ONE-DIMENSIONAL MODELING OF INDIVIDUAL WAVES AND WAVE-INDUCED LONGSHORE CURRENTS IN THE SURF ZONE

A probabilistic model (WAVIS-model) was developed to describe the prop agation and transformation of individual waves (wave by wave approach) . The individual waves shoal until an empirical criterion for breaking is satisfied, Wave height decay after breaking is modelled by using a n energy dissipation method, Wave-induced set-up and set-down and brea king-associated longshore currents are also modelled, Laboratory and f ield data were used to calibrate and verify the model. The model was c alibrated by adjusting the wave breaking coefficient (as a function of local wave steepness and bottom slope) to obtain optimum agreement be tween measured and computed wave height. Four tests carried out in the large Delta flume of Delft Hydraulics were considered, Generally, the measured H-1/3-wave heights are reasonably well represented by the mo del in all zones from deep water to the shallow surf zone. The fractio n of breaking waves was reasonably well represented by the model in th e upsloping zones of the bottom profile. Verification of the model res ults with respect to wave-induced longshore current velocities was not extensive, because of a lack of data. In case of a barred profile the measured longshore velocities showed a relatively uniform distributio n in the (trough) zone between the bar crest and the shoreline, which could to some extent be modelled by including space-averaging of the r adiation force gradient, horizontal mixing and longshore water surface gradients related to variations in set-up. In case of a monotonically upsloping profile the cross-shore distribution of the longshore curre nt velocities is reasonably well represented.