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Wagonaar and others see restoration as only the first step, however. They agree that the city's protection must be raised to Category 5 levels. Congress would have to appropriate much more money for this work, whether it went to the Corps or a different contractor.

When it comes to the comprehensive plans, people become more contentious. Despite local differences, the plans outlined by Shaw Coastal (part of the Shaw Group), Mashriqui and Wagonaar follow a somewhat similar route. To the south and west, the course would link and raise existing, piecemeal levees now maintained by independent levee districts and would protect most major towns. The planners disagree, though, on who should do the work as well as on how long construction would take and what it would cost. Wagonaar estimates the Corps' plan "would take us five to 10 years to build" and that the cost "would be $25 billion to $35 billion--but remember, this is still in the concept stage."

Wagonaar says he is not familiar with Malbrough or with Shaw's plan and notes that companies are unlikely to be involved unless Congress opens bids for the work. The Corps has had a de facto monopoly on federally funded flood protection for a century.

Residents in the hurricane danger zones hope that whoever gets the job incorporates new understanding of how Katrina and Rita ravaged New Orleans, and some worry that the Corps may not be fully responsive to external scientific information. For example, Mashriqui at L.S.U. has determined that a wide breach in the Industrial Canal, which flooded the eastern section of the city after Katrina, was caused by what is called a funnel effect. Computer simulations, and physical evidence Mashriqui obtained in October as a member of the state inspection team, show that Katrina pushed water from the east up a wide navigation channel called MRGO and simultaneously up an adjacent channel, the Intracoastal Waterway. The two wave fronts met where the inlets join and narrow into the Industrial Canal. This geometry amplified the height of the water by 20 to 40 percent, Mashriqui says. That increase raised the water pressure so high that the canal wall burst.

MRGO must be closed and gates must be put across the Intracoastal Waterway to protect the city, Mashriqui says. Numerous other experts speaking to the national press have concurred, noting that it supports very little ship traffic and costs a lot to maintain. But the Corps built MRGO, Mashriqui notes, "and for them to agree, they would be admitting a mistake was made in the first place."

Mashriqui is not the only one worrying about the need to avoid funnel effects. This very phenomenon was a chief reason for building the Thames Barrier in 1982, to prevent storm surges from piling up along the Thames Estuary close to London. "As the channel narrows by 50 percent, the water piles up by 100 percent," says Martin Earlam, chief engineer for the barrier at the country's Environment Agency, which operates it. And S. Jeffress Williams, a coastal scientist with the U.S. Geological Survey who worked for 20 years in Louisiana and has studied deltas worldwide, says funnel effects "have been underappreciated."