Tsunami threat to Whittier less severe than early estimates, scientists say

The Barry Arm fjord this May. (Alaska Division of Geological and Geophysical Surveys)

Geologists have been warning Alaskans for over a year about a tsunami that could hit Whittier following a potential landslide at Barry Arm in Prince William Sound.

They’re still ringing the alarm bells. But now, armed with more information about the area, they’re saying that the largest wave they would expect is smaller than earlier estimates.

The new data has allowed researchers to drop their worst-case estimates for Whittier from a 30-foot wave to a 7-foot wave.

“And get a little less concerning result,” said Jonathan Godt, who coordinates the landslide hazards program for the U.S. Geological Survey.

Barry Arm is part of a fjord northeast of Whittier. There are several glaciers there, and for years they’ve been rapidly retreating, leaving a steep slope of material behind. Until 2012, the water in the arm was still covered by the glacier.

That material left by the glacial retreat is very unstable. And scientists say if enough of it slides into the water at once, it could trigger a tsunami in Whittier.

Godt said they’re still trying to learn more so that they can better anticipate a catastrophe.

“This report is just one of what is likely to be many others coming out in the next few years to really provide the people who live, work and play in Prince William Sound a better understanding of the risk,” Godt said.

Last year, researchers mapped the floor by the toe of the glacier and the landslide itself. Through a system of equations, they were able to simulate the resulting wave and come up with that 7-foot estimate.

This is the first time researchers have done a simulation like that, Godt said.

Scientists are still still concerned about the threat of a landslide and tsunami. As for what exactly that threat would look like to the people of Whittier, Godt said that’s still a big question mark.

“What isn’t in this report is a description of what the water does once it reaches the shore, in Whittier in particular,” he said. “And that’s a piece of work that remains to be done.”

Researchers are conducting additional studies in the area this summer. Godt said they’ll install equipment that will help them figure out how the landslide is moving, for example, and how it is impacted by the environment.

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