OVERVIEW

The National Wetlands Inventory (NWI) project, administered by the U.S. Fish and Wildlife Service (USFWS), was established to generate information about the characteristics, extent and status of the Nation's wetlands and deepwater habitats. This information is used by Federal, State, and local agencies, academic institutions, U.S. Congress, and the private sector.  The Emergency Wetland Resources Act of 1986 directs the Service to map the wetlands of the United States. For full details on the national mapping project visit the National Wetlands Inventory web site.

MassGIS distributes two NWI layers created by the USFWS:

• NWI_POLY - This data set represents the extent, approximate location and type of wetlands and deepwater habitats in the Commonwealth of Massachusetts. These data delineate the areal extent of wetlands and surface waters as defined by Cowardin et al. (1979).  The dataset was created by the National Wetlands Inventory program (http://www.fws.gov/nwi/) within the U.S. Fish & Wildlife Service.
  
  Certain wetland habitats are excluded from the National mapping program because of the limitations of aerial imagery as the primary data source used to detect wetlands.  These habitats include seagrasses or submerged aquatic vegetation that are found in the intertidal and subtidal zones of estuaries and near shore coastal waters.  Some deepwater reef communities (coral or tuberficid worm reefs) have also been excluded from the inventory.  These habitats, because of their depth, go undetected by aerial imagery.    
  
  By policy, the Service also excludes certain types of "farmed wetlands" as may be defined by the Food Security Act or that do not coincide with the Cowardin et al. definition.  Contact the Service's Regional Wetland Coordinator for additional information on what types of farmed wetlands are included on wetland maps.
   
  
• NWI_ARC - This polyline layer represents river and stream features as created by the National Wetlands Inventory (NWI) program, administered by the United States Fish and Wildlife Service.
  
  The NWI project was established to generate information about the characteristics, extent and status of the Nation's wetlands and deepwater habitats. This information is used by Federal, State, and local agencies, academic institutions, U.S. Congress, and the private sector.  The Emergency Wetland Resources Act of 1986 directs the Service to map the wetlands of the United States. The Act also requires the Service to produce a digital wetlands database for the United States.
  

The wetland maps were produced as topical overlays using U.S. Geological Survey topographic maps as the base.  The hard copy product is a composite map showing topographic and planimetric features from the USGS map base and wetlands and deepwater habitats from the Service's topical overlay.  Thus, the data are intended for use in publications, at a scale of 1:24,000 or smaller. Due to the scale, the primary intended use is for regional and watershed data display and analysis, rather than specific project data analysis.  The map products were neither designed or intended to represent legal or regulatory products.

Comments regarding the interpretation or classification of wetlands or deepwater habitats can be directed to the U.S. Fish and Wildlife Service, Division of Federal Program Activities, Branch of Habitat Assessment http://www.fws.gov/duspit/contactus.htm

These data were developed in conjunction with the publication 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. Department of the Interior, Fish and Wildlife Service, Washington, DC.  FWS/OBS-79/31.  Alpha-numeric map codes have been developed to correspond to the wetland and deepwater classifications described.

MassGIS received a statewide layer from theWetlands Mapper Team at the U.S. Geological Survey, Water Resources Division, and clipped to the extent of the major watersheds in the state.

The polygon layer NWI_POLY contains the following items:

Item Name		Description
ATTRIBUTE		USFS detailed wetland type code (Source: Cowardin et al. 1979. See http://wetlandsfws.er.usgs.gov/NWI/webatx/atx.html)
WET_TYPE		Wetland type:   Estuarine and Marine Deepwater    Open water estuary, bay, sound, open ocean Estuarine and Marine Wetland Vegetated and non-vegetated brackish and saltwater marsh, shrubs, beach, bar, shoal or flat Freshwater Emergent Wetland Herbaceous march, fen, swale and wet meadow Freshwater Forested/Shrub Wetland Forested swamp or wetland shrub bog or wetland Freshwater Pond Pond Lake Lake or reservoir basin Riverine River or stream channel Other Farmed wetland, saline seep and other miscellaneous wetland For more details see http://wetlandsfws.er.usgs.gov/NWI/tips.html.
ACRES		Area of the feature in acres
DECODE		Metadata reference Web site
GLOBALID		Unique feature identifier

The line layer NWI_ARC contains the following items:

Item Name		Description
ATTRIBUTE		USFS detailed wetland type code (Source: Cowardin et al. 1979. See http://wetlandsfws.er.usgs.gov/NWI/webatx/atx.html)
GLOBALID		Unique feature identifier

MassGIS provides these data for use with other data in Mass. State Plane projection and does not maintain or update the database. Data not currently in digital format will be added to database when made available by NWI.

The October 2007 updated replaced all previous versions of these layers.

For more wetlands data, also see the DEP Wetlands (1:12,000) layer.

Last Updated11/1/2007
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