Drain System, Topography Avert Damage : Locally, major flooding and landslides have been avoided so far. But some surface streets were under water, and there were power outages.

While much of Southern California was reeling from this week’s pounding winter storms, the South Bay was spared the flooding, landslides and major street closures that the downpour wrought elsewhere.

City and county authorities say they are not surprised.

Thanks both to nature and man-made facilities, they say, the South Bay’s topography and vast network of storm drains virtually preclude the severe rain-driven damage that has brought mudslides to Malibu and left parts of the San Fernando Valley and Ventura County resembling the Mississippi Delta.

“It’s hard for me to imagine (the South Bay) having that type” of damage, said John Schubel, planning chief for the water resources section of the U.S. Army Corps of Engineers.

Added John Mitchell of the Los Angeles County Flood Control District: “There is very little concern about the South Bay area (because) the existing facilities should handle the rainstorm.”

Still, the South Bay has not totally escaped the impact of the storms. In isolated pockets from San Pedro to El Segundo, some streets have been flooded. On Wednesday, up to 15,000 homes and businesses in Torrance and Rancho Palos Verdes were without electricity for several hours because of the storm. And concern remains that both beaches and several seaside bluffs along the Palos Verdes Peninsula could erode as the rains continue.

But interviews suggest that, although there is concern, there is no panic.

“It’s been raining hard all day. The graveyard shift said it was coming down so hard that the windshield wipers on their cars were useless,” Torrance Police Lt. Jim Herren said Wednesday. “But we haven’t gotten reports of anything major at all, so I guess the South Bay is doing pretty well.”

Significantly, officials say, the South Bay is distinguished from many regions of the county by its relatively flat terrain, large-scale commercial and residential development accompanied by the construction of extensive storm drainage facilities, and the absence of any large reservoirs, such as the Sepulveda Dam, where runoff in Monday’s storm flooded a low-lying basin in the San Fernando Valley.

Along the eastern border of the South Bay, for example, the Dominguez Channel has greatly increased storm protection for many local communities. The channel, built between 1949 and 1967 at a cost of $26.4 million, serves as a drainage point for parts of Gardena, Torrance, Carson and other cities that once had vast areas of marshland.

“Prior to the channel, most of the ground south of Artesia Boulevard in Torrance and Carson were basically swamps,” said the county flood control’s Mitchell, a lifelong resident of the South Bay. “Since the channel was built,” he said, many areas in the South Bay “no longer flood as they used to.”

Just east of that channel, Mitchell and others said, the Los Angeles River holds the potential for $2 billion or more in damages to nearby cities if its banks overflow--as projected by the Army Corps of Engineers--in a huge 100-year flood. Such a flood would be roughly twice as powerful as the storm that dropped six inches of rain on the San Fernando Valley in less than 24 hours.

But even in such a flooding of the Los Angeles River, officials say, the damages are likely to be slight in the South Bay because most cities are far from the river. In fact, the Corps studies show only one South Bay city--Carson--would be among the dozen damaged by a giant flood. And even then, like the Los Angeles community of Wilmington, only a small portion of Carson’s largely industrial, eastern boundaries would be affected.

Just as the flood control channels are credited with sparing the South Bay from widespread damage in heavy rains, the area’s storm drain system, driven by booming residential, commercial and industrial development in the 1960s, is credited with relieving much of the flooding that occurs elsewhere in the county’s older areas.

In the industrial centers of the harbor, Torrance and El Segundo, for example, the growth of huge plants, such as refineries, required extensive sewer systems that also help relieve flooding of nearby streets in storms. Similarly, other local developments--relatively new by the standards of much of Los Angeles--have allowed the South Bay to avoid widespread flooding, according to officials.

“Pacific Coast Highway, Artesia Boulevard, Hawthorne Boulevard, all the major highways are open and doing fine,” said Redondo Beach Police Sgt. Paul Rossiter. “Twenty years ago, we would have had major problems with rain this heavy. But now, it is just routine.”

But, if the South Bay’s streets and channels are not as prone to rain damage as other parts of Los Angeles County, there are areas locally where the threat to property is constantly monitored during storms.

For instance, officials in San Pedro and Rancho Palos Verdes have been carefully monitoring the storms’ effects on seaside bluffs. In San Pedro, that concern has been directed at Point Fermin and in Rancho Palos Verdes, officials have kept watch on both Portuguese Bend and Abalone Cove--two locations where slides and ground movement have been tracked for decades.

“Right now, we’re watching Point Fermin . . . but the drainage pattern there is pretty favorable, so I don’t think we would have any extensive flooding,” said Louie Yamanishi, a supervising engineer with Los Angeles’ Board of Public Works.

Similarly, Rancho Palos Verdes City Manager Paul Bussey said his city is watching the two areas that over the years have been prone to slides.

“We hope we have done things to minimize the impact of the rains, but we really don’t know,” Bussey said, noting that the city has in recent years dug wells in the areas to drain water from rainstorms and other sources.

Even if slides were to occur, however, Bussey said the location of the seaside bluffs do not pose a threat to homes or roads, as is the case in other areas of the county, such as Malibu.

“This is a big, flat, level area and when it moves, the whole area moves slowly. Now there could be erosion and even some cliffs falling into the sea. . . . But it is not anticipated that we will have a Malibu-type situation with landslides,” Bussey said.

Last year, he said, the strong March rains that pummeled the region did not endanger local cliffs at all.

At the same time, however, Bussey said the overall impact of the current winter storms will be impossible to assess because their rains will bring an accumulated threat of erosion.

“Many residents have pointed out that we’ve had five years of dry weather. So does this wet weather mean (the bluffs) will move? No, it doesn’t,” Bussey said. “But we have to wait and see what happens. . . . We don’t know what one, two, three or four years of wet weather could do.”

Handling the Deluge

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.

Water running off from mountains and canyons is trapped by the dams, then channeled into the Los Angeles, Rio Hondo and San Gabriel rivers. The Los Angeles River collects water from the northwestern portion of the county. Water from the east flows into the Rio Hondo and San Gabriel rivers. Supplementing the dams are 2,370 miles of underground storm drains that collect runoff from streets, curbs and gutters.

Despite heavy rain this week, the dam, basin and canal system is not near capacity. The 15 county dam areas have a storage capacity of 116,000 acre-feet of water. As of Tuesday--the most recent day when figures were available--about 40,000 acre-feet of water were in the dammed areas.

Officials say there also has been no danger of the Los Angeles River flooding downstream. At its peak, more than 51,000 cubic feet of water per second rushed through the lower river to the ocean; the river could have taken as much as 146,000 cubic feet.

IN THE SOUTH BAY, much storm water is captured by the Laguna Dominguez Channel and an elaborate honeycomb-like underground storm drain system.

South Bay areas of East Wilmington and Carson that run between the Dominguez Channel and the Los Angeles County Flood Control Channel could possibly be flooded in a powerful 100-year storm. By comparison, the Sepulveda Dam Basin overflowed Monday under rainfall roughly equivalent to a 50-year flood.

Otherwise, the flat topography of most of the South Bay, coupled with residential and industrial development that brought in the extensive storm drain system, should protect most local cities from any serious flooding during most rainstorms.