The order to evacuate New Orleans set off a rush for the exits that exposed the limits of the city’s options: Interstate 10 east and west, I-55 north and U.S. 61 north and 90 west. Completing I-49 from Lafayette to connect with I-310 is a key need, but the work is not yet funded, says Tracy Horne, spokesman for the Louisiana Dept. of Transportation and Development. “It would cost $1 billion to upgrade (U.S. 90) to Interstate standards, he says.” The hurricanes this year have helped to make people aware of the need to move the project forward, Horne adds.

New Orleans could ride out a fast-moving Category 3 hurricane with the existing protection systems, designed in the mid-1960s and now “substantially complete,” says Albert Naomi, senior project manager for the Army Corps of Engineers’ New Orleans District. Levees ranging from 13.5 ft to 19 ft in height could stop an 11.5-ft storm surge plus waves. Pumping stations empty drainage canals lacing the city into Lake Pontchartrain.

But he says successfully fielding a Category 5 storm, while "feasible," would take additional engineering and a huge expenditure, which he can’t even estimate because the Corps has no funds or authorization to conduct a study.

“There’s a certain amount of percentage that you’re playing here,” Naomi says. The odds are that a Category 5 storm would strike once in 600 to 1,000 years.