King County, WA

Heavy rains and snow melts lead to frequent river flooding in the Seattle area. In 1990, King County officials recognized the value of the Community Rating System (CRS) in reducing risk to floodplain property owners. By 2007 King County had received a Class 2 rating under the Community Rating System, making it the highest-rated county in the nation at the time.

Snohomish River, February 1996. Photo via  King County, WA .

Snohomish River, February 1996. Photo via King County, WA.

Project Overview

In order to reduce flooding risks and lower insurance premiums, King County has incorporated every category of projects and programs for which FEMA grants CRS credit. King County has preserved over 100,000 acres of open, natural space, providing beneficial floodplain functions. The county has also purchased and removed more than 40 structures from the floodplain. The King County Flood Control District was established to manage and fund such projects, including the Annual Inspection and Maintenance Program, operation of a Flood Warning Center, and the Washington State Dam Safety Program. As a result, the National Weather Service designated the county as a “storm ready” county. Other specific examples of flood improvement include:

  • Providing Flood Insurance Rate Map (FIRM) information online
  • Creating and maintaining detailed GIS maps of floodplains, channel mitigation hazard areas, and surveyed benchmarks, and making that information readily available to the public
  • Restricting and regulating development in areas where flood depths exceed 3 feet and velocity exceeds 3 feet per second, including channel migration zones
  • Restricting non-residential structures in the FEMA floodway, including critical facilities (with some exceptions)
  • Requiring a 3-foot freeboard standard for most structures above the 100-year flood elevation and zero-rise standard throughout the zero-rise floodway to provide flood conveyance
  • Requiring the removal of temporary structures and hazardous materials from the floodplain during the flood season


Implementation and Funding

The development of their Flood Hazard Mitigation Plan in 2006 provided the county with guidelines and objectives regarding necessary improvements to an aging system of over 500 levees and revetments within the urban and rural floodplain. In order to manage and fund the $335 million in priority repairs and upgrades necessary over the next decade, the Kind County Flood Control District was created in 2007.


Economic Advantage

King County’s contemporary methods of flood hazard mitigation reduce flood risks to thousands of people and the loss of billions of dollars in property and infrastructure. The county’s Class 2 rating provides a 40% discount on flood insurance premiums for properties within special flood hazard areas, and a 10% discount in non-special flood hazard areas. King County has been able to maintain its class 2 rating, as of October 2012.