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This is the Army Corps of Engineers explanation of the Mississippi River flood control system and how it would be used to control a flood. It details the the use of the floodways and the river flow levels that will trigger their use.[…]
At least as to river heights, the Flood of 2011 may be second or third largest Mississippi River Flood in modern times. Total volume of the flood is hard to compare because the river and the tributaries are more constrained than in the past. Water in a leveed river will be much higher than in a river without levees where it can spread out horizontally.
The Mississippi flood of 1927 resulted in the Flood Control Act of 1928 (FCA), the controlling legislation for flood control activities of the Army Corps of Engineers. The most important provision in the FCA is the blanket immunity for damages caused by flood control activities. FCA cases are collected here:
John McPhee has written a fascinating history of the River Control Structure at Morganza. While it is not clear that the Mississippi still wants to go down the Atchafalaya, losing the River Control Structure in a flood would still be a…