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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 Update September 23, 2022

We still see continued deformation and movement in the Barry Arm landslide as reported on September 16. Scientists at the U.S. Geological Survey, the Alaska Division of Geological & Geophysical Surveys, and the National Tsunami Warning Center have suspended non-essential boat-based operations and will continue to monitor the landslide movement and provide further details on Friday, September 30, unless significant changes warrant earlier updates.

Information statement from September 16, 2022

  • The spatial extent of the area currently moving within the Barry Arm landslide has increased since initial motion was detected on August 23. Movement now includes the entirety of the "Kite," and large portions of the "Prow" and "Core."
  • The U.S. Geological Survey, Alaska Division of Geological & Geophysical Surveys, and the National Tsunami Warning Center have indefinitely postponed Barry Arm fieldwork requiring water access.
  • Movement in these parts of the landslide is common, but current rates of motion are at or above the range of rates that have been measured since 2020.
  • The thickness of material that is moving is currently unknown.
  • This ground motion does not mean that a failure will occur. However, it is notable because of the areal extent of motion, elevated rates of motion, and that the portion of the landslide experiencing movement is right above the water.
  • If the part of the landside that is currently moving fails rapidly, anyone in the immediate vicinity, including Barry Arm and Harriman Fiord, would face a life-threatening tsunami. Dangerous currents and onshore impacts would be expected in Port Wells, Blackstone Bay, Cochrane Bay, Passage Canal, and in Whittier, Alaska.
  • The interagency team will continue to monitor the landslide area and the water beneath it with existing instrumentation and satellite data.

The potential landslide and tsunami threat remain. The full interagency information statement is also available here. This page will be updated on September 30, 2022, or earlier if the threat level changes. Previous updates have been archived here.

 

Current observations

(Last updated September 16, 2022)

A ground-based synthetic aperture radar instrument installed on the east side of Barry Arm revealed the movement of a portion of the Barry Arm landslide beginning early in the morning on August 23, 2022. More recent data identified additional areas that are also moving. Satellite data and imagery from nearby cameras confirmed that a larger portion of the Barry Arm landslide is now moving at rates between 40 and 70 millimeters per day (1.6 to 2.7 inches per day). We are currently unable to estimate potential slide volumes as the depth of the current motion is unknown.

Based on analysis of historical topographic and satellite data for the Barry Arm landslide, movement at this part of the landslide is common. Previous studies at Barry Arm have identified ground movement at similar or much greater rates since 2008. However, the recent ground movement identified in multiple data sources is notable in that (a) it includes a much larger area than previous data, (b) the movement is at rates at least 2x greater than the last period of similar patterns of motion in 2020, and (c) it is in a location that is perched directly above the water.

Prognosis

Localized ground movement is not necessarily a precursor to partial or complete failure of the Barry Arm landslide. Continued movement at this rate, or increases in the rate of motion, would further increase the potential for failure of this portion of the landslide. If the area failed rapidly, it would generate a life-threatening tsunami in nearby waterbodies, such as Harriman Fiord, Barry Arm, College Fiord, Port Wells, Cochrane Bay, Blackstone Bay, and Passage Canal. Tsunami inundation and dangerous waves and currents would also be expected in Whittier, Alaska.

Current monitoring

(Last updated September 16, 2022)

U.S. Geological Survey scientists will continue to track the landslide for signs that hazard may be increasing, such as an acceleration in the rate of movement. Systematic monitoring of optical imagery and remote sensing data is conducted throughout the year. Ground-based radar observations are made multiple times per day during avalanche-free conditions (May through October). New satellite observations are available bi-monthly with favorable atmospheric conditions.

There is a local monitoring network in Barry Arm that includes two seismometers, an infrasound array, a ground-based radar, several weather stations, and four cameras. In addition, there is an infrasound array located in the town of Whittier, Alaska, approximately 50 km (31 miles) from the Barry Arm landslide. The National Tsunami Warning Center (NTWC) also operates three water level sensors in Barry Arm.

The National Tsunami Warning Center in Palmer, Alaska, is testing a developmental real-time warning system in place for the Barry Arm landslide and potential tsunami. Updates on the status of the landslide as determined by current monitoring capabilities will be provided through the Alaska Division of Geological & Geophysical Surveys Barry Arm landslide webpage and email list (linked below).

Background

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, catastrophic failure of the landslide could generate a tsunami that would be life-threatening for anyone in Barry Arm, Harriman Fiord, and parts of Port Wells. A significant risk might also exist in other, more distal locations of western Prince William Sound, including the town of Whittier, Alaska.

The existence of the landslide is evident in imagery dating back to the 1920s. Slow ground motion has been documented going back several decades. Increased movement was documented during the rapid recession of the Barry Glacier from 2010 - 2016, with observed rates up to 26 ± 3 m/yr observed from May 2010 to September 2013. Deformation rates returned to a background level of approximately 1.3 ± 0.7 m/yr in March of 2017 as the retreat of the Barry Glacier ceased.

Ongoing hazards

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.

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 September 30, 2022, 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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