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King County has completed draft studies identifying channel migration zones in two watersheds – the South Fork Skykomish River and the Tolt River. These studies and their accompanying maps identify areas that are considered at risk due to natural changes in the rivers’ locations. Read more about the Draft South Fork Skykomish River Channel Migration Zone. Read more about the Tolt River Channel Migration Zone. And visit the channel migration hazards page to learn more about this kind of riverine hazard.

Staff from the River and Floodplain Management Section can assist with the following flood map information by calling 206-477-4727.

  • Confirming if a property is located within a FEMA mapped Special Flood Hazard Area (SFHA), or flood prone area identified by King County.
  • Provide flood insurance rating information such as FIRM zone, panel number, suffix, panel date and index date.
  • Provide FEMA elevation certificates if available. King County has elevation certificates for many properties within the SFHA.
  • Determine what regulatory provisions may apply to a specific property.
  • If available, provide information on past flood damage to a property.

King County Code >> Critical Areas (Acrobat PDF format) 
County definitions and rules on development standards, restrictions, and requirements as well as permitted uses in King County floodplains and other sensitive areas. Codes pertaining specifically to floodplains can be found under sections 21A.24.230 to 21A.24.275 of this document.

Flood map information for realtors, lenders and insurance agents

iMap floodplain boundaries
Navigate, view and print custom maps using King County data including parcels, floodway and floodplain boundaries.

FEMA Flood Map Service Center (external link)
The official online location to find all flood hazard mapping products created under the National Flood Insurance Program (NFIP).

For questions about the floodplain mapping, please contact Ken Zweig, Project Manager, River and Floodplain Management Section.