River Response to Dredging

Abstract

Examination of the impact of dredging when employed in support of engineering requirements for river system development on the Mississippi River system reveals that the dredge provides the river engineer with a means of rapidly altering channel configuration and accelerating morphologic processes. In this respect, dredging constitutes a morphologic agent responsive to engineering requirements. This application is overshadowed by the volume of material moved and the number of reaches involved in dredging operations for navigation channel maintenance. Dredging and disposal of dredged material in support of channel maintenance implies the repeated moving of alluvial sediments from the main channel region toward the periphery of the channel. The combined use of dredging, contraction dikes, and disposal of dredged material in the dike fields can induce major changes in the cross‐sectional characteristics of a river. This direct physical displacement of bed material and the resulting change in channel shape can retard the movement of bed‐load sediments through a river system. In both the Columbia and Mississippi River systems this lateral redistribution of sediment by dredging, when combined with contraction works, has constituted an agent for long‐term morphologic change.