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Rain Flows Into Intricate System of Dams, Channels : Storm: Engineers from the Department of Public Works monitor the weather-control system from their 'war room.'

February 13, 1992|BERKLEY HUDSON | TIMES STAFF WRITER

REGION — Donald F. Nichols, the man in charge of keeping floodwaters at bay in Los Angeles County, surveyed his troop of engineers as they tried to keep track of every drop of rain falling across the 4,000-square-mile Los Angeles Basin.

"This is not a major war," Nichols, who has seen many a storm over the decades, said Tuesday night. "But it's a pretty good battle. None of the dams are over the spillway, and nobody's panicking."

Nichols, however, knows how fast floodwaters can gather force in the San Gabriel Mountains. By Wednesday, as the heavy rain continued, he was less sanguine: "I've got a heavy storm working, and I'm not sure what the results will be."

Except for drills, it was the first time since 1983 that the county Department of Public Works had staffed the storm "war room" on the second floor of its 13-story building in Alhambra.

Still, Nichols said, the intricate system of 15 major dams, 500 miles of concrete channels, 2,370 miles of underground storm drains, acres of spreading grounds to shunt aside a torrent of water and football-field-sized craters known as debris basins normally can control rainwater and the accompanying flow of mud and sticks.

"The system works," said Nichols, who is assistant deputy director of public works for hydrology and water conservation.

In the Glendale area, there are two major dams: Big Tujunga Dam about five miles north of La Canada Flintridge and Devil's Gate Dam in Pasadena north of the Rose Bowl, along the Arroyo Seco.

Rainwater was rapidly filling the reservoirs behind these two dams Wednesday, but county officials said no significant problem had occurred at either.

More water was going out of the Big Tujunga than was coming in, officials said. But by midday Wednesday, more water was coming into Devil's Gate than the flood control officials said they could safely release from it.

Glendale public works department officials were having to cope with minor mudslides, and workers were unclogging catch basins to prevent local flooding. "But we've had nothing of major proportions," said Kerry Morford, assistant director of public works.

A good dozen of the county's major dams are socked into the mountains roughly between Pasadena and the county line at Claremont.

Then there are the 130 debris basins, large troughs that catch the torrent of mud, boulders and timber that can wash down during a storm. About 90 of them are dotted about the mountainsides from Glendale to Claremont.

On Wednesday, public works engineers electronically monitored rainfall with gauges spread across the county. By phone, they spoke with dam keepers at facilities spread across the tops and sides of the San Gabriel Mountains, where the average rainfall can reach 35 to 40 inches, more than three times what normally falls in downtown Los Angeles.

On a television monitor flickered a color weather map of Southern California, obscured by whirling wisps of storm clouds. On another television, the evening news gave reports from throughout the county: a landslide blocking Highway 39 north of Azusa, the flooded Sepulveda Dam area where dozens of motorists were trapped, and a mudslide in Malibu.

"If it rains the way it's supposed to the rest of the week, we will have flow over the spillways," said supervising engineer Ken Swanson.

Controlling the upstream flow keeps the reservoirs from overflowing and flooding the cities below. Studying weather reports and charts, Swanson and others were calculating how much water they should release from the reservoirs.

Two special phones in the war room are direct lines to the U.S. Army Corps of Engineers and the Los Angeles County Sheriff's Department. The Corps operates the Santa Fe Dam in Irwindale and Whittier Narrows, which is in unincorporated county area next to South El Monte and Rosemead. Like Sepulveda, these facilities have parks, nature and recreation areas, and roadways.

The big difference from the Sepulveda flood is that Santa Fe and Whittier Narrows are protected upstream by reservoirs, Nichols said.

Could the Sepulveda situation happen elsewhere? "Sure, given the right weather patterns," Nichols said.

Corps officials said Wednesday that Santa Fe Reservoir was filled to 2% of its capacity and Whittier Narrows to 3%. Nichols ticked off big storms of the century: 1978, 1969, 1938, 1934. "We're not even close to those events," Nichols said.

Still, he said, Devil's Gate Reservoir in Pasadena had more water in it than it has ever had since it was built in 1920.

Flood Controls

A huge network of dams, basins and canals that channels most runoff water to the ocean protects the 4,000-square-mile Los Angeles County basin from major flooding during storms. The Sepulveda Dam Basin, which was flooded Monday, is one of five such facilities operated by the U.S. Army Corps of Engineers in the county. In addition, the county Department of Public Works operates 15 dams.

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