Abstract
The BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept) was used to simulate the shoreline evolution caused by the high-angle wave instability discussed by Ashton et al. Three calculations were carried out: the wave direction was assumed to be obliquely incident from 60Ëš counterclockwise (Case 1) or from the directions of ±60Ëš with probabilities of 0.5:0.5 (Case 2) and 0.65:0.35 (Case 3), while determining the incident wave direction from the probability distribution at each step. The three-dimensional development of multiple sand spits and cuspate forelands with rhythmic shapes was successfully explained using the BG model. The results of the previous study conducted by Ashton et al. were reconfirmed and reinforced.
Highlights
INTRODUCTIONZenkovich (1967) showed that multiple sand spits with rhythmic shapes may develop in a shallow water body such as the Azov Sea and a lagoon facing the Chukchi Sea, as shown in Fig. 1, and concluded that under oblique wave incidence with the angle between the direction normal to the shoreline and the wave direction being larger than 45 ̊, shoreline instability may develop, and during the development of sand spits, the wave-sheltering effect due to the sand spits themselves plays an important role. Ashton et al (2001) adopted this mechanism in their model and successfully modeled this shoreline instability using the upwind scheme in their finite difference method to prevent the numerical instability on the basis of the conventional longshore sand transport formula
We used the BG model developed by Serizawa and Uda (2011) to simulate the shoreline evolution caused by high-angle wave instability (Ashton and Murray, 2006) and showed that the threedimensional (3-D) beach changes associated with the shoreline instability can be explained using this model
Regarding the development of multiple sand spits and cuspate forelands with rhythmic shapes owing to the instability mechanism along the shore of the Azov Sea (Zenkovich, 1967), Ashton et al (2001) successfully developed a numerical model that can predict this shoreline evolution on the basis of the longshore sand transport formula of the one-line model
Summary
Zenkovich (1967) showed that multiple sand spits with rhythmic shapes may develop in a shallow water body such as the Azov Sea and a lagoon facing the Chukchi Sea, as shown in Fig. 1, and concluded that under oblique wave incidence with the angle between the direction normal to the shoreline and the wave direction being larger than 45 ̊, shoreline instability may develop, and during the development of sand spits, the wave-sheltering effect due to the sand spits themselves plays an important role. Ashton et al (2001) adopted this mechanism in their model and successfully modeled this shoreline instability using the upwind scheme in their finite difference method to prevent the numerical instability on the basis of the conventional longshore sand transport formula. We used the BG model (a three-dimensional model for predicting beach changes based on Bagnold’s concept) developed by Serizawa and Uda (2011) to simulate the shoreline evolution caused by high-angle wave instability (Ashton and Murray, 2006) and showed that the threedimensional (3-D) beach changes associated with the shoreline instability can be explained using this model In this case, the fundamental equation of the BG model defined by Serizawa and Uda (2011) was employed as the sand transport equation, the sand transport flux was assumed to be proportional to the wave energy dissipation rate instead of the third power of the amplitude of the bottom oscillatory velocity due to waves, and the wave energy dissipation rate was given by that due to wave breaking at each point determined in the calculation of the wave field.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
