So, I got to thinking, if New Orleans is under 12 feet of water in 2 or so days, how much water is that? Can the pumps possibly drain that much? So I figure...do the math.
According to a number of site, the best number for pump capacity is 47,000 cubic feet per second, or about 22,701,000 gallons per minute. For this thought experiment, I'm assuming that the water is pumpable (ie, at the mouth of the pump). Reality won't bear that one up, but anyhow.
About 181.6 square miles, or 119,040 acres, will be submerged to a depth of 12 feet. There are 325,851.427 gallons to the acre foot, so the total water in the basin is about 465,472,246,441 gallons. Looks like a lot of water, to be sure. This amounts to about 15 straight days of pumping. Most of these conversions courtesy of Google Calculator, which actually knows Acre Feet!
1) The pumps will not be able to run full bore, they will certainly get clogged with debris and require frequent maintenance.
2) The basin is not uniform.
3) The levees will take some time to repair.
4) The pumps will have to be powered up, and electrical power delivery will be tricky.
The solutions (pure, sci-fi speculation)
1) Maybe more pumps can be brought online..
2) Levees could maybe be fixed by sinking old single skin oil tankers filled with sand/cement and dropping those massive sandbags (3000lb ones) as filler. Fill em with quick setting cement and you're golden. Before you worry about the environmental cost, consider an entire city disintegrating into the Mississippi, that's not good for the fish at all.
3) Australian used diesel/electric locomotive engines to power their cities when they had some power delivery problems, this would be a decent way to deliver the electrical power needed for the pumps.
This of course doesn't address the vast crushing destruction that this much water will wrought.
1) The jump in the unemployment rate when these people can't go to work tomororrw.
2) The vast cost of rebuilding or,if warranted, mass relocation. (if $100,000 per family, then 250 billion, still less than Iraq, mind you.)
3) The loan defaults on the housing, and what that will mean to the home loan architecture in the united states.
4) The cost to the insurance industry almost guarantees they'll pull the same stuff they did during northridge here in California. This will bankrupt a great number of large insurance companies.
5) No more beads will be sold in New Orleans. I suspect Tampa's Ybor will become the cajunesque party capital of the US.
Sorry folks in New Orleans, my condolences, this is very sad. California welcomes you! Update: No way to get tankers into the lake.