Ashley Harper had hoped to ring in the new year surrounded by friends and family at her home in the northern California town of Soquel, along the United States west coast.

But as successive storms blanketed the state in heavy rainfall, Harper started to worry. The normally peaceful creek next to her house had started to swell.

“I woke up one day and thought ‘Wow, that creek is very high and rising very quick,’” she told Al Jazeera during a recent phone call.

Soon, a fence bordering her property collapsed, and within 20 minutes, her entire backyard was filled with water. In the scramble to leave she lost her car to the floodwaters. Some of the buildings on the property remain filled with mud and sludge to this day, as persistent rains forced them to evacuate three more times.

Harper is one of the millions of residents in California who continue to grapple with the effects of a historic storm system that dropped record amounts of rain in places like Los Angeles and San Francisco.

Now, after three straight weeks of narrow, intense storms – known as “atmospheric rivers” – cleanup efforts across the state have begun. Heavy winds and torrential rains have left roads buckled and power lines downed. Many areas remain vulnerable to floods and landslides.

Experts warn the storms could ultimately cost the state billions in damages. US President Joe Biden plans to visit the state on Thursday after issuing an emergency declaration last week.

“Luckily it’s sunny today, and it’s not supposed to rain again,” Harper said. “But we’re still trying to get things back together. We’ve had to clear everything ourselves and we just reached the floor of our garage last Friday. Another building is so full of mud we can barely open the door.”

And clearing out her home is just the beginning. Harper and her family still have to sort out their flood insurance, catch up on their jobs and find a place to move the massive heaps of mud spread across their property.

“What do we do with all of this sludge?” asked Harper. “Thankfully we’re all safe, but the cleanup has been a mess.”

Evacuation orders lifted but hazards remain

About 150km (93 miles) north of Los Angeles, the coastal city of Santa Barbara received nearly 90 percent of its yearly rainfall average in less than two weeks, with thousands of people evacuated due to the risk of landslides and neighbourhoods inundated with waist-deep waters.

While the weather is expected to moderate, county officials are urging residents to continue exercising caution.

“All evacuation orders have been lifted but there are still some areas where road access is an issue,” said Kelsey Buttitta, a spokesperson with the county. “A lot of roads were covered with mud and rocks. It’s going to take some time to get things up and moving again.”

The hazardous conditions have led to a number of dramatic rescue efforts. Scott Safechuck, a spokesperson for the Santa Barbara County Fire Department, said more than 100 water rescues had taken place in the last several weeks as residents have been pulled from homes and vehicles trapped by rising waters.

On Monday, emergency responders rescued two people who flipped their kayak off of the coast amid turbulent ocean conditions.

“One person was exhausted and clearly overwhelmed by the time rescue swimmers reached them,” said Safechuck. “During a time of extreme weather, it’s important to think things through. Something that might usually be routine can become very dangerous.”

Treacherous roads lead to cliffside rescue

California Highway Patrol officer Chris Murphy saw firsthand how a routine trip could turn into a life-threatening event. On Friday, he was serving the Santa Cruz area, just south of the San Francisco Bay, when the emergency dispatcher alerted him to reports of motorists stuck in a “ditch”.

“It had been a pretty active week with power lines and trees and mudslides,” Murphy recalled. He found himself wondering what the urgency was: If the car was in a ditch, why did the passengers not just climb out?

“When I got there, it was clearly more than a ditch. It was a very deep ravine, and there was water flowing from all directions,” he said. He estimates the drop was 30.5 metres (100ft) straight down and the vehicle was teetering over the edge.

Three people were stuck inside, and Murphy feared the car might come loose, rolling to its side and landing “on its roof at the bottom of the ravine”. He believes the “unpredictable weather” was responsible for the predicament: The driver was familiar with the mountain roads and had not been going at a high speed.

“The rain was so heavy, it might have obstructed her vision,” Murphy said. When he opened the car door, he found the driver in a state of panic. “She still had the vehicle in drive and her foot on the brake. She was just frozen solid. She was afraid to move because she did not want the car to risk rolling forward.”

After calming the driver down, he instructed her to slowly lift the foot off the brake. Satisfied that the car was not going to fall, Murphy helped the driver and the passengers to safety. He encourages other drivers to be aware of their surroundings in the weeks ahead.

“There are a lot of roadways that still aren’t opened, that they’re still trying to clean up,” Murphy said, pointing to ongoing issues with sinkholes and other hazards. “It’s going to be pretty lengthy to fix those roadways, especially in areas where they washed out, that are usually pretty mountainous.”

Mudslides force evacuation of homes, train

Mudslides continue to threaten the state as well, with commuters on Tuesday forced to evacuate a westbound train passing through Niles Canyon, just east of the San Francisco Bay Area, after a 30.5-metre (100ft) mudslide blocked the tracks.

Just one day earlier, about 40km (30 miles) north in Berkeley Hills, another mudslide pushed through the Park Hills neighbourhood, forcing evacuations.

Berkeley city councilperson Susan Wengraf had received a call at about 7:30 in the morning from the city manager, alerting her to what was unfolding. When she arrived at the otherwise quiet cul-de-sac on Middlefield Road, she discovered a wall of mud more than 3 metres (10ft) high, resting against the northern end of a one-story ranch-style house.

The mud had broken through the wall where the dining room and the kitchen were. As she spoke with the residents there, Wengraf learned that the morning had started just like any other.

The homeowner, she said, “went into the kitchen to make coffee. And he sensed that the room was darker than it usually is. And he looked north and he saw the whole wall was broken through and there was mud right there.” They hadn’t heard anything, he told Wengraf. They hadn’t felt any shaking. It was a complete surprise.

“They were both pretty much in shock,” Wengraf said of the homeowner and his wife. The city of Berkeley had to “red-tag” the house, preventing the couple from going back inside.

“As of last night, it was still considered an active slide. Water was clearly still moving down the hillside,” Wengraf explained.

Risk for ‘bigger landslides’ remains

Alan Kropp, a geotechnical engineer who volunteered at the scene, said that what occurred was “a special kind of a landslide called a debris flow”. They occur when landscapes become so inundated with water that they flow rather than slide, carrying with them rocks, trees and other debris.

“I’ve seen several thousand landslides in my time,” Kropp said with a nod to his 50-some-year career.

“But these [debris flows] unfortunately can be some of the most dangerous because they’re so fluid. That’s why they called it a flow. They can move very quickly. And if they hit a house where there’s occupants, it can, unfortunately, cause death at times. It can move so fast that you often don’t even have a chance to get out of the way.”

With California’s weather anticipated to dry out over the coming weeks, Kropp said the possibility of further “debris flows” is set to diminish. They happen once every 50 or 100 years in a given area, he explained.

But that does not mean the danger is completely over. “If there’s still water in the hills and it’s slowly working its way down, you can sometimes – even after some dry weather – have other kinds of bigger landslides,” Kropp said. “It takes a while for the water to get the depth into the ground.”

Wengraf, the Berkeley city council member, told Al Jazeera that the takeaway is that “nature wins”. She hopes the recent storms will bring attention to the ongoing effects of climate change across the state.

“Just in my tenure as a city councilperson, I’ve dealt with major earthquakes, with major wildfires and with major mudslides. It’s almost biblical how much natural disaster we are vulnerable to,” she said. (Al Jazeera)

•PHOTO: A car lies trapped in mud in Santa Barbara County, where heavy rain led to flooding and evacuations [Al Jazeera via Santa Barbara County Fire Department]

Update news