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 the rip current are known. For example, about the rip current at the sand beach that has the cusp topography. However, the rip current occurs near the structures such as the groins or the detached breakwaters. In Niigata, there is not many large beach, and ordinary the beach is semi-enclosed by the groins or the detached breakwaters those were built to protect from the coastal erosion.
This study tried to know the current regime of the rip current at the semi-enclosed beach by detached breakwaters. Firstly, this study made the field survey, and comprehended the 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 UAV. Secondary, this study reproduced the rip current by the numerical simulation. Finally, this study concerned that the rip currents occur at both end of the cusp topography, and the wave conditions will be decided whether the both currents will merge or not.
