Hydraulics and Dynamics of North Inlet, South Carolina, 1975-76.

Abstract : North Inlet, South Carolina, was selected as a natural tidal inlet for investigation within the scope of the Army Corps of Engineers' program on General Investigations of Tidal Inlets. Over a 2-year period, from July 1974 to June 1976, eight 2-week intensive field sessions were conducted at the inlet. Three tide gages provided nearly continuous water surface elevation records for the ocean and tidal creeks throughout the period of investigation. The analysis presented in this report focuses on three attributes of the inlet environment: (1) the inlet hydraulics; (2) the longshore currents adjacent to the inlet; and (3) the seasonal morphologic change of the North Inlet tidal deltas and adjacent beaches. North Inlet is hydraulically ebb dominated. For the throat section, the peak ebb velocity exceeded the peak flood by a factor of 1.22. The model presented to account for this difference explains the ebb dominance as a result of the different efficiency of water exchange between the ocean and the bay at high and low tide. Topographic mapping of inlet shoals and adjacent beaches, combined with bathymetric profiling of the throat and the major channels, suggest that there is a sediment exchange between the channels and the beaches. During periods of fair weather, the beaches accrete and the channels appear to scour. During high-energy conditions, the reverse seems to occur.