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‘It’s still significant’: New data reveals Barry Arm landslide’s threat level to Whittier

Published: Dec. 13, 2021 at 7:15 PM AKST
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ANCHORAGE, Alaska (KTUU) - New data has been released showing how waves from a potential tsunami triggered from the Barry Arm landslide could impact Whittier.

For about 18 months, the people of Whittier have known that the slow-moving landslide — about 30 miles from the town — could trigger a destructive tsunami.

But in July, scientists determined the waves that could hit Whittier would likely be smaller than previously feared. Scientists said this is good news for the costal town, but the threat is still real and can still cause destruction.

The original report predicted that in a worst-case scenario, a 30-foot tall tsunami could hit Whittier, but now scientists have said it will likely only be up to 7 feet tall. That’s a quarter of the previous prediction.

“I think it’s really important to stay focused on how dangerous this still is,” said Dave Snider with the Tsunami Warning Center. “We’re talking about a wave that could reach 3 to 6 feet up onto the shore.

“A catastrophic amount of water could be moving through there suddenly and with little to no notice at all,” he continued. “So it’s still very dangerous. It’s still significant, and it’s still something we’re very concerned about.”

Snider said right now though, it looks like the greatest threat is along the coastline in the bays and harbors around Whittier.

The wave is expected to take about 20 minutes to travel to the town. Snider said it would likely look something like a boar tide as it moved into Passage Canal.

“We’re not talking about a breaking wave or a surf-like wave. But it would be an unusual amount of water that’s moving very quickly up through Port Wells and eventually onto the coastline around Whittier,” Snider said.

Katy Barnhart is the main author of the new study.

“The water level will gradually increase and then gradually decrease,” she said. “In this case ... it would increase over about five minutes and then decrease over about five minutes.”

Barnhart said new water-depth data helped scientists come to new conclusions.

“Science evolves as we get better information,” she said.

Originally, there was concern the entire 650 million cubic yard landslide may fall into the water all at once.

“The first guess was, well, if this huge block all at once drops into the water, we’ve got a big problem. Obviously, yeah, that would be bad,” Snider said. “Now it looks like, you know, pieces of this rock are a little bit more likely to go at any one time, but not all at once. And that makes a huge difference in how much water is suddenly moving throughout Port Wells and Passage Canal.”

The amount of water is still dangerous, he said.

“It could still do a significant amount of damage for all the businesses and the people that use and recreate along the coastline near Whittier,” Snider said.

The people of Whittier should continue to monitor the situation and treat it like a serious threat, Snider said.

When a tsunami warning goes off, he said, right now people in the town won’t know if it’s from Barry Arm.

He said people should take the siren seriously, and move to high ground. If someone is on a boat, Snider said they should get off as soon as possible, or go to deeper water.

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