Numerical Modeling for Gravel Beach Deformation Using 2-Way Method

Fluid motions of waves interact with bed materials mainly through the bottom shear stress caused by water particle motion near the bottom, which leads to topographical changes. The altered bottom profile, in turn, affects the wave fields, and changes in these fields can lead to sequential bottom profile change. Most of the studies on the sediment problems, however, have not considered the effects of the altered bottom profile on wave fields. To predict topographical changes more accurately, the changed bottom profile should be reflected in calculation of wave fields over time, i.e., the 2-way method is required. In this study, a numerical model considering dynamic interactions between wave fields and topography change caused by on-offshore sediment transports is proposed to estimate the topographic change of gravel beaches. The new feature of the present model is the integration of the wave and sediment model. Comparison between numerical and existing experimental results showed that the present model is useful to simulate wave fields and the beach topographical change of gravel beaches. In particular, the newly developed model based on the 2-way method, in which the dynamic interaction between fluid motion and sediments can be considered through the feedback process, greatly improves prediction of the gravel beach profiles.