Morganza Spillway emergency use to divert additional water from the Mississippi River into the Morganza floodway, which merges downstream with the Atchafalaya floodway before entering the Gulf. Diversion of water from the Mississippi's main channel has the effect of lowering water level in the Mississippi downstream of the spillway, helping to relieve stress on levees and other flood control structures both upstream and down. Besides controlling flooding in a given event, the system is also designed to prevent the Mississippi River from permanently altering course down the Atchafalaya River, bypassing Baton Rouge and New Orleans. Water that passes the Morganza Spillway first
6th Missouri Volunteer Cavalry May 18-July 4. Assaults on Vicksburg May 19 and 22. Mason's Ford. Big Black River, June 9. Advance on Jackson, Miss., July 4–10. Near Baker's Creek July 7. Bolton's Station July 8 (detachment). Near Clinton July 8 (detachment). Near Jackson and near Clinton July 9 (detachment). Siege of Jackson July 10–17. Brookhaven July 18 (detachment). Near Morganza, La., September 8. Atchafalaya September 8–9. Hornersville, Mo., September 20 (2nd Battalion). Sterling's Farm, on Bayou Fordoche, near Morganza, September 27. Western Louisiana Campaign October 3-November 30. Reconnaissance toward Opelousas October 20. Opelousas, Barre Landing, October 21. Washington October 24. Bayou Bourbeaux November