Quasi-2DH Modeling of the Shoreline Evolution Around an Offshore Breakwater

Abstract

In the present study, a quasi-two-dimensional (2D) numerical model developed to model shoreline evolution under wave action near various coastal defense implementations is applied to laboratory experiments on shoreline evolution around an offshore breakwater. The model uses a spectral wave model based on the energy balance equation with wave breaking and diffraction terms. A method is proposed to distribute bulk longshore sediment transport rates over the surf zone for 2D applications. The proposed method agrees with the one-dimensional methods and 2D laboratory measurements. The model also comprises cross-shore and swash zone transport modules for maintaining the equilibrium profile, which is tested using a theoretical case governed solely by cross-shore transport. The test shows that the cross-shore transport module can restore any user-defined equilibrium beach profile. For the laboratory experiments, the model results for the nearshore wave heights and bottom contours agree well with the experimental results, especially for the initial cases of laboratory experiments. As the salient progresses through the offshore breakwater and a tombolo forms, the wave approach and local orientation angles increase, and the computed bottom contours begin to differ from the measured contours.

Keywords

• sediment transport
• shoreline change model
• quasi-2dh
• offshore breakwater