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
1st Missouri Regiment of Colored Infantry of Morganza, Dept. of the Gulf, to September 1864. 2nd Brigade, 1st Division, United States Colored Troops, District of Morganza, Dept. of the Gulf, to September 1864. Port Hudson, La., Dept. of the Gulf, to September 1864. Brazos Santiago, Texas, to October, 1864. 1st Brigade, 2nd Division, United States Colored Troops, Dept. of the Gulf, to December 1864. Brazos Santiago, Texas, to June 1865. Dept. of Texas to March 1866. Ordered to Baton Rouge, La., March 23, 1864, and duty there till June. Ordered to Morganza, La., and duty there till September. Expedition from Morganza to Bayou Sara September 6–7.