California’s Highway One, stretching more than 650 miles along the Pacific Coast, is one of America’s most popular roadways because of its breathtaking views. Yet, since 2023, large chunks of it have been closed.

That year, a series of atmospheric rivers pummeled the state with rain, triggering landslides and rockslides that the iconic thoroughfare wasn’t built to withstand.

“When they engineered these roads, they made big assumptions that we weren’t going to have big changes in precipitation,” says Paul Chinowsky, professor emeritus of civil engineering at the University of Colorado at Boulder. Planners also didn’t anticipate severe erosion that’s become more common on a warmer planet. “We literally built the roads on the edge of land,” he says.