Floodplain Development Code

See also: Environmentally Critical Areas (ECA) Code

What Is It?

Our floodplain development ordinance has standards and restrictions for construction and development in designated flood hazard areas in the city. Areas affected by the regulations are located within the designated floodplain along the:

  • Thornton, Pipers, and Longfellow Creeks
  • Duwamish Waterway 
  • Puget Sound coastline

Areas that Seattle Public Utilities has identified as having problem drainage are also regulated by our floodplain development ordinance.

If you are considering construction on property located in any of these areas, you should consult our regulations before starting the permit process. The King County Flooding Services and the FloodSmart.gov websites are also helpful resources.

Read the Code

Flood Insurance Rate Maps (FIRMs)

Please see FEMA’s Flood Map Service Center for the complete set of official FIRMs for Seattle. You can also find Preliminary FIRMS on FEMA's web site by selecting Show ALL Products. Although the Preliminary FIRMS are not in effect for insurance purposes, most of them are in use for regulatory purposes.

The FIRMs identify flood-prone areas under current conditions. The maps do not take into account the increasing risk of flooding due to sea level rise or stronger storms. More information about the effects of climate change in Seattle is available from Seattle Public Utilities, including an interactive Sea Level Rise Map.

Proposed Changes

FEMA expects to adopt our preliminary FIRMs in 2019.