Particle size distributions of bed sediments along the Mississippi River, Grafton, Illinois, to Head of Passes, Louisiana, November 2013

Abstract

Changes in Mississippi River bed material gradations between Cairo, IL, and Head of Passes, LA, have been previously determined in 1932 and 1989. In November 2013, bed material samples were collected from the thalweg and across the channel width along a reach extending from Grafton, IL, to Head of Passes, LA. In all, 754 samples were collected at 496 locations, and results were compared to the earlier sampling programs. Results show that since 1932 the Lower Mississippi River bed sediments have become more uniform, the reach-averaged D₅₀ median grain diameter has reduced by approximately 50%, and the river has relatively fined upstream and coarsened downstream with little change since 1989.