Improved representation of breaking wave energy dissipation in parametric wave transformation models

Abstract

An improved formulation to describe breaking wave energy dissipation is presented and incorporated into a previous parametric cross-shore wave transformation model [Baldock, T.E., Holmes, P., Bunker, S., Van Weert, P., 1998. Cross-shore hydrodynamics within an unsaturated surf zone. Coastal Engineering 34, 173–196]. The new formulation accounts for a term in the bore dissipation equation neglected in some previous modelling, but which is shown to be important in the inner surf zone. The only free model parameter remains the choice of γ, the ratio of wave height to water depth at initial breaking, and a well-established standard parameter is used for all model runs. The proposed model is compared to three sets of experimental data and a previous version of the model which was extensively calibrated against field and laboratory data. The model is also compared to the widely used model presented by Thornton and Guza (1983) [Thornton, E.B., Guza, R.T., 1983. Transformation of wave height distribution. Journal of Geophysical Research 88 (No.C10), 5925–5938]. The new formulation leads to an important improvement in predicting wave height condition close to the shoreline in non-saturated surf zone conditions. The approach overcomes a problem in the original model, where amplification by shoaling could exceed energy dissipation by breaking in very shallow water, i.e. approaching the swash zone. In dissipative conditions an improvement is also noticeable. Of the four models considered, the new model gives the smallest error between predicted and measured wave heights for all three data sets presented.