2019 Volume 75 Issue 2 Pages I_151-I_156
A water accident occurred in August 2017 at Koga beach. This beach has the groins at the both ends of the beach. When the accident occurred, two children played at the shallow depth area of the edge of the beach, however big waves suddenly incidented to the beach, and the children carried away to the offshore. In this research, we tried to grasp the reason why the accident occurred. Firstly, we conducted the field survey, and we interviewed the rescuers of Fire Department and Japan Coast Gurad of this resion, furthermore, we got the geographic feature of the domain. After the survey, we made the geographical grid data for the numerical simulation. Secondary, we analyzed the wave data of a wave observatory where locates about 20km away from the beach. As the result, the wave from NNE direction was prevalent in this domain. However, Koga beach is located at the base of a peninsula, therefore, when the wave incidents from NNE, the peninsula impedes the wave incident directly. Therefore, we consider the wave height decreases. When the accident occurred, the wave direction fluctuated from NNE to NNW, therefore, wave incidented directly and the wave height increased. We considered that this phenomenon was the one of the reason why the accident occurred. Thirdly, we tyied to grasp when the same phenomenon might occur by the weather chart. As the result, we considered when the low pressure passses the south of the beach and passes the east, the same phenomenon might occur.Finally, we simulated the wave dynamics in the beach when the wave increased. As the result, the wave velocity became over 3 m/s around the accident occurred point.
PROCEEDINGS OF COASTAL ENGINEERING, JSCE
PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING
