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Wetland & Open Water Area

This script produces the spatial datasets of "Open Water" and "Wetland" land coverage, based on the USFWS National Wetlands Inventory. In each raster, a value of 1 represents the presence the specified land cover classification and a 0 represents the absence.

Data Sources

Layer Source
Wetlands Layer U.S. Fish & Wildlife National Wetlands Inventory
State Boundaries National Atlas of the United States

Steps to Run:

The folder structure is set up within the scripts. In general, the existing structure in the repo should be followed. Raw data should be unzipped, but otherwise kept in the same format as it is downloaded.

  1. Open the script fwsWetlands.py

  2. Change the values in the "Specify inputs" section of the script

  • baseDirectory is the path to the folder where results are written
  • states is the list of state abbreviations that identify the layers to use from the FWS data
  • stateNames is the list of state names to match the FWS layers used. These names should match the names in the "STATE" column of the state boundaries shapefile.
  • wetlandsFolder is the source folder of the wetlands datasets by state
  • statesFile is the filepath to the state boundary shapefile
  • outputName is the name that will be associated with this particular run of the tool (e.g. "NHDHRDV2")
  1. Run the script in ArcPython. It does the following:
    • Sets up the folder structure in the specified directory
    • Ensures constistency of projections
    • Creates an empty raster of the entire specified range based on the State Boundaries shapefile
    • Loops through the state polygons, creating state rasters of the categories described below
    • Mosaicks all of the state raster and the full range empty raster
    • Saves completed rasters to the [baseDirectory]\gisFiles\[outputName]\outputFiles directory

Output Rasters

Open Water

Raster name: fwsOpenWater
Description: This layer represents the FWS wetlands defined as "open water" (where "WETLAND_TYPE" = "Freshwater Pond", "Lake", or "Estuarine and Marine Deepwater").


Raster name: fwsWetlands
Description: This layer represents the FWS wetlands defined as "open water" (where "WETLAND_TYPE" = "Estuarine and Marine Wetland", "Freshwater Emergent Wetland", or "Freshwater Forested/Shrub Wetland").


  • The states listed in the "Specify inputs" section of the script will determine the spatial range of the output

  • The layers for Maryland (MD) and the District of Columbia (DC) overlap in the FWS data, but not in the state boundary layer. DC is not included in "states" (only MD is used). In the state boundaries layer, "District of Columbia" must be specified if including Maryland.

Next Steps

  • Classification definitions can be changed with relatively minimal effort.