Geomorphology and initiation mechanisms of the 2020 Haines, Alaska landslide

Abstract In early December 2020, an atmospheric river (AR) and rain-on-snow (ROS) event impacted the Haines, Alaska area, resulting in record-breaking rainfall snowmelt that caused flooding dozens of mass movement events. We consider AR—a one-in-500-year event—as trigger for devastating Beach Road Landslide (BRLS), which destroyed or damaged four residences took lives two people. The BRLS started as a debris avalanche transitioned into flow, with total approximate landslide volume 187,100 m 3 . Geomorphic analysis using lidar data identified evidence paleo-landslides displaced masses rock, one served source area BRLS. Significant structural features weak ultramafic bedrock defined head scarp formed failure plane. This study illustrates importance identifying pre-existing areas likely to produce future landslides. As increase ROS events is projected Southeast warmer wetter winters, we recommend development AR scale coupled geological information region, enhance warnings residents landslide-prone areas.