Lower Mississippi River Tarbert Landing to East Jetty Sedimentation Study; Numerical Model Investigation
1992
Copeland, Ronald R. | Thomas, William A.
A one-dimensional numerical model (TABS-1) of the Mississippi River between Tarbert Landing, at river mile 306, and East Jetty, at river mile -20, was developed. The model was used to evaluate long-term aggradation and degradation trends, the effect of various flow diversion schemes on dredging in Southwest Pass, and washout of a sediment sill at river mile 63, and for preliminary evaluation of dike fields for Redeye Crossing at river mile 224. The numerical model was adjusted to simulate measured degradation and aggradation that occurred between the 1963 and 1975 hydrographic surveys. The model was further adjusted to simulate reported dredging quantities in Southwest Pass. Circumstantiation of the model was attempted by comparing calculated and measured aggradation between 1975 and 1983, and calculated and measured bed material gradations between 1975 and 1989. The model was also circumstantiated by simulating measured 1989 sediment accumulation in the vicinity of Cubits Gap and the 1988-89 washout at the sediment sill at river mile 63.4. Decreases in the supply of sediment from upstream of Tarbert Landing were found to be the primary cause of degradation in this reach of the river. It was also determined that diverting flows may provide a temporary benefit for dredging in Southwest Pass, but in the long run an increase in dredging would occur.
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