Photo by Hugh Shipman.

VSP Wetland Resources

Regulatory exemptions and protections for farmed wetlands

In some cases, wetlands have long been used for agricultural production. Ongoing agriculture in these areas is exempt under state and federal wetland protection statutes. We recognize that these wetland areas may continue to be farmed under state wetland protection statutes.

Even though they are in production, farmed wetlands can continue to provide important wetland functions, such as waterfowl migration or overwintering areas. Use of best management practices and conservation practices can help enhance these functions while complementing ongoing farming operations.

Wetlands in agricultural areas are subject to state and federal regulations when:

  • A farmed wetland is proposed to be converted to non-agricultural uses.
  • There is a conversion of existing non-farmed wetland in order to expand agricultural operations or to convert it to other uses.
  • There is construction of new agricultural drainage facilities on farmed wetlands.
  • There is expansion and deepening of drainage ditches. This requirement would not include the shallow (18-24” deep) drainage ditches constructed to drain water from the farmed wetlands in the spring.

While the evaluation of wetland protection is at the watershed scale under the Voluntary Stewardship Program, restoring and enhancing wetlands in one part of a watershed do not compensate for new wetland impacts in other areas of the watershed.

Protection and enhancement activities under VSP are intended to reduce impacts and enhance critical areas in agricultural areas through voluntary measures, not to offset new impacts. 


We assist local governments in their efforts to adopt local critical areas wetland regulations that protect wetlands and their functions based on best available science.   

Creating maps

To create a baseline map of wetlands for VSP planning and implementation, we recommend the following, depending on your location and what data are available in your area. In some areas we recommend using multiple datasets which you can download in a digital form. 

The Washington Department of Agriculture maybe able to assist with creating GIS maps displaying the intersection of wetland and agriculture. For assistance please contact Perry Beale at the Washington Department of Agriculture at or 360-951-9098.

  • Locations with local inventories - Where available, use wetland inventories and maps that have been completed by local entities, such as Thurston and Douglas counties. Local efforts may have produced better maps than available at the state or national level by using high resolution imagery or improved technology. These may be the most complete source of information.
  • Western WA/east slopes of the Cascades without a local inventory - Use the Wetlands Change Analysis - Modeled Wetland Inventory maps together with the National Wetlands Inventory (NWI) maps. The NWI may identify some smaller wetlands not mapped in the Modeled Wetland Inventory. Also use the National Hydrography Data (NHD) to map streams and other waterbodies.
  • Other parts of Eastern Washington without a local inventory - Use NWI with National Hydrography Data.

Wetland Change Analysis and the Modeled Wetlands Inventory

Our Wetland Change Analysis project project partnered with NOAA's Coastal Change Analysis Program (C-CAP) to develop a method to create a Modeled Wetlands Inventory to more accurately map wetlands in the state. The inventory is based on a land cover classification which utilized Landsat scenes which were analyzed according to C-CAP protocol to determine land cover. This involved extracting the wetlands land cover classifications from the overall land cover layer.

NOAA applied the improved wetland layer to previous C-CAP analyses, including 2011, 2006, 2001, 1996, and 1992. C-CAP will use the improved wetland layer for land cover mapping and analyses every 5 years. For detailed information, see the C-CAP Wetland Assessment Report.

The Modeled Wetland Inventory:

  • Is more accurate than NWI for wetlands larger than one acre, especially in agricultural/pasture, forests, and stream corridors.
  • Includes a "Potentially Disturbed Wetlands" category for areas that have a high potential to be wetland, but have an observed land cover of "pasture/hay" or "cultivated".
  • Can be used for planning purposes and for initial permit review.


Map Data

Data limitations

  • Most wetlands one acre or less in size are not mapped.
  • The data are less accurate detecting forested and slope wetlands.
  • The inventory identifies areas that have a high potential to be wetland. Locations of mapped wetlands are approximate due to the medium resolution scale. Absence or presence of a wetland on the map does not mean absence or presence of wetland in the field.


Patricia Johnson

National Wetlands Inventory

The National Wetlands Inventory is the only statewide map of wetlands. It was created by the US Fish and Wildlife Service (USFWS) for the entire country over time using interpretation of aerial photographs at various scales.

In much of eastern Washington it is the only wetlands map available. However, the USFWS policy was to exclude certain types of "farmed wetlands" from the inventory. There is no record of the types or locations of farmed wetlands that were excluded from the NWI covering Washington State.


Map Data

Data limitations

  • The maps are nearly 40 years old and much has changed.   
  • As mentioned, certain types of "farmed wetlands" were excluded from NWI mapping.
  • Certain wetland habitats are also excluded such as seagrasses or submerged aquatic vegetation. Forested wetlands and wetlands on slopes may either be missed or mapped as smaller than what occurs on the ground.
  • A USFWS web site describes the data limitations.


National Hydrography Dataset

The National Hydrography Dataset (NHD) is used to portray surface water on The National Map at a 1:24,000 scale. These data are designed to be used in general mapping and in the analysis of surface water systems such as rivers, streams, canals, lakes, ponds, coastline, dams, and stream gages. The NHD is produced by the United States Geological Survey, and we manage the data for Washington.

This data set can be used to supplement the wetland inventories to portray how mapped wetlands relate spatially to other surface water bodies.

Map Data

Data limitations

  • To maintain mapping clarity not all water features are represented and those that are use a moderate level of detail.
  • They divide their map units by HUC watersheds. However, you can download HUC 4 region and add WRIA boundaries.


Anita Stohr

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