POTENTIAL EXTENTS AND VOLUME SCENARIOS OF LANDSLIDE INDUCED IMPOUNDMENT LAKES WITHIN DEER CREEK DRAINAGE, WASHINGTON

Landslides are prevalent geologic hazards which can cause injury or death, and result in significant damage to property and infrastructure annually. The steeply walled valley of Deer Creek, directly upstream from the town of Oso, WA, experiences high annual precipitation, driving rapid incision of a thick sequence of young unconsolidated glacial sediments, resulting in regular and ongoing slope failures. When a landslide occurs along a streambank, debris can partially or completely obstruct the stream’s flow, creating an impoundment lake and flooding upstream. Overtopping is the main cause of failure of landslide dams which can lead to an outburst flood, endangering populations and infrastructure downstream. Our research investigates potential slope failure scenarios, ensuing landslide dams, and extent of corresponding impoundment lakes in the Deer Creek drainage. Several models considering a range of landslide scenarios were generated by modifying the High-resolution LiDAR digital terrain model (DTM) to assess potential impoundment lake volumes. This project was developed to contribute to disaster risk reduction efforts of city planners and emergency personnel with the ambition of providing vital information about the nature of landslide dam related hazards in this locality.