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King County Flood Control District wants to update landslide mapping

In the wake of the Oso landslide, the King County Flood Control District Executive Committee wants to use advances in technology to dramatically improve the collection and use of landslide data.

The Executive Committee will send to the full Board of Supervisors a resolution calling for an update to King County’s river basin landslide hazard mapping, according to a Wednesday county media release. By mapping landslide hazards in light of flood and channel migration hazards, the Flood Control District will be better prepared to act to reduce risks to people, property, and critical infrastructure.

“This project is a prudent and timely update of potential landslide locations along King County rivers,” said Flood Control District Chair Reagan Dunn. “Recently there was a landslide on the Cedar River in my district, thankfully the impacts to residents were minimal, but it illustrates the need to have updated information so the Flood District can be in a better position to protect people, property and critical public infrastructure.”

“Having accurate data is vital to our land use decisions. The old maps used 1990 technology. Now LiDAR (Light Detection and Ranging) will provide the maximum benefit and more safety to the taxpayers,” said Flood District Supervisor Kathy Lambert whose district includes part of the Snoqualmie River basin. “I’m encouraged that this new landslide data collection technology will enable us to be better prepared for any future flooding or landslides.”

“This is truly a public safety issue,” said Flood District Vice Chair Larry Gossett. “Outdated information can put lives in danger and impact property. Taking advantage of available technology is a step in the right direction.”

“It is crucial that we initiate improved measures to protect our communities—the better prepared we are today, the less damage we will face as a county when an emergency does strike,” said Flood District Supervisor Pete von Reichbauer, who represents parts of the Green and White Rivers.

The District will provide approximately $200,000 in 2014 for these updates, with additional funds coming through 2016. The work in 2014 includes landslide hazard characterization along major rivers and significant tributaries, as well as listing high-risk sites where landslide and floodplain hazards intersect. Preliminary maps along major rivers and significant tributaries will be available by October, and potential high-risk sites will be identified by December.

Further mapping improvements will follow through July 2016, including identification of different landslide hazard types, public safety consequences, historically active sites, landslide run-out zones, areas of moderate and severe channel migration, and areas at risk for debris dam formation that could lead to upstream flooding.

The King County Flood Control District will fund more than $1.4 million for the two-year project. The King County Water and Land Resources Division will conduct the mapping study, under agreement with the District.

The resolution was adopted by the Flood Control District Executive Committee at its May 19 meeting and is awaiting final action by the full Flood Control District Board of Supervisors.

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