Performance of Beach Nourishment at Hilton Head Island, South Carolinaby Kevin R. Bodge,
Erik J. Olsen,
Christopher G. Creed,
Abstract: Between May and August, 1990, approximately 2.34 million cubic yards of sand were placed along 35,000 feet of the Atlantic shoreline of Hilton Head Island, South Carolina. The project was constructed mostly through the use of hydraulic fill from two offshore borrow sources. During the 26-month period subsequent to project construction, the project as a whole has generally performed within about 10% of design predictions. About 1.4 MCY of the total project volume was placed above mean sea level. Of this amount, 0.59 MCY were predicted to re-distribute to the profile below mean sea level-resulting in an initial post-equilibration berm width of 65 to 75 ft. Within the first year, the 150-to 180-ft wide construction berm retreated to an average width of 79 ft, and 0.46 MCY were lost from above MSL. Within two years, the measured changes across the profile (averaged project-wide) matched predictions almost exactly - if one assumes that all of the overfill losses occur from the toe of the beach fill. Considering overfill losses (19%), the average volumetric loss rate from the project area, about 209,400 cy/yr, is 7% greater than the pre-project prediction. After 26 months, 81% of the placed volume remained within the project area above closure. Of the 453,600 cy thought to have been transported out of the project area, at least 370,000 cy is accounted for by accretion adjacent to the project area. While the average, project-wide performance agreed well with predictions, local and temporal performance has varied.
Subject Headings: Beach nourishment | Islands | Coastal management | Hydraulic fills | Landfills | Berms | Sand (hydraulic) | Offshore construction | South Carolina | North America | United States
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