Southeast Alaska has seen several geohazards recently – glacial flooding last month in Juneau, a landslide-driven tsunami last year in Tracy Arm, and a deadly landslide in Wrangell in 2023. That followed deadly landslides in Sitka, Haines and Ketchikan in the last decade.
To learn how to prepare for such events, Wrangell residents gathered at City Hall last week for presentations from experts on earthquake, tsunami and landslide risks and preparedness.
The first presentation, given by the Alaska team for the National Tsunami Hazard Mitigation Program, showed attendees how earthquakes can drive tsunamis and why the waves are so destructive.
I think it’s important to stress that it is a misconception that communities in the Southeast are completely protected from tsunamigenic earthquakes.
Barrett Salisbury is the hazard program manager at the Alaska Division of Geological and Geophysical Surveys.
Salisbury says several earthquake scenarios could directly affect Wrangell Island, including quakes from the Aleutian subduction zone, the Haida Gwaii [HYE-duh GWHY] section of the Queen Charlotte Fault offshore British Columbia and activity in the Cascadian Subduction Zone in the Pacific Northwest.
These scenarios will be included in a report that Salisbury and his colleagues are preparing, along with draft maps to provide the borough with the information needed for hazard planning.
Once approved, those maps will also be published for the public [Web: at DGGS.Alaska.gov.]
The report will also show potential tsunami inundation lines, where the top of the flood waters may reach on the island, which will allow the borough to establish tsunami evacuation routes.
The landslide presentation was given by Jill Nicolazzo [Nee‑KOH‑LAt‑Soh], a geological engineer with the Alaska Landslide Hazards Program. Nicolazzo shared models created after Wrangell’s landslide three years ago that killed six people.
The maps showed that – like most other islands in Southeast – the risk for landslides is higher on the western-facing slopes, which are more exposed to ocean winds and storms. This is also where most of the island’s population resides.
The modeling also found that the steeper the landscape, the higher the landslide risk – and that there is a high correlation of landslides and proximity to creeks and waterways.
Landslide Program Manager Molly McCreary says that someone asked after the presentation why they mapped the whole island.
Doing the whole island is good because also people recreate and they drive anywhere there’s a road. So just to keep people aware of the hazards in these areas, I think is the main purpose. But also maybe they can use the map in a productive way to one, be informed and also two, maybe I was thinking of building here and maybe I want to alter my plan.
She says that while the maps’ intended purpose is to inform development, they can also be used to inform people recreating in the backcountry where there may be increased danger during periods of high rainfall.
Mike Lucio [LUCY-OH] is the geohazards mitigation coordinator for the Division of Homeland Security and Emergency Management.
We want everyone to be aware of what’s going on, but we also want people to be well educated, understand what’s going on, so we’re not talking from a place of fear or a place of misconceptions or bad information.
[Optional: Residents can learn more about tsunami hazards at K S T K-dot-org and see those inundation lines once published at Tsunami.Alaska.edu.]
