Mapping the Flood Risk

Flood Insurance Rate Maps

The county partnered with the Federal Emergency Management Agency (FEMA) to update and digitize the Flood Insurance Rate Maps (FIRMs) for Snohomish County. The new maps, called Digital Flood Insurance Rate Maps (DFIRMs), were adopted by the county in June 2020.

The DFIRMs update flood hazard data in the Flood Insurance Study (FIS) and FIRMs for areas in Snohomish County subject to riverine and coastal flooding. Products produced in association with the new DFIRMs include a flood risk database and a flood risk report. These products provide information such as:

  • Areas of higher flood risk by census block
  • Areas of highest expected damage
  • Potential future losses to existing structures
  • Areas within and upstream of the watershed that may be contributing to flood risks
  • Improved risk data for mitigation planning

 In the future, the above information will be used by planners, developers, community officials and emergency managers to support efforts to reduce flood risks and losses and to improve design and construction standards for development in coastal areas.

Technical Support Data Notebooks (TSDNs)

Available TSDNs for flood mapping projects completed in Snohomish County are listed below:

Other Flood Hazard Mapping Efforts

In 2021, the Community Floodplain Solutions (CFS) program funded flood hazard mapping studies in the Lower Skykomish River in an effort to better understand and predict future flood risks associated with changing river conditions. Topics included:

  • Hydraulic and hydrologic modelling
  • Geomorphic assessment and channel migration zone studies
  • Infrastructure assessment

View the complete reports on the Flood Hazard Mapping webpage

Learn more about Community Floodplain Solutions on the CFS webpage.