I did hear that until they close the breach they can't even begin pumping, so questions about pumps are moot? Is there any danger of the Miss. River (which I've read is higher than the lake) overflowing because of the increased volume?
I don't know the local topography/hydrology/watershed dynamics well enough to give you a good answer- but another poster earlier on this thread said that s/he has heard that the Army Corps of Engineers reports that the levee breaches have been closed and that the pumping has begun.
If true, that's very good news. Much easier to close without a huge flow going through the breach.