Photo of house in Magnolia Bluffs
House in the Magnolia Bluffs area overlooking Puget Sound that was struck by a rapidly-moving landslide.The flow deposited material in the garage (upper level) and collapsed the front wall of the iving quarters (lower level).

When wet winter weather sets in, many residents of the Puget Sound area begin to worry about landslides. Landslides that occur on bluffs and hillsides of communities surrounding Puget Sound, Washington, pose a serious hazard to people, property, utilities, transportation, and businesses. After major storms caused hundreds of destructive landslides during the winter of 1996-97, the USGS began studies of landslides in the Seattle area. Subsequently, at the beginning of Seattle's Project Impact in February 1998, the USGS and Seattle agreed to collaborate on producing state of the art landslide and seismic hazard maps for the city. The USGS recently completed its suite of landslide maps for Seattle and developed methods that can be used to forecast the occurrence of landslides.

Photo of landslide
Landslide on the flank of a small drainage in northwest Seattle. Foundation of house on right edge of photograph and decks of neighboring houses were undermined.

The recent USGS landslide hazards analyses have benefited from several allied efforts, including the Seattle-sponsored compilation of its century-long landslide database, by its consultant, Shannon and Wilson, Inc.(see OFR-00-303 - Preliminary map showing landslide densities, mean recurrence intervals, and exceedance probabilities as determined from historic records, Seattle, Washington), acquisition of high-resolution topographic data by the Puget Sound LIDAR Consortium, and detailed geologic mapping by the Pacific Northwest Geologic Mapping & Urban Hazards. Landslide monitoring in cooperation with the Burlington Northern Santa Fe Railway, the Dominican Reflection Center, of Woodway, and the Washington Department of Transportation has contributed to understanding of the action of precipitation in causing shallow landslides as well as deep-seated landslides.