Background

In Washington, the existing statewide wetland maps (NWI maps) are out of date and inaccurate in many locations. They are based on imagery and data from the 1980’s and do not reflect current wetland location and extent. Additionally, wetlands are missing from the NWI maps. These errors of omission have been recorded to be as high as 50% in some areas, and may be as high as 90% in some forested areas.

Inaccuracies and errors of omission are due in part to the difficulty of photo-interpreting certain land cover types (e.g., forested wetlands, wetlands on slopes, and vernal pools), especially when using lower quality spectral, spatial, and temporal resolution imagery from the 1980s. Also, many wetlands on agricultural lands were not mapped. NWI classified wetlands to identify wetland habitat types. It lacks abiotic information such as landscape position, landform, and water flow path, which can be used to predict functions and, in combination with land uses, condition. Remote sensing data sources such as LiDAR, high-resolution aerial imagery, Landsat imagery, digital elevation data, hydrography, and updated soil maps, provide an opportunity to address these known shortcomings. Moreover, recent developments in automated remote sensing technologies (e.g., object-based image analysis) allow for more efficient coverage of large areas.

An improved, statewide map of wetland location and type is critical to the ability of local governments to protect wetlands. Under Washington State’s Growth Management and Shoreline Management Acts, local governments play a critical role in wetland protection and management. They do this through comprehensive planning, zoning, and permit review. Planners and permit reviewers rely on existing NWI maps for these processes. A few local jurisdictions have conducted their own wetland inventories and improved their maps, but these are limited due to lack of resources, and none have predicted functions and conditions of wetlands. This leaves many local governments with inadequate maps and information on local wetlands, and the state with uneven coverage. A primary role of Ecology’s wetlands program is to support protection of wetlands at the local level by synthesizing the best available science and using it to create tools for local jurisdictions.

In addition to the regulatory and planning needs of local governments and Ecology, several agencies and non-profit organizations rely on wetland maps to identify areas of priority for research, conservation, and restoration, such as The Washington Natural Heritage Program, Puget Sound Partnership, and the Northwest Indian Fisheries Commission. Some specific examples include the U.S. Fish and Wildlife Service, which has used wetland map data to identify potential critical habitat areas for Oregon Spotted Frogs. Biologists from Turnbull National Wildlife Refuge and Ducks Unlimited have identified a need for improved wetland mapping and classification to inform habitat restoration and protection activities for waterfowl and wildlife. The Wetland Science Advisory Group for Washington’s Forest Practices needs improved wetland maps to select sites for research on the effectiveness of Washington’s Forest Practices Rules at protecting wetland functions. The ever-growing demand for readily accessible information on wetland location and status provides a clear need for Washington to pursue a multi-lateral, phased approach to improving wetland mapping and classification using the latest technology.

Our Work

This project will improve the ability to more efficiently and accurately identify the location, size, and type of Washington's (WA) wetland resource. This will be accomplished using remote sensing data to identify (digitally map) wetland locations and classify wetland types.

UW, in collaboration with Ecology and Department of Natural Resources (DNR) will develop a systematic process that will result in an updated, statewide map of wetland locations, with attributes covering multiple classification schemes. For Phase One of this project, UW, in collaboration with Ecology will determine the most efficient and accurate statewide approach for remotely mapping and classifying wetlands. The approach will be applied in areas representative of land use and ecological diversity in WA. This will allow UW the opportunity to estimate the accuracy of mapping in areas where unique challenges have contributed to errors in existing maps.

Project results will be available as a publicly accessible, web-based map. Information about the maps, and any analyses using the data, will be disseminated through articles and presentations to state and federal agencies, and local governments and planners' forums.

Results

Deliverables