Morganza Spillway emergency use to divert additional water from the Mississippi River into the Morganza floodway, which merges downstream with the Atchafalaya floodway before entering the Gulf. Diversion of water from the Mississippi's main channel has the effect of lowering water level in the Mississippi downstream of the spillway, helping to relieve stress on levees and other flood control structures both upstream and down. Besides controlling flooding in a given event, the system is also designed to prevent the Mississippi River from permanently altering course down the Atchafalaya River, bypassing Baton Rouge and New Orleans. Water that passes the Morganza Spillway first
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