15 May 2011

The Great Mississippi Flood Rolls South

Posted by Dan Satterfield

The image below is the Miss. River on 10 May, 2010 from NASA’s Aqua satellite.

The image below is 6 May, 2011

Now the reason why; the image below is the rainfall departure from normal over the past 30 days.

Click the image for the full resolution.

Late word (this evening), that the Morganza spillway has been opened to reduce the threat of massive flooding in the cities along the river. The spillway was last opened in 1954 1973 and was completed in 1954, but it looks as if this flood will be far worse, and the opening will submerge nearly 8,000 square kilometers (3,000 sq. miles) of land. See the map below from the US Army Corps of Engineers.

From USACE- click for higher resolution image. Purple is water inundation from 0-5 ft. Yellow is over 15 feet!

Thousands of people will now have to be evacuated and many homes, businesses and farms will go underwater, and not just for a few days, it will be weeks. Well over a billion dollars has been spent to keep the Mississippi from changing naturally to a new channel, and Jeff Masters has a great writeup on his blog today. He links to a fabulous article by John Mcphee about the Mississippi, and the folly of fighting it. McPhee is justly famous for the best book on Geology ever written. It’s a doorstop, but well worth reading (it’s on my must have list in case of being stranded on a tropical island!).


Flooding along the Miss. is a natural occurrence, but it’s interesting to look at the very warm Gulf right now. Temps. are running about 1-2 C above normal, and NASA just released their global temp. data; this April was surpassed in land and ocean warmth by only 3 other years (all of which were in this century). Is this the cause? No, but the added warmth of the planet makes these events more likely to occur.


The food control structures on the Miss. are being strained to their design limits and more flood gates may be opened (leaving more land submerged), to keep the Miss. from going her own way. If the wet pattern of early April makes a return appearance in May, all bets are off.