The interagency science team reports no changes to the landslide that warrant a change in status for the past several months. The potential landslide and tsunami threat remain present and unchanged. Additional water-level monitoring equipment in Barry Arm is scheduled for late April to support an early warning system for tsunami events. Field-based surface monitoring of the unstable slope is currently not possible due to snow cover.
DGGS Geohydrologist Ronald Daanen collects ground control on Mt. Coville Ridge; Barry Arm landslide visible in the distance. Photo 4/7/21 by Katreen Wikstrom Jones
Signals likely associated with industrial activity in Whittier continue to be recorded on the Alaska Volcano Observatory (AVO) infrasound array. No signals suggesting activity from the Barry Arm landslide were detected in the past two weeks.
Preliminary analysis of radar satellite imagery (collected from early January into early April) by the U.S. Geological Survey (USGS) indicates no detectable motion other than small changes at the coastline since late October 2020. Small rockfalls and noise from nearby glaciers are observed daily on the functioning Alaska Earthquake Center (AEC) seismometer.
There is no evidence at this time to indicate a significant landslide failure is imminent or will happen any time soon. Alaskans should be aware of the ongoing risk and follow the advice of emergency managers and have a plan in place if a tsunami occurs.
State and federal agencies are monitoring the slow-moving landslide 28 miles from Whittier, Alaska, in Prince William Sound that could fail and generate a tsunami.
AVO installed an infrasound array in Whittier in early February; this system could aid in a future real-time warning system. AVO provides background information on how infrasound monitoring works.
The USGS recently published a structure map of landslides at Barry Arm. The landslide structures and movements shown on this map will be used to monitor landslide evolution and help estimate landslide volumes for tsunami modeling. New satellite data, available approximately every 24 days, is examined by USGS scientists. In snow-free conditions, these satellite observations can provide a regular assessment of movement for the entire Cascade, Barry, and Cox glaciers area. However, current winter conditions substantially limit these monitoring techniques.
DGGS conducted airborne surveys of the area in June and October 2020, and April 7, 2021. Additional repeat flights are planned for Spring 2021. High-resolution (10 cm) elevation data, collected June 26, 2020, are available. Repeat airborne surveys provide information about centimeter-scale slope movement but require ideal flying and snow-free ground conditions and substantial time for data processing. Lidar scans conducted during the wintertime provide tools to map snow distribution and calculate snow water equivalent in the Barry Arm area.
One of the two seismic stations and a camera operated by AEC are currently not sending data due to heavy snow load. We expect communications to improve as snow loads subside later in the spring. When operational, these systems are not intended to provide real-time warnings, but will be used to support the tsunami early warning system once it is installed.
NOAA conducted a bathymetric survey of the Barry Arm and upper Port Wells area in August, 2020. These data will be used to improve models of potential tsunami propagation across Prince William Sound. NOAA Coast Survey is conducting previously planned bathymetric surveys in Port Wells and near Whittier. This activity is not directly related to the Barry Arm landslide tsunami risk, but may yield helpful data. The National Tsunami Warning Center will install tsunami warning gauges during the extreme low tide in the last week of April 2021. When in place, these gauges will support development of a real-time tsunami warning system for nearby communities.
The City of Whittier performed maintenance on and tested their existing tsunami siren this week and is investigating adding a second alert siren.
The Alaska Department of Homeland Security & Emergency Management (DHS&EM) provided the City of Whittier with new tsunami evacuation signage.
Coastal communities, mariners, and all visitors in Prince William Sound should remain informed, heed U.S. Coast Guard (USCG) and U.S. Forest Service (USFS) warnings to avoid the immediate area, and review emergency response and evacuation plans in the event of a tsunami. For more information, please contact your local emergency management authority and see these web resources:
If you have questions or more information about the Barry Arm landslide, we encourage you to reach out to DGGS via Facebook or Twitter, or by emailing barryarm@alaska.gov.
This message will be updated on April 23, 2021, or earlier if the threat level changes. For more information, please see our Barry Arm Summary Information & FAQ page.
