Heavy rain from a powerful Pacific storm that swept through California on Tuesday flooded a freeway and sent residents in some wildfire-scarred communities scrambling to evacuate as authorities warned of mudflows from unstable hillsides.
The rain began falling overnight in Northern California, but the heaviest downpours were expected in Southern California later in the day, prompting both relief in the drought-stricken state and concern about flooding and mudslides on denuded slopes.
Coastal residents also braced for the thick tangle of garbage and debris that gets washed from city streets, into storm drains and then onto beaches during the first major winter storm each year.
Three years of devastating drought has left the Sierra Nevada snowpack — which counts for most of the state's water supply — at just 24 percent of normal for this time of year. Downtown Los Angeles has had less than half of the rain it would have in a normal year.
In Camarillo Springs, about 50 miles northwest of Los Angeles, the immediate concern was not drought but mudflows that began before noon from hillsides that burned more than a year ago.
A dozen homes were under a mandatory evacuation order as heavy rain pounded the Ventura County community. Water gushed into the street, and large bulldozers moved rocks and debris from stormwater channels. A mudslide in the same area on Halloween buried one home in mud 3 feet deep.
"It's coming down pretty good," Ventura County Fire Capt. Scott Dettorre said. "We are in a heightened state of readiness."
In Orange County, roughly 100 miles to the southeast, about 60 homes in rural Silverado Canyon were under a voluntary evacuation notice as authorities braced for heavy rains later in the day. The area burned over the summer and has been the site of previous mudslides, including one that killed a girl in 2005.
"There's only one way in and out of the canyon," Orange County Fire Authority spokesman Steve Concialdi said. "If the mud and debris comes down and blocks the road, then those people will be trapped on the other side."
In the foothill city of Glendora northeast of Los Angeles, residents packed sandbags along their property lines and lined the streets with concrete barriers to keep mudflows out.
Los Angeles County Fire Department Acting Chief Steve Martin said a mild rain two weeks ago caused mudflows that damaged four homes in the burn area in Glendora. He warned residents to heed any evacuation orders that are issued.
"We know it's an inconvenience, we know it's hard to leave your homes behind," Martin said. "But the fact of the matter is, when the mountain does cut loose, it happens so fast you're already behind, and you're going to be stuck and stranded, and it's going to be very difficult to get to you."
A National Weather Service meteorologist said that burn areas from the May wildfires in San Diego County, including the Cocos fire in San Marcos, are at high risk of mud and debris flows.
In Northern California, officials have been scrambling to control erosion following the King Fire, which burned 153 square miles in the mountains east of Sacramento last summer, as well as the Rim Fire, which burned more than 400 square miles in and around Yosemite National Park a year ago.
The weather caused flights arriving at San Francisco International Airport to be delayed nearly four hours after more than an inch of rain fell overnight.
There also were some delays at Los Angeles International Airport, and flooding on Interstate 405 briefly shut down two southbound lanes south of Los Angeles.
Rain at this early point in California's wet season has yet to make much of an impact on the state's main reservoirs.
Lake Shasta and Lake Oroville have less than 50 percent of their usual water levels for the start of December, while Folsom Lake stands at 59 percent, National Weather Service forecaster Eric Kurth said.
A weaker storm over the weekend caused a mudslide that blocked the Pacific Coast Highway west of Malibu when a section of the Santa Monica Mountains charred by a wildfire last year gave way.
