FORMATION OF DYNAMICALLY STABLE LAKESHORE UNDER SEASONALLY CHANGING WAVE DIRECTION

In the Ukishima region of Lake Kasumigaura, beach nourishment along with the construction of groins has been carried out to recover a sandy beach. After the beach nourishment, part of the nourishment sand was transported away from the beach, turning around the tip of the downcoast groin owing to the oblique wave incidence in winter. To enhance the stability of the beach, the groins were extended and a spur dike was constructed. To design these structures, a numerical simulation using the BG model was carried out, and the optimum shapes were determined by taking into account the seasonally changing wave direction. The effectiveness of the spur dike was numerically evaluated using the BG model.