L.A. Region Faces Major Flood Risk, U.S. Warns

Federal disaster authorities on Friday warned that a vast swath of the Los Angeles Basin is at risk of being swamped during El Nino storm conditions unless the region’s flood control system is improved or restored.

U.S. officials Friday designated a low-lying zone, 75 square miles stretching from Pico Rivera to Long Beach, as a “special flood hazard area” in serious need of better storm runoff systems. Their findings closely match those of local experts who have mapped an 82-square-mile “inundation area” encompassing the same communities--and up to half a million people--that could be threatened by a so-called 100-year flood, a deluge so severe it only occurs, on average, once a century.

“It is critical that people know the risks facing their neighborhoods so that they can take action to protect their families and their properties,” said James Lee Witt, director of the Federal Emergency Management Agency.

The last widespread 100-year flood in the Los Angeles Basin occurred in 1938, another El Nino year. Forecasters aren’t saying that will happen again this winter, but they are saying that if it does happen, part or even most of the inundation area could be under water.

Friday’s warning from FEMA officials came as Los Angeles County finally received permission to clear miles of choked flood control channels. Work is expected to begin at dawn today in a handful of areas around the county considered most susceptible to overflowing in the heavy rains expected this winter, a Public Works Department spokeswoman said.

In the event of a 100-year flood, the water in some places could be eight feet deep and the flood could last for several days.

A complex system of dams, debris basins, storm drains and sculpted river channels built over the last 70 years is designed to handle 100-year floods, and for the most part, it has. But much of the system was designed more than 40 years ago. Since then, massive urban sprawl has sharply reduced the amount of unpaved ground available to absorb water, and runoff has increased about 25%.

In addition, thickets of brush and trees have sprouted in many of the flood control corridors, often left to grow unchecked as environmental groups and government agencies wrangled over how best to clean out the channels.

With Friday’s granting of permission, county officials hope to clear away most of the overgrowth by Dec. 1. The sites slated for cleanup starting today include channels along the San Gabriel River near Irwindale, the Santa Clara River in Santa Clarita and the Los Angeles River in Long Beach--part of the zone newly designated as high risk by FEMA. More sites will be added next week.

The Army Corps of Engineers has spent millions of dollars shoring up the concrete-lined flood control corridors of the Los Angeles River. Those improvements will continue, chief spokesman Fred-Otto Egeler said.

Still, flood control experts like Diego Cadena, a Public Works engineer, say that if the 100-year deluge occurs this winter, the flood control system that has worked so well for so long could be overtaxed.

“If we have a major overflow on the Los Angeles River--and in the worst case, we could--that would be really bad,” Cadena said.

Widespread flooding could leave as many as 117,000 structures awash in the county-designated inundation area, Public Works engineers say. Projected damage estimates run as high as $2.3 billion.

“We have a problem,” is the way Public Works Deputy Director Carl Blum puts it.

This problem became evident after a particularly heavy downpour in February 1980.

A Public Works engineer patrolling the banks of the Los Angeles River found twigs, sticks and other debris atop a levee in Long Beach--clear evidence that water had come over the top. The flood control system was failing to control the flooding.

Not that any of that is news to some of the people who live along the banks of the river.

“We’ve got water pouring in here every time it rains a lot,” said Carl Roberts, 68, who lives in an aging mobile home in the shadow of a Los Angeles River levee in Paramount.

Like most of the inundation-zone residents interviewed about the possibility of flooding in their neighborhoods this winter, Roberts had made few preparations and seemed relatively unworried.

“I’m not going to get any sandbags,” he said. “They wouldn’t work here anyhow. I feel kind of like the guy standing on the trapdoor with a rope around his neck. There’s no point in worrying, ‘cause you can’t really do anything about it.”

Blum said the 1980 overflow left his department with two options: Build more upstream flood control dams, or raise the levees in the places most likely to spill over the top.

“A relatively simple solution was found,” he said. “We started building 4-foot-tall walls on top of the levees in the danger areas.”

Of course, it wasn’t actually that simple.

Congress authorized funding for its share--65%--of the project. Complaints by some environmentalists, who said the walls would be ugly and contended that the rivers should be returned to their pristine condition, were eventually resolved in court.

But the environmentalists managed to tie up state funding, and the state still hasn’t agreed to pay its share of the bill.

Despite the lack of state funds, and despite delays caused by all the bickering, the construction project finally got underway two years ago.

Plans call for building 21 miles of walls along the lower reaches of the Los Angeles River and the Rio Hondo. But by next month, when rains are expected to commence, only two miles will have been completed.

“We had to start at the bottom,” Cadena said. “If we’d started at the top, we’d simply have transferred the problem downstream. Unfortunately, what we’ve completed so far really won’t have any effect if we have El Nino problems.”

