Green River Impact Study

December 3, 2010

Residents, businesses, and farms in the valley downstream of the Howard Hansen Dam are preparing for the increased likelihood of severe flooding. The winter of 2008 was one of the rainiest on record in Western Washington and runoff filled the dam reservoir to record levels. Water through an earthen bank next to the dam is seeping at greater rates than ever before, creating increased risk of flooding in the Green River Valley. Until the U.S. Army Corps of Engineers makes permanent repairs to this bank, it must limit the amount of floodwater stored behind the dam.

Another high volume of rain or snow melt could put excessive pressure on the weakening dam, creating the potential of catastrophic failure. Recently, the Corps installed a "grout curtain," which has reduced the risk substantially. However, the risk of flooding is still significant until a permanent solution is implemented. This report considers the economic and tax revenue impacts that the area and the county can anticipate if flooding of the Green River Valley should occur. In early December 2010, the Chief Economist presented an update to the Puget Sound Regional Council (PSRC) on the economic impact Green River flooding poses.

Report's include:

Chief Economist's update to the PSRC - December 3, 2010

Chief Economist's report to the King County Council - January 13, 2010

Chief Economist's briefing to the King County Council - January 21, 2010

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