2025 Volume 81 Issue 17 Article ID: 25-17037
The change in foreshore area along the east Enshu-nada coast was investigated using the aerial photographs. The foreshore areas in area I between Tenryu River mouth and Fukude fishing port and area II between Fukude fishing port and the Kikukawa River mouth decreased by 9.3×104 m2 and 8.9×104 m2, respectively, during 2010 and 2024. When multiplied the change in these foreshore areas by the characteristic height of beach changes of 12 m on this coast and divided by the elapsed time of 14 years, the rate of decrease in sand volume in areas I and II were estimated to be 8.6×104 and 8.2×104 m3/yr, resulting in the rate in decrease in sand volume of 1.68×105 m3/yr in areas I and II. The decrease in foreshore area I is due to the imbalance between eastward longshore sand transport and the rate of sand supply from the Tenryu River. In contrast, regarding area II, not only the imbalance in longshore sand transport but also the loss of sand by windblown sand are assumed to occur. Furthermore, in area III located at the eastern side of the study area, the foreshore area decreased by 5.01×105 m2 due to erosion between 1962 and 2010, resulting in exhaustion of shoreline sand.
