A Numerical Model Study of the Effect of Channel Deepening on Shoaling and Salinity Intrusion in the Savannah Estuary

• Main Authors: Johnson, Billy H., Trawle, Michael J., Kee, P. G.
• Other Authors: United States. Army. Corps of Engineers. Savannah District.
• Format: Report
• Language: English
• Published: U.S. Army Engineer Research and Development Center (ERDC) 1989
• Subjects: Ingenieurwissenschaften (620); Estuary; Estuaries; Stream channelization; Sediment transport; Mathematical models; Numerical models; Environmental aspects; Savannah River; Georgia; South Carolina; Salinity; Salinity intrusion; Saltwater encroachment; Channel; Channel deepening; Dredging; Back River
• Online Access: https://hdl.handle.net/20.500.11970/111877

Source: https://erdc-library.erdc.dren.mil/jspui/ A numerical laterally averaged estuary model called LAEM has been modified to handle sediment along with flow, temperature, and salinity computations. A bed model that allows for multiple layers when the sediment is cohesive has been incorporated to simulate the exchange of sediment between the bed and the water column. The resulting model, called LAEMSED, is a useful tool in assessing the impact of changes in channel geometry on salinity intrusion and shoaling in either a single channel or a multiple-connected system of channels. Results from a study in the Savannah Estuary show good agreement with 1985 field data on tides, velocities, and salinities. In addition, good agreement with shoaling rates estimated from dredging records was obtained. Results from applications of the verified model to assess the impact on salinity intrusion and shoaling of deepening the navigation channel by 3 and 6 ft are presented. General conclusions are that deepening the navigation channel as much as 6 ft moves the primary shoaling region upstream about 10 miles to the river reach containing the Kings Island Turning Basin with an overall increase in shoaling volume of about 14 percent. For the same increase in depth, salinities along Front River will increase by a maximum of 2-4 ppt, depending upon tidal and freshwater inflow conditions, whereas the maximum increase in salinity near the wildlife refuge on Little Back River will be less than 1.0 ppt.