Application of Warning Decision Process System for Rip Current Generation at Haeundae Beach

摘要

Rip currents can pull swimmers into deep water beyond offshore sand bars, thereby posing a significant danger to beachgoers worldwide. Many people were rescued in 2014 from fast moving, seaward rip currents at Haeundae Beach in Busan, located in the southeastern part of South Korea. In response to such threats to public safety, the Korean Meteorological Administration (KMA) plans to install automatic monitoring systems to forecast rip currents at Haeundae Beach. Accurate prediction of this phenomenon is essential for preventing coastal disasters; therefore, the main objective of this study is to provide a warning decision process for rip current generation to protect human life in areas where these currents occur. In this study, we analyze field measurements conducted at Haeundae Beach in the summers of 2011 and 2013 to clarify the generation mechanism of rip currents. The developed system couples a Haeundae current model (HAECUM) with a nearshore rip current predictive system for Haeundae (NERiPS-H). NERiPS-H is used for the initial warning decision step, which involves calculation of a predictive rip current index by using wave height, wave period, and wave direction, provided by three coastal prediction systems, to provide guidance on the likelihood of safe and dangerous rip currents. NERiPS-H predicts the strong possibility of dangerous rip currents along the coast, and HAECUM predicts safety and current vectors by using wave and wind data based on simulation of a numerical prediction system. We determine four warning levels for KMA weather forecasting of rip current generation: “concern,” “cautious,” “dangerous,” and “fatal.” We couple the predictive index and the rip current forecast model to perform numerical simulations by using wave data and forecast information supplied by the KMA. The results of this study allow the KMA to provide a 36-h rip current forecast on its Website.