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.

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