Flood’s Lesson--It’s Going to Happen Again

Two days before Valentine’s Day, 1986, the front edge of a band of moisture thousands of miles long began passing over a 300-mile belt in the upper half of California.

“It was a tropical storm from the South Pacific. The jet stream up high was coming in at 200 miles an hour, and there was nothing in the way,” recalled Bill Mork of the state’s flood center in Sacramento.

From Feb. 14 through Feb. 18, more rain fell at some places in the Central California mountains than ever had been measured in such a short period.

“We got half a year’s rain in four days,” said Kelly Purdom, director of the office of emergency services in Yuba County, one of the hardest-hit regions.

First Days the Worst

The first five days of the storm were the worst. After that, the rain eased but did not tail off until Feb. 21.

Streams overflowed. Dikes washed out. Roads flooded, and their paved surfaces crumpled. Mountain snow, melted by the warm rain, swelled rivers running down into the Sacramento Valley. In western Nevada, an interstate gas pipeline ruptured.

Thirteen people died in flood-related mishaps.

About 50,000 fled their homes, half of them after a levee break flooded the low-lying communities of Linda and Olivehurst in Yuba County 100 miles northeast of San Francisco.

In March, the state office of emergency services issued a final damage estimate of $532 million, including the flood-fighting costs to federal, state and local governments.

Yet outside the flood belt, the storm was a boon to California. Before the cloudburst in the Sacramento Valley and the Central Sierra, there had been little rainfall anywhere, and some thought the state was on its way to a repetition of the 1976-78 drought.

In California water politics, it is a rule of thumb that two-thirds of the state’s surface water supply is generated in the stormy north. Two-thirds of the demand for water is in the arid south, including the urbanized strip from Los Angeles to San Diego, where 14 million of the state’s 27 million people dwell.

Threat of Drought Vanishes

When the storm passed, water was high in the big dams on the Sacramento, Feather and American rivers in the northern half of the state. The threat of another drought on the scale of the 1976-78 dry spell had been pushed back for at least a year.

Both environmentalists and government water engineers agree on one point: If a similar storm lands in Central California this winter, or for many winters to come, the results probably will be just about the same.

Or they could be worse. The state Department of Finance estimates that California’s population last year grew by 623,000, pushing close to the 27-million mark. The flood-prone Central California counties, like Sacramento, have some of the highest rates of growth.

Local funding for flood control projects is drying up following the property tax freeze enacted by voters in 1978. Federal deficits

have slowed the flow of money from Washington. Environmental lobbyists and the state’s water establishment are at odds over building more dams. Even if they were not, the cost of big water projects has risen out of sight. And the environmental movement’s campaigns to check building development in flood-prone regions have shown few results.

At Guerneville, in the canyon of the Russian River 55 miles north of San Francisco, periodic floods are a way of life. About 2,400 people were evacuated from the resort town last February, after the river crested at 48.75 feet above sea level, a foot higher than the previous record set in 1955.

‘Always Come Back’

“They all came back. They always come back,” said Pete Peterka, coordinator of emergency services for Sonoma County.

“It would take a lot of dams on a lot of the tributaries, most of which are small, to prevent a similar flood in the future. The cost would be prohibitive,” said Bill Stillman of the Army Corps of Engineers. He said small local dams partly control the water flows in only about one-sixth of the Russian River’s watershed.

In the Napa Valley, centerpiece of California’s wine industry 50 miles northeast of San Francisco, 20 inches of rain fell in four days. Stations in the nearby mountains reported about 40 inches during the storm.

About 400 homes were flooded by the Napa River, which flows down the center of the valley, and 2,500 people had to be evacuated.

Yet Napa County’s flood control district has had virtually no operating funds since Proposition 13 was passed in 1978. A voter initiative to generate money for drainage projects was defeated. Napa Public Works Director Harry Hamilton has recommended that the flood control agency be abolished unless a way is found to tax property owners.

“People don’t believe the kind of damage the river can do,” Hamilton said. “There are no funds for any kind of capital improvement. If the same storm happened again this year, we would have the same kind of flooding.”

