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
175th New York Volunteer Infantry 26-30. Siege of Port Hudson May 30-July 9. Assault on Port Hudson June 14. Surrender of Port Hudson July 9. Moved to Baton Rouge July 22, and duty there until March 1864. Operations about St. Martinsville November 12, 1863. Red River Campaign March 23-May 22. At Alexandria March 25-April 12. Cane River April 23-24. At Alexandria April 26-May 13. Retreat to Morganza May 13-20. Mansura May 16. At Morganza until July. Expedition from Morganza to the Atchafalaya May 30-June 5. Atchafalaya River June 1. Moved to Fort Monroe, Va., then to Washington, D.C., July 5-29. Sheridan's Shenandoah Valley Campaign August