Members of the New Orleans City Council are determinedly talking about rebuilding the city in the wake of Hurricane Katrina. The recent AP-IPSOS opinion poll surveyed Americans about rebuilding New Orleans: 42 percent said it should be rebuilt as it existed before; 54 percent said the parts below sea level should be abandoned and rebuilt in some other location above sea level. I suggest that the best path is to pursue both ideas. It would be much cheaper and more effective.
This could be done by simply relocating the city vertically, to achieve rebuilding sites that would be well above flood level. Buying fill is cheap, compared with buying land to be abandoned.
Guess what, folks? We know how to do it. We did it, 100 years ago, in a city devastated by the deadliest natural disaster in US history: Galveston, Texas. Not only did the state construct the first segment of the Galveston seawall (the most visible result), but it also raised 500 blocks by an average of 5 feet (and some by over 11 feet) by jacking up buildings and pumping sand beneath them.
Rebuilding New Orleans in the same place (and, FWIW, I believe we should) only makes sense if we take steps to make sure that we won't have the same devastating flooding again. As Dr. Sykes points out, levees and dikes won't do the job alone. The city needs to be raised.
One other note: One of the folks who designed the Galveston seawall and grade raising was someone whose work I've been talking about a lot lately, in an entirely different context: US Army Corps of Engineers Brigadier General Henry Martyn Robert...yes, the same guy who wrote Robert's Rules of Order.