A Perturbation Method for Wave and Wave-Induced Currents Computations in Beach Morphology Models

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A new method to update wave and current values in a time evolving beach morphology model is developed. The method is based on the assumption that small bottom perturbations induce small variations in the hydrodynamic magnitudes resulting in a new set of linearized perturbed equations that can be solved easily. The method has been tested for I-D as well as for 2-D bathymetries showing its capabilities. INTRODUCTION Evaluating the responses of beach morphology to changing wave conditions, particularly during a storm, is one of the most important challenges of coastal scientist and engineers. A number of conceptual, physical and numerical models have been developed during the last decades in order to characterize and determine beaeh processes and changes. Coastal area morphodynamic models are used to predict the short-term (hours to days) and medium-term (weeks to months) bathymetric changes associated with varying wave and current conditions. Schemes of this type have been under intensive development for the past twenty years, see De Vriend (1996) as a general reference, work having concentrated on two-dimensional, depth-averaged (2DH) schemes 0Hicholson et al., 1997). These models begin operations by calculating the initial wave and current fields on a fixed bed. The sediment transport field is then computed using either a semi-empirical sediment transport formulation or by solving the time-dependent diffusion-advection equation for suspended sediment concentrations. Next, bed level changes are computed 1) Postdoctoral Researcher, Ocean & Coastal Research Group, Dpto de Cienclas y Tecnicas del Agua y del Medio Ambiente, Universidad de Cantabria, Avda de los Castros sin 39005 Santander, Spain. fmi@puer.unican.es 2) Professor, Ocean & Coastal Research Group, Dpto de Ciencias y Tecnicas del Agua y del Medio Ambiente, Universidad de Cantabda. medina@puer.unican.es