One factor being considered in the evaluation of the feasibility of deeper draft access to the ports of New Orleans and Baton Rouge is the impact of a deeper channel on salinity intrusion in the Lower Mississippi River. To address this question, a laterally averaged mathematical model called LAEM that couples the flow and salinity computations through a baroclinic contribution to the longitudinal pressure gradient has been employed for 40-, 45-, 50- and 55-ft channels (with overdepth dredging) using historical low-flow hydrographs. In addition, LAEM has been applied with increased heights of the natural river crossing at river mile 63.4 to determine if such sills provide an effective means of controlling salinity intrusion during critically low-flow periods. A separate question concerning the stability of such sills constructed from natural river sediment dredged from upstream has been addressed by applying the sediment transport model, HEC-6. General conclusions are that an increased channel depth up to 55 ft will result in significant increases in the extent and duration of salinity intrusion during extended low-flow periods. Sills constructed at a crossing by depositing material dredged from upstream appear to provide an effective method for controlling the intrusion of the salt wedge, although tests on a sill at elevation -55 ft indicated the deposited material will be eroded away fairly quickly when the riverflow rises above 400,000 cfs. This will necessitate rebuilding the sill at the onset of each critically low-flow period expected on the Lower Mississippi River.
A Mathematical Study of the Impact on Salinity Intrusion of Deepening the Lower Mississippi River Navigation Channel
Technical Report ; HL-87-1
1987
1083925
Report
Elektronische Ressource
Englisch
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