Medary.com

The New Orleans levee system has suffered at least three breaches and water continues to pour in to the city of 500,000 people. Contrary to prior reports, the U.S. Army Corps of Engineers has not suspended efforts to seal the largest breach, in the 17th Street Levee, with 3000-pound sand bags dropped from helecopters.

It isn't an exaggeration to say that everything depends on closing the levee breaches. Most of New Orleans is below the natural water level of Lake Ponchatrain, so it will not go down by itself. The water will need to be pumped out, and they won't be able to start that until the levees are repaired.