Actually the NOLA politicians said they were going to ride the storm out downtown, at the Superdome. That's where their Emergency services HQ is. Likely if you are in buildings of more than three stories that are strong enough, you will survive. The real problem comes if the Lake Pontchartrain dikes get breached. Then you run the real risk of drowning like what happened in the tsunami.
Areas around NOLA are mostly 3-6 feet above sea level, so they are at great risk to surge, if the survive the winds.
Here are some after the fact pictures from Camille ... Camille