Save the city? Those levees weren't meant for a Category 4 storm. The part of the levee that broke was an area that had been fixed. When a hurricane of that magnitude is coming, it's too late to start repairing anything. It's time to run for cover. Evacuate. Load up the buses and get the hell out.
Yes saved the city. For whatever reason, the levee broke after the storm. At this critical time, who was inspecting the levees? Why were repairs stopped at night? Why weren't all available resources thrown at the broken levee?