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|Title:||Effectiveness of contraction training dikes at Charleston Harbor, Charleston, South Carolina|
|Authors:||United States. Army. Corps of Engineers. Charleston District.|
Teeter, Allen M.
Pankow, Walter E.
Heltzel, Samuel B.
Knowles, Stephen C.
|Keywords:||Contraction training dike|
|Publisher:||Hydraulics Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; HL-92-1.|
Abstract: Charleston Harbor is formed by the junction of the Ashley, Wando, and Cooper Rivers. Prior to 1940, the three rivers had an average freshwater inflow of about 415 cfs (Ashley, 261 cfs; Wando, 82 cfs; and Cooper, 72 cfs). In 1942, the Santee-Cooper Hydroelectric Project was completed, and the flow from the Santee River was diverted through the Pinopolis Power Plant into the west branch of the Cooper River. The average annual freshwater inflow of the Cooper River was increased from 72 cfs to about 15,000 cfs weekly average. Density currents associated with a flow-induced stratified condition changed the characteristics of the system and caused significant shoaling in the harbor. To ameliorate shoaling conditions, three contraction dikes were constructed in the Cooper River. One contraction dike was constructed on the west bank opposite the Naval Base Channel Realignment, while the other two contraction dikes were constructed on the east and west banks just south of the Shipyard River entrance. The dikes were constructed to increase channel velocities and redistribute shoaling material from this channel reach. Inflow to the Cooper River was subsequently rediverted back to the Santee River. Since 1985, a 4,500-cfs weekly average freshwater inflow has been maintained. This significant decrease in flow returned the estuary to a vertically mixed condition and is expected to substantially reduce shoaling in the harbor. Recent inspection of the contraction dikes by the US Army Engineer District, Charleston, revealed that the dikes are in a severely deteriorated condition. The objective of this study was to evaluate the overall effectiveness of the Federal dike project based on utility to the adjacent navigation project. This study collected and developed information related to the possible removal or rehabilitation of the three dikes in Charleston Harbor. The study found that the contraction dikes were successful not only in increasing channel flow velocities but also in training the channel. After the construction of the dikes, the channel reach evolved towards a more ideal configuration: smoother and with a greater fraction of cross section in the channel. Numerical model results indicated a relatively small change in current conditions caused by the complete removal of the three dikes. The study recommended (A.) shortening two dikes and removing the third, or (B.) removing two dikes and retaining the third. NOTE: This file is very large. Allow your browser several minutes to download the file.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Miscellaneous Paper|