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Tidal inlets along the southeastern coast of the United States from Cape Hatteras to Cape Canaveral (the Georgia Bight) and along the North Sea coast from the Netherlands to Denmark (the German Bight) reflect a range in physical processes from wave dominance (at the flanks of the two bights) to tide dominance (at the center of the German Bight). Studies of the hydraulics, sediment dispersal, and historic morphologic changes of several inlets within the two bights have led to the identification of a continuum of inlet types from microtidal wave-dominated inlets at one end to macrotidal tide-dominated inlets at the other. The factors controlling the inlet types are: (a) the longshore sediment-transport rate caused by the momentum flux of the breaking waves, (b) the onshore- ffshore sediment-transport rate resulting from tidal currents, and (c) the flood-ebb asymmetry in tidal-current velocities. This last factor is determined by the hydraulic geometry of the back-barrier bay.
The wave-dominated inlets have all their shoals on the bay side of the inlet throat. The mixed-energy inlets have shoals landward of, in, and seaward of the throat, and there is a distinct increase in the volume of the seaward shoals (ebb-tidal deltas) with increasing tide range. The tide-dominated inlets reflect situations where the longshore sediment-transport rate is completely subordinate to the onshore-offshore transport. In these situations, barrier islands cease to exist and tidally controlled lunate, sigmoidal, and linear sand bodies occur throughout the estuary entrance.
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