Hurricane Helene creates landslide conditions in western North ...

Published September 27, 2024 at 11:00 AM EDT

Already by midday Friday, word-of-mouth reports of landslides in the Blue Ridge Mountains were coming in. Scientists predict any rainfall over 5 inches is enough to create the conditions for landslides in western North Carolina. The National Weather Prediction Center has forecast 6 to 12 inches in the Southern Appalachian Mountains during Hurricane Helene.

“To me, the biggest concerns around here are debris flows, which are very wet, very fast moving and can travel long distances,” said Brad Johnson, who studies landslides and erosion at Davidson College.

These flows can travel over a mile, carrying rocks, trees and other hazards. The 2004 Peeks Creek landslide traveled over two miles, killing five people and destroying 15 homes.

The best defense against these disasters is to not be there when they happen — but people have built prodigiously in the mountains over recent decades.

During that same time, the burning of fossil fuels continues to warm the Earth’s atmosphere. Warm air can hold more water, creating the conditions for more devastating rainfall events. However, Johnson said the impacts of climate change are difficult to uncouple from other human impacts on the landscape:

“Rather than water falling on a tree, trickling through and soaking into the soil, it hits a roof, goes down a downspout and it's immediately on the ground,” Johnson said. “Everything we do that creates impervious surfaces is a problem at the end of the day.”

In 1940, a Category 2 hurricane brought 20 inches of rain and over 2,000 landslides to the Blue Ridge Mountains. Those mountains had been recently logged, removing any erosion control that the trees had provided.

Because insurance does not usually cover landslides, these disasters are financially devastating as well as life-threatening. The threat of landslides passes soon after the storm, but people living where landslides have happened in the past should evacuate before heavy rains.

“If I lived in a floodplain during an event like this, I'd probably get a hotel room somewhere that wasn't in the floodplain,” Johnson said. “And if I think I lived in a house that was on a debris flow, I would just treat it the same way.”