A STUDY ON WIND DRIVEN CURRENT AND NEARSHORE CURRENT AT ISHIKARI-HAMA BEACH

Abstract

 In August 2016, the accident occurred that four swimming people curried away to offshore and die at Ishikari-hama beach in Hokkaido. The several other accident that the swimming people curried away occurred around the Ishikari coast in recently years. The current analysis in Ishikari Bay due to the sea-sonal wind was studied in the past research. However, the current dynamics due to the wind direction change in short time has not studied yet. Therefore, we tried to comprehend the feature of the current dynamics in Ishikari bay, expressly around Ishikari-hama beach.
 As research contents, we grasped the history of the accident around the Ishikari coast. In this case, we used the on-line database and extract the newspaper article about the accident at Ishikari coast. As the result, we comprehended the feature of the accident in Ishikari Bay. Secondary, we made the field survey at Ishikari-hama beach in July 2017. This beach has cusp topography. The interval spacing of cusp topography was about 100m, and the slope of the bottom was about 1/80. In the field, we pig-mented the rip current by the sea water colorant, and the pigmented current was recorded as the aerial photography by the UAV. Thirdly, we confirmed the fluctuation of the current in Ishikari Bay due to the wind direction fluctuation. As a result, we comprehended that the current direction changed in several hours after the wind direction changed. Finally, we simulated the rip current and the wind driven current in Ishilari Bay.