Atchafalaya Basin Atchafalaya River has been a backswamp, low area between the paths of the Mississippi River through the process of delta switching, which has built the extensive delta plain of Louisiana. The natural levees of the Mississippi River (on the east) and the levees along its previous course (now Bayou Teche) on the west define the Atchafalaya Basin. The central basin is further bordered by man-made levees designed to contain and funnel floodwaters released from the Mississippi at the Old River Control Structure and the Morganza Spillway south toward Morgan City and eventually to the Gulf of Mexico. Historically there were
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,