Rain Plan, Luck Save Laguna : Storm: Officials say a downpour like one that drove mud into Malibu could have meant disaster.

As workers dealt with downed trees and debris left in the path of tornado-like winds in Irvine, emergency officials and residents alike marveled that fire-ravaged Laguna Beach had escaped Monday’s most damaging rains with its muddy hillsides mostly intact.

While winds whipped Laguna Beach, the lack of a prolonged and heavy downpour probably saved Laguna Canyon from ending up like mud-swamped Malibu, officials said.

“I think we were lucky,” said City Engineer Terry Brandt. “Basically, you have to look at how much rain (Malibu) got compared to us. They got twice as much as we did, and they got it all in one fell swoop.”

What most helped the city Tuesday was that only about 0.8 of an inch of rain fell throughout the day, compared to two inches that pounded Malibu in a short time. According to Laguna officials, 15 minutes of heavy rain would have saturated the ground and caused flooding.

Laguna had rain-induced mudslides shortly after a devastating fire last October burned nearly 17,000 acres and 366 homes. But that time, rain fell in a shorter period.

The city was fortunate this time, but some precautions also may have helped Laguna brave the worst storm of the season so far, according to Woodward-Clyde, a Denver-based consultant the city hired after the fire.

The consultant crafted a plan to control future floods and mudslides. Woodward-Clyde also worked for the cities of Malibu and Oakland, both devastated by fires.

“Laguna moved forward very quickly, probably the fastest . . . the most aggressive and proactive . . . of all the cities we worked with,” said Carol Forrest, a Woodward-Clyde vice president.

By early December, the consultant’s plan was put into effect, Forrest said. The plan, which cost $1 million to implement, involved building a network of small dams, water-runoff barriers and hillside reseeding.

“Some of the other cities have been confused and worried about the funding issues,” Forrest said. “But Oakland advised Laguna: ‘Don’t worry, the (Office of Emergency Services and Federal Emergency Management Services) will be there.’ ”

At Malibu’s Big Rock area, which was hit hard by heavy mudslides Monday, the consultant’s plan to control flooding and mudslides was not yet in place, according to Woodward-Clyde officials.

Ironically, the mudslides that struck Laguna Beach two weeks after the October fire gave Woodward-Clyde an opportunity to chart how key areas of the city reacted, particularly the fire-ravaged areas of Canyon Acres and lower Skyline Drive, Forrest said.

As a result, slopes on Skyline Drive and Canyon Acres were treated with different mixtures of wood, seed and strong adhesives sprayed from a truck.

By early December, Laguna city workers, aided by the Civilian Conservation Corps, had fashioned 1,400 silt dams made of bales of hay and millions of sandbags. At the base of vulnerable hillsides were placed heavy concrete rails, called “K rails,” and 18-inch-high mesh fences that allow water through while trapping silt.

“The entire system diverts all the mud and water flow into manageable areas and, that way, if we stay ahead of the storm, we’re OK,” said Patrick Brennan, a Laguna Beach Fire Department spokesman.

While the California Department of Forestry was reseeding 3,000 acres of undeveloped land around Laguna Beach, the city was reseeding several hundred acres within the city limits, said Brennan.

Woodward-Clyde officials singled out the Laguna Beach Fire Department for praise in helping prepare for floods and mudslides.

“Nobody is classically trained in this stuff, but the way Laguna Beach Fire Department reacted you would have thought they had done this before,” said Michael Harding of Woodward-Clyde and a past president of the International Erosion Control Assn.

Despite the city’s preventive measures, it won’t really be known how well they work until they’re tested by a stronger storm. For now, the relatively light rainfall Monday is what saved the day, officials said.

Brennan said it is hard to predict how vulnerable the still-fragile Laguna hillsides would be in a torrential rainstorm.

“There’s no amount of preparation we can do if nature gives us three-quarters of an inch of rainfall in an hour,” Brennan said. “It could be our turn next.”

Times staff writer David Haldane contributed to this report.

Storm Trackers

Storm intensity is monitored from 76 sites across the county. Electronic sensors feed into a mainframe computer at the county’s Emergency Management Agency. The computer supplies information to local emergency response agencies so they can head off potential flash floods and other rain-related problems.

System Sensors

1. Funnel collects water; drains into tipping bucket.

2. When .04 inches of rain fills one side of bucket, it tips, dumping out rain, activating switch that transmits radio signal to EMA computer.

3. Rain fills other side of bucket; process repeats.

4. When computer registers one-half inch in 30 minutes at a site, emergency alert system activates. In Laguna Beach, the rain gauge is in a canyon. Signals are broadcast to a nearby hilltop from where they are relayed to Santiago Peak and on to the EMA command center.

Standpipe

Funnel

Tipping bucket

Switch

Antenna mast

Chain Reaction

The Laguna Beach Fire Department began monitoring storms itself last month to cope with fire-ravaged hillsides that become waterlogged by rain. Laguna Beach’s emergency response system includes:

Equipment: Backhoes and graders to clear streets and storm drains of mud and debris.

Command center: Up to 15 fire officials are paged or called to establish a command center. County EMA, Caltrans and Laguna Beach Municipal Services participate in logistic planning.

Crews: Up to 68 people in strategic locations throughout city mobilize to keep storm grates free of straw and other reseeding debris.

Evacuation: Senior citizens living alone in the flood plain are offered evacuation help.

Rescues: Swift Water Rescue Team, a combination of lifeguards and firefighters trained to rescue people caught in flash floods, goes on alert.

Mudslides: System of silt dams and concrete barricades used to divert water flow and mud from main streets.

Sources: Laguna Beach Fire Department, Orange County Emergency Management Agency

Researched by CAROLINE LEMKE / Los Angeles Times