"We've got crews going door to door to tell residents to get out," said Los Angeles County Fire Insp. Frederick Stowers. "Some of the roads up there are a complete mess."
At least a foot of debris was reported in some houses. Family photographs, furniture and other personal items were spotted among the rocks and debris that flowed into yards and streets.
By midmorning, the rain had tapered off, but forecasters said another storm system was expected Saturday afternoon.
The evacuations were ordered in foothill areas of La Canada Flintridge, La Crescenta and some parts of Acton.
Leslie Fernandes, 49, said he awoke in his La Canada Flintridge home just before 5 a.m. to a thunderous rain. "I heard a roar and a rumble and I went to look outside and there were cars swept down the street," Fernandes said.
A retaining wall on his property burst and 2 feet of mud was piled on his driveway, topped with a layer of ash from last summer's wildfires.
Fernandes said he ignored an evacuation order to stay and try to divert the debris flow away from his house and into his empty swimming pool.
"I'm glad I didn't leave otherwise we'd really be in trouble," he said.
Down the street, Steve Brown, 52, said he helped a neighbor escape her mud-filled home after she was trapped upstairs.
"There were logs floating in her living room," Brown said.
An evacuation center was set up at La Canada High School, and the Red Cross was working to establish other locations to shelter displaced residents.
Crews used bulldozers and other heavy equipment to clear masses of mud and rocks that blocked suburban streets and intersections.
At least 30 of the damaged homes were on Ocean View Boulevard in Pickens Canyon.
Five homes were tagged with a red notice warning they were unsafe to enter. At one house, mud was piled up to the handle on the front door and the yard was completely washed away, replaced with muck, rocks and a tangle of tree roots. Two white Toyotas were smashed up against front of house.
At another nearby red-tagged home, crews dug by hand through at least 4 feet of mud to try and find the source of a natural gas leak.
Workers in the area said at least one house had shifted off its foundation.
Looming above the damaged houses were the wildfire-scarred foothills, with blackened tree stumps and bare slopes.
No injuries were reported as a result of the mudslides.
A heavy downpour at sunrise followed a steady overnight rain of nearly 2 inches in a mountainous 250-square-mile scarred by wildfires last summer. The National Weather Service warned of floods likely in foothill areas of Santa Anita, Sierra Madre, Arcadia and Monrovia.
Widespread flooding and downed trees tied up traffic and caused accidents across Los Angeles County.
A section of the Long Beach Freeway was shut down early Saturday because of high water.
Water almost a foot deep flowed into businesses on Melrose Avenue. To the east, Topanga Canyon Boulevard was closed by a rock slide just north of Pacific Coast Highway, and scattered rocks and mud fell on roads in Malibu.
Scattered power outages affected more than 10,000 customers in the Los Angeles area.
