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King County Flood Management Plan

The Flood Management Plan guides how King County manages flood risks along our rivers, creeks, and shorelines. On June 6, King County Executive Dow Constantine proposed the 2024 King County Flood Management Plan to the Metropolitan King County Council. The Council’s Local Services and Land Use Committee will review the plan and associated legislation and issue a recommendation for full Council action. Please check the Local Services and Land Use Committee webpage for updates about the Council’s review.

Public involvement summary

King County solicited public comments on the Draft Flood Plan and associated Draft Environmental Impact Statement earlier this year, and the comment periods closed mid-March.

During the comment period, King County hosted two online public meetings on Feb. 15 and March 7. Visit the King County Engagement Hub to view the presentations and videos from those meetings and a public comment summary.

About the flood plan update

As our most common natural disaster, flooding is part of life in King County. The plan will set floodplain management policy for unincorporated King County and could inform flood management actions by cities, the King County Flood Control District, and other floodplain partners.

Our core values in developing the flood plan are:

  • To stay community-centered.
  • Embrace transparency and openness.
  • Work with local partners.
  • Strive for full accessibility.
  • Have communities that are often left out of flood risk reduction conversations at the table. 
People work to assess damage to State Route 202 caused by the flooding of the Snoqualmie River in 2009.

Why is King County updating the flood plan?

Rivers and streams are alive—they change over time. King County last updated the flood plan in 2013. Since then, nearly 10 seasons of flooding have changed how our rivers look and function. Our population has grown, and we’ve added more homes and businesses to the landscape. How we develop land, manage waste, accommodate traffic, grow food, and recreate affects our rivers and coastal areas.

How will this flood plan be different?

To create a flood resilient future, the plan must represent the diverse perspectives of our community. Due to unjust historical practices, some communities are more at risk of flooding. Some people are less able to prepare or recover from flood disasters. Understanding what all communities need and their proposed solutions is King County’s priority.

Past plans have focused on flooding along King County’s major rivers. This plan will capture a broader range of flood hazards that affect people. It will include coastal flood hazards and sea level rise, small stream flooding, and urban flooding.

The updated plan will look for ways that we can reduce flood risks while delivering other community benefits. How can our projects and programs support farming or create new jobs? Improve salmon habitat and provide recreational areas? What's most important to you and what does your community need?

Partner Planning Committee

The Partner Planning Committee was one avenue for gathering public input on the flood plan, and the committee discussed topics addressed in the flood plan in depth through 10 meetings over 16 months. Learn more about the purpose of the committee and committee meetings on the Partner Planning Committee webpage.

Coastal flooding on Vashon Island in 2021.

State Environmental Policy Act process

An important part of our process to update the Flood Management Plan is to prepare an environmental impact statement (EIS). An EIS is a document that describes proposed actions and how they would affect the environment and people. Through the EIS process, King County analyzes potential impacts of the plan on threatened or endangered species, water quality, historical and cultural resources, transportation, and more.

King County explored the impacts of two scenarios, called “alternatives,” in the EIS. As a standard part of the EIS process, a “no action alternative” was considered. The analysis considered the impacts of not adopting the new flood plan (the no action alternative) and continuing to use the 2006 and 2013 flood plans to guide floodplain management policy and activities and also evaluated the impacts associated with adopting the new flood plan.

The County’s 2006 and 2013 flood plans focus on flooding and erosion hazards on major rivers and streams like the Snoqualmie and Cedar rivers and Issaquah Creek. The new flood plan proposes to address flooding more broadly on smaller streams and tributaries, lakes, and in urbans and coastal areas. 

King County invited the public, tribal governments, and local, state, and federal agencies to comment on the range of alternatives, areas of impact, and possible mitigation measures that should be evaluated within the EIS during the EIS scoping period. A 30-day comment period was held from Monday, Nov. 7 to Friday, Dec. 9, 2022. The submitted comments provided valuable information about topics to consider in evaluating potential environmental impacts.

Public comment was also requested on the Draft EIS. The Draft EIS was issued on Feb. 16, 2024, and the comment period was open until Mar. 18, 2024. Changes were made to the Final EIS in response to comments submitted, which are detailed in Chapter 18 of the final document (link below). 

EIS Resources

2024 King County Flood Management Plan Final Programmatic Environmental Impact Statement (June 2024)

Review the King County Flood Plan Environmental Impact Statement (EIS) Scoping Summary (May 2023), (PDF, 190 KB)


Past flood plans

The most recent flood plan was completed in 2006 and adopted by King County Council in January 2007. The flood plan was last updated in 2013 and adopted by King County Council with the passage of Ordinance No. 2013-0419.

Download the 2006 flood plan and 2013 flood plan update. These reports are provided in Adobe Acrobat .pdf format.

2006 King County Flood Hazard Management Plan (16.6 MB)

2013 King County Flood Hazard Management Plan Update and Progress Report (4 MB)

Printed copies of the 2006 flood plan and 2013 flood plan update are available at the following King County libraries:

  • Auburn Library
  • Bellevue Regional Library
  • Bothell Regional Library
  • Carnation Library
  • Duvall Library
  • Fairwood Library
  • Fall City Library
  • Issaquah Library
  • Kent Library
  • Maple Valley Library
  • Muckleshoot Library
  • North Bend Library
  • Redmond Regional Library
  • Skykomish Library
  • Snoqualmie Library
  • Tukwila Library