Southeast lives with risk of landslides - and more in the future

Over the past decade, landslides have cost Southeast Alaska communities in both death and destruction - 11 deaths and tens of millions of dollars in property and infrastructure damage.

Now communities around Southeast are reckoning with a future in which more destructive landslides are likely, as climate change fuels the extreme rainfall events and storms that scientists say may lead to increasingly powerful events in the future.

The most recent major landslide, on Nov. 20 at 11-Mile Zimovia Highway in Wrangell, was the deadliest Southeast Alaska slide in decades.

"It was a traumatic experience," said Mason Villarma, Wrangell's interim borough manager. "For the entire town."

Three years earlier, a winter storm caused widespread flooding in Haines and triggered a landslide that destroyed homes, killing two residents.

In August 2015, it was Sitka where heavy rain triggered a landslide into a subdivision of homes under construction, leaving three people dead.

Around Alaska, between 30 and 40 scientists, engineers and others are working on landslide research, including a project to inventory historic slides to better understand zones of vulnerability over a vast landscape, said Lorraine Henry, a spokesperson for the Alaska Department of Natural Resources.

Unlike areas exposed to tsunamis, however, Southeast doesn't have a unified landslide warning system. Instead, communities have been developing their own mitigation and response strategies, one by one. Some Sitka residents have gone so far as to pioneer a grassroots landslide warning system that provides daily danger assessments.

But officials across the region emphasize how difficult it is to accurately predict landslides.

The Beach Road area in Haines where the 2020 slide hit wasn't considered a high-risk area, said Robert Venables, executive director of Southeast Conference and a former Haines Borough manager.

"We went through quite a few storm events, and cataloged areas that we thought would be at risk, and kept an eye on those, but where that landslide happened, no one had a clue," he said. "Not a clue."

In the meantime, communities must balance the risk of future landslides with pressure to develop new housing on scarce buildable land.

"You're either building at the foot of the mountain, or you're building on the side of the mountain," said Haines Mayor Tom Morphet. "We have very few flat areas that are not flood-prone or landslide-prone."

The way two quintessential Southeast Alaska elements - mountains and rain - combined into a deadly and destructive force has left some residents with a lingering sense of dread.

After the 2020 Haines landslide that killed two people, including her son's kindergarten teacher, the joy of living surrounded by mountains was tempered by a sobering realization, said Sylvia Heinz, a Haines resident.

"Mountains are supposed to be strong. They're part of our identity as Alaskans," Heinz said. "The reality that those mountains - both figuratively and literally - can come down and kill your people at any time is hard to come to terms with."

Many Southeast Alaska towns are strung along narrow strips of land between the ocean and the base of steep, forested slopes. The topography of the region is part of its allure - a place where mountains seem to rise straight out of the sea.

It's also a landscape that can give rise to sudden landslides. The U.S. Forest Service has documented thousands of landslides across Southeast in the Tongass National Forest alone.

Scientists know what triggers landslides: A steep slope in combination with weather, wind, destabilized soils and rock. In the future, a warming climate means Alaska is likely to see more intense rainfall events, according to Rick Thoman, an Alaska climate specialist at the University of Alaska Fairbanks.

Models predict that a warming climate will bring increased precipitation to high latitudes like Alaska in the coming decades. In Haines, record rainfall in December 2020 preceded the deadly landslide, according to the Haines Long Term Recovery Group.

"We fully expect that these extreme, short-duration rainfalls are going to go up, simply because there is more water vapor in the air," Thoman said.

Weather is just one factor, along with unstable soils, steep slopes, and seismic activity that can trigger landslides, scientists say.

While landslides are a natural part of the Panhandle's rainforest ecosystem, research generally shows logging can destabilize soils and expose slopes to saturation with rain, influencing the frequency and size of slides, according to reporting in The Seattle Times. A 2017 Washington State University study found landslides on logged forests in the Northwest would become more widespread as the climate changes.

The climate factor is "unequivocal," said Gabriel Wolken, a geologist with the Alaska Department of Natural Resources' geologic hazards program: "The climate is changing and producing more storms and worse storms, and those tend to influence how landslides happen."

In the hours before the Wrangell landslide in November, the town received about 2 inches of rain and saw wind gusts of up to 60 mph, according to the National Weather Service.

Compared to countries such as Switzerland or Japan, which have advanced mapping and mitigation plans for landslide risks, Alaska still has a long way to go in understanding its landslide hazards, Wolken said.

Still, the recent landslides have elevated the issue to a new level of public attention. Hundreds of questions about landslides have come to his division in recent months, Wolken said.

