Nearshore Circulation in Complex Regions

Abstract : As ocean surface waves propagate over the continental shelf and break in shallow nearshore areas, their energy is dissipated in the surf zone. The gradients in the wavelets and momentum give rise to the generation of wave-induced nearshore circulation. Wave forcing of circulation in the surf zone is a major cause of sediment transport and beach morphology evolution; its understanding and prediction are essential from military application such as amphibious landings and mine warfare. Semiempirical expressions for the nearshore circulation exist over planar bathymetry. However, over more complex bathymetric configurations, such as sandbars, rip channels, and canyons, numerical models are required form comprehensive descriptions of the wave-driven flow. Most of these extant numerical models either use irregular wave forcing but simplify the hydrodynamics (as is the cases for nearshore circulation models in the operational Navy), or allow more involved hydrodynamic formulations but reduce the forcing to that of monochromatic wave theory. Wither modeling option can potentially lead to nearshore hydrodynamic predictions that do not exhibi the variability seen in nature.