THE OSO LANDSLIDE, WASHINGTON, MARCH 22, 2014 SHOWS THE NEED FOR SUSCEPTIBILITY MAPS AND INSURANCE

On March 22, 2014 an 8 million cubic meter landslide moved at a velocity of 100 km/hr down the slope above the Stillaguamish River near the town of Oso in northwest Washington killing 41 people who lived at the base of the slope (2 are also still missing). A total of 45 houses were destroyed, and $10 million in homes and contents were lost. The rescue/cleanup operation cost over $150 million. This landslide is the fifth most deadly landslide in the last 200 years of American history. Geologists were surprised at the volume and speeds of this landslide coming off of a 180 meter high cliff of glacial till and outwash sediments. The landslide occurred on a slope where historic landslides had happened in 1949, 1951, 1967, 1988, and 2006. Geologists knew this was landslide territory, but that information was not conveyed to land use planners of the county and eventually to people living there. This devastating landslide highlights the need for the production of landslide susceptibility maps first, and then for those maps to be used by local planners in counties and cities giving out building permits. The ability to make high quality landslide susceptibility maps is now available through the use of lidar imagery and GIS programs. Examples of landslide susceptibility maps will be discussed. The need for landslide insurance is also highlighted, for all of these people lost everything because landslides are not covered by normal homeowner’s insurance.