A section of land along the Lemon Creek side of Thunder Mountain in Juneau has been identified as a potential landslide hazard.
A group of researchers and emergency management experts hiked into the area to assess the risk Thursday morning.
Juneau Emergency Programs Manager Tom Mattice and his team gathered in the parking lot of Dzantik’i Heeni Middle School to share their findings. For starters, Mattice said there’s no immediate danger.
“But I think it’s just important to recognize we’ve found some obvious signs and we have some ways to start to track those,” Mattice said.
The team examining cracks in the landscape — places where the mountain has sagged — and they plan to measure those over time.
“We want to know how active the concern is,” Mattice said. “If we went up and looked at those cracks in the mountainside this year and they were six inches apart and we came back six months later and they were six feet apart, we would know that we had a really active concern.”
The team used a combination of Light Detection and Ranging, or “LiDAR” data and pictures of the landscape to identify the area as a hazard. Mattice said he’s hoping the general public will also help them keep an eye on it through what he called ‘citizen science.’
“People that are looking at these things, people that are hiking in the mountains and paying attention. If they see obvious gaping cracks opening up in places, maybe they’ll bring them to our attention,” Mattice said.
Geologist Bretwood “Hig” Higman is a part of the research team. He owns a small nonprofit called Ground Truth Alaska, which aims to educate others on Alaska’s natural resource issues.
Last year, Higman helped identify an area of land that could potentially crash into Barry Arm of Prince William Sound, northeast of Whittier Alaska.
“One of the things that jumped out when we were looking at that is it’s a super obvious instability,” Higman said. “It’s something that any geologist could’ve identified. You don’t need much expertise, and yet, even though thousands of people visit that area, nobody had noticed it.”
Higman said that was a red flag and a sign that maybe researchers needed to spend a little more time looking for the obvious, which prompted him to identify other sites like this one.
Unfortunately, even with careful tracking, an extreme rain event or earthquake could cause an unpredicted landslide at any time.
“What I would say after my walk today is that if it’s been raining for the last two weeks and it’s an earthquake longer than 20 seconds and you live at the bottom of a mountain, you should probably go somewhere else,” Mattice said.
And even if they get a pretty good idea of when the slide is coming, Higman said there’s no way to prevent it from happening.
“Sometimes people say ‘can we just go and like if we know it’s gonna fall anyway can we let it loose right now so at least we know when it’s gonna happen or maybe we can do it in little pieces?’ There isn’t really a way to do that.”
That means with the exception of being 100% evacuated, there’s no way to prevent damage or loss.