(CNN) - Heavy rains unleashed destructive rivers of mud and debris in Southern California on Tuesday -- leaving at least 13 people dead, destroying homes and spurring rescues as the flooding forced heavily traveled roads to close.
Santa Barbara County Sheriff Bill Brown said the death toll could rise. Officials said many of the deaths are believed to be in the coastal Montecito area, where mudflows and floodwater have inundated areas downstream from where the Thomas Fire burned thousands of acres last month.
At least two dozen people were unaccounted for and authorities rescued at least 50 people in the Montecito area. The Santa Barbara Sheriff's Department is working toward determining whether those "missing" were accounted for in other locations or among those who are deceased.
"It looked like a World War I battlefield," Brown said of the destruction. "It was literally a carpet of mud and debris everywhere, with huge boulders, rocks, down trees, power lines, wrecked cars -- lots of obstacles and challenges for rescue personnel to get to homes."
• Thirteen storm-related deaths were reported in Santa Barbara County, Sheriff Brown said.
• The 101 Freeway in parts of Montecito and Santa Barbara, will remain closed for at least 48 hours after muddy, debris-filled water flooded parts of the seaside roadway, according to Capt. Cindy Pontes with the California Highway Patrol.
• By early Tuesday afternoon, more than 5.5 inches of rain had fallen in parts of Ventura County over two days, the National Weather Service said. In Carpinteria, nearly 1 inch fell in just 15 minutes, the agency said.
• The weather forced the closure of several theme parks, including Six Flags Magic Mountain in Valencia and SeaWorld in San Diego.
'Call after call' from stranded residents
Before the storm hit, Santa Barbara issued mandatory evacuations for more than 6,000 people, including living in those parts of Carpinteria, Montecito and Goleta, located below areas scorched by wildfires, including the Thomas Fire, county spokeswoman Gina DePinto said.
Voluntary evacuation warnings were in effect for another 20,000 people, including others in those same communities, she said.
Brown said deputies and search and rescue team members went door-to-door Monday conducting evacuations in the mandatory evacuation areas. Those notifications were all made by nightfall, Brown said.
"While some residents cooperated with the evacuations, many did not. Many chose to stay in place, "Brown said.
The sheriff said the storm hit hard around 3 a.m. Tuesday. Between 3 and 6 a.m., dispatchers with the sheriff's office handled more than 600 telephone calls for assistance.
"They received call after call from people who were distressed, stranded in their homes or vehicles and were in need of immediate rescue," Brown said.
He added: "Once daylight came, we had a very difficult time assessing the area and responding to many of those areas to assist those people."
Brown said the mud was "knee-deep" in many places on the roadways and even deeper in the canyons.
Teenager trapped for hours in Montecito
The rain fell in areas charred by recent wildfires, triggering warnings of flash flooding and mudslides because vegetation that otherwise would hold hills together and make the terrain flood-resistant has burned away.
In Montecito, six homes were "wiped away from their foundations" by mudflow and debris, Santa Barbara County fire spokesman Mike Eliason said.
Eliason said firefighters rescued a 14-year-old girl, who had been trapped for hours in a collapsed Montecito home. The girl, coated head to foot in mud, was led by firefighters from the pile of wood and debris that was once a house, a photo from the county fire department shows.
In another part of Montecito, Eliason said he saw "utter devastation."
"There were three houses that were completely knocked off their foundations. Debris and wood everywhere, looking like matchsticks," he said.
Eliason recalled looking at the red band on a radar, indicating heavy rainfall.
"When that hit those hillsides, it just came rushing down," Eliason said. "Time and time again, I found myself waist deep in floodwater.
The mud and debris left roadways and neighborhoods in Montecito unrecognizable.
'Mud came in an instant, like a dam breaking'
Ben Hyatt said a river of mud had crashed through a neighbor's house in Montecito, a community of about 8,000 east of Santa Barbara,
"Apparently, one of their cars ended (up) in their backyard. We have neighbors at (the) top of the street that evacuated to their roof," Hyatt said.
Hyatt said his Montecito house was "surrounded by mud," and a washing machine had drifted into his front yard.
Hyatt said he was awake when power went out during heavy rain around 2:30 a.m. Eventually, he heard a loud swish and banging on the exterior of his house.
"Mud came in an instant, like a dam breaking. (It) surrounded the house, 2 to 3 feet," he said.
"Seems calm now. We feel safe. But definitely stuck here for a bit."
There were several glimmers of hope, as emergency officials rescued stranded residents.
Eliason, the Santa Barbara County fire spokesman, posted photos of firefighters leading people through mud and floodwater to safety.
Also in Montecito, a ruptured gas line led to a fire that consumed a building, Eliason said.
Surveillance camera video appears to show an explosion connected to that fire, said Eric Trautwein, who posted the footage on Twitter.
Cars mired in the muck
Photos of vehicles stuck in mud in Los Angeles County and nearby areas dotted Twitter feeds. One post showed a California Department of Transportation crew trying to help a trapped motorist.
In another, a Los Angeles police squad car was mired in the muck. "Officers were responding to help with evacuations. Within seconds their vehicle was consumed by the mud," the post reads.
'Praying' for Santa Barbara
Oprah Winfrey, who has home in Montecito, said she was "praying for our community again in Santa Barbara."
"Woke up to this blazing gas fire," she posted on social media.
Winfrey also showed photo of mud in her backyard.
"Helicopters rescuing my neighbors. Looking for missing persons. 13 lives lost," she wrote.
More than 1 inch of rain per hour
The rainfall rate of more than 1.5 inches per hour in parts of Southern California overwhelmed the landscape.
About a half inch per hour is enough to start mudslides, said Robbie Monroe of the National Weather Service in Oxnard.
The downpour is overpowering a terrain especially vulnerable in the wake of recent fires.
The Thomas Fire -- the largest wildfire in California's recorded history -- has burned more than 281,000 acres in Santa Barbara and Ventura counties since it began in early December. It was 92% contained, and officials don't expect full containment until later this month.
Montecito and Carpinteria are vulnerable to mudslides because the steep terrain in some places goes from thousands of feet above to sea level to sea level in "a matter of just a few miles," said Tom Fayram, a deputy public works director with Santa Barbara County
"That's definitely at play here. It's just a mess," he said.
Fayram said crews working to clear mud and debris from roadways saw "boulders the size of trucks that came rolling down the hillsides."
"This is a disaster, much worse than the mudslides of 1995," Fayram said. We're trying to get help from federal and state officials."
The region has suffered from years of drought, and officials say they need the rain to regrow plants and trees that help keep the hillsides together and floodproof.
Mudslides are not uncommon to the area and can be deadly.
In January 2005, a landslide struck La Conchita in Ventura County, killing 10 people and destroying or damaging 36 houses.
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