Atchafalaya Basin from the Mississippi, Red and Black rivers is diverted into the Atchafalaya at the Old River Control Structure. This flow diverts on average 25 percent of the Mississippi River flow down the Atchafalaya. In times of extreme flooding, the US Army Corps of Engineers may open the Morganza Spillway and other spillways to relieve pressure on levees and control structures along the Mississippi. On May 13, 2011, in the face of a rising Mississippi River that threatened to flood New Orleans and other heavily populated parts of Louisiana, the USACE ordered the Morganza Spillway opened for the first time since
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.