What he said
[A]ssuming that, indeed, New Orleans has been spared the worst--as now seems plausible--we can't rest easy. Instead, it will be time for the real work to begin. We must call, immediately, for a massive engineering project, perhaps almost TVA-size in its scale, to bring the city's hurricane protections up to Category 5 levels. There will be no excuse to delay even a single day.....The Big Easy dodged a bullet, but not by much.
One factor that's easy to overlook as a reason why storms are more dangerous to New Orleans than they might once have been is loss of wetlands. Where waves once would have broken on the wetlands between the Gulf and New Orleans, now there's a lot of open water or land that people built on. Wetlands provide a buffer against the waves and against the wind, and even give the hurricane a chance to weaken before it hits town.
Any comprehensive plan for hurricane proofing the Louisiana coast has to involve restoring coastal wetlands and preserving existing wetland. Dikes and levees are important too, but wetlands are natural buffers, they serve valuable purposes for local populations, including filtering out water pollution and attracting wildlife. I know lots of people who've gone on trips outside of New Orleans in order to see the birds and beasts in the swamps, so that's tourist money outside of Bourbon Street.
Of course, Katrina is still a threat and the first step is to protect the rest of the people in its path, rebuild what was damaged, and bury the dead. Then we have to make sure no one else has to be unprotected.