ABSTRACT

Patterns of erosion and deposition along the shoreline of Price Inlet, South Carolina, are strongly influenced by ebb-tidal delta processes. The ebb delta goes through cycles of growth and decay (15-20% change in volume) which last from 4 to 7 years. In the growth phase, large intertidal bar complexes are formed on both sides of the main ebb channel by the coalescence of landward-migrating swash bars. During this stage, waves refracting around the southern bar complex produce a reversal in the longshore-transport direction on the downdrift shoreline. This results in little sediment escaping the inlet and delta system. The sand-trapping mechanism ceases and the delta reduces in volume when the bar complexes migrate onshore and attach to the beach.

The inlet shoreline also goes through cycles of 7- to 42-years duration in which its offset configuration changes. The shift in shoreline alignment is controlled by the orientation of the main ebb channel and the resulting ebb-tidal delta morphology. When the inlet has a downdrift, offset configuration, the ebb-tidal delta is skewed along the updrift shoreline. In this position bar complexes preferentially accrete along the updrift beach causing a progradation of the shoreline. At the same time, the downdrift shoreline erodes due to little sediment bypassing the inlet. This pattern of sedimentation eventually produces an updrift, offset inlet. The erosional-depositional processes are reversed when the ebb flow in the channel thalweg is deflected off the prograding updrift, inlet shore ine. This causes a clockwise rotation of the main ebb channel and a shift in the ebb delta to a position along the downdrift shoreline. In this configuration the updrift shoreline erodes and the downdrift shoreline accretes. This study documents the close relationship that exists at Price Inlet, South Carolina, between the ebb-tidal delta and landward shoreline. Evidence is presented to show that this relationship may hold for other mixed-energy tidal inlets as well.