How much is flood insurance in Seattle?

Flood insurance in Seattle ranges from $300/year in Zone X to $4,500+/year in AE zones along the Duwamish River. Creek-adjacent properties in Zone A average $1,200–$3,500/year. Risk Rating 2.0 now considers proximity to waterways and Green River dam risk.

What is the Green River dam flood risk?

Howard Hanson Dam on the Green River provides flood control for the Duwamish Valley. Seepage issues discovered in 2009 reduced the dam's capacity, expanding the effective flood risk for downstream communities. The Army Corps of Engineers has made repairs, but the dam's flood storage remains a concern during extreme events.

Does Seattle have urban flooding?

Yes. Seattle's steep terrain and heavy winter rains create urban stormwater flooding in low-lying areas, even outside FEMA zones. Combined sewer overflow, clogged storm drains, and creek overflow cause localized flooding in the Rainier Valley, South Park, and Georgetown neighborhoods.

Can I build in a Seattle flood zone?

Yes, with requirements. AE zones require elevation to BFE plus 1 foot of freeboard. Environmentally Critical Area regulations add setbacks from creeks and wetlands. The Shoreline Master Program restricts construction within 200 feet of major waterways. Consult SDCI for specific requirements.

What are Environmentally Critical Areas in Seattle?

ECAs include flood-prone areas, steep slopes, wetlands, and fish and wildlife habitat. Properties in ECAs face additional development restrictions including larger setbacks, vegetation preservation, and stormwater management requirements. ECA designation can significantly affect what you can build on a property.

Seattle, Washington · FEMA Region 10

Is Seattle in a Flood Zone?

Q: Is Seattle in a flood zone?

Parts of Seattle are in FEMA flood zones. The Duwamish Valley, South Park neighborhood, and areas along Longfellow and Thornton Creeks are in AE or A zones. Most of Seattle's hilly terrain is in Zone X (minimal risk), but urban stormwater flooding occurs in low-lying areas. Enter your address at ReadyPermit for property-specific data.

Moderate Flood Risk

Seattle has moderate flood risk primarily from the Duwamish River, Green River system, and urban stormwater flooding. The Duwamish Valley industrial area and South Park neighborhood sit in FEMA floodplains. The Howard Hanson Dam on the Green River provides critical flood control, but capacity concerns have led to expanded flood planning. Climate change is increasing atmospheric river intensity and winter rain-on-snow events.

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FEMA Flood Zones in Seattle

100-Year Floodplain (Detailed)

Found along the Duwamish River, lower Green River, and portions of Longfellow Creek. BFE established. Flood insurance required for federally backed mortgages.

100-Year Floodplain (Approximate)

No detailed BFE study. Found along smaller creeks including Thornton Creek and Pipers Creek.

X (shaded)

500-Year Floodplain

Moderate risk. Found in areas adjacent to the Duwamish and in low-lying neighborhoods near Lake Union and Lake Washington.

X (unshaded)

Minimal Risk

Most of Seattle. Hilly terrain provides natural drainage, though urban stormwater flooding can still occur in low spots.

Flood Insurance Costs in Seattle

Zone AE (Duwamish): $1,500–$4,500/year
Zone A (creek corridors): $1,200–$3,500/year
Zone X (shaded): $400–$900/year if purchased voluntarily
Zone X (unshaded): $300–$600/year (Preferred Risk Policy)
Risk Rating 2.0 factoring in Green River dam risk for downstream properties
King County Flood Control District offers mitigation assistance programs

Building Requirements in Flood Zones

AE zones: lowest floor at or above BFE; Seattle adds 1-ft freeboard requirement
Environmentally Critical Areas (ECA): additional setbacks from creeks and wetlands
Duwamish industrial area: floodproofing for commercial/industrial buildings
Substantial improvement (>50% of value) triggers full floodplain compliance
Green building standards: stormwater management required for all new construction
Shoreline Master Program: additional restrictions within 200 ft of major waterways

How to Check Flood Risk in Seattle

1
Check your flood zone
Enter your Seattle address into ReadyPermit or FEMA's Flood Map Service Center. King County iMap also provides interactive flood zone mapping.
2
Check Environmentally Critical Areas
Seattle's ECA maps show flood-prone areas, steep slopes, and wetlands that trigger additional development restrictions.
3
Get an Elevation Certificate
Required for flood insurance in A and AE zones. Hire a Washington-licensed surveyor ($400–$700).
4
Obtain flood insurance
Required for A/AE zones with federally backed mortgages. Duwamish Valley and South Park properties should maintain coverage even if maps change.
5
Review building requirements
Check Seattle Department of Construction and Inspections (SDCI) for flood, ECA, and Shoreline Master Program requirements.
6
Assess Green River dam risk
Howard Hanson Dam capacity concerns affect downstream flood risk. King County Flood Control District provides dam-related flood information.
7
Plan for climate change
Increasing atmospheric river events and rain-on-snow flooding are expanding Seattle's effective flood risk. Factor climate projections into long-term property decisions.

Frequently Asked Questions — Seattle Flood Zones

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