세월호 침몰지점의 조류 특성

Abstract

Departing Incheon port heading for Jeju Island, 6,825-ton the ferry, Sewol sank about 1.5 miles away from the North Sea in Byeongpung Island, Jindo-gun, Jeollanam-do at 8:48 a.m. on April 16, 2014. Right after the accident, Navy, National Emergency Management Agency, Coast Guard, and private divers were entered to save survivors and the missing underwater. However, 172 people were saved out of 476 people on board and 295 people died as of November 11, 2014. 9 people were missing. At the initial stage of rescue operation, for diving works, the data on tides (West Geocha Island) and currents (Maenggol Channel) were used. There were many difficulties encountered in the initial search operation as forecast location and ferry sinking point do not match, producing a lot of differences in the slack time and the velocity. Therefore, Korea Institute of Ocean Science & Technol-ogy(KIOST) installed ADCP (Acoustic Doppler Current Profiler) to observe real-time tidal current for 202 days from April 23 to November10 from the missing support barge for search operations. Analyzing the data, the trends of water speed, direction, flow, etc. were identified. The real-time tidal current data and analyzed findings were offered to divers and relevant agencies on site and effective search was supported. As a result of analyzing the observed data, slack time after flood tide was similar to that on broadcast for Maengol Channel at Sewol sinking point but slack time after ebb tide appeared average about 50 minutes in advance from the sinking point (based of July, 2014). In particular, at slack time after ebb tide, under 0.5m/s current velocity for diving-possible didn’t appear but lasting time appeared very short. On the other hand, at slack time after flood tide, the retention time for current velocity under 0.5m/s was long. From time to time, it lasted more than three hours. Besides, ebb tide started. In about two hours, short-cycle tidal current variability appeared. It is considered it was caused by geographical impact, in other words, the impact of Geocha Island, Maenggol Channel, Geocha Channel, etc. Such results were also found in the numerical model results for the relevant areas.