Sediment Supply From Bank Caving On The Lower Mississippi River, 1765 To Present

Bank caving rates and associated total sediment supply were calculated along the Lower Mississippi River (LMR) from Cairo, IL, to Baton Rouge, LA, using historical maps between 1765 and 1992. Comparison of these maps reveals that the added sediment loads from bank erosion have greatly declined through time. During the Pre-cutoff period (1765–1931), the cumulative sediment supply from bank caving between Cairo, IL, and Baton Rouge, LA, ranged from about 395 million cubic yards/year (MCY/yr) to 535 MCY/yr with a median value of approximately 470 MCY/yr. The 1880-1931 period had the highest rate of sediment supply from bank caving with a median value of approximately 610 MCY/yr. By the 1990s, the sediment supply from bank erosion was essentially eliminated as a result of the revetment program, with significant erosion being observed at only a few locations, totaling approximately 17 MCY/yr. This equates to approximately a 96% reduction in the amount of total sediment being supplied to the channel system from bank erosion. Of these total loads, a significant amount of the material supplied to the LMR during the pre-cutoff era was sand-sized sediments (>0.0074 mm). This dramatic reduction in bed material and bedload sized- sediments have significant morphologic impacts to the river system that must be investigated with future studies.