'Stay alert': With more rain on way, officials warn of landslide danger

Landslides buried Southern California roads and highways in mud and debris as storms last week drenched already-soaked hillsides. Now, more rain is on the way.

A stretch of Highway 150 near Santa Paula remained closed indefinitely with a pile of mud roughly 15-feet high covering lanes. The slide – one of at least four reported locally during the recent days-long storm – prompted an evacuation warning for several nearby homes.

Another slide just north of Ventura sent soupy mud into backyards.

With steady, but lighter rain expected Friday and Saturday, authorities don't expect major flooding. But they urged anyone near a slide or another problem-prone spot to watch for changing conditions.

"Anybody living near those areas should be very vigilant about knowing their surroundings and keeping an eye on things," county geologist Jim O'Tousa said.

Forecast calls for up to an inch of rainfall

After some drizzle or light showers Thursday, steadier rain could start overnight.

The best chance for rain likely will run Friday through Saturday night, said David Gomberg, a meteorologist with the National Weather Service in Oxnard. Most areas are expected to see a half-inch to an inch of rainfall over that 48-hour period. Some foothill and mountain areas could see slightly higher totals.

While the forecast shows a less intense storm, any additional rain could cause issues with mud or landslides, Gomberg said. The recent storms rolled through week after week, leaving little time for the ground to dry out in between soakings. That can cause the potential for problems with even light to moderate rainfall, he said.

Two wet rainy seasons may be to blame

Officials say it is difficult to predict if or when a landslide happens because of the complex nature of the hazards. Why so many were reported last week also isn't entirely clear.

The amount of rain leading up to a storm and the intensity of the rainfall are among the factors contributing to whether a slope fails. The problems don't always show up during the rain but can happen weeks later.

Ventura County had one of its wettest rainy seasons last year and several intense storms, but few problems with landslides were reported. The recent storms may have just taken different tracks, or in some spots, the risk could be higher because of past wildfires. Back-to-back rainy seasons also could be to blame, officials said.

The county was on the heels of a drought going into the last rainy season, said Patrick Maynard, director of the sheriff's Office of Emergency Services. The soils were dry, but that has changed over two particularly rainy seasons.

O'Tousa described the storm-drenched earth like a sponge full of water. If the soil gets too wet and too heavy, it can start to slide.

Highway reopening remains unknown

The slide on Highway 150 near Bridge Road, north of Santa Paula, was the most significant of the four reported during last week's stormy weather. The slopes in the area had failed previously during a wet winter in the late 1990s.

This time, mud initially washed onto the highway early last week. The California Department of Transportation said a contractor cleared the road and put concrete rails in place to help protect it. But overnight, the slide dumped more mud and debris, Caltrans spokesman Michael Comeaux said. By Wednesday morning, the pile was roughly 15-feet high and 170-feet long; the concrete barriers buried underneath.

The route between Santa Paula and Ojai is closed in both directions from Steckel Park to Stonegate Road. As of Thursday morning, Caltrans had no estimate for reopening the highway.

Geologists continued to assess the slide, which remained unstable, Comeaux said. The rain in the forecast also added to the uncertainty, he said.

Slides spotted near Santa Paula, Ventura

Smaller, thinner slides scarred hills above a Santa Paula neighborhood during the storm. At the spot roughly a half-mile south of Bridge Road, dirt or mud didn't make it down to any roads or backyards, O'Tousa said.

But across the county, mud did reach a neighborhood, spreading into a couple backyards in the Norway tract just north of Ventura. The slope directly above the homes also had failed previously, O'Tousa said.

Since then, water has flowed out of the hillside. As it drains, the soils dry up and hill becomes more stable, he said. In the meantime, the county notified residents that additional rain could cause the same or worse problems.

Dirt moves on La Conchita hillside

Along the coast, La Conchita, a community of about 300, sits below an unstable hillside, one that gave way in 1995 and again in 2005 when a landslide killed 10 and buried homes with no warning.

Authorities have declared it a geological hazard zone. Last January, debris from an older landslide fell about 150 feet but the mud stopped before reaching homes. Last week, a small amount of dirt moved again, this time within the 1995 slide area.

Officials say they have no surefire way to predict if or when the La Conchita hillside could fail. But the county does look at historical triggers. As of Thursday, rainfall totals fell below those marks.

Maynard urged residents to stay alert. Even with a few days of drying, the soils remain saturated and won't absorb much rain, he said.

During the upcoming storm, higher elevations also could see nearly a foot of snow. The forecast calls for 5 to 10 inches in spots over 7,000 feet, Gomberg said. Areas from 5,500 to 7,000 feet could get up to 5 inches of snow. There’s also a chance of light snow later Saturday night and into Sunday morning on Interstate 5 through the Grapevine.

To sign up for emergency alerts in Ventura County, go to readyventuracounty.org/vc-alert. For information about evacuations and potential road closures, go to vcemergency.com.

Cheri Carlson covers the environment and county government for the Ventura County Star. Reach her at cheri.carlson@vcstar.com or 805-437-0260.

This article originally appeared on Ventura County Star: Southern California weather: Landslide danger still looms