STUDY ON FEASIBLE CONDITIONS OF THE NATURAL SAND-STEAMING HOT SPRING BASED ON FIELD OBSERVATION IN IBUSUKI PORT COAST

Abstract

 In Ibusuki port coast, a coastal improvement project is in progress applying the idea of integrated shore protection system combining several coastal works and beach nourishment. In the project, the local groundwater environment including the “natural sand-steaming hot spring” should be carefully conserved, because that is an important tourism resource in the region. The natural sand-steaming hot spring bathing in Ibusuki is a unique one that warms the body in a layer of sand heated by hot spring groundwater. This method is unprecedented in the world, and the conditions for its practice are not fully understood. We have been conducting field observations on the groundwater and the thermal environment since 2018. This study intends to clarify the conditions for the implementation of the natural sand-steaming hot spring by analyzing these results. The feasible conditions are found to be specified as that the ground table is T.P. +0.7 m to +1.4 m, the surface temperature (the temperature at 0.2 m below the sand surface) is 65 °C to 80 °C, and the distance from the sand surface to the groundwater level 0.3 m to 0.6 m. It is also clarified that the surface temperature decreases linearly with the distance from the sand surface to the groundwater table.