LANDSLIDES IN THE PACIFIC NORTHWEST: RECENT ADVANCES, ONGOING CHALLENGES

The wetter regions of Oregon, Washington, and British Columbia produce a variety of mass movements broadly defined as “landslides.” Initial slope failures initiate diverse styles and rates of downslope debris movement that can threaten communities, transportation and public utility infrastructure, and natural resource industries. Major advances in landslide science have occurred over the past several decades: new imaging and detection technologies (e.g., LiDAR, InSAR, CRTDP, and TLS); more powerful data analysis and sharing capability; the advent of GPS to precisely locate slides and track their movement; improved mapping and analysis capability with GIS; improved data telemetry for real-time tracking of slides; a new field-scale experimental flume to improve understanding of debris-flow mechanics; and improved slope stability, debris-flow-runout, and failure-initiation models (e.g., SHALSTAB, SINMAP, SCOOPS, LAHARZ, and TRIGRS). In addition, automated real-time landslide and debris-flow warning systems are now a reality. Yet frustrating obstacles to progress remain: limited understanding of the inherent complexity of natural slopes and precipitation; inadequate coverage of landslide inventories; limited funding for landslide investigations; a disconnect between academic researchers and geotechnical practitioners; the lack of regional systems for documenting landslide occurrence; and the reluctance of regulatory agencies (in the face of development and “property rights” interests) to fully utilize landslide studies and maps to regulate development or provide adequate hazard information in landslide-prone areas. Many emergency managers have a relatively good understanding of landslide hazards, especially if their jurisdictions have had recent activity, but some elected officials, high-level agency managers, and residents in at-risk areas have only a minimal awareness of landslide hazards. A poll of Northwest landslide experts suggests that more educational outreach to the public, more use of the media to raise awareness, more interaction between academic researchers and engineering practitioners, more exposure of agency heads and elected officials to landslide issues, and more government sanctioning of landslide hazard maps are needed.