Yes, the levee has been overtopped but has not broken. Now, NPR just interviewed an Army Corp of Engineers guy who says that the city can handle 6 to 8 inches of rain, which is just a bit more than the current forecast. Do we believe this?
Water is "waist deep and rising fast."  

"Our worst fears came true," a National Guard official said. "The levee will breach if we keep on the path we are on right now."

http://www.msnbc.msn.com/id/9438536/

Live Data from a buoy in the lake pontchartrain is available here (takes about 30 sec. to load). The water level is 1 feet above normal.