Call it Earthquake Katrina: a hypothetical temblor that blows out the California Delta with the same devastating consequences as the August natural disaster whose storm surge overpowered two New Orleans levees, leaving the city in ruin.

The Delta's geography shares much with the Mississippi Delta. Both are bounded by fragile levees that protect land that has subsided below sea level. Both are fed by large rivers.

New Orleans, of course, is a major American city while the California Delta is sparsely settled.

But that's changing.

The suburbs are moving in. Tens of thousands of houses are proposed in the Delta region.

"One of the things that struck me in the Katrina story was how similar it was to what's going on around here," said Lawrence Kolb, assistant executive officer of the San Francisco Bay Regional Water Quality Control Board. "For California to continue on a New Orleans-like (path) by urbanizing behind levees is the height of idiocy."

Even without more suburbs, levee failures in the Delta could create a statewide economic disaster. State officials have estimated the economic damage of a major earthquake in the Delta at $30 billion to $40 billion.

That is because the flooding could destroy highways, houses, natural gas pipelines, power transmission lines and other infrastructure.

More broadly, however, the levees, many of which were first built more than 100 years ago, are a critical link -- and a weak link -- in the state's massive water-delivery system.

Today's levees still sit on fragile peat foundations; and though they have gotten taller and wider over the decades, they are still vulnerable. State officials have no solid estimates of what it would cost to fortify the levees to an acceptable level of safety; but a representative of the state Department of Water Resources recently told lawmakers the work could easily run up to many billions of dollars.

The state is embarking on a study to better understand risks in the Delta.

"Multiple simultaneous levee failures caused by storm or earthquake would have a devastating physical and financial impact on the entire state," according to the state.

In June 2004, California got a small hint of how badly things could go when a single levee west of Stockton failed on a dry summer day.

As water poured into the Jones Tract, water managers were forced to turn off pumps to prevent brackish water from being sucked from the San Francisco Bay into the water supply for 23 million Californians and 7 million acres of farmland.

They also had to send more water into the Delta from a Sacramento River reservoir to push that salty water back.

By the time the flood fight was over, 12,000 acres on the Jones Tract were underwater. Damage, including the impact of the flooding and the cost to fix the breach, totaled more than $100 million.

It could have been worse. In fact, it probably will be.

Jeff Mount, a leading scientist on California rivers and the Delta, has estimated a 2-in-3 chance that multiple levee failures will occur in the Delta during the next 50 years.

His calculation looks at increasing pressure on the levees caused by the continued subsidence of the islands on one side and rising sea level on the other side.

Throw in the likelihood of earthquakes and floods, and it's a recipe for disaster.

Mount's conclusion: The California Delta, the linchpin for California's water delivery system, is not reliable.

"Business as usual is not sustainable over the near term," Mount said. "There's a lot of stuff if you lose the Delta. It's a $30 billion to $40 billion blow to the state's economy."

Stabilizing fragile levees was one of the four pillars in the 2000 CalFed plan to fix the California water picture.

But CalFed's levee program has been largely neglected, and some of the early plans may not even be relevant any longer.

"There has been no significant progress on any of the CalFed (levee program) actions; however, several of the ... (original) actions may no longer be applicable," concluded a recent state Department of Finance audit.

Unless the way the Delta is managed changes, Mount says, he envisions levee failures that will flood many of its islands and leave the Delta as an extension of Suisun Bay -- a vast open water bay -- ringed by a seawall. The suburbs would inevitably creep to the edge of it.

The water could be too salty for drinking or irrigation, and its quality could be threatened by polluted suburban runoff.

Spurred by warnings from Mount, the recent Jones Tract flood and sobering images of New Orleans underwater, policymakers have begun looking anew at the Delta's fragility and how its levees can be shored up.

"We need a different long-term vision for the Delta," said Lester Snow, director of the Department of Water Resources.

Kolb, of the San Francisco Bay water quality board, does not believe Mount's dire prediction will fully materialize, although he agrees some levees will certainly fail and the threat is increasing every year.

"I can't believe all the levees will turn to Jell-O and disappear," Kolb said.

Still, it might make sense for the state to build an entirely new plumbing system that routes water directly from the Sacramento River to Southern California around the Delta, instead of through it.

Such a proposal would be highly controversial. In 1982, voters rejected the state's effort to build the Peripheral Canal on the strength of overwhelming opposition in Northern California.

In Contra Costa, for example, voters rejected the canal by a margin of 96 percent to 4 percent.

If a canal, or a smaller version of it, were built, how would the state prevent the Delta -- and Contra Costa's water supply -- from becoming a sump of agricultural runoff and pollution?

"The whole Delta turns into the drain for the San Joaquin and Sacramento rivers. You have all that sloshing around," said Greg Gartrell, assistant general manager at the Contra Costa Water District.

The CalFed agreement signed in 2000 considered building a modified peripheral canal -- which it renamed an "isolated conveyance facility" -- but rejected the idea, mostly because of the controversy surrounding it.

The 82-page decision document added, however, that if CalFed failed to meet its goals by 2007 -- which is now just about a year away -- "additional actions including an isolated conveyance facility will need to be considered in the future."

Mike Taugher covers natural resources. Reach him at 925-943-8257 or mtaugher@cctimes.com.