Nasty Surprise

If the floods were predictable in Napa and the Russian River country, they came as a nasty surprise to the residents of Linda and Olivehurst on the plain south of Marysville.

On Feb. 20, the worst of the storm appeared to be over. Much of the day was sunny. Linda and Olivehurst are protected by a levee along the Yuba River, which separates them from Marysville. Water in the Yuba was still 10 feet higher than the plain on which the two communities are built, but there had been no serious problems with the levees. The Yuba had peaked at 76 feet above sea level and was going down.

Shortly after 6 p.m. the levee on the south side of the river washed out, leaving the region defenseless against a wall of water 10 feet high pouring through a gap that gradually widened to 150 feet.

By 9 p.m., 24,000 or more people alerted by peace officers and firefighters had fled for their lives.

“The cause of it may never be known,” said Art Aseltine, administrator of the Yuba County Water Agency.

The flood revived talk of two countermeasures.

One is building another dam to hold back the water of the Yuba, especially its south fork. Another is dredging the channel of the Yuba, which is plastered with a thick layer of silt as the result of hydraulic gold mining operations in pioneer times.

Both would be expensive, and the money is nowhere in sight.

Sacramento’s Narrow Escape

Sacramento had a narrow escape. The state’s capital is wedged between the Sacramento River on the west and its tributary, the American River, on the north. In high water periods, most of Sacramento’s 280,000 people are protected by levees and by Folsom Dam, which checks the American River 22 miles to the east.

In the American River watershed in the Sierra, the railroad village of Blue Canyon recorded 33.8 inches of rain during the storm. On the Feather River, another tributary of the Sacramento, 55.7 inches fell at one station.

On the night of Feb. 18, Folsom Dam was close to full. On the morning of the 19th, U.S. Bureau of Reclamation Engineers held their breath and stepped up the outflow, pouring 130,000 cubic feet of water per second into the American River channel whose levees were designed for no more than 115,000.

Sacramento residents packed their cars and kept their radios and TV sets on. But the soggy levees held, and by the 20th Sacramento was safe.

North of the city, the creeks feeding the high-running American had no place to go. Water spread over the plain, and there were more evacuations.

Even before the American River receded, the whole episode was entangled in water politics. Advocates of the long-stalled Auburn Dam on the north fork of the American River pointed to the flood protection that could be had by completing it.

The proposed 680-foot dam, which would flood much of the American River Canyon, is an anathema to the environmental movement. Friends of the River and other environmental groups trotted out their own experts, who charged that the Reclamation Bureau had failed to heed storm forecasts. They argued the release of water from the dam should have begun earlier to make room for the torrent flowing in from the mountains.

Reports of Misery

As the storm slackened, more reports of misery flowed in.

A levee on the Mokelumne River broke, flooding the town of Thornton in the Sacramento-San Joaquin River Delta. Another 1,850 persons fled their homes.

A interstate gas line supplying western Nevada and the Lake Tahoe region in California ruptured at Wadsworth, Nev. The break left 80,000 people in a chilly mountain region without gas to heat their houses. There were more evacuations, this time not because of water but because of the cold.

Nobody is sure what the ultimate storm might be in Northern and Central California.

Weather records in California go back no farther than the middle of the 19th Century, when large-scale settlement of the state by immigrants from the Eastern Seaboard, Europe and Asia got under way.

In many important parts of the Sierra, rain gauges and river flow meters were not in place until well into the 20th Century.

New England has accurate rainfall records going back more than 300 years. In Central Europe, water engineers can review 700 years of accurate records of the rise and fall of rivers like the Danube.

In California, the data base is shallow. Folsom Dam, completed in 1964, has been tested at least three times by American River runoffs larger than it was designed to handle.

Large dams typically are built to cope with a theoretical “100-year flood,” whose size is estimated from experience with past storms.

In Northern California, the 100-year flood grows larger as the engineers adjust their computers to include storms like that of February, 1986.

Nobody really knows if the ultimate flood has already happened or if it still lies ahead.