Morganza Spillway its present course through the major port cities of Baton Rouge and New Orleans to a new course down the Atchafalaya River to the Gulf of Mexico. The Morganza Spillway, operated by the U.S. Army Corps of Engineers, was opened during the 1973 and 2011 Mississippi River floods. The Great Mississippi Flood of 1927 was the most destructive river flood in the history of the United States, in large part due to the Mississippi River swelling to wide in spots. To prevent a repeat of the Great Flood of 1927, and better control river flooding in general, Congress passed the
Morganza Spillway still open. All bays were closed on July 7, 2011. The Corps had estimated that it would take opening one-fourth of the spillway’s 125 bays — or 31 bays — to control the flow of the river through Baton Rouge in response to a forecast crest of anticipated on Tuesday, May 17, 2011, which must remain below of water per second through Baton Rouge to ensure the integrity of the levee system. Since Morganza never operated above , the flooding in the Atchafalaya Basin was considerably lower than had been anticipated during the initial estimates of . By May 29,