The largest-ever landslide in Vermont came crashing in the spring of 2019, as 12 acres of earth tumbled from a hillslope near Waterbury.

The slide blocked the Cotton Brook, buried a trail and spewed rock and sediment into one of northern Vermont’s most visited lakes.

The next year, the same hillslope slid again.

That’s not uncommon, said Keith Klepeis, a professor in the Department of Geology and an expert on geologic motion and bedrock aquifers.

“Often, at sites of landslides, it's not a one-off,” Klepeis said. “It can happen multiple times.”

Klepeis, along with other researchers at ̽̽, has taken up a vital role in observing landslide events around the state.

Landslides occur around the world as a natural process, typically in mountainous regions. But these events can devastate local ecosystems and human infrastructure.

Vermont has had more than 3,000 recorded landslides, with many more thought to have occurred. Many of these mapped landslides happened in the northern and central parts of the state, nested along the spine of the Green Mountains. Klepeis and fellow researchers at ̽̽, Norwich University and the Vermont Geological Survey investigate the how and why behind these repeated disasters.

Models using satellite imagery show the impact of the 2019 landslide at Cotton Brook, which swept away much of the surrounding foliage.

Common consensus tends to favor the idea that large, heavy rainfall events trigger landslides.

“In the last 100 years, more frequent massive Gulf-Atlantic hurricanes are hitting New England,” Klepeis said. “These storms are thought to have the potential to trigger these large events.”

With changing climate, New England is expected to see storm events gain magnitude, which ultimately brings more flooding and triggers landslides, he said.

“So, this avenue of research, it’s timely but urgent, very urgent,” Klepeis said. “We're trying to get a handle on it. I'm not the only one. There's lots of people doing it, and it's taking a community.”

Klepeis stressed the idea that it takes a team to solve this complex natural problem.

“Then as a group, you kind of look at the whole picture and as a system and try to see how the different parts interact and what we can do about it,” he said.