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Catastrophic domino effect could topple Delta

Published in the Stockton Record on 05/30/05

Catastrophic domino effect could topple Delta

By Hank Shaw and Dana Nichols - Record Staff Writers
Published Monday, May 30, 2005

MANTECA - A voice over loudspeakers jolted Stacey Cody awake. “Everybody evacuate! Everybody evacuate!" It was happening.

The 1997 floodwaters were howling down the San Joaquin River, clawing at the narrow levee channels that crisscross the county like an earthen spider web. For four days, the flood had devoured levees and flooded thousands of people out of their homes. Two days before, the sheriff had recommended that Cody‘s family evacuate, along with the 2,000 other residents of Wetherbee and Oakwood lakes. Four nearby levees collapsed that day. But the Cody family stayed, and so did most others. They moved their RV and boat to higher ground but stayed in the family home, built high off the ground atop a cement-block garage. So when Cody put her daughter, Kayla, and son, Kolt, to bed Monday night, she hoped the nearby levee would hold and wasn‘t worried about what would happen if it didn‘t. At 2 a.m. Tuesday, that hope burst. “The water is coming. We‘ve got to go," Cody told her children as they jumped into their car and drove to Manteca.

Nearly two dozen levees failed during that flood. Fortunately, most were in rural areas. Another major systemwide levee failure can happen, emergency officials say. The levees that protect thousands of area homes fail for all kinds of reasons, from burrowing critters to erosion to storms or poor maintenance. And once one levee fails, it can trigger a domino effect that causes its neighbors to collapse.

Then there‘s the unthinkable: a catastrophe such as an earthquake, which could level the Delta‘s levees and cut off the primary source of drinking water for 22 million Californians. But perhaps the most likely disaster, experts say, is simply a rainy winter, like the one that just ended, followed by another wet winter and a warm, early spring rain that melts the thick Sierra snowpack. This would send more water through the Valley than its manicured river channels could handle.

Fighting a flood plain

San Joaquin County‘s rivers make the area a natural flood plain.

According to state Department of Water Resources records, the county has been inundated at least 65 times since 1805. That‘s an average of once every three years. Dams upstream have calmed the waters, but about once every eight years, major floods still break levees.

It has been eight years since San Joaquin County Emergency Services director Ron Baldwin gave the order that forced Cody‘s family to flee their home. Baldwin thinks we‘re due for another deluge. He and other flood experts say it would require far less than an earthquake to cause major damage. Baldwin said all it would take to re-create the experience of 1997 would be a late-winter rainstorm blowing up from Hawaii, the so-called Pineapple Express, which would melt the snowpack and force upstream dams to spill.

Most levees would hold, but not all. They are old and not well-maintained, because levee-maintenance budgets have eroded in recent years. Such a storm could present flood fighters with twin threats: levee breaks that flood neighborhoods and a Delta levee failure, which could threaten the heart of the state‘s delicate water-supply system.

It is a battle without end.

Cody‘s neighbor Jim Lyberger knows what a flood can do. After all, he was born and raised in Johnstown, Pa., the site of the worst flood disaster in U.S. history. More than 2,200 people died in 1889 when a dam above Johnstown disintegrated, sending 20 million tons of water screaming through the little steel town.

Nothing so horrible has ever touched San Joaquin County. But about 33 miles north of Wetherbee Lake, near the intersection of Cameron and Thornton roads, there is a small historical marker honoring the former Mokelumne City. Established in 1850, Mokelumne City was the county‘s third-largest town — until it was annihilated in the flood of 1862. Since then, floods have repeatedly soaked the cities of Stockton, Lodi, Manteca and Lathrop. Most of Tracy is on higher ground.

In 1997, nearly 520 homes were damaged or destroyed in San Joaquin County. Twenty levees failed. No one was killed, but the water caused more than $60 million in damage in San Joaquin County and left 4,000 people temporarily homeless, including the Codys. When the water finally receded, silt and mud 8 feet deep surrounded their house. Animals had chewed though whatever the flood hadn‘t destroyed. Everything stank.

Inside the levee

The levee that broke near Wetherbee Lake is built on hard-packed earth. It can be built higher and wider or even moved back to let future floodwaters pass through more easily. Drive west a few miles, however, and nature makes that task nearly impossible.

