Don't know, trying to research where the level control really is. There must be a spillway, lock or something.
Found this: It shows the back corner (green line) being open marsh. The protective wall(more like a fill bulkhead) outlined in red/pink is there to keep tidal surges out of the lake. I'm guessing the flooded areas to the south of the lake are what is backing up the flow.
This area by nature drains very, very slowly. I don't know that blowing the bulkhead would speed up the process that much faster but it would definitely lead to more disaster later on when storm surges could enter the lake unimpeded over a wider swath than they can now.
http://pubs.usgs.gov/of/2002/of02-206/geology/sepontchartrain.html