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California's Highway 1 collapse in Big Sur was caused by weather, waves, gravity. That's the good news

Grace Toohey, Los Angeles Times on

Published in News & Features

He said rockfalls like the one near Rocky Creek Bridge are a natural part of the coast's erosion, but they can also be exacerbated by more extreme climate conditions, including particularly wet seasons or wildfires. Though this winter in Big Sur hasn't been quite as wet as the last, Warrick said his team is still seeing movement on a similar scale to what was recorded last year.

"Water both adds weight and [acts as a] lubricant to the rocks out there," Warrick said. "It's occurring on the landscape that was already wet from last winter. ... We've had two wet winters in a row, so we're seeing quite a bit of hydrologic sliding."

The Rocky Creek slip-out is only one of several areas that saw destabilizing shifts and slides this wet winter and spring, adding to a list of vulnerable sites along Big Sur's coastline. For decades the USGS has been monitoring coastal cliff erosion along Big Sur, and in recent years the agency has been using remote-sensing technologies and aerial imaging to better document, track and analyze such coastal changes, as well as inform state officials and residents of potential issues.

In cases of deep-seated landslides, like Paul's slide — located about 40 miles south of the Rocky Creek Bridge — Warrick said his team has been able to help forecast new movement.

A section of Highway 1 near Paul's slide, just north of Limekiln State Park, has been closed since last winter when the massive landslide buried the roadway. CalTrans officials are hopeful it could reopen by this summer.

Construction across the region, however, continues to be affected by inclement weather as well as any new land movement. So far, at least, officials said there hasn't been any additional movement around the site of the Rocky Creek Bridge collapse since the initial slip-out.

Caltrans' contractors recently started work on more long-term stabilization there, planning to drill vertical and horizontal supports deep into the cliffside. Crews have also built a concrete wall along the road's center line to increase one-lane traffic safety, and they have improved drainage in the area, according to the agency.

"The drainage improvements will also help the roadway better withstand extreme weather events, which are becoming more common in the area due to climate change," CalTrans' latest update said.


While repairs plug along, Warrick said the USGS will continue to monitor that spot, and many along the coastline.

"We see erosion almost on the entire section of Big Sur," Warrick said. "Are there areas that are especially stable on Big Sur? Not really."

The newest USGS images that document changes over the last two months include before-and-after photos from eight different sites, each of which recorded "substantial movement or potential for it to influence the highway," Warrick said.

"It's not just one site, it's a whole handful of sites," he said.

He said his team will be out flying in a couple weeks to take more images to monitor and track movement, especially after rains have continued since their last images.

"Things are still moving out there," Warrick said. "We're going to keep our eyes on that."


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