Estimating tidal currents at the Sewol ferry tragedy site: Insights into slack water determination in the Yellow Sea

Abstract

Errors in estimating slack water timing can lead to catastrophic consequences, as evidenced by the Sewol ferry tragedy, where initial search and rescue failures were attributed to misjudging slack water timing, resulting in substantial loss of lives. This study estimated real-time tides across the entire Yellow Sea using a finite element method (FEM) model. To verify the accuracy of the model, observed tide levels were compared with model results at five major stations in the West Sea of the Korean Peninsula, while observed tidal currents were compared with model predictions at three major stations. The model results were consistent with the observations, particularly the tide level and phase. This validated the reliability of the model in slack water determination. Moreover, an analysis of the time difference between high (low) tides and slack water revealed strong currents during high (low) tides in areas farther from the coast toward the open sea, transitioning to weaker currents near the coast during high (low) tides. Based on this result, a spatial distribution map of slack water time differences in the western seas of the Korean Peninsula was developed, along with a revised terminology dictionary to reflect the tidal environment characteristics. This study offers valuable insights for rapidly determining slack water times, crucial for search and rescue operations in the Yellow Sea, by simply determining high (low) tide times.