King County Drainage Analysis & Water Flow 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. Enter any address to see parcel-level surface drainage analysis and water flow direction based on terrain shape.

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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4.0× Horizontal:Vertical
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