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The following presents the products completed for this project along the river corridors of King County.

Landslide hazard mapping along the river corridors of King County

The final products for this project include the following:

The final landslide GIS datasets are as follows:

These GIS datasets are available through the King County GIS Center. A hard copy of the GIS datasets is not provided as part of this document.

Landslides inventory
It is common knowledge to landslide practitioners that where a landslide has occurred, it may happen again. An inventory of historic landslides was completed for the study limits. Historic landslides are landslides that are known to have occurred either from observation, studies, or monitoring.

Geotechnical reports, landslides studies and maps, permit applications, and field reports are commonly stored at city, county, and federal agencies. Five divisions or sections within King County were contacted to inquire about landslide-related data . Additionally, 11 cities, two Washington state agencies, three local public utilities, the United States Forest Service, Burlington Northern Santa Fe Railway, and the University of Washington were also queried.

These data are included as a dataset in the web viewer as "Historical landslides" and as a point shapefile in the KC GIS Center in the GIS Data Portal (lsr_historicallandslides).

Report ( 9.4 MB PDF) — The report accompanies the mapping and summarizes all work completed by the Flood Control District for mapping along the river corridors in King County. This mapping does not cover all of King County.

Web tool
The web tool includes all map layers, inventory, and summarized information about landslides types.

Phase 1 - Results of preliminary landslide investigation in King County, phase 1

Technical Memorandum (2.7MB PDF) — The Phase 1 technical memorandum presents a preliminary map of the status of work to date at the end of 2014, and includes areas where landslides have occurred in the past and could be subject to landslides in the future. This mapping was preliminary and not appropriate for determining the safety or stability of any parcel in the study area.

King County used LiDAR (Light Detection and Ranging) technology to add to the existing information to show landslide hazard areas along major rivers and significant tributaries, in both cities and unincorporated areas, and Vashon-Maury Island. The preliminary investigation does not cover all of King County.

The Phase 1 preliminary map does not replace existing Landslide Hazard Mapping used for permitting and regulations.