Exterior bathymetric effects in elliptic harbor wave models

Traditional elliptic harbor wave models are based on the assumptions that t he region outside the computational gr is of constant depth and that the ex terior coastlines are collinear and fully reflecting. These assumptions, wh ich are associated with the open boundary, are generally not met in practic e. This paper demonstrates that the effects of exterior depth variations on model results can be substantial, leading to unreliable simulations even w ith sophisticated modern wave models. A technique is developed to overcome these Limitations. It is based on a one-dimensional representation to bette r simulate the effect of the exterior bathymetry. The results of the one-di mensional model are then interfaced along the open boundary of a two-dimens ional finite-element harbor wave model. The new model is tested against ana lytical solutions for the case of wave propagation on a sloping beach, whic h is a difficult problem for harbor models in use today. Excellent results are obtained, suggesting that improved representation of the cross-shore sl opes while treating the open boundaries may enhance the usefulness of these models.