After Fires Subside, Mudslides Will Threaten California

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As fires whip their way through Southern California, burned and destabilized terrain will be more susceptible to devastating mudslides once winter rains come.

“Pretty much anywhere there’s a fire on a steep slope, there’s cause for concern," said Jason Kean, a research hydrologist for the U.S. Geological Survey, according to Reuters.

When flames consume trees and bushes, the soil that it held in place becomes less stable. A waxy layer forms near the surface and prevents water from seeping deep into the ground.

Ventura and Santa Barbara counties, which have been battling the 234,000 square foot Thomas Fire since Dec. 4, are prone to mudslides. One rainy day could cause a whole mountain face to come tumbling down.

"It doesn’t take a lot of rain to get the soil and rock moving," said Carla D‘Antonio, chairman of the University of California, Santa Barbara's environmental studies program. "So to have burned soil on top of this and no significant plant cover creates huge potential for landslides."

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Santa Barbara faces a high risk of mudslides, as do the smaller communities of Carpinteria, Summerland and Ojai.

The small, coastal community of La Conchita -- which suffered a damaging mudslide in 2005 that killed 10 people -- was surprisingly spared from the blaze despite being in its path, the San Francisco Chronicle reports.

"We honestly thought we would lose it," said 70-year-old Mike Bell, the unofficial mayor of the town of 300 residents. "We really did."

The fire was initially predicted to bypass the town, but instead came toward it in a last-minute change of course during the early hours of Dec. 7.

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Luke Hart, 24, recalls driving down the streets and blaring his car horn to wake people up. Thierry Brown, 61, began running sprinklers and showerheads to drench his banana trees and ficus out front. He says it felt like Northern California with all the artificial "rain."

But the wind shifted and the fire subsided.

"We deserved that break," said Brown the following morning.

Nicholas Pinter from the University of California, Davis' department of Earth and Planetary Sciences said local officials will have to build retention walls in steep areas as soon as the fire passes, Reuters reports.

Helene Schneider, mayor of Santa Barbara, said rains could also damage water quality by washing silt and debris into reservoirs.

"We don’t see any rain in the immediate forecast, which is a curse and a blessing," she said. "We could use the water to fight the fire, but we don’t want some kind of big downpour that would cause significant mudslides so soon after the area’s been burnt to nothing."

Sources: Reuters, San Francisco Chronicle / Featured Image: John Shea/FEMA / Embedded Images: Pam Irvine/California Geological Survey via U.S. Geological Survey/Flickr, Antandrus​/Wikimedia Commons

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