SACRAMENTO — Unlike hundreds of levees in Northern California that failed during the past week's siege of rainstorms, the levee that broke Thursday evening on the Yuba River met federal standards and was maintained by a local reclamation district with one of the best records in the state, officials said Friday.
They could not explain why the Yuba River levee broke virtually without warning--forcing thousands to evacuate from two towns--and said they may never know the cause.
The officials said the flooding throughout Northern California demonstrated that the patchwork system of earthen barriers leaves the people who live near them much more vulnerable than they may realize.
State officials "don't use the term flood control any more," said G. Donald Meixner, chief of flood management for the state Department of Water Resources. "We have found through bitter experience that we can't control floods. When they come, we do our best to try to manage them."
Surprisingly relaxed in the midst of a continuing crisis, Meixner noted that natural forces frequently overwhelm the very best efforts to hold back floodwaters.
Double Standard Noted
He pointed out that there is a double standard for construction and maintenance of the levees that channel thousands of miles of rivers and streams that flow through the Sacramento and San Joaquin valleys.
For 1,760 miles of levees under federal jurisdiction, construction is paid for with federal funds and must meet federal standards. The state Department of Water Resources conducts inspections twice a year to ensure that these levees are properly maintained and that the districts responsible for them are ready for high water like that from the recent series of storms.
Five Breaks in 31 Years
Meixner said there have been only five breaks in the federal levee system in California in the last 31 years, including Thursday's break.
But local flood control and reclamation districts, as well as landowners, are free to build additional levees to their own specifications. Most of them fall far below the federal standards and the builders know they are likely to fail in times of heavy runoff, Meixner said.
Some state money--about $2 million a year--is available for construction and maintenance, but efforts to increase the sum have failed for years in the state Capitol.
Opponents argue that those who benefit--mostly farmers--ought to pay the price of protecting the land that they want to farm. Supporters counter that some levees have deteriorated dangerously and that the barriers protect not only farms, but people as well.
In one recent flight over the Cosumnes River, Meixner said he counted 27 levee breaks just on his side of the helicopter.
One of State's Best
Department of Water Resources inspection records indicate that Reclamation District 784, which is responsible for maintaining 36 miles of levees--including the 150-foot section that collapsed on Thursday--was one of the best in the state.
Among about 100 levee districts in California, District 784 is one of 28 that inspectors found to be "outstanding" in their overall maintenance records--the highest rating possible. It has been given the same rating each year since 1976, when it was considered "good"--only slightly below federal standards in some areas.
In 1985, state inspector Gene Snow found signs of erosion caused by motorcycles on the district's levees, as well as evidence of rodents, whose burrows can cause leakage problems, particularly when water levels rise as they did in recent storms.
But, Snow concluded, "A very good levee maintenance program is in effect."
When rivers rise, it is common to see signs of levee seepage--water sometimes bubbling to the surface several feet away like a natural spring, noted John Michael Smith, an engineer with M H M Consulting Engineers Inc., which provides services to District 784.
Leakage Is Expected
But levees are expected to leak, and as long as the liquid is clear, levee district officials simply watch closely, sometimes for days, to see if the water turns muddy. That is the first sign that the water side of the levee has begun to erode.
In most cases, the leaks stop by themselves. However, when the seepage becomes serious, crews place a ring of sandbags around the leak--building it high enough so that the pressure of water in the column stops the water coming from the levee.
Both Meixner and Smith were puzzled about why the Yuba River break happened so suddenly, without any of the usual signs of seepage that normally precede a breach.
Both speculate that the surging river might have carved a cave underneath the levee, and that the whole mound of earth and rock collapsed into the hollowed-out space.
Meixner said that the cause may never be known. "When a levee collapses, the evidence is washed away."
"It just happens," Smith said. "Most people don't realize that a little gopher hole can cause a catastrophic problem that can flood the town. . . . When people move to this region, they don't realize that it just like living in Holland."