Old River Control Structure such that the volume of the two rivers is split 70%/30%, respectively, as measured at the latitude of Red River Landing. This flow split was not based on science, but rather was based on the approximate flow allocation between the two rivers that existed at the time of construction. Water diverted at Old River flows into the Atchafalaya Basin, first entering the Red River, then continuing down the Atchafalaya River to the Gulf of Mexico, bypassing Baton Rouge and New Orleans (see diagram). The Morganza Floodway, between the Mississippi and the Atchafalaya Basin nearby downstream, is normally closed, but can
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