WASHINGTON — As scores of communities scramble to repair levees threatened by years of poor maintenance, the recent spate of disastrous floods across the country raises a new concern: Will those levees be strong enough even when they're fixed?

In many cases, no one really knows, according to the National Committee for Levee Safety, a federal panel assessing the condition of the nation's flood controls.

There is no comprehensive inventory of the nation's levees and no set of national safety standards for how much protection they should provide, the committee says in preliminary findings released this month. Many levees across the country are outdated and "not designed to protect the population they now have living behind them," the panel finds, although no one knows how many people do.

Next month, the committee — which was formed after Hurricane Katrina in 2005 — will call for a new national levee safety program in a formal report to Congress, says Eric Halpin, the panel's chairman and special assistant for dam and levee safety in the Army Corps of Engineers.

"We need to change the way we look at (flood) risk in this country," Halpin adds, noting that levees have not gotten the attention they need to ensure the safety of the millions of people who rely on them. "People see (floods) as really infrequent events from which they don't have to protect themselves, when the opposite is true. If you live behind a levee, you are seven times more likely to be flooded than to have a fire in your home."

The federal government should catalog all of the nation's levees and determine their adequacy, the report will say. It will also recommend setting safety standards based on "tolerable risk" and creating a federal-state program to ensure that all levees meet those standards, according to the committee.

It's unclear how the program will be funded or how quickly it can be started. Committee members see a federal-state partnership backed by federal grants and other incentives to get states to develop new levee inspection programs, but they haven't settled on details, says Mike Stankiewicz, a committee member and chief of flood control for the New York Department of Environment Conservation.

"We didn't get to our current state of affairs overnight," Halpin adds, and correcting the problems will "take some time."

Assessing the problem

The committee estimates that there may be 100,000 miles of levees nationwide.

Many larger systems, often along major waterways or in flood-prone coastal areas such as New Orleans, were built by the federal government, and most of those were turned over to communities that took responsibility for maintaining them. Others were built independently by states and cities. But there also are thousands of smaller levees put up by private landowners to guard everything from cropland to golf courses.

Taking inventory of all the nation's levees and assessing their strength and condition is a huge task, says Stankiewicz. In California alone, he notes, there are about 14,000 miles of levees, and 80 percent are privately owned.

Many smaller levees now guard areas that became more developed and populated than when the levees were built. No one knows how many levees are inadequate to protect the communities now behind them.

Even major levee systems designed and built for the biggest storms may not provide the protection they once did. Nature takes a toll on levees through, for example, natural settlement, erosion, animal burrows and tree roots. Some regions also have become more prone to big storms than engineers anticipated when the levees were designed.

The devastation of New Orleans and much of the Gulf Coast by Hurricane Katrina put a new focus on the need to assess and upgrade the nation's levees. And June's disastrous Midwest floods further underscored "the importance of getting a handle on our levee system," says Les Harder, a safety committee member and former California flood management official now in the private sector.

Redefining the risks

Developing a new way to assess flood risks is a key challenge in creating levee safety standards.

Halpin notes that the de facto standard today is built on protecting communities from a 100-year flood, or an event so extreme that it has just a 1 percent chance of occurring in a given year. That approach is built in part on requirements set by the federal flood insurance program: properties behind a levee that does not protect against a 100-year flood are required to be insured.

But, Halpin said, "many communities need something beyond 100-year protection." A levee's level of protection, he said, should be evaluated on three risk factors: the likelihood of a major flood, the potential for the levee to fail and the consequences for the people it protects.

Once a risk-based standard is adopted, state and federal agencies would have to re-evaluate all of the nation's levees.

The corps already is building a new assessment program for levees in its maintenance inspection program. But that program, which typically includes corps-built levees and others added by community request, covers only a fraction of the nation's levees.

Building a program that effectively assesses the adequacy of all levees is a far bigger job. But that must be the ultimate goal, Halpin says, and "we can make a compelling case for action."