Seattle (King County), WA Flood Zone & Drainage Map

Address
Overview

Where does rainwater drain in King County? This interactive map shows surface drainage patterns across Seattle, Bellevue, Kent, and surrounding areas based on terrain shape - where gravity directs rainwater based on elevation and slope. For official flood risk information, see the FEMA flood zone layer on the Hazards tab.

King County spans from Puget Sound to the Cascade crest, with dramatic elevation changes driving rapid drainage. The Snoqualmie, Green, and Cedar Rivers carry mountain snowmelt and rainfall through narrow valleys into urbanized lowlands. Atmospheric river events can raise river levels 10+ feet in hours, and the Howard Hanson Dam on the Green River is critical flood infrastructure for the Kent Valley. Choose a location to see surface drainage analysis and water flow direction based on terrain shape. The first three locations are free.

Interpretation

Select a location on the map or enter an address to see terrain analysis.

3D Terrain Visualization
Where does rainwater flow based on terrain shape? Blue areas show where water collects and drains downhill.
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Terrain drainage map of King County, WA: modeled paths where rainwater runs and collects, from USGS 3DEP elevation data, with the county boundary Click any spot on the map to analyze it
4.0× Horizontal:Vertical
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King County flood history

FEMA records 3,384 flood insurance claims in King County since 1978, with about $66 million paid. 27% of the claims with a rated flood zone came from moderate- or low-risk zones (X, B or C), outside the high-risk areas on FEMA’s flood maps.

Among the 50 largest U.S. cities, Seattle ranks #45 for FEMA flood insurance claims per home: 0.7 claims per 1,000 homes since 1978 (274 claims within city limits). See all 50 citiesA low rank doesn’t mean Seattle is safe! Only insured buildings file claims, and local runoff can still flood a house here.

Bar chart of FEMA flood insurance claims per year in King County, WA, 1978 to 2026, highest in 2009 with 668 claims.

Biggest flood years

  1. 2009 · 668 claims
  2. 2006 · Torrential rain · 447 claims
  3. 1990 · 408 claims
  4. 1996 · 298 claims
  5. 1995 · 241 claims

ZIP codes with the most claims

ZIPClaimsShare
980651,19435.3%
980452447.2%
980272387.0%
980382096.2%
980141765.2%
98019712.1%
98047631.9%
98166601.8%

How to read this. These are National Flood Insurance Program claims, so they count only insured buildings and miss flooding where owners had no flood insurance. FEMA publishes them without names or addresses: they show which years and areas flooded, never whether a particular house did. ZIP codes are as reported on the claims, and a ZIP code can extend beyond the county. The “rated” flood zone is the one used to price the policy and may come from an older map. Data as of 2026-09-08, from FEMA OpenFEMA.

Next: look up the flood zone for an address · how to check whether a specific house has flooded · why Zone X can still flood · how to read the drainage map

Sunlight and soil in King County

Sunlight. Ground here gets about 3.4 kWh of sunlight per square meter per day on average (3.0 to 4.2 across the map), below the middle of the lower 48 (4.5). South-facing slopes get more, north-facing ones less.

Soil. The ground is mostly loamy soil (Cambisols 58%, Andosols 5%), with sandy soil (Podzols 36%). Rain soaks in at a moderate rate.

The Solar and Soil tabs on the map above show both for any address. Read more: how much sun does my property get? · what soil type is my property, and how it affects drainage

Sunlight: long-term average on flat ground from the National Solar Radiation Database (National Laboratory of the Rockies, formerly NREL). Soil: most likely soil types from ISRIC SoilGrids, a 250 m model, not a survey of any lot. Both cover the map area above.

Explore more flood and drainage maps

Browse all 64 flood and drainage maps · Flood insurance claims in the 50 largest cities · How Terreflow uses terrain and FEMA data