Beaches and the adjacent surfzone (the region of breaking waves near the shoreline) are used for recreational and commercial activities, and provide habitat to a variety of fish and benthic species. These environmental and economic resources are threatened by polluted terrestrial runoff that frequently drains onto the shoreline where it is mixed and dispersed in the surfzone. A model predicting the transport and dilution of surfzone pollutants would improve beach management, but the processes that disperse pollution within and across the surfzone are understood poorly.
Strong horizontal eddies drive rapid surfzone mixing, but the factors controlling surfzone eddy energy are not known. Short-crested breaking waves are a source of vorticity about a vertical axis (i.e., horizontal eddies), and may be a primary forcing mechanism for nearshore eddies and pollution dispersal. The structure and magnitude of vorticity generated by short crested breaking waves will be examined with a numerical surfzone model that resolves individual waves as they cross the surfzone and break. Realistic simulations will be performed using observed bathymetry and wave conditions, and comparisons with field data will be performed. The model will be used to examine how vorticity generation varies between the shoreline and seaward edge of the surfzone, and to develop a budget for vorticity within the surfzone and nearshore regions. These investigations will support future work connecting short-crested breaking waves with predictions of pollution dispersal.
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