Abstract
In Ibusuki Port Coast, a coastal improvement project is in progress applying the idea of integrated shore protection system combining jetties, offshore breakwaters, seawalls and beach nourishment. The preservation of the hot spring groundwater environment, especially the "Natural Sand Bath", which is an important tourism resource in this area, is an essential issue in the project. Incorporating understandings by the field observations focused on feasible conditions of the sand bath, this study analyzes the impact of the beach nourishment on the groundwater and sand temperature characteristics both for the present and after nourished beach forms based on a groundwater and heat transport model. The sand temperature after the beach nourishment work was estimated from the computed ground water level and by use of an empirical formula to relate the level to the sand temperature. As a result, although even after the nourishment the sandy beach meets the feasible conditions of the sand bath at the same ground level as the present situation, it is predicted that various risks may arise by the beach nourishment, such as narrowing of the feasible area for the sand bath and decreasing in the ground surface temperature at the optimum sand bath level by shifting the beach area offshore where the temperature is affected by a cooler water mass of the sea.
