2009 Hazard Mitigation Plan
Four types of landslides can potentially affect Shoreline. They are deep-seated, shallow, bench and large slides. Puget Sound’s shoreline contains many large, deep-seated dormant landslides. Shallow slides are the most common type and the most probable for Shoreline. Occasionally, large catastrophic slides occur on Puget Sound. The soil covering much of King County was left behind by the Vashon Glacier and is prone to slides.
A large slide occurred in the town of Woodway, just north of the Richmond Beach neighborhood during the early morning of January 15, 1997. It cut fifty feet into the property above, passed over the railroad tracks and knocked a freight train into the Sound.
The Holiday Blast Storm of December and January 1996-1997 was the cause of this massive landslide. The storm also caused a large washout/landslide within Shoreline along NW 175th Street near 6th Avenue NW that was a federally declared disaster. The 100 foot long sinkhole cost 2 million dollars to repair. However, the sinkhole provided opportunities to implement a series of Low Impact Development concepts ultimately reducing flooding and water quality problems while increasing fish habitat and providing recreation opportunities.