Portion of California's Highway 1 Collapsed Into the Ocean After a Mudslide

A portion of California's coastal Highway 1 collapsed last week due to mudslides from heavy rain.

Both lanes of the highway sunk into the Pacific Ocean on Jan. 28, leaving a gaping hole in the road about 15 miles south of Big Sur. The collapse will cost millions of dollars to repair, and it is unclear when the highway will reopen, according to the Los Angeles Times.

Travelers who are driving through the area will have to reroute to alternate roads to avoid the closures. The town of Big Sur is now only accessible from the northern side of the washout.

The area received more than 15 inches of rainfall last week, which caused damage to more than 25 structures.

The type of damage caused to the highway is known as a "slip out," a collapse that happens when the soil on either side of the road becomes so saturated that nothing can hold it in place.

The area is particularly vulnerable to mudslides after a season of intense wildfires. Last fall, a wildfire burned more than 48,000 acres in the area, leaving the soil unstable. Without vegetation to hold the soil in place, there is an increased risk of mudslides when heavy rain falls.

"The heavy rainfall is always a challenge, but when you've got the fires and the rainfall within a few months of each other, even a few years of each other, you generate a whole new category of risks," Stanford University environmental studies professor Chris Field told NBC News.

Dramatic drone footage from Caltrans shows the impact of the mudslide and a steep drop into the Pacific Ocean.

This is not the first time that a portion of Big Sur's stretch of Highway 1 has collapsed into the sea. In 2017, the highway closed for several months after repeated mudslides in the late winter and early spring.

Cailey Rizzo is a contributing writer for Travel Leisure, currently based in Brooklyn. You can find her on Twitter, Instagram, or at caileyrizzo.com.