2011 Mississippi River floods feet per second just upstream from the Old River Control Structure. The US Army Corps of Engineers refers to this design goal as Project Flood. the expected flow will be on the high side, but still within that maximum capacity, assuming everything works as expected. On May 14, a single floodgate of the Morganza Spillway was opened in order to divert of water from the Mississippi River to the Atchafalaya Basin. This diversion was deemed necessary to protect levees and prevent major flooding in Baton Rouge and New Orleans, with the tradeoff of exacerbating flooding in the Atchafalaya Basin, and
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,