A Coastal Area Model Considering Wave-Current Interaction and Its Application to Wide-Crested Submerged Breakwater

Abstract

This study is concerned with development of a 3D morphodynamic predictive model for considering wave-current interaction by using wave action balance equation. The developed model was applied to model tests associated with a detached breakwater and wide-crested submerged breakwaters, and the influences of strong currents around the structures into wave height distribution and bathymetry change were investigated. Furthermore, the morphodynamics around the artificial reefs in the Uradome Beach, Tottori, Japan, was computed. From the computed results, a large scour hole due to strong rip-currents in the opening of the reefs was reproduced. The applicability of the model was confirmed. Keywords: morphodynamic; submerged breakwater; rip-current; numerical simulation INTRODUCTIONWide-crested submerged breakwater, which is so-called "Artificial reef", is an effective structure for preventing sandy beach erosion due to wave and nearshore current actions, and for the landscape of sea-view in front of sandy beaches, especially Japan. Uradome beach in Tottori, which is a pocket beach facing the Sea of Japan, has been suffered from beach erosion. In order to prevent the beach erosion, two artificial reefs with the crest depth of 2m and the crest width of 40m were constructed in 1996, as shown in Fig.1. However, very large scour around a gap of the artificial reefs occurred due to strong rip currents at the gap, as shown in Fig. 2. Therefore, in order to take reliable countermeasures for preventing the large scour, maintaining stability of the submerged breakwaters, and evaluating the morphodynamics around the breakwaters, a coastal area model for considering the hydrodynamic in wave-current coexistence field such as the strong current generated at the gap is also required. Many three-dimensional beach evolution models have been proposed and then applied to practical evaluation of the construction of coastal structures, the accretion problems of the navigation channel of ports and so on. We have develop a coastal area model with shoreline change based on the quasi-three dimensional (Q-3D) nearshore current model (Kuroiwa et al., 2004), and applied to 3D morphodynamics around river-mouth (Kuroiwa et al.,2008) and after shoreface nourishments (Kuroiwa et al.,2010). However, the hydrodynamic module in the previous models, which is based on the wave 1 Tottori University, Department of Civil Engineering, 4-101,Koyama,Tottori,680-8552, Japan 2 National Water Resource Center, Coastal Research Institute, 15 El-Pharaana St. 21514, Alexandria, Egypt 3 Tottori University, Department of Civil Engineering, 4-101,Koyama,Tottori,680-8552, Japan 4 Mikuniya Corporation, 3-1-10, Naniwa-ku, Saiwai-chou, Osaka, 556-0021,Japan 5 Disaster Prevention Research Institute, Kyoko University, Gokasho,Uji, Kyoto, 611-0011, Japan 6 Department of Environmental Engineering, the Islamic University of Gaza, Palestine COASTAL ENGINEERING 2012 2 energy balance equation and the Q-3D nearshore current model, was not considering the wave-current interaction. Taji...