LAST month, a 30-foot section of levee ruptured in Fernley, Nev. While the cause of the breach, which swamped 450 homes and forced dozens of people to evacuate, is unknown, anyone familiar with the drowning of New Orleans by Hurricane Katrina will tell you this: Levees fail.Indeed, there are more than 100 antiquated earthen berms across the country in danger of collapsing. What happened in Nevada is a harbinger of a much larger problem nationwide.In Texas City, Tex., for instance, levees protect 50,000 residents and $6 billion worth of property, including almost 5 percent of the nation’s oil-refining capacity. Imagine the consequences, in this day of $100-a-barrel oil, if those defenses fail.Even more vulnerable are the 1,100 miles of levees in the Sacramento-San Joaquin River Delta, north of San Francisco. Cobbled together 150 years ago to provide farmland, they are now part of an intricate, fragile system that supplies fresh water to California, the eighth-largest economy in the world.On a recent visit, I noticed that the water had risen nearly to the top of the levee on one side, while the land had subsided at least 30 feet below on the other side. The water pressure against the decrepit berm was palpable. Should the levee crack, be overtopped by a storm or liquefied by an earthquake, saltwater will surge inland, destroying lives, perhaps flooding Sacramento and paralyzing California.A year ago the United States Army Corps of Engineers, which builds and maintains many of these levees, admitted that 122 are at risk of failure. California, with 37 at-risk levees, and Washington State, with 19, are the worst off. But the list includes levees near Albuquerque, Detroit, Hartford, Honolulu, Los Angeles, Omaha and Washington.

These levees were designed poorly and built of whatever material was close at hand — clay, soft soil, sand mixed with seashells. Tree roots, shifting stones and rodents weaken them further. The land the berms are built on often subsides, while the waters they restrain constantly probe for weak spots.

Sadly, America’s flood-protection system has long been undermined by bureaucratic turf wars, chronic underfinancing by Congress and a lack of political leadership. The heart of the problem is the Corps of Engineers, which Congress has “streamlined” relentlessly for decades, imperiling its mission through budget cuts and neglect. The Corps has a good set of engineering guidelines for levees, but it doesn’t always follow them. Now largely staffed by civilians, the Corps has a backlog of projects it does not have the money to accomplish.

Business has also ignored the levee problem. Developers, abetted by the Supreme Court’s vague 2006 ruling on the Clean Water Act, have rushed to fill in wetlands and build in floodplains.

But water is an inexorable force that, sooner or later, will assert itself. This is a lesson others have taken to heart. In 1953, a hurricane in the North Sea breached dikes and flooded the Netherlands, setting off a period of national soul-searching. Realizing that they had suffered from poor engineering and communication, the Dutch spent billions of dollars to create a world-class flood control system and are now armed for a once-in-10,000-year event.

The United States isn’t even prepared for a once-in-100-year event. In light of climate change, we need to emulate the Netherlands and make flood protection a national priority.

For starters, we need to reinvigorate the Army Corps of Engineers and give it a mandate to build and maintain a coherent, robust, nationwide flood protection system — as opposed to the ineffective, piecemeal measures that failed so catastrophically in New Orleans.

Second, the laws stemming from the 1928 Flood Protection Act, which immunize the Corps from prosecution when its levees fail, must be repealed. Already, the Corps has quietly begun to decertify some of its levees, effectively abdicating responsibility when disaster strikes.

And finally, citizens and businesses who benefit from levees should apply their skills and resources to their upkeep. For years, we have relied on dredging, bulldozing and building ever-taller walls to control nature. Instead, the Corps should work with other government agencies, businesses, scientists and environmental groups to develop a greener, more intelligent system that integrates traditional engineering with natural defenses like wetlands, islands and reeds. Such an approach will be costly and require maintenance, but will prove far more effective than our current methods.

The need to eliminate dangerous levees gives Congress the chance to rethink land and water use, and how they are connected. We should integrate nature and technology, build only in areas that can be adequately protected and allow some wetlands to return to their naturally unconstrained state. After all, experts say, there are only two types of levees: those that have failed, and those that will fail. If we have learned anything from Hurricane Katrina, it’s that we cannot simply wish natural flooding away.