Dean, R.G.; Wells, J.T.; Fernando, H.J., and Goodwin, P., 2014. Sediment diversions on the lower Mississippi River: insight from simple analytical models.

River diversions offer a mechanism by which sediment-laden waters can be introduced into interdistributary basins and bays to build new land that provides a substrate for wetland growth. Two geometric models were developed to allow calculation of future performance of river diversions with emphasis on the Mississippi River. These geometries, a truncated cone and a uniform width geometry, assume a constant discharge of sediment into the receiving basin and thus avoid many of the complexities of the evolutionary processes. Model results from both geometries show a clear life cycle of growth and deterioration in a diversion that experiences relative sea level rise and, under certain combinations of relative sea level rise, depth of receiving waters and sediment discharge rate, situations in which a subaerial platform will never form. A comparison of subaerial deposits in larger versus smaller diversions, assuming the same total sediment discharge in both cases, reveals that the total subaerial land area for the larger diversions is substantially greater than the sum of the two volumes of the smaller diversions. Model results have been used to illustrate, through examples, the effect of bottom slope and sea level rise on diversion performance. Recommendations have been made for the selection (quantification) of diversion parameters to be used in the models. These include annual sediment input, proportion of sediment retained in the diversion deposit, sediment bulking factor, foreset slope, and subsidence rate. Other required input parameters are considered to be known, namely, average diversion water discharge, initial depth of receiving waters, bottom slope, deposit angle or width, and future sea level rise. We also include general recommendations for selection and utilization of diversion sites.