The average rainfall in Los Angeles during the last nine El Nino winters, beginning in 1951-52, was about 22 inches, almost 50% higher than the overall 120-year average of 14.98 inches. The 1982-83 El Nino season--the worst in recent years--caused 14 deaths and damage estimated at $265 million.

Ants Leetmaa, director of the National Oceanographic and Atmospheric Administration, predicted a few days ago that this winter would be comparable to 1982-83. He forecast rainfall in Southern California “in the order of 200% of normal.”

The Los Angeles Basin endured a series of damaging floods during the early part of this century, and especially devastating rains during the El Nino winter of 1913-14 finally led local leaders to form the Los Angeles County Flood Control District in 1915. Bonds were sold and the construction of flood control projects began during the 1920s.

Pacoima Dam was the first, completed at the mouth of Pacoima Canyon in 1929. At 372 feet tall, it was then the second-tallest dam in the nation.

More major flood control and water conservation dams followed, built by the district and other agencies. These include Big Tujunga Dam in the Angeles National Forest north of La Canada Flintridge, Hansen Dam in Lake View Terrace, Devil’s Gate Dam in Pasadena and Sepulveda Dam in Encino. A series of dams runs downstream from the West Fork headwaters of the San Gabriel River--Cogswell, San Gabriel and Morris dams in the forest above Azusa, Santa Fe Dam in Irwindale and Whittier Narrows Dam in Whittier.

The channels of the Los Angeles Basin’s three principal drainage systems--the Los Angeles River, the Rio Hondo and the San Gabriel River--were cleaned out, streamlined and, in many areas, lined with concrete, often to the dismay of environmentalists and lovers of nature.

Defending the channelization, Blum--whose agency eventually absorbed the flood control district--says that the storm runoff problems in the basin are unique.

“Water flowing through our system drops 1,500 feet in 50 miles,” he said. “That’s as far as the Mississippi River drops in 2,300 miles. Without concrete channels, the swift-moving water here would cause severe erosion problems.”

But Blum says that to do their job as designed, these channels must be kept clear of brush and trash. And because many of the channel bottoms were left unpaved to permit runoff to percolate into the ground, brush grows rapidly and trash tangles in the undergrowth.

For years, Public Works cleared the channels annually. Then, starting about a decade ago, a swarm of federal and state agencies--concerned about preserving as much of the environment as possible--began asserting jurisdiction over the channels, restricting permission to clear them out.

In some places, Public Works is permitted to clear only half the width of the channel each year. In other places, it’s less than half.

A few days ago, a Public Works crew was slowly hacking a 130-foot swath down the center of the Canada de Palos Verdes storm channel, using hand tools instead of bulldozers.

“The Fish and Game people say we have to do it by hand, so we won’t disturb the environment as much,” Cadena said. “We’ve got 12 to 20 men working with chain saws and machetes, and the job will take them a month. Three or four guys with tractors could have done the whole thing in a week.”

Because the crew is required to leave the stubble and roots in place, “everything probably will grow back in six months,” Cadena said. “We cut a 17-foot swath upstream six months ago, and you can’t even find it now.”

Environmental activists Friday promised to monitor new clearance to make sure the rules are followed.

“We’re not trying to stand in the way of flood control here,” said Melanie Winter of the Friends of the Los Angeles River. “We’re just trying to see that they do it responsibly.”

The county map of the Los Angeles Basin’s 100-year flood overflow zones includes a few relatively small areas beside Big Tujunga Wash in the San Fernando Valley, along the Los Angeles River on the northeast fringes of Griffith Park and in the old commercial district between the Los Angeles River and Alameda and North Main streets in downtown Los Angeles.

But most of the zones are in the low-lying areas between the San Gabriel River on the east and the Rio Hondo and Los Angeles River on the west, with some of them pushing west of the Los Angeles River into the communities of Carson, Compton and Lynwood.

Interviews with inundation zone residents showed that most of them were at least vaguely aware of the threat.

“The neighbors talk about it, but we’re like everyone else,” said Tony Lomelin, 69, who lives in Pico Rivera. “We won’t do anything about it, and then, when it comes, we’ll be drowned out.”

Jack Lee, 60, who lives in Downey, had at least made some preparations. “I bought some flood insurance,” Lee said. “And I’m planning to get some sandbags. One of my neighbors has a boat. We joke about getting it ready.”

FEMA’s Witt urged homeowners to follow Lee’s example and purchase insurance now. With the federal designation of the area as high-risk, premiums are set to increase by next summer.

“Flood insurance is your first line of protection,” Witt said. “We urge everyone living in flood hazard areas to take action now.”

Times staff writer Dave Lesher contributed to this story.

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Areas at Risk

A wide swath of Los Angeles County that is home to about 500,000 residents could be flooded if El Nino rains this winter cause widespread overflows along some of the Los Angeles Basin’s principal rivers and drainage channels, county and federal officials say. Shaded areas show zones that could be inundated an average of once every 100 years.

Source: Los Angeles County Department of Public Works