Surface Water Management Division

River Flood Warning Program

For all emergencies, dial 9-1-1.

The Snohomish County River Flood Warning Program provides warning of impending floods on major rivers so that residents, school districts, emergency services, and others can make preparations before serious flooding occurs. The warning system does not take the place of an individual, family, group, or agency flood disaster plan.

The purpose of our flood hazard planning efforts is to reduce threats from major flooding and to improve emergency response to citizens, businesses, and agencies during times of flooding. For land owners in flood-prone areas we provide technical assistance and on-site investigations to help reduce damage caused by flooding.

 When do floods typically happen
 in Snohomish County?

Floods most commonly occur between November and February during periods of heavy rain or rapid snow melt. However, floods can occur in any month.

 How does the flood warning system work?

During heavy rains, County officials begin a "flood watch" and activate the Flood Operations Center at the Snohomish County Department of Emergency Management (DEM) headquarters in Everett.

Surface Water Management operates a network of rain gages and river level stations that comprise the flood warning system. Information from river gages and forecasts from the National Weather Service are used to make flood predictions.

The DEM Center issues warnings about the severity of expected flooding for each individual river. The DEM Center updates the warnings based on continuous river flow and stage (water level) data received from the gages and on information from volunteer "river watchers" and County field staff.

During the flood watch, close coordination occurs between Snohomish County's Department of Emergency Management, Public Works Department, and Sheriff's Department. The County also coordinates with the U.S. Army Corps of Engineers about the status of dikes, and with emergency service agencies such as the Red Cross, for help with persons evacuated from their homes.

Agency responses occur in four phases depending on the severity of the expected flooding, with Phase 4 being the most severe.