The basic deal is that for every two miles inland you need another foot of storm surge to get across it, even if it's flat. New Orleans used to be 30 miles from the sea. It's only 18 today. You see where this is going? The storm surge probably wouldn't have made the city.
The real problem though is that New Orleans is 22 feet below the level of the Mississippi River right next door. Yes, that's greater then its depth below sea level. The Mississippi wants to change its channel, see, but the city of New Orleans and the federal government don't want it to because they'd have had to spend roughly 20bil to build a ship channel from the new course of the river to New Orleans. (Which would have been a bargin, it turns out...) So they built up the levees to keep the Mississippi from changing its course. Now, let's be honest here, in the end that's not going to happen, you can't fight the damn Mississippi River and win for any length of time. They tried anyways. Poke nature with a stick, it'll poke back, and it has bigger sticks, as Katrina proved.
The other thing that bothers me is that sure, New Orleans got screwed up. It's still there though. Biloxi got wiped right off the map. It was at ground zero where Katrina came ashore. It's just not there anymore, and you don't hear jack schiznit about that.