Barry Arm Landslide and Tsunami Hazard

Highlights of Recent Activity

Scientists from the U.S. Geological Survey (USGS), Alaska Division of Geological & Geophysical Surveys (DGGS), University of Alaska – Fairbanks Alaska Earthquake Center (AEC), National Tsunami Warning Center (NTWC), and University of Utah recently completed a productive summer field season in Prince William Sound.

Highlights of this summer season include:

• Installation of a temporary 4-element infrasound array in Yale Arm to perform a preliminary characterization of mass movement activity on several slow-moving landslides in the area
• Routine maintenance of multiple meteorological stations in the vicinity of Barry Arm that will allow us to better characterize the environmental conditions that may contribute to hillslope instability
• Routine maintenance of a ground-based radar system in Barry Arm that is used to measure slow rates of movement across the Barry Arm landslide
• Routine maintenance of a network of water level sensors that are used to detect a wave generated by failure of the Barry Arm landslide for warning purposes
• Geologic and structural mapping in multiple locations throughout southwestern Prince William Sound that will allow us to better understand the geologic controls on the regional distribution of landslides
• Installation of temporary seismometers in Barry Arm and Yale Arm for the purpose of characterizing the depth of potential sliding surfaces and their geometry and the seismic signals associated with slow landslide movement
• Outreach activities in Whittier, Alaska
• In addition to fieldwork, scientists from the USGS, DGGS, AEC, and U.S. National Park Service travelled to Norway in mid-September to meet with colleagues at the Norwegian Geological Survey to exchange insights, experiences, and ideas related to monitoring large, slow-moving landslides in sub-arctic environments and characterizing their hazard

Upcoming Fieldwork

• No fieldwork is currently planned
• Maintenance trips may occur during winter should systems go offline and when conditions permit

Upcoming Public Events - November 2024

• No public events planned
• Scientists from all partner agencies will be presenting their scientific progress at the upcoming annual meeting of the American Geophysical Union (AGU) in Washington, D.C. in early December

Current Landslide Status

An ongoing landslide and landslide-generated tsunami threat exists in Barry Arm, northwestern Prince William Sound, Alaska. The landslide is stable or exhibiting slow rates of deformation (<50 mm/d). Localized areas of higher velocities may be evident, but movement is largely surficial. While potential failure of these areas may result in a localized tsunami, failure is unlikely to represent a region-wide tsunami threat. Partial or catastrophic rapid failure is unlikely without external forcing, such as that associated with a strong regional earthquake. "Small" but infrequent rockfalls and shallow landslides may be commonly observed.

Mariners should remain vigilant when in the vicinity of Barry Arm or nearby waters and be prepared to depart the area if any unusual rockfall activity is seen or heard, or if unusual waves, currents, or tides are observed.

Background

(Last updated February 2, 2024)

The Barry Arm landslide is a large (~500 M m³ or 650 M yd³) landslide located in the northwestern corner of Prince William Sound, Alaska. Rapid failure of the landslide has the potential to create a tsunami that results in life-threatening waves and currents in Barry Arm, Harriman Fjord, Port Wells and adjacent fjords. The existence of the landslide is evident in photographs dating back to at least 1935, with possible evidence of the landslide in photographs dating to 1913.

Throughout the observational record, the Barry Arm landslide has experienced slow movement punctuated by episodes of acceleration. While slow downslope movement is both common and expected, rapid increases in the rate of movement may be a possible precursor to catastrophic failure. As such, observations and hazard messages are often centered around trends in the observed rates of downslope movement at Barry Arm, as measured by ground-based, aerial, and satellite surveillance methods.

The Barry Arm landslide is being monitored by a multiagency team of scientists from the U.S. Geological Survey (USGS), National Tsunami Warning Center (NTWC), Alaska Division of Geological & Geophysical Surveys (DGGS), and the University of Alaska Fairbanks Alaska Earthquake Center (AEC). For more information on monitoring activities, equipment and data availability, please visit https://landslides.usgs.gov/storymap/barry-arm/.

Continuity of Operational Monitoring Network

(Last updated February 2, 2024)

Scientists at USGS, DGGS, AEC, and NTWC will continue to make every effort to minimize outage of this critical network of sensors. The Alaska environment and its inhabitants can wreak havoc on our sites: strong winds can damage sensors, power components, and antenna; deep snow can bury instruments and solar panels and makes it difficult to access (and even find) sites, rain can work its way into sensitive electronics, and our four-legged neighbors, such as bear, deer, and goats, have a taste for our wiring and enclosures. While we have made our best effort to harden the sensors, power systems, and telemetry for continuous operation of the equipment and to resist weather and animals, it is necessary to have reasonable expectations given the difficulties of working in this harsh environment. Reasonable expectations include:

• Safety of the scientists and engineers who maintain the systems is paramount. Poor weather conditions may prevent us from traveling to Barry Arm via helicopter or boat for immediate repair and restoration of system functionality.
• Prolonged outage of one or more sensors is possible. All efforts will be made to keep equipment operating throughout the year. However, high winds, deep snow, and other hazards such as snow avalanches and rockfall may prevent us from fixing instruments even if we are able to reach the sites.
• Deep snow, evolving snowpack, and variable atmospheric conditions make it difficult to precisely measure landslide deformation. As such, our ability to inform the public about landslide movement is significantly diminished during winter or when clouds or rainfall obscure the view from the air or space.

Instrumentation Status

An 8 element seismic array installed in cooperation with the Alaska Earthquake Center is planned for early August and will be operated for 2-3 months. There will be maintenance on the infrasound array and a timelapse camera system installed in early August as well.

Monitoring Method	Agency	Operational Status	Notes
Water Level	NTWC	Online
Seismic - BAE	AEC	Online
Seismic - BAT	AEC	Online
Infrasound - BAEI	USGS	Online
Ground-Based Radar	USGS	Online
Deformation camera	USGS	Online
Satellite InSAR and imagery	USGS	Limited	Loss of coherence in winter as a result of snow conditions
Hydrometeorology - BAE	DGGS	Online
Hydrometeorology - BAW	DGGS	Online
Hydrometeorology - Mt Doran	DGGS	Online

Recent Publications

• None

Next Update

This message will be updated on January 3, 2025, or earlier if the threat level changes. For more information, please see our Barry Arm Summary Information & FAQ page.