Early August Landslide in Kenai Fjords National Park triggers tsunami, scientists recommend caution in area

ANCHORAGE, Alaska (KTUU) - Scientists and Kenai Fjords National Park officials are recommending people going to an area near Seward to be aware after they say a major rain event resulted in an estimated 2.6 million cubic yards of land to slide and trigger a tsunami in Pedersen Lagoon earlier this month.

The massive slide occurred around 5 a.m. on Aug. 7.

The calls for caution around Southcentral and Southeast Alaska’s fjords where glaciers have retreated are not new, especially since the Barry Arm Landslide was discovered.

Preliminary data shows the wave reached at least 56 feet high in the upper part of the lagoon.

National Park Service (NPS) Alaska Regional Geologist Chad Hults said the landslide came down over the rapidly receding Pedersen Glacier and dug a trench into the ice as it trailed out into the lagoon and created a wave.

“Then the tsunami, as it went across the lagoon, it ran up on some of the hill slopes on the opposite side of the lagoon and took out some forest,” Hults said.

Hults heard the tsunami wave at the lodge was about three feet and a boardwalk was damaged.

He says a park steel bear container at a campground was also moved 20 feet.

Scientists say no one was hurt.

Geologist Bretwood “Hig” Higman said the danger in these situations is not over just because the landslide has happened. He cautioned that a slide could invite the possibility of another landslide.

Hults said people in the area don’t necessarily need to be worried, but should recognize the hazard if they are doing anything in the Pedersen Lagoon area, like boating or deciding where to camp.

He said it’s important to know tsunami warning signs and when to get to high ground.

Hults said a fellow scientist has now cautioned against doing research in the lagoon area this time of year.

“August seems to be the time of year that the slopes become more unstable,” Hults said. “It’s because you’re through the summer, so high altitude permafrost is thawed, and then the rains start coming in August.”

He said rain can cause rocks to crack, which can make the slope unstable.

“Major rain events are definitely times when you have to be wary about a potential landslide, and landslide generates tsunamis,” he said.

Interestingly, when the Kenai Fjords Glacier Lodge alerted scientists to a possible tsunami, they knew to look at the landmass nearby. They had already noticed it was likely unstable and had planned field work.

“It was actually planned for about the same time that it went off, that it released,” Hults said. “So we had it planned. We were going to do it. We had a flight for measuring the tidewater glaciers the week prior, but we had a technical issue that kept us from continuing the operation that day, so we weren’t able to capture it before the landslide released.”

USGS and the Park Service are working together on numerous projects across Southcentral and Southeast Alaska, he said. They’re looking to identify unstable slopes and to model potential landslide-generated tsunamis.

He said this event will be a really good test case for that research.

“There are some unstable slopes that we’ve identified that are above glaciers that are retreating, and just like this one, they could potentially release and land on the glacier and then flow down the glacier before they hit the water,” Hults said. “So, this is a really good test case where we can collect a lot of good data.”

This is not the only area of Alaska with the same hazard.

“Southern Alaska has very steep slopes that could be potentially unstable, just like this, and recognizing that that hazard exists is important for your making your decisions,” Hults said.

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