Abstract
The rip current occurs at the wave breaking area near the beach, and the accident that is related to the rip current occurs every year in the world. Some generation mechanisms of rip current are known. For example, the rip current occurs at the sand beach that has the cusp topography, and occurs near structures such as the groins. In Niigata, there is not many large beach, and ordinary the beach is enclosed or semienclosed by the groins those were built to protect from the coastal erosion. This study tried to comprehend the generation mechanism of the rip current at the enclosed or semi-enclosed beach by the groins. Firstly, this study did field survey and comprehended the large scale and velocity of the rip current. In this method, the rip current was pigmented by the sea water colorant, and the pigmented current was observed by the velocity meter and recorded as the aerial photography by the UAV. Secondary, this study reproduced the rip current by the numerical simulation. The result was compared with the field data.
