One of the most important current problems with which the Corps of Engineers, U. S. Army, must deal in connection with navigation and flood control in the Lower Mississippi Alluvial Valley is the threatened diversion of the lower 300 miles of the Mississippi through one of its major distributaries, the Atcha-falaya (Fig. 1).
Of primary concern was a determination of whether such a diversion would occur and, if so, how soon. A report published in 1952 concluded on the basis of geological and engineering evidence that the possible diversion would be the latest of a number of similar occurrences in the recent geologic past, and that, unless the gradually increasing amount of flow from the Mississippi through its Atchafalaya distributary is controlled, a critical state in the diversion process can be expected between 1965 and 1975 (Fisk, 1952; Kolb, 1955).
Consequently, the Corps is now in the early phases of work designed to preclude development of the Atchafalaya into the main channel of the Mississippi River. The control plan calls for maintenance of the status quo. Flow that now passes through the Atchafalaya must continue; floodwaters currently carried off through the Atchafalaya must continue to escape through this natural outlet; navigation from the Atchafalaya and the Red rivers must continue to have access to the Mississippi; and, finally, the gradual increase of flow through Old River and the Atchafalaya River must be stopped. A low-sill structure excavated to a depth of 50 feet, capable of taking water from the Mississippi