TOWARDS THE ESTABLISHMENT OF AN EARLY WARNING SYSTEM FOR A LANDSLIDE WITH TSUNAMIGENIC POTENTIAL: BARRY ARM, PRINCE WILLIAM SOUND, ALASKA

Glacial recession leaves adjacent slopes vulnerable to mass wasting processes, including rockfall, rock avalanches, and both shallow and deep-seated landslides. In Arctic and sub-Arctic coastal environments, these slope instabilities cause an elevated potential for the generation of large tsunamis that could impact nearshore communities, infrastructure, marine traffic, and other important natural and cultural resources. In northwestern Prince William Sound (PWS), Alaska, one example of this cascading hazard is found in Barry Arm, where the relatively rapid retreat of the Barry Glacier has exposed the toe of a slow moving ~500 M m³ deep-seated landslide. Should the landslide fail catastrophically, it could generate a wave that would have impacts to near-field activities, and to more distal communities and marine traffic. To reduce the risk, a consortium of federal, state, and local agencies is working under a Congressional mandate to establish an operational warning system to alert the public of a landslide-generated tsunami. The overall inaccessibility, harsh environmental conditions, and lack of established communication channels for the transmission of monitoring data, exacerbate the complexity of this interagency objective.

An operational early warning system requires much more than a network of sensors and a method for disseminating an alert. Additionally, it is necessary to establish and maintain several critical system components, including a robust surveillance and monitoring network for landslide monitoring, forecasting, and detection, a science-based hazard and risk assessment protocol, a framework for communication and preparedness activities, and a sustainable plan for system operation and maintenance. Here, we present the protocol and status of this collaborative effort in PWS, with a focus on the development of a system that is robust and sustainable and a discussion on progress and lesson learned since work commenced in late 2020. While this effort is currently focused on hazards specifically related to the Barry Arm landslide, the methods and processes developed here could be used for other potential tsunamigenic landslides in coastal Alaska, North America, and elsewhere.