RED RIVER

also called Red River Of The South, navigable river rising in the high plains of eastern New Mexico, U.S., and flowing southeast across Texas and Louisiana to a point northwest of Baton Rouge, where it enters the Atchafalaya River (q.v.), which flows south to Atchafalaya Bay and the Gulf of Mexico. Until the mid-20th century, the Red River contributed flow to both the Atchafalaya and, via the Old River, the Mississippi. With the construction of a flood-control system on the Old River, however, the Red River ceased to act as a tributary of the Mississippi. The Red River drains an area of some 93,000 square miles (241,000 square km). The Red River is 1,290 miles (2,080 km) long; for about half this distance it serves as the Texas-Oklahoma boundary. Its principal tributaries are the North Fork of the Red, the Kiamichi, Little, Black (Ouachita), Pease, Sulphur, Wichita, and Washita rivers and Bodcau and Cypress bayous. Early navigation above Natchitoches, La., was impeded by a 160-mile (260-kilometre) log jam known as the Great Raft. In the 1830s Henry Miller Shreve created the first snag boats to clear the Raft. A second log jam was cleared in 1873. Though southwestern Arkansas, about 450 miles (725 km) upstream, is now considered the head of navigation, vessels drawing more than 4 feet (1.2 m) can reach that far only a few months of the year. Most traffic is in the lowermost 35-mile (56-kilometre) portion of the river. Denison Dam (1944), 726 miles (1,168 km) above the river's mouth, forms Lake Texoma. Many reservoirs have been built on tributaries of the Red River in Texas, Oklahoma, Arkansas, and Louisiana as part of a flood-control and river-development program. The river and its valley were the site of the Red River Campaign (q.v.) in the American Civil War. Vietnamese Song Hong, Chinese Yan Chiang principal river of northern Vietnam. It rises in central Yunnan province, southwestern China, and flows southeast in a deep, narrow gorge, across the Tonkin region, through Hanoi, to enter the Gulf of Tonkin after a course of 750 miles (1,200 km). Its two major tributaries, the Song Lo (Rivire Claire, or Clear River) on the left bank and the Black River (Rivire Noire, or Song Da) on the right, boost the flow of water, which during the rainy season may reach 335,500 cubic feet (9,500 cubic m) per second. The Red River has a very irregular volume throughout the year and carries huge quantities of silt because of the large proportion of easily crumbled soil in its basin, especially in the red lands from which its name derives. This material is deposited in the river's delta, a flat, triangular region of about 2,700 square miles (7,000 square km), which extends 93 miles (150 km) inland and 50 miles (80 km) along the coast. The delta constitutes a large part of northern Vietnam and is densely populated and intensively cultivated. Haiphong, the outport of Hanoi, is on a northern arm of the delta.