wetlands and is used to assist in wetlands classification and in determining wetland boundaries. The list is produced by reviewing taxonomic and ecological information from numerous scientific sources such as botanical manuals and floral checklists. Information is recorded on wetland indicator, synonomy, common names, State-level distribution, and habitat. This information is compiled for each species and is then computer-entered for generation of the actual list. Candidate species for addition to or deletion from the list are submitted and evaluated by an interagency review panel. The list is available in national, regional, and State subdivisions.

1.11 Cost Sharing and Availability of Products

A. Cost Sharing . NWI will accelerate wetland mapping on a 50/50 cost-share basis for areas without existing NWI maps. In areas where photointerpretation and mapping have not been funded, all contractual and in-house costs will be covered with 50:50 cost sharing. Conversion of existing photointerpretation to draft maps will be on a 50:50 cost share basis covering all contractual and in-house costs. Draft maps will be converted to final maps on a 75:25 cost sharing basis (NWI share is 75 percent covering all contractual and in-house costs).

B. Ditigiting Final Maps. All contractual digitizing costs will be on a 100-percent user-pay basis. NWI will supply the space and staff needed for quality control and oversight. This will include contracting quality control of Other Mapping Organization (OMO) digitizing as necessary.

C. Updating Final Maps. Updating of final maps will be accomplished on a 100-percent user-pay basis covering all contractual and in-house costs. The costs for updating will be estimated on a project-by-project basis. Once the total costs of the task order are determined, a 45-percent overhead will be added to the estimate to recover the costs of the contract base, the Denver Finance Center, and administration.

D. Military Mapping. Wetland mapping on military installations will be accomplished on a 100-percent user-pay basis covering all contractual and in-house costs. The costs for this effort will be estimated on a project-by-project basis. Once the total costs of the task order are determined, a 20-percent overhead charge will be added to the estimate to recover the costs of the contract base, the Denver Finance Center, and administration.

E. Mapping Wetland versus Non-Wetland. Occasionally a cooperating agency or organization will request that habitat features other than wetlands and deepwater habitats be added to the standard NWI wetland mapping effort. In these instances the non-wetland features will be added on a 100-percent user-pay basis covering all contractual and in-house costs. The costs for this effort will be estimated on a project- by-project basis. Once the total costs of the task order are determined, a 45-percent overhead charge will be added to the estimate to recover the costs of the contract base, the Denver Finance Center, and administration (5 percent).

F. Data Applications. All publications related to application of NWI wetlands data will be maintained on a 100-percent user-pay basis covering all contractual, printing, and in-house costs. The costs for this effort will be estimated on a project-by-project basis by the Regions.

G. Map Availability. All Ecological Services offices will receive copies of draft NWI maps for field review. The offices will also receive one copy of each final map when it is completed. Beyond the initial maps, all Service users including Ecological Services offices, will be required to provide the NWI Center in St. Petersburg, Florida, with a charge number as part of their map requests. The cost of individual maps will be $5.00 for paper maps and $6.50 for Mylar. The NWI will continue to provide one copy of each final map to its cooperators. These include agencies that have cost-shared wetland map production or have provided field review of draft maps. Digital NWI maps can be obtained free of cost by offices with Internet connectivity. The URL for these maps is The NWI will provide one set of reproducible maps to State-run distribution centers. The Service, through its Regional and field offices and the NWI, will direct all other users to the State-run distribution centers or to the U.S. Geological Survey to purchase NWI maps. Information on ordering maps can be obtained by calling 1-800-USA-MAPS.

H. Report Availability.

(1) Regional and State Wetland Reports. Copies are available from the appropriate Regional Wetlands Coordinator.

(2) National Reports. Copies of the National wetland status and trends reports are available from the Service Publications Unit, Shepherdstown, West Virginia (304-876-7203). Regional and field offices also have copies. The reports are also available for sale from the Superintendent of Documents, U.S. Government Printing Office, Box 37194, Pittsburgh, Pennsylvania 15250-7954.

(3) Wetland Plant List. Copies are available from the National Wetlands Inventory, 9720 Executive Center Drive, Suite 101, St. Petersburg, Florida 33702 - 2440 (813-570-5412), or the Service Publications Unit. The final list is available on the Internet at The list is for sale from National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161 (703-487-4650). NTIS stock numbers vary depending on if a national, regional, or State list is desired. The national list is available for sale from the Superintendent of Documents (see paragraph (2) above).

For additional information regarding this policy, contact the Service National Wetlands team. For more information about  this Web page, contact Krista Bibb, in the Division of Policy and Directives Management.

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