SEDIMENT BYPASSING AT MIXED ENERGY TIDAL INLETS

Duncan M. FitzGerald

Abstract


Inlet sediment bypassing, through the previously recognized mechanisms of stable inlet processes and ebb-tidal delta breaching, has been documented at six mixed energy (tide-dominated) coasts around the world including the coasts of: central South Carolina, Virginia, southern New Jersey, New England, the East Friesian Islands, and the Copper River Delta in Alaska. Regardless of the mechanism, the end product of the bypassing process is the formation of a large bar complex that migrates onshore and attaches to the downdrift inlet shoreline. Thus sediment bypassing is a discontinuous process at mixed energy tidal inlets. The morphology of the bar complexes is highly variable with widths ranging from 40-300m and lengths from 300 to over 1500m. Generally, the size of the bar complexes increases as inlet size increases and as the rate of longshore sediment transport increases. The frequency of bar welding events at mixed energy inlets varies from 3-7 years. The location where the bars attach to the downdrift beach and length of shoreline that is affected by the bar welding process is dependent on inlet size, orientation of the main ebb channel and wave versus tide dominance of the shoreline.

Keywords


sediment bypassing; tidal inlet; mixed energy

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