Stage adjustment in the Lower Mississippi River, USA

Abstract

This study documents the stage adjustments in the Lower Mississippi River during the pre-cut-off (1880s-1930s), and post-cut-off (1943-1994) periods. The study reach extends from Columbus, Kentucky, just downstream of Cairo, Illinois, to Natchez, Mississippi, a distance of about 970 km. The analysis shows that the majority of the pre-cut-off study reach was not undergoing any significant system instability such as channel aggradation or degradation, and, therefore can be considered to have been in a state of dynamic equilibrium during this period. However, the analysis did show that the upper portion of the study reach in the vicinity of Columbus was undergoing a significant aggradational trend during this period. Specific gauge records and peak stage-peak discharge plots for the time period 1950-1994 were analysed to document stage adjustments and to divide the river into the following seven reaches based on observed stability: Columbus to New Madrid (dynamic equilibrium); New Madrid to Fulton (transitional/dynamic equilibrium); Fulton to Sunflower (degradational); Sunflower to Rosedale (transitional); Rosedale to Lake Providence (dynamic equilibrium); Lake Providence to Vicksburg (transitional); and Vicksburg to Natchez (aggradational). Thus, the entire Mississippi River, between Natchez and Columbus is responding in a manner similar to the response of a stream to a single cut-off as described by Lane (1947). Recognition of this evolutionary trend is a first step in developing a comprehensive understanding of this complex system, and will help the engineers and scientists of the US Army Corps of Engineers to develop management strategies for the Mississippi River in the long and short term. © 1997 John Wiley & Sons, Ltd.