St. Louis City County Drainage Analysis & Water Flow Map

Address
Overview

Where does rainwater drain in St. Louis? This interactive map shows surface drainage patterns across the city 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.

St. Louis sits on bluffs above the Mississippi River, but the city's combined sewer system creates severe flash flood risk during heavy rain. The July 2022 event dropped over 9 inches in hours, overwhelming the River Des Peres channel and flooding neighborhoods. Aging infrastructure and impervious urban surfaces amplify runoff far beyond what the terrain alone would suggest. 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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