We saw a story on PBS a few months ago about how New Orleans will probably be destroyed by flood (part of a great story on the Mississippi River Delta). The very levees built to protect the city are likely to be the cause of its destruction:
When they stopped the river from flooding, they also prevented the wetlands from getting the regular doses of floodwater and mud that they need to survive. Studies show that if the wetlands keep vanishing over the next few decades, then you won’t need a giant storm to devastate New Orleans — a much weaker, more common kind of hurricane could destroy the city too.
What’s more, the way the city’s built, the evacuation routes would flood. Tens of thousands would be trapped. A big storm is all it will take to completely wipe out the city, and sooner or later it will happen.
Here’s a related American RadioWorks story: Hurricane Risk for New Orleans.
A Washington Post article yesterday (registration required) explores the possibility that Hurricane Ivan might be The One: the storm that takes out New Orleans. Ivan is expected to make landfall to the east but keeps shifting closer to the city. It’s not expected to make a direct hit, but nevertheless the threat it represents is terrifyingly real. I pretty much expect New Orleans to be underwater in my lifetime.