Earthquake: The Long Road Back : Danger of Mudslides Grows Worse

What’s next?

With forecasters predicting showers Sunday and a likely return to normal winter weather patterns--including frequent rainstorms--there is rising danger of catastrophic rockslides and mudslides in the fire-scorched canyons of Malibu, Altadena and Laguna Beach.

And experts say the danger has been worsened by Monday’s earthquake and subsequent aftershocks, which have loosened surface soil and opened new fractures in rocks above and below the surface. Unlike a fire, which at least has smoke to announce its presence, a slide comes with virtually no warning.

“Fire you can run from, but flood you can’t,” Arnold York said.

York would know. The publisher of the weekly Malibu Times lost his East Malibu home in the October wildfires and nearly lost his business when flames raced to within garden-hose distance of the newspaper’s office in the mouth of Las Flores Canyon.

Now, with the upper canyon denuded of plants, the soil fluffed up and boulders cracked and loosened by tremors, just add water and the Malibu Times is history.

York’s emergency plan is basic: “If we start getting rain of any intensity, we’re clearing out.”

A Pacific-based storm system that had seemed to be targeting the coastal ranges looks as though it will dump most of its moisture farther north, weather forecaster Bruce Thoren said Friday evening. He predicted a quarter- to half an inch of rain for Malibu and Altadena, beginning Sunday morning and continuing intermittently through the day.

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But the longer-term outlook is ominous. The high-pressure zone that has been keeping the Southland warmer and drier than usual this winter seems to be giving way to a more typical stormy pattern, said Thoren, who works for WeatherData Inc. in Wichita, Kan. Another storm developing behind the first one could arrive with harder rain by late next week, he said.

Tom Benson, hydraulic engineer with the U.S. Department of Agriculture’s Soil Conservation Service, toured Las Flores and some of the other Malibu canyons after the Monday earthquake. It didn’t look good.

“The quake loosened things up,” he said Friday. “It adds new breakage to rocks underneath. There are always hairline fractures, but now the fractures are bigger. Water acts as a lubricant, and when it gets into those crevices, things will move.”

By stripping the surface of chaparral and other cover, the wildfires more than tripled the chances of catastrophic slides, Benson estimates. It usually takes about 10 inches of rain over a three- or four-day period to trigger a devastating slide.

“With the fire,” he said, “three inches will do it.”

There is virtually no private insurance against mudslides or landslides.

A possible source of relief is the National Flood Insurance Program. However, a homeowner’s ability to collect on a federal flood insurance policy hinges on the seemingly arcane distinction between a mud slide and a mud flow .

Even if a homeowner has bought national flood insurance--and most people don’t--mud damage will only be covered if a government insurance adjuster declares the event a mudflow, said Jack Eldridge, the program’s chief for the Western U.S. region.

The simplest way to tell the difference is to scoop up a shovelful of the wet debris, he said. If it pours off the shovel like liquid, it’s probably a mudflow--a form of flood. But if it falls off in clumps, it’s a slide, and the program doesn’t cover slides.

The program could be a bargain for homeowners in the fire-ravaged canyons. Many parts of Malibu, Altadena and Laguna Beach have not been identified as flood zones, so coverage is available at rates as low as $75 a year. The coverage, available through insurance companies, is limited to $185,000 for the dwelling and $65,000 for its contents.

Beyond encouraging people to enroll in the flood insurance program, government officials have been scrambling to complete other measures to lessen the impact of hard rain.

The state Office of Emergency Services and the Federal Emergency Management Agency hired the environmental consulting firm of Woodward Clyde to assess the danger in Laguna Beach, Malibu and Altadena.

Tom Turton, the geotechnical engineer who oversaw the project, identified Las Flores and Big Rock canyons in Malibu and the Eaton Canyon area in Altadena as particular problem areas.

Laguna Beach spent $3 million--reimbursable by the federal and state governments--to cover scorched areas with fast-growing seed and a glue-like binder material, which should reduce its risk considerably, Turton said.

In Malibu and Altadena, huge metal grillwork was installed at key drainage areas to prevent big rocks from blocking runoff. Culverts were also installed in some creek beds to steer water away from streets and other places where it could gather speed and force.

But when an intense storm hits, federal engineer Benson said, “this stuff is really like putting a Band-Aid on it. One way or another, this debris is going to find its way down to the ocean.”