Numerical Study of Rip Current Generation Mechanism at Haeundae Beach, Korea

Abstract

Haeundae Beach is one of the most famous tourist attractions in Busan, Korea. Every year, millions of people visit the beach. Recently, however, numerous rip current accidents have occurred along the middle of the beach. For example, in 2013, more than 500 people were swept away by a strong channel of water flowing seaward from the shore and were rescued after being dragged into deeper water. Fortunately, no casualties were reported, but the authorities said that, given the right weather conditions, rip currents could occur again at any time, not only at Haeundae Beach but also at other beaches. Some studies have been conducted to determine the rip current generation mechanism at Haeundae Beach. Previous research suggests that a known mechanism of rip current generation associated with the nodal line area of honeycomb-patterned wave crests was one of the significant factors in rip current occurrences at Haeundae Beach. In this study, we performed numerical experiments to identify the rip current generation mechanism based on the hypothesis proposed in the study mentioned. A well-known Boussinesq equation solver, FUNWAVE-TVD, was employed to simulate nearshore circulation at Haeundae Beach. The model was verified by generating a rip current for a simple beach for honeycomb-patterned incident wave conditions. The model was then used in numerical simulations of wave transformation to identify the rip current generation mechanism for Haeundae Beach, and wave transformation characteristics were examined in detail to identify the possible origins of rip currents. The original bathymetry was modified and applied to simulation of nearshore circulation to understand how reefs located off the shore of Haeundae Beach contribute to rip current generation. The numerical results corresponded to a slightly different rip current generation mechanism. It is thought that honeycomb-patterned incident waves may induce rip current event at Haeundae Beach but the other factors may contribute as well.