Mechanism of Rip Current Generation at Deoksan Beach, South Korea

초록

The coast serves as a buffer by reducing the energy of high waves and also serves as a leisure space for people. The east coast of Gangwon has become popular for its beach and for surfing in summer. Most beaches are sandy, and they have well-developed crescentic bars owing to exposure to high waves. The study site, Deoksan Beach, had an accident in which two college students drowned owing to rip currents at around 5:40 pm on July 13, 2019. The flow velocity and direction of the rip currents were identified using CCTV images at the time of the accident, and the causes of the currents were analyzed using data obtained from five water depths surveys conducted in 2017. At the time of the accident, the significant wave height was 0.6 m, the period was similar to 7.5 s, and the wave direction was 54 degrees. The survey results indicated that an environment suitable for rip current generation existed at this site. A numerical model experiment was conducted using the non-hydrostatic Surface Waves till Shore (SWASH) model to reproduce the occurrence of rip currents at the time of the accident, and the flow (surface: 0.38 m/s, average: 0.3 m/s) was found to be on the offshore side of the accident.

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