Eight Types of BG Models and Discretization

Abstract

Eight types of the BG models are introduced in this chapter. The Type 1 is a model using wave parameters at the breaking point. In the Type 2, the effect of longshore sand transport due to the effect of the longshore gradient of breaker height is included with an additional term given by Ozasa and Brampton. In the Type 3, the intensity of sand transport P is assumed to be proportional to the third power of the amplitude of the bottom oscillatory velocity u m due to waves, and in the Type 4, P is given by the wave energy dissipation rate due to wave breaking at a local point. In the Type 5, wave power is calculated using the coordinate system different from that for the calculation of beach changes to predict the topographic changes of an island or a cuspate foreland in a shallow water body under the action of waves randomly incident from every direction. In the Type 6, the height of wind waves is predicted using Wilson ’ s formula using the wind fetch distance and wind velocity, and then sand transport fluxes are calculated. The Type 7 is a model for predicting the formation of the ebb-tidal delta under the combined effect of waves and ebb-tidal currents with an analogy of the velocity distribution of ebb-tidal currents to the wave diffraction coefficient, which can be calculated by the angular spreading method for irregular waves. In the Type 8, the effect of the nearshore currents induced by forced wave breaking is incorporated into the model by calculating the nearshore currents, taking both the wave field and the current velocity at a local point into account.