Preface: an overview of the Atchafalaya River

Abstract

The Atchafalaya River is one of the great rivers of the world but it is virtually unknown outside of Louisiana, USA; it is great yet obscure because of its peculiarity, its size, and its wildness. The Atchafalaya River is peculiar because it originates in central Louisiana and gains only 57 m s of water as it flows 275 km to the Gulf of Mexico, yet only four rivers in North America contain more water (Table 1). This is possible because the Atchafalaya River originates where all of the water from the Red River (1,585 m s) meets 22% of the water from the Mississippi River (4,728 m s) (Fig. 1; Table 1). Its watershed includes that of the Red River (241,387 km) and the Mississippi River (2,978,468 km) as well as the floodplain downstream of its origin (4,921 km) (Kammerer, 1990). Waters from New Mexico, USA, Saskatchewan, Canada, and New York, USA, mingle in the Atchafalaya River, which makes its watershed the largest in North America. Basic facts of the Atchafalaya River are often obscured because different authors report its discharge, length, and watershed as various combinations of the portion downstream of its origin, the portion associated with the Red River, and the portion associated with the Mississippi River. The Atchafalaya River is also peculiar because inflow to it from the Mississippi River is managed daily, so that the Atchafalaya River contains 30% of the combined flow of the Red River and Mississippi River. This level of control is achieved with the Old River Control Structure, an engineering marvel completed in 1963 to prevent the Atchafalaya River from capturing the flow of the Mississippi River. Such capture would be a natural development in the delta lobe cycle (Roberts, 1998), but would be catastrophic to international trade dependent upon ocean-going vessels that utilize deep draft ports on the Mississippi River downstream of the Old River Control Structure, including those at the Port of Baton Rouge, the Port of South Louisiana, the Port of New Orleans, the St. Bernard Port, and the Plaquemines Parish Port. In addition to having the largest watershed and the fifth largest discharge of any river in North America, the Atchafalaya River has one of the largest and wildest floodplains in North America. This wildness may seem a peculiar contrast to the daily human control of its inflow, but is a product of the extent of its floodplain and the large seasonal difference in water levels. The floodplain is known as the Atchafalaya Guest editors: M. Ford & J.A. Nyman / Interactions among rivers, floodplains, and coastal areas examined at the Atchafalaya River