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Flooding services

King County, Washington

To offer a suggestion or report an error on the King County flooding services and information website, please contact Fred Bentler, webmaster.

Flooding services and information in King County, WA

Preliminary Flood Insurance Rate Maps and Flood Insurance Study
King County, Washington

MapThe Federal Emergency Management Agency has produced Preliminary Flood Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) for the incorporated and unincorporated areas of King County.

The four volumes (PDF) of the February 1, 2013 Flood Insurance Study (FIS) includes revisions to these areas: The Sammamish River and tributaries (Bear Creek, Evans Creek, North Creek, Swamp Creek), Coastal areas (Vashon Island and mainland), White River (from ¼ mile downstream of Hwy 410 near Enumclaw to the Outlet Works at Mud Mountain Dam).
Volume 1
Volume 2
Volume 3
Volume 4

The four volumes (PDF) of the November 6, 2010 Flood Insurance Study (FIS) includes all floodplain areas in King County.
Volume 1
Volume 2
Volume 3
Volume 4

Part of the national Map Modernization Program, the new digital maps can be used with geographic information systems. The mapped information is widely used by lending institutions and insurance agents in determining who must purchase flood insurance and the cost of that insurance should it be necessary. In addition, the maps will be used by the county and local communities for floodplain management and permitting purposes.

The most recent Preliminary FIRMs are dated February 1, 2013 and reflect areas where mapping studies that have occurred over the past few years. All other areas in King County are included the Preliminary FIRMs dated November 6, 2010.

If you have questions about the Map Modernization Program, please contact Ted Perkins, FEMA Regional Engineer, 425-487-4684.

King County flood studies submitted to FEMA

The below flood studies were submitted to FEMA to produce the most current Preliminary Flood Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) dated February 1, 2013 (above), show proposed special flood hazard areas that are subject to inundation by the base flood (100-year flood) as well the regulatory floodway. Check out our frequently asked questions for more information.

Vashon-Maury Island coastal flood hazard mapping

The work maps (linked below) were submitted to FEMA and included in the February 1, 2013 Preliminary Flood Insurance Rate Maps.

Sheet 1 Sheet 5
Sheet 2 Sheet 6
Sheet 3 Sheet 7
Sheet 4 Sheet 8

Sammamish River

The work maps (linked below) were submitted to FEMA and included in the February 1, 2013 Preliminary Flood Insurance Rate Maps.

Sheet 1 (Lake Washington) Sheet 6
Sheet 2 Sheet 7
Sheet 3 Sheet 8
Sheet 4 Sheet 9
Sheet 5 Sheet 10 (Lake Sammamish)

White River

The work maps (linked below) show the areas from the King-Pierce County line to Stuck River Drive and from SR410 to Mud Mountain Dam. The February 1, 2013 Preliminary Flood Insurance Rate Maps includes only the White River (near Enumclaw) area from approximately 1,275 feet downstream of State Highway 410 to the Outlet Works at Mud Mountain Dam.

White River (Pacific/Auburn) White River (near Enumclaw)
Sheet 1 (King-Pierce County Boundary) Sheet 1 (SR 410)
Sheet 2 Sheet 2
Sheet 3 Sheet 3
Sheet 4 Sheet 4
Sheet 5 (Stuck River Drive) Sheet 5 (Mud Mountain Dam)

Lower Snoqualmie River and Patterson Creek work maps

The work maps (linked below) were submitted to FEMA and included in the November 2010 Preliminary Flood Insurance Rate Maps.

Lower Snoqualmie River Patterson Creek
Sheet 5 (King-Snohomish County Boundary) Sheet 1
Sheet 6 Sheet 2
Sheet 7 Sheet 3
Sheet 8 Sheet 4
Sheet 9 Sheet 5
Sheet 10 Sheet 6
Sheet 11 Sheet 7
Sheet 12 Sheet 8
Sheet 13
Sheet 14
Sheet 15
Sheet 16
Sheet 17 (Snoqualmie Falls)

*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. FEMA technically reviewed the work maps and included the hazard mapping in the November 2010 Preliminary Digital Flood Insurance Rate Maps. The reviewed maps have some slight illustrative revisions as compared to the 2008 draft maps. Please note that no technical changes were made to the flood study analyses. The final-reviewed work maps are linked below.

Middle Green River
State Route 18 to Flaming Geyser State Park
(each file exceeds 2Mb)
Lower Green River
Duwamish Waterway to State Route 18
(each file exceeds 5Mb)
Sheet 1 Sheet 1
Sheet 2 Sheet 2
Sheet 3 Sheet 3
Sheet 4 Sheet 4
Sheet 5 Sheet 5
Sheet 6 Sheet 6
Sheet 7 Sheet 7
Sheet 8 Sheet 8

Sheet 9

If you would like information about King County’s floodplain mapping program please contact Ken Zweig, Project/Program Manager or Jeanne Stypula, Supervising Engineer of the King County River and Floodplain Management Section.