Phase 1 Landslide Hazard Investigation Completed

The King County Flood Control District has completed the first phase of a two-year investigation to update landslide hazard information for King County’s river valleys and floodplains.

The investigation is the first step in assuring the county has the most current information to protect people, property and critical public infrastructure.  Earlier this year, King County began using Light Detection and Ranging technology – known as LIDAR – to identify potential landslide hazards along major rivers and significant tributaries.  The technology will be used in both cities and unincorporated areas. “With new technology we can see more clearly where there are risks of potential landslides, and gather the kind of information that will protect homes and lives,” said King County Executive Dow Constantine.

The data will be further refined with additional information, and then consolidated into a geographic information system (GIS) database. No regulatory changes are planned at this time.

The work to date has focused on identifying areas of past instability because such areas are sometimes subject to further movement. While many such areas are located in undeveloped portions of King County, they are also present in areas with more intense land use. King County has provided briefings to the 11 communities where areas of apparent past instability have been mapped: Auburn, Bothell, Kent, Issaquah, Kenmore, Renton, SeaTac, Skykomish, Snoqualmie, Tukwila and Woodinville.

The next phase of the Flood District’s investigation will further refine the data to include different landslide 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. Additional work and funding from the King County Flood Control District will continue through 2016.