With Fire Out, the New Priority Is Mudslide Prevention

With El Nino rains possibly just weeks away, residents in the canyons devastated by this week’s fire could be facing cataclysm No. 2: mudslides.

Experts from the county’s Public Facilities and Research Department will assess the area during the next couple of days to determine what precautions should be taken, said William Zaun, the department’s deputy director.

“Conditions are there that could lead to some problems,” he said.

A likely solution will be temporary dams and barriers to keep sediment and debris from flowing down hills and clogging drainage ditches and culverts, Zaun said.

Because most of the burned area was uninhabited, the greatest mudslide danger could be to roads. Unchecked runoff could flow across highways, blocking them, or could clog ditches and force rain to flow over roads. At the very least that would create dangerous sheets of water across the pavement, Zaun said, and at worst it could wash out the roads themselves.

Which is exactly what some residents are worried about.

Dawn O’Kelly, who lives in Silverado Ranch, a recreational-vehicle park in Baker Canyon, said residents there could be devastated by heavy rains.

“There is one hill just behind the park that has the potential to slide. If it does, debris and water could wash down right on top of us. We’d be goners. But there isn’t much we can do about Mother Nature. When it comes to El Nino, we just have to live with it.”

But O’Kelly found one silver lining. Sort of.

“The residents of this RV park are being forced to move in a few weeks because the owners are filing bankruptcy,” she said. “The only good thing about it is that, in a few weeks, we won’t be having to face the problems of having to deal with any possible mudslides.”

After the Laguna fires of 1993, county officials seeded much of the barren area to hasten the return of vegetation. But many residents opposed the work, citing the danger of introducing nonnative plants to the area, Zaun said.

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David Gill, a professor of plant ecology at Cal State Fullerton, agreed the seeding has a downside, because it can slow the return of native plants. But, he said, “obviously mudslides and having half a cliff side come into your backyard is not desirable either.”

The coastal sage scrub that had dotted the areas burned this week could take 10 to 20 years to grow back to the same level, Gill said. But after the next rain, low grasses, flowers and other plants will start to appear and help to create natural barriers to erosion.

Some of the regenerating scrub will grow from roots undamaged by the fire. Others will sprout from seeds that have been dropping from the plants for years, and which will sprout now that they have been heated by the fire.

“It’s essentially a cue to tell them, ‘Hey, the environment has changed. It’s time to start growing,’ ” Gill said.

But some type of ground cover will be needed before the heaviest rains hit, said Douglas E. Hammond, an earth science professor at USC.

“Any time you remove the vegetation, you create the potential for much more erosion, landslides and mudflows,” he said.

The tricky part is getting enough water to sprout the seeds that remain dormant in the ground without getting so much that mudslides begin.

“You’re in a tough place,’ Hammond said. “A bit of gentle rain would be very nice.”

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Times correspondent Lisa Addison contributed to this story.