California's drought plus El Niño increase the threat of a muddy disaster

An intense October rainstorm that pounded the Grapevine's barren hillsides offered a sober preview of what El Niño might unleash in the rest of drought-stricken Southern California.

The rain hit the dry, hardened terrain where the drought had shriveled vegetation. The topsoil easily gave way, with mudflows cascading onto Interstate 5 and local roadways and trapping motorists, many overnight, in several feet of debris.

Heavy rains often bring mudflows. But experts warn that the deluges expected this winter with El Niño are likely to be exacerbated by the dry conditions in countless hillside and canyon communities. Even a little rain can set off a fast-moving debris flow, sweeping up anything in its way — loose boulders, tree limbs, cars, even homes.

"The drought, it's just made this whole situation worse. … That area that slid [in October]? It's not green. There's not even grass on it. It's so dead because of lack of rain," said Deborah Wong, a deputy director for the California Department of Transportation. "If there's no root structure to hold the mountain back, or at least the topsoil, it's coming down."

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