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 sandbars, thereby posing a significant danger to beachgoers worldwide.Many people were rescued in 2014 from fast moving, seaward ripcurrents at Haeundae Beach in Busan, located in the southeastern partof South Korea. In response to such threats to public safety, the KoreanMeteorological Administration (KMA) plans to install automaticmonitoring systems to forecast rip currents at Haeundae Beach.Accurate prediction of this phenomenon is essential for preventingcoastal disasters; therefore, the main objective of this study is toprovide a warning decision process for rip current generation to protecthuman life in areas where these currents occur.In this study, we analyze field measurements conducted at HaeundaeBeach in the summers of 2011 and 2013 to clarify the generationmechanism of rip currents. The developed system couples a Haeundaecurrent model (HAECUM) with a nearshore rip current predictivesystem for Haeundae (NERiPS-H). NERiPS-H is used for the initialwarning decision step, which involves calculation of a predictive ripcurrent index by using wave height, wave period, and wave direction,provided by three coastal prediction systems, to provide guidance onthe likelihood of safe and dangerous rip currents. NERiPS-H predictsthe strong possibility of dangerous rip currents along the coast, andHAECUM predicts safety and current vectors by using wave and winddata based on simulation of a numerical prediction system. Wedetermine four warning levels for KMA weather forecasting of ripcurrent generation: “concern,” “cautious,” “dangerous,” and “fatal.”We couple the predictive index and the rip current forecast model toperform numerical simulations by using wave data and forecastinformation supplied by the KMA. The results of this study allow theKMA to provide a 36-h rip current forecast on its Website.