The biggest problem facing a rebuilt New Orleans is subsidence -- both of the levees and the land they protect, and of the wetlands. The very thing that makes New Orleans so important to our economy, besides tourism, happened to be a factor in its destruction.

The local oil and gas industries have been removing oil and gas deposits from beneath the Gulf coast for decades. It was believed that the deposits were deep enough not to affect the wetlands, but that belief has since been proven terribly wrong. The land under the wetlands has steadily subsided and removed New Orleans' and a large chunk of the Gulf coast's first line of defense against storms. Restoring wetlands, while not impossible, is made more difficult still by a changing climate and rising ocean levels.

Subsidence of dry land is also an issue. If New Orleans was filled with enough dirt to bring it above sea level, the weight of that dirt would accelerate the rate at which the land is already subsiding. It's a sticky issue.

I agree that the city should definitely be rebuilt, and that a modern levee system needs to be created. I was listening to NPR the other day and they were using the term "Disneyfication" while discussing the rebuilding process. People are saying there's a great risk of the rebuilt New Orleans being a "Main Street Disneyland" version of the former reality.

Lots of tough decision lie ahead for this city.