Development and Validation of a Quasi-Three-Dimensional Coastal Area Morphological Model

Abstract

A quasi-three-dimensional coastal area morphological (Q3DCAM) model has been developed using the process-based approach. It is for simulating complex multiscale coastal processes, primarily morphodynamic changes of the seabed. This software package has integrated three key submodels for simulating irregular wave deformations, nearshore currents, and morphological processes. The quasi-three-dimensional capability of the depth-averaged model has been developed to consider the vertical flow structure inside the surf zone and the cross-shore movement mechanisms of nearshore currents, e.g., undertow and mass flux. To this end, the calculations of the radiation stresses inside the surf zone have been improved by introducing the nonsinusoidal wave model for surface roller effects due to the breaking wave. To predict accurately the wave field and the morphological processes near coastal structures, the wave diffraction effects were included in a multidirectional spectral wave transformation model. The morphodynamic change was modeled by considering the sediment transport due to the combinations of waves and currents. These three submodels were validated by simulating three laboratory experimental cases in regard to: (1) irregular wave deformations over a shoal; (2) longshore currents in a wave basin; and (3) moveable bed evolutions around an offshore breakwater under attack of an incident wave. The numerical results of the morphological modeling confirmed that the Q3DCAM model consisting of the diffraction effects and the surface roller effects is capable of predicting waves, currents, and morphodynamic changes more accurately than before. Therefore, this validated model can be applied to simulate more realistic morphological processes in coastal zones including structures.