GEER Response to Washington Landslide

A team from the Geotechnical Extreme Events Reconnaissance (GEER) Association, supported by the National Science Foundation, is mobilizing to collect information on the effects of a landslide that occurred on March 22, 2014 on a steep slope above the North Fork of the Stillaguamish River adjacent to a rural residential community near Oso, Washington. GEER members and other geotechnical professionals are documenting the effects of the Washington landslide on the built and natural environments. Dr. Jeffrey Keaton, a principal engineering geologist at AMEC Americas and member of the GEER Steering Committee, along with Dr. Joseph Wartman, Associate Professor of Civil and Environmental Engineering at the University of Washington and GEER member, are coordinating the investigation of the geotechnical impacts of the landslide and resulting unchannelized debris flow. Advancing strategies for adapting to climate-triggered geotechnical processes requires that we understand what happened leading to the collapse of the slope so that communities and infrastructure systems can be designed for greater resiliency and enhanced public safety.
Also participating in the investigation are Mr. John deLaChapelle (Golder Associates), Dr. David Montgomery (University of Washington), Dr. Jean Benoît, (University of New Hampshire and GEER member), and Dr. Scott Anderson (Federal Highway Administration and GEER Steering Committee member). These geologists and engineers will benefit from work performed by the Washington State Department of Natural Resources (DNR), Washington State Department of Transportation (WSDOT), U.S. Geological Survey (USGS), U.S. Department of Agriculture – Forest Service, and others. GEER teams focus on documenting geotechnical effects of extreme events as part of a National Science Foundation (NSF) program to turn disaster into knowledge.
The March 22, 2014 Oso Landslide (also known as the Hazel Landslide and the Steelhead Haven Landslide) occurred on a valley slope with a history of intermittent landslide occurrence going back to the 1940s, with the previous landslide movement in 2006 that blocked the river but did not affect any homes. The Oso Landslide is one of many landslides that have occurred on slopes in the valley of the North Fork of the Stillaguamish River. The March 22, 2014 Oso Landslide became a rapidly moving, unchannelized debris flow that spread out as it travelled about ½ mile, damming the North Fork of the Stillaguamish River, destroying and carrying away about 50 homes, and burying about 1 mile of State Highway 530. By March 29, 2014, the confirmed death toll was 17, with another nine bodies found but not identified, and about 30 people still unaccounted for.
Precipitation in March leading up to the Oso Landslide was nearly twice the average amount. At 10:37:22 AM Pacific time on March 22, a seismograph in the Pacific Northwest Seismic Network about 11 km southwest of the landslide recorded vibrations for about 2-1/4 minutes generated as the landslide mobilized from a steep slope above a bend in the North Fork of the Stillaguamish River that separated the landslide from the rural residential community. The landslide dam blocked the river for approximately 24 hours, at which time it started breaching gradually, without releasing a major flood.
Extreme events engineering is an experience-driven field where immediately following the occurrence of an event (e.g., earthquake, tsunami, hurricane, landslide, or flood), perishable data that can be used to advance our understanding is systematically collected. Observations of actual events are particularly important in the field of geo-engineering, because it is difficult to replicate in the laboratory soil deposits built by nature over thousands of years and sediment-water slurries that include large boulders. Detailed mapping and surveying of damaged areas provides the data for well-documented case histories that drive the development of many of the design procedures used by engineers. Documenting and sharing the key lessons learned from major events around the world contributes significantly to advancing research and practice in engineering.
After the Oso Landslide field investigation is complete, observations and findings will be posted on the GEER website. Images from the various investigators also will be posted on the website and visible through Google Earth. Additional information is available on the GEER website at: http://www.geerassociation.org/