Record 100+ year flood expected on Mississippi River
Posted by JAC on 4/28/2011, 2:31 pm
From Dr Masters







Snow melt from this winter's record snow pack across the Upper Mississippi River has formed a pulse of flood waters that is moving downstream on the Mississippi, and is currently located in Iowa. When this floodwater pulse moves south of Cairo, Illinois over the next two weeks, it will join with the record water flow coming out of the Ohio River, and create the highest flood heights ever recorded on the Mississippi, according to the latest forecasts from the National Weather Service. Along a 400-mile stretch of the Mississippi, from Cairo to Natchez, Mississippi the Mississippi is expected to experience the highest flood heights since records began 100 or more years ago, at 5 of the 10 gauges on the river along this stretch. The records are predicted to begin to fall on May 3 at New Madrid, and progress downstream to Natchez by May 20. Areas that are not protected by levees can expect extensive damage from the flooding, and it is possible that the Army Corps of Engineers will have to intentionally dynamite a levee at Birds Point and New Madrid, Missouri to protect the town of Cairo from flooding.

The Mississippi River at New Madrid, MO, about 40 miles downstream of the confluence of the Mississippi and Ohio Rivers, is currently at 44', the 3rd highest flood in history. The river is predicted to crest on Tuesday very near the all-time record height of 48 feet. The NWS warns that at this height, "Large amounts of property damage can be expected. Evacuation of many homes and businesses becomes necessary." Previous record heights at this location:

(1) 48.00 ft on 02/03/1937
(2) 44.60 ft on 04/09/1913
(3) 43.60 ft on 04/04/1975
(4) 43.50 ft on 02/16/1950
(5) 42.94 ft on 03/17/1997

The timing of the floods crests will depend upon a complex mix a factors, including how much rain falls over the next month, the possible influence of southerly winds holding up the floodwater pulses, the potential opening of flood control structures and reduction of flows from flood control reservoirs, and potential levee failures (no levee has failed on the Lower Mississippi south of the Ohio River junction since 1950, however.) The Mississippi River is expected to crest at 17 feet at New Orleans on May 22, three feet below the top of the levees. This would likely require opening of the Bonnet Carre Spillway 28 miles upstream from New Orleans, to relieve pressure on the city's levees. Opening the spillway drains 250,000 cubic feet per second of flow into Lake Pontchartrain.






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MS Flooding. Corps of Engineers plan to blow levee in MO - JAC, 4/28/2011, 6:08 am
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