Modelling Wave-Driven Setup

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ABSTRACTOCE-0622844In this study, scientists at Woods Hole Oceanographic Institution will develop and validate models for the fluid and sediment processes that affect the evolution of the shoreline over periods of days to months. Gradients in wave momentum fluxes (radiation stresses) drive the near-shore circulation which in turn drives sediment transport. One important facet of the near-shore circulation is wave-driven setup, which is an elevation of mean water levels near the shoreline. Observations of setup were made in 1997 near Duck, North Carolina and in 2000 and 20003 near La Jolla, CA. These studies have shown that prior estimates of the cross-shore radition stress, which were based on a linear theory of onshore wave energy from sea swell, are smaller than what is observed. This study will extend a numerical model to include four previously neglected processes: wave rollers, bottom stress, wave nonlinearities, and infragravity wave reflection. The predictions of that model will then be compared with existing field and laboratory observations.Laboratory observations of the vertical profile of flows will be used to compare linear and nonlinear expressions for wave energy and radiation stress. If nonlinearities are shown to be important, depth-averaged nonlinear expressions will be examined and incorporated in the setup models. Additionally, the importance of alongshore bathymetric inhomogenities to the wave-driven setup will be examined using simulations of the quasi three-dimensional NearShore Community and Delft3D models.During storms, wave-driven setup has been observed to increase the seal level more than a meter. As became clear during Hurricane Katrina, flood damage by a combination of storm surge and wave setup can result in a significant cost to society. The model that is being developed in this study could be useful to coastal managers who are tasked with the prediction of coastal flooding. This study forms the basis of a PhD dissertation and results will provide material for internet-based undergraduate classes in New England.