Morganza Spillway Structure (ORCS), in use since 1963, where floodgates are routinely used to redirect the Mississippi's flow into the Atchafalaya River such that the volume of the two rivers is split 70%/30%, respectively, as measured at the latitude of Red River Landing. During the 1973 Mississippi flood, the ORCS was being damaged due to high flow rates, leading to the opening of the Morganza Spillway to help relieve this pressure. Subsequently, the nearby Old River Control Auxiliary Structure (ORCAS) was constructed, adding additional floodgates for use during major floods. The Morganza Spillway, about downriver from ORCS and ORCAS, is designed for
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