Waves from a potential landslide into the Barry Arm of Prince William Sound could reach heights up to 7-feet just offshore Whittier, according to a new report by the U.S. Geological Survey. This “worst-case scenario” is much less severe than the preliminary 30-foot-high wave assessment previously issued by an interdisciplinary team of scientists in 2020.
The updated wave height estimates come after a months-long effort by state and federal scientists to investigate the Barry Arm landslide and assess its risk to those around the Prince William Sound. The newly reported values represent the most extreme of four of the report’s scenarios considering what would happen if the entire landslide fails catastrophically into the arm. The other three scenarios in the report resulted in smaller, but still potentially hazardous, wave heights.
The new USGS study draws upon two recent partner datasets that allowed researchers to better refine what might happen if the landslide were to enter the Barry Arm fjord. One of these was collected in the fall of 2020, when the National Oceanic and Atmospheric Administration mapped the seafloor near the landslide, generating high-resolution bathymetric data vital to modeling tsunami wave conditions. USGS models also relied upon recent lidar landscape data from the Alaska Division of Geological and Geophysical Surveys, which was used to estimate the landslide volumes applied in each of the scenarios.
“There were a lot of unknowns early on,” said Jonathan Godt, USGS Landslide Hazards Program coordinator. “But with the new landscape and seafloor data we now have a better idea what might happen if the unstable slope was to fail. This summer we’ll get an even better idea as field activities ramp up and we put eyes on the landslide up close.”
Scientists continue to study the situation in Barry Arm. Last month, DGGS announced a $2.2 million cooperative agreement with the USGS Landslide Hazards Program as part of a $4 million investment in 2021 by Congress to address landslide hazards in Prince William Sound. Currently, the USGS is actively monitoring slope movement using a combination of remote satellite imagery, seismic sensors and infrasound arrays.
Residents, businesses, mariners and recreationists throughout Prince William Sound should be aware of the potential risk, follow the advice of emergency managers and have a plan in place if a tsunami occurs. Bi-weekly updates on the status of the Barry Arm landslide can be found on the DGGS website at https://dggs.alaska.gov/hazards/barry-arm-landslide.html.