Mudslide threat looms

As Southern California braced for heavy rainstorms that could bring flooding, Yorba Linda officials said Monday that they plan to use a reverse 911 system to warn residents about potential mudslides this week, even though the network didn’t work properly during the recent wildfire.

The system called some residents long after the Nov. 15 blaze had swept through their neighborhoods. It took up to six hours from the time fire officials ordered evacuations in parts of Yorba Linda for the emergency calls to be made to residents in the fire zone, according to data provided by the Orange County Fire Authority and the county’s executive office.

AlertOC is operated by the county and uses computer databases of addresses to call large numbers of residents at one time.

Yorba Linda officials said the lag may have been because the system was only a few months old and the city and county did not yet have a process for passing along the evacuation notices.

But since the fire, the city and county have worked out an agreement in which the city has control over the alert messages, city spokesman Mark Aalders said.

“These are things we’re fixing and it shouldn’t be an issue,” he said, adding that in light of the recent incident, the county accelerated bringing the city on board.

As forecasters predicted heavy rain and thunderstorms to hit Southern California today, officials and residents in Yorba Linda, Brea, Anaheim Hills, Montecito and parts of the San Fernando Valley -- areas hit by destructive fires -- braced for possible mudslides.

Worker Jose Amezcua-Morales wiped sweat from his brow Monday, taking a moment to catch his breath after five hours of heaving orange sandbags up Aliso Canyon in Porter Ranch. He had a few more hours to finish laying 3,000 sandbags up and down the canyon, racing with fellow workers to build barriers to prevent mudslides. Next to him was a hillside covered in fresh, light green mulch; below him, hundreds of homes nestled in their gated communities against a blackened hillside.

Forecasters said the storm would bring the most rain the region had experienced in more than nine months -- with as much as half an inch per hour at its heaviest -- but was expected to taper off in time for Thanksgiving evening.

Flash flood warnings were in effect throughout areas recently ravaged by fires in Los Angeles, Orange, Santa Barbara and Ventura counties for this afternoon through Wednesday evening, when heaviest rains were expected.

“These burn areas, it’s not like sand, it’s very loose ash, and as the rain comes down, and especially if it’s a lot of rain all at once, the first six inches of soil will sop up the rain and it will just come crashing off of there, like an avalanche,” said Stuart Seto, a weather specialist with the National Weather Service in Oxnard. “What makes it so bad is that it’s not just water anymore, it’s mud, debris. It carries a lot of stuff and weight, and that’s what can wipe out houses, cars and push things around.”

Up to two inches of rain were expected in the coastal and valley areas by the end of the storm, with up to three inches in the mountains. The last significant rainfall in Los Angeles was 0.46 inches on Feb. 24, Seto said.

In Santa Barbara County, which was recently hit by the Tea fire that burned hundreds of homes in and around Montecito, fire officials rearranged engine staffing in preparation for today’s rains, said Santa Barbara Fire Capt. Eli Iskow.

“We’ve got a serious potential situation, and we’re prepared for it,” Iskow said.

In Yorba Linda, officials passed out thousands of sandbags, and many hillside dwellers spent the weekend laying out plastic sheets. Spokesman Aalders said the areas most threatened by mudslides were the denuded slopes along Chino Hills State Park. If enough rain falls, mud could ooze down the hills and into the city’s canyons.

Yorba Linda planned to send reverse 911 calls about the possible mudslides to residents Monday evening. Another set of calls would go out if officials called for either voluntary or mandatory evacuations.

Officials believe the system will work better this time. During the Freeway Complex fire, which started Nov. 15 and destroyed more than 190 homes in Brea, Yorba Linda and Anaheim Hills, the Orange County Fire Authority issued evacuation notices before 10:30 a.m. on the first day of the blaze. But the warning calls didn’t start going out to thousands of Yorba Linda homes until 4:11 p.m., said Brooke De Baca, a spokeswoman for Orange County’s executive office.

Yorba Linda officials pointed out that law enforcement officials went to the fire zone, using bullhorns and going door to door trying to warn residents.

As officials shift their focus from fires to potential flooding, some of the most significant protections are going up along San Antonio Road, which runs along hillsides that lead into and up against Chino Hills State Park. On Monday afternoon, concrete freeway barriers 3 feet high lay horizontally positioned up the canyon wash, abutting homes that had sandbags lined along their backyards.

City workers were granted access to Chino Hills State Park over the weekend to set up the barriers and sandbags to divert potential mud and debris away from homes.

“If there is a mudflow, there’s no stopping it,” Aalders said. “The only thing you can do at this point is channel the mudflow away from homes to limit damage to property.”

Meanwhile, fire department units with the city and county of Los Angeles were out Monday patrolling burn areas and helping residents with sandbags, officials said.

Fire stations supplied bags and sand to those who needed them.

Officials said they were particularly worried about O’Melveny Park in Granada Hills. Though sandbags were not visible on much of the hill, trenches had been bulldozed above the park to create a “water bar” to divert rainfall into areas with green vegetation.

“You have to understand, this fire actually occurred in the last 10 days,” said Los Angeles City Fire Battalion Chief Greg Reynard of the Sayre fire in Sylmar as he surveyed burned areas Monday in the park. “It’s not like Griffith Park [in spring 2007], where they had months and months to prepare.”

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tony.barboza@latimes.com

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