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State of Alaska Alaska / Natural Resources DNR / Geological & Geophysical Surveys DGGS / Geologic HazardsHazards / Barry Arm LandslideBarry Arm

Barry Arm Landslide and Tsunami Hazard

Status Report: Updated July 30, 2021

Summary

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. Summer fieldwork to evaluate the landslide and its potential for failure is underway with several field crews on site.

Updates

  • The U.S. Geological Survey (USGS) announced the release of new landslide-generated tsunami models for Prince William Sound (PWS) in the event of a Barry Arm slide failure. Note that although these model results suggest a landslide-generated tsunami may be less severe than previously thought, potential wave heights and currents may still be hazardous to nearshore communities, port entrances, marinas, and boatyards throughout PWS. If you have a boat, please see the "Ongoing Hazards" section below for general recommendations for recreational and commercial boaters.
  • Previous updates have been archived here

Ongoing hazards

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 local emergency managers and harbormasters and have a plan in place if a tsunami occurs. Although there are several instruments operating near the Barry Arm landslide, a real-time landslide and subsequent tsunami warning system is not yet operational. From the National Tsunami Hazard Mitigation Program and the California Office of Emergency Services:

For a large, local-source tsunami that may arrive in 10-20 minutes:

  • If you are on land or tied up at the dock: Do not attempt to take your vessel offshore. Leave your boat and go to high ground on foot as soon as possible. You do not have time to save your boat in this situation and put your life (and potentially the lives of others) at risk if you try to do so.
  • If you are in deep water or very close to deep water: Take your vessel further offshore beyond the "minimum offshore safe depth" of at least 30 fathoms (180 ft).
  • If you are on the water but very near shore: Use your best judgement to decide between two options: safely beach/dock the vessel and evacuate to high ground, or go beyond the minimum offshore safe depth of 30 fathoms (180 ft). Attempting to beach the vessel could be challenging and dangerous depending on wave conditions, coastlines and terrain, water levels, and the presence of sand bars. It is easy for a boat to run aground or capsize before reaching the shore only to then be swept away by the incoming tsunami. However, if you can safely beach or dock your boat and get to high ground before the tsunami, then this is your best option. If that is not possible, head to deep water as quickly as possible.

In general:

  • Contact your harbormaster or community emergency services to sign up for tectonic tsunami alerts.
  • Know where deep water (30 fathoms or more, 180+ ft) is and how long it will take you to get there.
  • Have adequate supplies (water, shelter, food) and fuel to remain at sea for 24 hours or more and do not return to the harbor until the harbormaster or port captain indicates it is safe to do so. You may be forced to return to a different harbor.
  • Do not take your boat offshore if you do not have these essential preparedness items.

Federal and state monitoring and warning

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.

The National Tsunami Warning Center (NTWC) installed water level gauges during the extreme low tide in the last week of April, 2021. These gauges will support development of a real-time tsunami warning system for nearby communities but the warning system is not yet operational.

Aerial reconnaissance on May 13, 2021 confirmed that the Alaska Earthquake Center (AEC) seismic station located on the Barry Arm slide was destroyed in late April, 2021. The most probable cause was a snow avalanche. Work to repair and upgrade the seismic monitoring stations and webcam was completed by the AEC on July 11, 2021, restoring real-time seismic data and hourly camera images from station BAE across the fjord from the landslide. Equipment destroyed in the April slide was partially recovered.

The Alaska Volcano Observatory (AVO) installed an infrasound array in Whittier in early February 2021; Signals likely associated with industrial activity in Whittier continue to be recorded on the infrasound array. No signals suggesting activity from the Barry Arm landslide were detected in the past two weeks, but AVO reports that the infrasound array is fully operational and functioning well. 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. Preliminary analysis of radar satellite imagery from early January through July 15, 2021 by the USGS indicates no detectable motion other than small changes at the coastline since late October 2020.

The Alaska Division of Geological & Geophysical Surveys (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.

The National Oceanic and Atmospheric Administration (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 conducted previously planned bathymetric surveys in Port Wells and near Whittier. This activity was not directly related to the Barry Arm landslide tsunami risk, but may yield helpful data.

Preparedness

The City of Whittier recently performed maintenance on and tested their existing tsunami siren 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:

Public input

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.

Next update

This message will be updated on August 13, 2021, or earlier if the threat level changes. For more information, please see our Barry Arm Summary Information & FAQ page.

Contact Information

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Alaska Department of Natural Resources
Division of Geological & Geophysical Surveys
3354 College Road
Fairbanks, AK 99709
907-451-5000
barryarm@alaska.gov

U.S. Department of the Interior
U.S. Geological Survey
Landslide Hazards Program
12201 Sunrise Valley Drive
Reston, VA 20192
703-648-5953
https://www.usgs.gov/natural-hazards/landslide-hazards

U.S. Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
National Tsunami Warning Center
910 S. Felton Street
Palmer, AK 99645
907-861-4202
https://www.tsunami.gov/
Twitter: @NWS_NTWC
Facebook: facebook.com/nwsntwc

U.S. Department of Agriculture
Forest Service
Chugach National Forest
161 East 1st Ave., Door 8
Anchorage, Alaska 99501
907-743-9500
https://www.fs.usda.gov/chugach/

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