Inventory of Large Slope Instabilities, Prince William Sound, Alaska

Steep glacial and paraglacial landscapes often exhibit evidence of gravitationally-driven slope deformation. In recently deglaciated coastal environments, catastrophic failures of these bedrock instabilities as rapid landslides have the potential to generate tsunamis that may pose hazards for communities, infrastructure, mariners, and important natural and cultural resources. We present a first inventory of manually mapped bedrock instabilities in western Prince William Sound and nearby locations in the Chugach Mountains. Slope instabilities included in this inventory are defined as large areas (> 0.01 km2) that exhibit evidence of slope deformation, including scarps, tension cracks, and signs of recent smaller-scale landslides. Areas of repeat rock avalanches, that may indicate areas of larger deformation, are also included. All instabilities in this inventory were identified from a combination of field observations, satellite and airborne optical imagery, InSAR (interferometric synthetic aperture radar)-derived elevation models, and limited local lidar elevation models. This inventory is not exhaustive or complete, nor should it be considered a statistically representative sample of instabilities in this region. Furthermore, it is our intention to continue to add records to this inventory as previously unidentified instabilities are discovered or develop in changing conditions. The data presented here represent bedrock instabilities in western Prince William Sound identified prior to February 2023.