Levees under construction by the Army Corps of Engineers aren't being built to a high-enough flood protection standard, said the report by the National Academy of Engineering and the National Research Council.
The independent panel of experts was asked by the federal government to review the corps' investigation of levee failures during Hurricane Katrina and its work to avoid such a catastrophe again. The corps is spending about $14 billion to raise levees and build floodgates able to withstand a "100-year" storm, or a moderately dangerous hurricane with a 1-in-100 chance of hitting any given year. The corps plans to finish by 2011.
"For heavily-populated urban areas, where the failure of protective structures would be catastrophic - such as New Orleans - this standard is inadequate," the report said.
Instead, New Orleans should be protected by a "500-year or maybe 1,000-year protection," the type of engineering standards used in earthquake zones or along major rivers, said Richard Luettich Jr., the director of the Institute of Marine Sciences at the University of North Carolina and a member of the committee.
Friday's report was the final review of work done by a team of engineers hired by the corps to investigate levee failures and develop solutions. The leader of that team, which is called the Interagency Performance Evaluation Task Force, said the levee system being built by the corps was a good starting point.
"The current system being built is a very good baseline," said Ed Link, a civil engineer with the University of Maryland who led IPET. "It has a lot of resilience built into it, so the potential for catastrophic loss is much less."
The corps is considering construction of a system that would offer protection against a 500-year storm, but its studies are still in their early phases.
Friday's report also said the city should discourage people from moving into areas vulnerable to storm-surge flooding, in particular those that are below sea-level.
"If there is one thing we've all learned from this, living in New Orleans entails risk," Luettich said. "Smart decisions have to be made about where people live."
The issue of whether to abandon certain areas has come up several times as the city's continued rebuilding and has drawn sharp responses, particularly from those who believe they should be allowed to rebuild where they'd lived before the storm. Mayor Ray Nagin has said the government shouldn't dictate where people can live.
"We don't have a policy of holding back our investment in any of the areas," Nagin's director of policy, Maggie Merrill, said. City officials meet with the corps regularly to make sure the agency is on track with its rebuilding, and the city itself is trying to rebuild its facilities higher and stronger, she said.
LaToya Cantrell, president of the Broadmoor Improvement Association, said she generally agrees with the report but rejects any suggestion that areas below sea level should be avoided.