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
U.S. Route 190 the Beauregard Parish Jail, Beauregard Parish Courthouse, and the DeRidder Commercial Historic District. US 190 runs concurrently with US 171 to Ragley, where US 190 parts with US 171 heading east. From Ragley, the two-lane highway heads nearly due east almost parallel to I-10 until Opelousas. US 190 crosses the northern reach of the Atchafalaya Basin near the Morganza Spillway en route to Baton Rouge. From Baton Rouge, US 190 passes, in places divided, through Denham Springs, Albany, Hammond, Robert, Goodbee, Covington, Mandeville, before reaching the eastern terminus at Slidell. The stretch between I-12 south of Covington and the intersection