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King County Flood Control District presents findings from lower Snoqualmie River flood impact study


King County will present the findings of a flood impact study of the lower Snoqualmie River at a public meeting in Carnation on Tuesday, March 22.


The community is invited to a March 22 open house in the multipurpose room at Tolt Middle Flood Control Zone District LogoSchool, 3740 Tolt Ave., Carnation, at 6:30 p.m. to learn more about the impacts from two upstream flood-reduction projects done at Snoqualmie Falls in the past 12 years.

“We heard from residents along the lower Snoqualmie River that flooding seemed to be getting worse and they were concerned,” said King County Councilmember Kathy Lambert who serves on the Executive Committee of the King County Flood Control District. “I took these concerns seriously and wanted them investigated.”

In response to community feedback, the King County Flood Control District hired an independent consultant to study impacts to flooding in the lower Snoqualmie River from the U.S. Army Corps of Engineers’ 2004 Snoqualmie Flood Reduction Project, also known as Snoqualmie 205 Project, and Puget Sound Energy’s 2012 Snoqualmie Falls Hydroelectric Project.

The study, “Snoqualmie River Hydraulic Study: Evaluation of Effects of Snoqualmie Falls Projects on Downstream Flooding,” also evaluated the projects’ upstream benefits to determine whether they are providing the expected benefit of flood reduction in the City of Snoqualmie.

The study’s findings show that the two projects have had a large upstream benefit and much smaller downstream impacts. A peer review of the study’s findings was completed by hydrologist Ed McCarthy, PE, PhD and Certified Floodplain Manager.

While the results of the study do not point to the Army Corps and PSE projects as the cause of increased flooding the Flood District is continuing an investigation to try and understand why residents are experiencing worsening floods.

The second phase of the study is already underway. Phase two will evaluate trends in basin flood hydrology and identify possible changes that could be contributing to increased flood flows, such as land use, forestry practices, increased sedimentation, floodplain storage and weather patterns including climate change. King County will actively seek input from community members about their experiences with past floods to help guide this investigation.

To learn more about this study, submit comments or sign up for notifications about the second phase of the study, go to and follow the link for the Snoqualmie River flood impact study. The public comment period for the flood impact study ends April 8.

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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. The Flood Control District’s Board is composed of the members of the King County Council. The Water and Land Resources Division of the King County Department of Natural Resources and Parks develops and implements the approved flood protection projects and programs. Information is available at