What scientists don't know is whether there are actually more landslides happening in Southeast Alaska, or just more high-profile slides that cause human loss of life and property damage.

The state doesn't yet have a full inventory of slides in Southeast Alaska, Wolken said. But a project is underway to catalog past landslides, and to install more high-elevation weather stations to more accurately gauge the way weather influences landslides.

In August 2015, heavy rains inundated Sitka and caused more than 60 landslides in a day, according to state geologists. One landslide, on Sitka's Harbor Mountain, sent a torrent of trees and debris into a subdivision, killing the city's building inspector and two brothers who were hanging drywall at a home under construction.

The landslide touched something at the heart of what it means to be a Southeast Alaska resident, said Lisa Busch of the Sitka GeoTask Force: Rain felt ominous.

"We know and accept that rain is part of everyday life. All of a sudden, after this landslide, people were afraid," she said. When it rained hard, "we would look to the hills and think, is it safe? Is it safe to send our kids to school?"

"Our town had changed," she said.

Locals felt blindsided, said Busch, who is the director of the Sitka Sound Science Center.

"It seemed obvious that we should have been worried about landslides - we have steep, post-glaciated terrain and we have a lot of rain," Busch said. "We should have been worried, but we were surprised. We were shocked."

Busch and a group of other Sitka residents began calling scientists, asking questions.

The calls and meetings led to the Sitka GeoTask Force, a collaboration between more than a dozen tribal, governmental and educational and research entities that sought to conduct research on landslide risk and answer the questions of worried Sitka residents. It eventually led to the first-of-its-kind Sitka Landslide Warning System, which uses a statistical model developed by scientists to estimate the likelihood of landslide activity based on three-hour rainfall totals.

New weather monitoring equipment was installed in locations higher on mountain slopes because rainfall totals collected at sea level can vary dramatically from totals at higher elevations, Busch said. People can look at an online dashboard that puts landslide risk into red, yellow or green categories.

What worked for Sitka might not work for other areas, she said. But the group has received grants to extend the warning systems model to other communities, including Klukwan, Hoonah, Skagway and two small communities on Prince of Wales Island.

In Haines, there are currently no plans for the borough to adopt a Sitka-style monitoring system, though the Haines Avalanche Center maintains a webpage that warns residents of landslide risks by comparing the community's recent precipitation levels to the record rainfall in December 2020.

For Southeast Alaska communities, monitoring and mapping landslides could bring pitfalls, local officials say.

The city could have liability issues if it determines an area is safe from landslides and then one hits, said Juneau Mayor Beth Weldon and City Manager Katie Koester. Conversely, there could be problems if an area is designated unsafe and there are no landslides, which could lead to falling property values and homeowners struggling to get insurance.

Juneau officials say they're aware of Sitka's landslide monitoring system, but there are currently no plans to adopt something similar locally. Sitka's system is run by a nonprofit and not the municipality itself.

"It's a really high-risk business to get into," Koester said of landslide monitoring. "We don't have the science to make those determinations."

Rockslides, which scientists say are a form of landslide, have also caused damage to the economic and social heart of Southeast Alaska.

In Ketchikan, the city's beloved family-owned grocery store Tatsuda's IGA was destroyed by a sudden rockfall in February 2020 and never rebuilt. A large cliff that pressed close to the building came down in the middle of the night, said Katherine Tatsuda, who owned the store with her father.

"Never in a million, billion years would we have imagined it could come down the way it did," she said.

After the rockslide, the risk of rebuilding the store in the same spot ultimately wasn't feasible, Tatsuda said. It would have taken millions to rebuild and more to ensure that more of the hillside wouldn't come down again, she said. Tatsuda decided to close the store, ending more than century in business in Ketchikan.

In 2022 in Skagway, city officials watched in horror as huge boulders toppled down a steep slope onto a cruise ship dock, the economic linchpin of the roughly 1,200-person municipality, said Andrew Cremata, who was mayor at the time. At one point, a shipping container was crushed "like an aluminum can," he said.

The privately owned dock had to close and cruise ships were rerouted.

Cremata declared an emergency and the city received millions of dollars for mitigation work to stabilize the mountainside and protect the dock. The mitigation even included hiring people to camp near the rockslide, watching for movement so that staff could alert the hundreds of tourists traversing the dock daily, he said. The 2023 cruise season passed without any significant rockfalls.

The risk of future slides is a problem that literally looms over Skagway's economy, he said.

Living with landslide risk is something Southeast Alaskans will have to get used to, officials say. Wrangell is waiting on an analysis of the Nov. 20 landslide before making plans about potential warning systems or mitigation efforts.

"We're not going to prevent these things," Villarma said. "But we can provide people with information to make good personal decisions."