Mapping the risk: Which areas are vulnerable to landslides?

New map from USGS expands on previous attempts to document landslide risks across the country

By Chloe Bennett

A new map from the U.S. Geological Survey shows nearly all of the Adirondack Park is susceptible to mass movements of earth when triggered by a disturbance like rainfall.

Unlike much of the west or in the southern Appalachian range, the Northeast appears less likely to host constant slides. But the park’s mountainous terrain makes it a significant area at risk of the natural phenomenon, which could be exacerbated by global warming. 

“One possibility is that there are more landslides now due to more extreme storms or climate situations,” said Benjamin Mirus, a supervisory research geologist with the U.S. Geological Survey. Mirus is one of the scientists behind the interactive map, which was created after the passing of the 2021 National Landslides Preparedness Act. 

Landslides compelled by intense storms are not new to the Adirondacks. Slides and avalanches likely happen regularly in the High Peaks region, experts say, with records dating back hundreds of years. Yet a projected increase in precipitation events might trigger more slide scars on the park’s mountains. 

Recent extreme weather triggered Adirondack slides

The morning light of July 11, 2024, illuminated unrecognizable roads and ravines filled with mud in Essex County. Heavy rain from tropical storm Beryl the night before loosened the ground beneath rocks and vegetation from Split Rock Mountain and other slopes, washing the debris into adjacent neighborhoods. 

Gary Heurich, a resident of the town of Essex, said the cleanup of his neighborhood on Albee Lane near the base of Split Rock took more than two weeks. 

“It was just remarkable, and if there was a consistent comment among all of the highway crew and the contractor crew I worked with, nobody had ever seen anything like this before,” said Heurich. 

The community experienced a landslide, characterized by the downslope movement of dirt and debris. Officials from the town of Westport reported a similar scene after the deluge. 

One of the region’s most costly and damaging storms, 2011’s Tropical Storm Irene, also resulted in 20 new scars, a study from the University of Vermont states. One slow-moving slide earlier that year in Keene Valley was caused by sandy soil saturated with groundwater, likely worsened by severe rainfall. An 82-acre landmass moved 6 inches to two feet a day, damaging homes in the process. The steady current was deemed the largest slide in the state’s history.

Preparing for potential disasters

The new map from USGS expands on previous attempts to document landslide risks across the country. Mirus said he hopes the map will alert the public and decision-makers “to the fact that there could be landslide issues in their area and the time to learn about it is before a big storm, not afterward.”

Landslides that occur near populated areas can be just as damaging as a flood or wildfire, Mirus said. 

“Landslides are damaging, disruptive and deadly in that they can kill people,” he said. “They can destroy houses, they can block roads and damage roads, and they can also sever critical infrastructure.”

Yet there is no standard homeowner insurance policy that covers damage from such events. According to the Federal Emergency Management Agency, its National Flood Insurance Program might reimburse residents for mudflows, which move copious amounts of water through channels. It’s unclear if the same applies to rock and dirt that push downslope, causing landslides.

Mirus said preparation is key. Property owners can clear road culverts to make room for fast-moving debris downslope. Retaining vegetation on nearby slopes can also help lessen the flow’s velocity. 

“The best protection is arming yourself with knowledge,” Mirus said. “People typically don’t worry about landslides until they’ve impacted them or their community.”