King County Flood Control District home page
The King County Flood Control District is a special purpose government created to provide funding and policy oversight for flood protection projects and programs in King County.
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Investments by River Basin
Cedar / Issaquah / Sammamish River Basin
Green River Basin
Snoqualmie / S.F. Skykomish River Basin
White River Basin

Green River Basin

 The King County Flood Control District invests resources in the Green River Basin to protect public safety, the regional economy, and critical infrastructure.

King County Flood Control District Investments
Green River Basin
Green River Flooding Resources
King County Flood Control District Investments

Green River Basin

2016 Capital Budget: $2,562,152

2015 Capital Budget: $18,642,586

2014 Capital Budget: $18,335,740

2013 Capital Budget: $17,378,745

2012 Capital Budget: $30,465,152

2011 Capital Budget: $4,675,691

2010 Capital Budget: $9,714,727

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Green River Basin

The Green River flows northwest about 93 miles from its headwaters in the Cascades to its outlet in Elliott Bay via the Duwamish River. Major tributaries include Soos, Newaukum and Mill Creeks, and the Black River. The Green River flows through several cities, including Auburn, Kent, Renton, Tukwila, and Seattle.

Major flood control features along the Green River include Howard Hanson Dam, which is in the upper Green River sub-watershed, and the levee system that lines almost all riverbanks of the lower Green and Duwamish Rivers. Howard Hanson Dam and the levee system combine to reduce flooding in the lower river to a fraction of its historical magnitudes.

With major historical flooding largely controlled by a dam and levees, commercial and industrial land use in the largely flat and generally accessible lower Green and Duwamish River valleys has proliferated in what were formerly rural and agricultural communities. Agriculture endures in some parts of the lower Green River around the Cities of Auburn and Kent, and agriculture and rural residential development are the primary land uses in the middle Green River.

Residents, businesses and farms below the Howard Hanson Dam in the Green River Valley prepared for a higher risk of flooding due to damage that occurred to an earthen bank next to the dam after record high water in January 2009. While temporary improvements made by the U.S. Army Corps of Engineers successfully lowered the risk of flooding in the Green River Valley, the dam continued to operate at a limited capacity during the 2010/2011 flood season, creating a heightened risk of flooding in the lower valley.

In March 2011, the US Army Corps of Engineers announced the return of full operational capacity at Howard Hanson Dam. However, this functioning dam and levee system does not eliminate all risks of flooding. The dam was formerly thought to control water up to a 500-year flood event. Now, the US Army Corps of Engineers recognizes the dam capacity can control water up to a 140-year flood event.

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Green River Flooding Resources
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Flood Warning & Preparation

For assistance during a flood event call 206-296-4535/ 800-768-7932. If it is an emergency, call 911.

The King County Flood Warning Program warns residents and agencies of impending floodwaters on major rivers so they can take action and prepare themselves before serious flooding occurs. Once a flood warning is issued, residents should prepare for flooding.

- Learn how to prepare for a flood and what to do during and after a flood

-Learn more about what you can do

-Explore additional resources