Atchafalaya River (uh-CHA-fuh-lei-uh), navigable river, c.170 mi/270 km long, S central La.; 30°17'N 91°40'W; rises in N at confluence of Red and Miss. rivers; meanders S, in a former channel of the Mississippi, to Atchafalaya Bay in the Gulf of Mexico. A distributary of the Red and Mississippi rivers, the Atchafalaya flows to the gulf through an extensive system of guide levees and floodways. By law a set proportion of the water from the Mississippi R. is diverted into the Atchafalaya R. at the Old River Control Structure. The Atchafalaya Basin is filled with lakes, bayous, marshes, and cypress swamps. Because of the threat of flooding, the Basin is generally roadless and sparsely inhabited. The few roads follow tops of levees. Interstate Highway 10, which crosses the basin E-W, is a continuous bridge for most of the distance bet. Baton Rouge and Lafayette. Locally referred to as Tchafalaya.
