The tide would be coming in now, with high tide about 6 hours or so away. It's also likely that the levees are leaking through areas on the sides or the foundations that were weakened by the excess hydraulic gradient (not to mention the dynamic loading) caused by the storm surge and the wave action, what the dam breach experts call piping failures. Chances are the sewers are already as backed up as they're going to get.
As far as pumping goes, it'll takes LOTS of pumps to clear that much water, lots of time to set them up. Hopefully they can get enough pumping capacity on line quickly enough to save themselves from slowly drowning.