Peat is the culprit. This fertile amalgam of decomposed reeds and marsh plants brought farmers to the Delta in the first place. But peat poses problems. It squishes. Build on it, and whatever you build sinks. Levees can sink an inch a year. Build too fast, and the pressure on the levee‘s foundation can cause it to collapse altogether.

“This peat is just weird," said Bill Burkhard, an engineer with the state Department of Water Resources. “You can‘t let up on your maintenance. To work with peat is an art, not a science. Over time, you learn what works and what doesn‘t." Peat not only makes building Delta levees difficult, it also intensifies the risk of a mass collapse. The Pineapple Express scenario Baldwin worries about also strikes fear in Delta flood fighters. For them, the stakes aren‘t so much lives as livelihoods — both that of the farmers who till the peat and the economy of those who rely on Delta water.

Gigantic water pumps near Tracy drink deeply from the Delta to slake the thirst of 22 million Californians, most of whom live in Los Angeles, Orange County and San Diego. The levees keep the spigot open. When levees break in the Delta in summer — as Jones Tract did last year — it sucks in salty water from Suisun Bay and taints the fresh water near the pumps. Scientists call this the “big gulp."

The Jones Tract collapse forced the pumps to stop for two days. A break in 1972 shut the pumps down for a month. Knock a half-dozen islands down, and the tap could run dry indefinitely. Dante Nomellini of Stockton has been involved in fighting Delta floods for decades. He can rattle off levee failure dates at will and earns his living representing the reclamation districts tasked with maintaining them. Nomellini says good planning and quick response could prevent catastrophe.

“I don‘t want to pooh-pooh it, but that doesn‘t make me shudder," he said. “It‘s a matter of having a good emergency response. A good emergency response will keep the flood from running on you." A Delta island is essentially an unfilled reservoir, because the “islands" are as much as 20 feet below water level. In the Delta, the levees act more like earthen dams — similar to the one that stood above Johnstown.

When one of these islands floods, it forms a lake. Waves lap the inner sides of the levee, which are not protected. These waves erode the levees‘ inner walls. The bigger the surface of the flood, the bigger and more destructive the waves can get. This is called “fetch," and it is the real killer in the Delta. Left unchecked, it can have a domino effect on the entire system. It almost did last year at Jones Tract, and that flood was being closely attended. Even an individual levee break in the Delta can be costly. Jones Tract cost about $85 million in damage and repairs.

Other failures

For a real disaster, however, many levees would have to fail both in the Delta and around Stockton and Manteca. A storm could trigger such a scenario. So could an earthquake. Several active faults lie within 30 miles of the Delta, including the Hayward fault. Seismologists say this crack in the earth has a 1-in-4 chance of producing a large quake — magnitude-6.7 or better — within the next 30 years. “Those odds are worse than Russian roulette," said John Cain of the Natural Heritage Institute. “When you spin that chamber, you only have a 15 percent chance of death."

Such a quake could level many Delta levees at once, turning the region into an extension of San Francisco Bay. Cain says the current strategy for maintaining Delta levees does nothing to protect them from earthquakes. “They would liquefy," he said. Water engineers also say that in a big earthquake, bulldozers, cranes and construction crews would be busy digging people out of city buildings and couldn‘t go immediately to the Delta. If crews and equipment are elsewhere, the Delta could be doomed.

“This is a dynamic landscape," said University of California, Davis, geologist Jeffrey Mount, who has studied this “doomsday scenario." “These are processes that could take decades to evolve. Or it could happen tomorrow." Mount and Nomellini agree that constant maintenance is the only way to lessen the risk, even if it can never be eliminated. “We are heavily vested in the future of the Delta," Mount said. “It would be a mistake to just throw our hands up and let it go."

Stacey Cody hopes those with the power to fix things heed their warnings. “I think everybody learned a lot about this last event," she said. “So you keep your fingers crossed that the powers that be are doing the right thing and taking the necessary steps to be sure it doesn‘t happen again. “We forget how real the flood is. I‘d like to say I‘m ready for the next one. But I‘m not."

Contact Capitol Bureau Chief Hank Shaw at (916) 441-4078 or sacto@recordnet.com

Contact reporter Dana Nichols at (209) 546-8295 or dnichols@recordnet.com

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