Flood-Control System Holds Up for Most Part : Storms: O.C. network weathers pounding with one exception, a San Clemente channel ripped apart by sudden deluge.

Despite a two-week onslaught of severe storms, Orange County’s massive network of flood-control channels has held up to the pounding with only a few trouble spots, county authorities said Sunday.

Of dozens of crisscrossing creeks and channels, only one piece of the county’s network has failed to hold back storm water: A channel in San Clemente was ripped apart Saturday afternoon by a sudden deluge. That led to the destruction of a motel and a restaurant downstream.

“This one problem in San Clemente is the first major one we’ve had,” said Bill Reiter, a public works manager who runs the county’s Storm Center. “We haven’t really taxed the system yet. We’ve done heavy patrolling and there’s no damage except for that. The rest is road-related problems, mostly in the canyons.”

County public works teams were trying to determine why so much water came rushing down the San Clemente channel at once Saturday afternoon, ripping up its concrete banks. The damage caught county storm crews off guard.

“I’ve been manager here for 13 years and we have not had a problem there before,” Reiter said. “We have certain hot spots during storms, and this wasn’t one of them. But now it certainly is.”

The Storm Center team first thought that perhaps a small reservoir upstream had burst. But a helicopter tour of the area showed no such problems, leaving workers to assume it was simply too much rain deluging that part of San Clemente in a short period of time.

“We’re doing a lot of studies to see if there were any reservoirs that gave (way), but right now we just have to attribute it to a very, very heavy (storm) cell that must have gone over that area,” Reiter said.

Otherwise, the county’s worst flooding has been predictable. Modjeska, Silverado and Trabuco canyons--the remote, vulnerable canyons of eastern Orange County--have suffered mudslides and rockslides after being saturated with runoff from the Santa Ana Mountains.

Other trouble spots, as usual, have been low-lying areas of Costa Mesa, Pacific Coast Highway in Huntington Beach and Dana Point, Santa Ana Canyon Road in Anaheim and Laguna Canyon Road.

“It would not take a lot of rain to continue to have slippage problems in the canyons,” Reiter said. “You’ve got homes up there already damaged. We’ve sent crews night and day to Modjeska and Silverado trying to keep the roads open after mudslides. Any more rain will be a problem there.”

The urban core of the county, however, has fared pretty well. So far, the Santa Ana River, considered by the Army Corps of Engineers to be the worst flood threat west of the Mississippi River, has been behaving itself. No flooding or damage has occurred along its banks.

The corps controls the river, which collects runoff from the San Bernardino Mountains and most of the Inland Empire at Prado Dam, just past Anaheim in Riverside County. Most of the storm water has been released from the dam slowly enough that it can be collected in holding ponds that replenish Orange County’s ground-water basin.

Another trouble spot is Santiago Creek, which cuts through highly populated areas of Villa Park, Santa Ana and Orange. The creek has retained its natural, earthen bottom in some areas, making it prone to erosion.

Normally bone-dry, the urban creek contains substantial storm water for the first time in two decades because of runoff from Cleveland National Forest and the Santa Ana Mountains being released from Villa Park Dam.

Irvine Lake, which feeds the creek, is already filled to capacity, so the runoff must be released into the creek, which flows into the Santa Ana River and eventually the ocean.

Since houses and buildings have been built right up to Santiago Creek’s banks, the continuing downpour could test for the first time whether flood-control measures there will work. The flow, running several feet deep, could erode nearby property and uproot trees if it gets much deeper.

“It’s the first time in more than 20 years that we’ve had flow in that creek, and when it occurred 20 years ago, there was significant erosion and damage to public property,” said Tom Connelie, a county public works manager.

The area along the creek from the Santa Ana Freeway to the Santa Ana River is especially vulnerable because of heavy development.

“That’s a very old area of Santa Ana that is built very close to the creek bed. In fact, in 1969, there was considerable damage in a mile-long stretch down there. Many homes were damaged,” Reiter said. “The channel hasn’t been improved a great deal over that period of time, so we’re monitoring it very closely.”

Whether the creek continues to hold depends on how much more rain comes, and how quickly it falls.

“If we get a lot of rainfall in the next few days, five to 10 inches in the upper mountains, we may have to release quite a bit more into Santiago Creek. But that doesn’t look very likely right now,” Reiter said. “It sounds like we’re going to get some warmer and clear weather and it gives us a chance to dry out a bit and get water levels down in the dam.”

The true test, however, will be whether the flood-control system holds up through the rest of the winter. More than two months of the wet season remain.

“We’ve been getting six or seven inches a day in the local mountains and it’s not hurting us that bad. But we have two months of winter left,” Reiter said. “If this was March, I wouldn’t be concerned. But it’s mid-Januray and the brunt of our winter is yet to come.

“If we get high-intensity rainfall through the rest of the winter, we could have serious problems.”