The Morganza Spillway or Morganza Control Structure is a flood-control structure in the U.S. state of Louisiana. It is located along the western bank of the Lower Mississippi River at river mile 280, near Morganza in Pointe Coupee Parish. The spillway stands between the Mississippi and the Morganza Floodway, which leads to the Atchafalaya Basin and the Atchafalaya River in south-central Louisiana. Its purpose is to divert water from the Mississippi River during major flood events by flooding the Atchafalaya Basin, including the Atchafalaya River and the Atchafalaya Swamp. The spillway and adjacent levees also help prevent the Mississippi from changing 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 Me