Floods

Key Points

Nationally, floods are the most costly and destructive disasters. Most of the damage caused by Hurricane Katrina was caused by flooding.
Western Washington is very prone to flooding, and Seattle's flood profile is different from the rest of the state. Seattle has three distinct flooding hazards: riverine flooding, coastal flooding, and urban flooding. Urban and riverine flooding are most common.
Climate change is projected to cause sea level rise and increase the frequency of heavy rain events, heightening Seattle's future risk of urban and coastal flooding.
The area in the 100-year floodplains covers South Park and the drainage basins for Thornton and Longfellow Creeks. Flood control structures have been built in all of these areas. Small segments of two high-volume arterials cross the flood plain: SR99 crosses the South Park floodplain and SR 522 cross along three segments of Thornton Creek.
2014 Federal Emergency Management Agency (FEMA) data reveals that Seattle has had fewer than ten buildings (including residential) that have had more than one flood loss.