Non-hydrostatic Modeling of Wave Transformation and Rip Current Circulation: A Case Study for Haeundae Beach, Korea

Abstract

Haeundae Beach in Busan, South Korea, is one of the most popular destinations in South Korea, but poses the danger of irregular, fast moving rip currents. To investigate the dominant mechanism of rip currents in this region, a numerical simulation was carried out using the non-hydrostatic model Surface WAves till SHore (SWASH), with observed wave and topographical data. In this paper, the applicability of SWASH for modeling the wave transformation and rip current circulation near the shallow foreshore is investigated. Assuming that rip current dynamics are controlled by combination of variations in wave dissipation and morphological flow constriction, we tested the effects of wave parameters, such as wave heights, wave periods, wave directions, and changes in tidal conditions, on rip current generation. The model results showed good agreement with previous studies, as well as observations in this region. A numerical study showed that wave refraction by spatial topographical characteristics (several submerged reefs near the coasts) of Haeundae Beach cause wave energy propagation in different directions towards the beach. Rip currents were simulated when longshore currents flowed out through a channel with very small wave energy in the seaward direction. The occurrence of rip currents was increased under conditions of higher waves and longer wave periods. In the case of wave direction, we tested cases from SSW to SSE, and present the spatial characteristics of the simulation results. The locations of rip channels that generate rip current are significantly affected by incident wave conditions, such as wave direction, height, and period.