The Georgetown Harbor model, a fixed-bed model constructed to linear scale ratios of 1:800 horizontally and 1:80 vertically, reproduced a portion of the Atlantic Ocean, Winyah Bay including Mud Bay, North Inlet and marshes between Winyah Bay and North Inlet, the Sampit River including Georgetown Harbor, and the lower portions of the Pee Dee, Black, and Waccamaw Rivers and adjacent marshes. The model was equipped with necessary appurtenances for the accurate reproduction and measurement of tides, tidal currents, salinity intrusion, freshwater inflow, and shoaling distribution . The purposes of the model study were (A.) to determine the effects on the hydraulic, salinity, and shoaling characteristics of a deepening from 27 to 35 ft of the main navigation channel to Georgetown Harbor and (B.) to determine whether present maintenance dredging can be reduced by proposed plans involving channel revisions, sediment traps, and freshwater flow diversion. This report presents and analyzes the results of the testing of the following schemes : Western Channel and Turning Basin scheme (Plans 1, 1A, and 2-6), Marsh Island Channel and Turning Basin scheme (Plan 7), Upper Winyah Bay Side Channel Trap scheme (Plans 8 and 9), Inflow Diversion scheme (Plan 10), and Deepened Channel scheme (Plan 11). Western Channel and Turning Basin scheme, Plans 1 and 1A, reduced the overall annual shoaling (Western Channel plus Georgetown Harbor Channel) by 63 and 45 percent less than that for the existing channel, respectively. The effects of Plans 2, 3, 5, and 6 on shoaling when compared with Plan 1A were detrimental rather than beneficial and therefore cannot be recommended. The effects of Plan 4 on shoaling, when compared with Plan 1A, were definitely beneficial because of the much more even distribution of shoaling material along the Western Channel. Although the annual shoaling rate for Plan 4 is almost the same as that for Plan 1A, the elimination of the extremely high shoaling rate in one section (section WC3) should permit dredging to be performed on a less frequent basis. Since the overall annual shoaling rate was reduced to 43 percent of the existing rate and no unacceptably high shoaling rates occurred in any individual section, Plan 7 was an effective scheme for reducing the maintenance dredging requirements for the Georgetown Harbor project. Since the overall annual channel shoaling rate for Plans 8 and 9 was increased about 800,000-900,000 cu yd over the present shoaling rate and Georgetown Harbor (Sampit River) shoaling was reduced only about 350,000-450,000 cu yd, neither Plan 8 nor Plan 9 appears to be an effective solution to the existing maintenance dredging problem. Based on the assumption that the 90 percent reduction of the freshwater inflow to the bay would reduce the sediment supply by 90 percent, the overall annual channel shoaling rate for Plan 10 was 63 percent less than the existing rate. Plan 10 is an effective scheme for the reduction of maintenance dredging requirements for the Georgetown Harbor project. The overall annual channel shoaling rate for Plan 11 was 88 percent more than the existing shoaling rate.


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    Title :

    Georgetown Harbor, South Carolina. Report 2: Effects of Various Channel Schemes on Tides, Currents and Shoaling: Hydraulic Model Investigation



    Published in:

    Miscellaneous Paper ; H-78-6 rept. 2


    Publication date :

    1979


    Size :

    21171305


    Type of media :

    Report


    Type of material :

    Electronic Resource


    Language :

    English



    Classification :


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