Floodplain Mapping

Preliminary Digital Flood Insurance Rate Maps and Flood Insurance Study

As part of the Federal Emergency Management Agency (FEMA) national Map Modernization Program initiative, FEMA has produced Preliminary Digital Flood Insurance Rate Maps (DFIRMs) and the corresponding Flood Insurance Study (FIS) for both the incorporated and unincorporated areas of King County. The Preliminary DFIRMs and FIS, dated as September 28, 2007, show proposed special flood hazard areas that are subject to inundation by the base flood (100-year flood) as well the regulatory floodway.

Lower Snoqualmie River and Patterson Creek Work Maps
The work maps (linked below) were submitted to FEMA and included in the Preliminary Digital Flood Insurance Rate Maps.

*Lower Snoqualmie River Sheets 1-4 are Snohomish County floodplain work maps.

Lower and Middle Green River Work Maps
New flood boundary maps have been prepared for the Green River between the Duwamish Waterway in Seattle to Flaming Geyser State Park. The information was submitted to the Federal Emergency Management Agency (FEMA) on March 18, 2008 for the purpose of revising flood insurance rate maps. The work maps are linked below.

Flood Insurance and FEMA (Acrobat PDF format)
This bulletin explains the effect of the Federal Emergency Management Agency (FEMA) on the permitting process of the Department of Development and Environmental Services (DDES) and answers some common questions about the National Flood Insurance Program's (NFIP's) impact on development projects.

King County Code >> Environmentally Sensitive 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

Online Floodplain Boundary Maps
iMAP (high speed Internet connection required)
View and print custom online maps using King County data including parcels, floodway and floodplain boundaries.

FEMA Flood Hazard Maps (external link)
Information on locating Flood Insurance Rate Maps (FIRM), understand how to read them, and requesting a map change.

FEMA Flood Map Store, Online Map Viewer (external link)
Order or view current Flood Insurance Rate Maps online.
(registration required, no charge to view maps)

For questions about the Floodplain Mapping, please contact Ken Zweig, River and Floodplain Management Unit.