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
114th Ohio Infantry River Campaign April 26-May 22. Graham's Plantation May 5. Retreat to Morganza May 13–20. Mansura, or Marksville Prairie, May 16. Expedition to Atchafalaya May 30-June 6. Duty at Morganza until November 21. Moved to mouth of White River, Ark., November 21–26. Return to Morganza December 6. Expedition to Morgan's Ferry, Atchafalaya River, December 13–14. Moved to Kenner, La., January 8, 1865; thence to Barrancas, Fla., January 24. Campaign against Mobile, Ala., and its Defenses, March 20-April 12. March from Pensacola, Fla., to Blakely, Ala., March 20-April 2. Occupation of Canoe Station March 27. Siege of Spanish Fort and Fort Blakely