IT'S TIME for California to face up to its own potentially catastrophic levee problem: the 1,100-mile maze of levees in the Sacramento-San Joaquin Delta, much of it made from little more than sand and gravel.

In the event of a massive flood or earthquake, the levees could collapse. Millions of acres of agricultural land would be flooded. As seawater from the San Francisco Bay rushed in, the water supply to two-thirds of the state would be contaminated.

Also at risk are the levees that protect population centers along the Sacramento and American rivers -- including the state's capital city.

"New Orleans has lost the battle with the inevitable, and we will do the same," said Jeffrey Mount, a geologist who directs the Watershed Center at UC Davis. Mount, the state's leading researcher on the dangers of levee breakdowns, says there is a 2 in 3 chance of a flood or earthquake causing widespread levee failures over the next 50 years.

Mount points out the risk of major flooding is growing for two reasons:

One is that we are falling further and further behind with not only the maintenance but upgrading of the levees. The levee maintenance workforce has been reduced by 35 percent since 1986. Funds for flood management have been reduced drastically over the past five years.

In addition, the delta landscape is itself slowly changing -- with potentially devastating consequences. The delta is continuing to sink below sea level, at the same time that sea levels are rising. The Pacific Ocean is rising very slowly -- by about 2 millimeters a year -- but over the next 100 years, it is expected to rise between 1 and 3 feet.

The risk is heightened by climate changes that could bring less snow and more rain to the highest elevations of the Sierra Nevada. As a result, water surging into the Sacramento River and the delta will greatly increase the chances of winter floods. "The state's water policy and all its plans for restoration of the delta are predicated on one flawed assumption -- that the delta is a fixed landscape and will look the same for the indefinite future," says Mount. "And it won't."

The state's booming housing market has contributed to an explosion of housing developments in the floodplains of the Sacramento River, putting greater numbers of people at risk. Even more frightening, communities such as Stockton and Lathrop are encouraging housing developments on so-called "islands" in or adjacent to the delta.

One of the only positive outcomes of the Hurricane Katrina disaster is that it is focusing attention on this neglected problem in our own backyard. This week, in a rare example of bipartisan solidarity, Sen. Dianne Feinstein, D-Calif., and Rep. Richard Pombo, R-Tracy, the chairman of the House Resources Committee, sent a letter to Lt. Gen. Carl Struck, commanding general of the Army Corps of Engineers. They urged him to expedite levee projects in the delta. "If we don't address this problem, we may suffer the same fate as Louisiana," Feinstein and Pombo wrote. "It is just a matter of time."

Levee maintenance and upgrading could cost billions of dollars. But it is an investment that must be made. In addition, some creative thinking will be required to reduce overall risk levels. Peter Gleick, president of the Pacific Institute in Oakland, an independent nonprofit research organization, argues that the greater challenge will be to reduce the state's dependence on delta water, at least in the way we use it now. That would involve pumping less water from the delta, developing more water resources in Southern California and generally reducing water use.

It can't happen here. That's what too many people living along the Gulf of Mexico believed. California can no longer afford to ignore the risks we, too, are facing.