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Enhancing the National Wetland Database for Landscape-Level Wetland Functional Assessment

Ralph W. Tiner 1

1. U.S. Fish & Wildlife Service, 300 Westgate Center Drive, Hadley, MA 01035

The United States has a rich geospatial database on wetlands compiled by the U.S. Fish and Wildlife Service's National Wetlands Inventory (NWI) Program. To date, the NWI has produced wetland maps for 91% of the coterminous U.S. and 35% for Alaska and has digitized 47% of the maps for the former area and 18% of the latter. The availability of digital wetland data provides an opportunity to perform preliminary assessments of wetland functions for relatively large geographic areas. The NWI has developed a set of descriptors for landscape position, landform, water flow path, and waterbody type (LLWW descriptors) to enhance NWI data and facilitate their use for watershed-level wetland assessment. From these descriptors, wetland functions are match and correlated with wetland characteristics. Ten functions evaluated to date include: 1) surface water detention, 2) streamflow maintenance, 3) nutrient transformation, 4) sediment and particulate retention, 5) coastal storm surge and shoreline stabilization, 6) inland shoreline stabilization, 7) provision of fish and shellfish habitat, 8) provision of waterfowl and waterbird habitat, 9) provision of other wildlife habitat, and 10) conservation of biodiversity. The Service has worked with state and regional wetland specialists in the Northeast to develop correlations between wetland properties in the data base on the 10 functions listed above. Over the past several years, the Service has applied these descriptors to NWI map updates in the Northeast on a pilot basis and now plans to add these descriptors to all future updates in this region, whenever possible.

Keywords: Wetlands mapping; watershed wetland assessment; wetland functions.

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