BEACH CHANGES ALONG ENTIRE YUMIGAHAMA PENINSULA INCLUDING HINO RIVER DELTA AND THEIR REPRODUCTION USING CONTOUR-LINE-CHANGE MODEL

Abstract

 Long-term shoreline changes between 1899 and 1967 under the natural conditions and between 1967 and 2010 after the various alterations along the Kaike coast extending along Yumigahama Peninsula in Tottori Prefecture were investigated on the basis of old geographical maps and aerial photographs. The changes in fluvial sand supply from the Hino River, being a major sand source to the Kaike coast, and the distribution of longshore sand transport during these periods were estimated. The bathymetric survey data obtained since 1980 when various coastal structures had been constructed was also analyzed. Given the estimated fluvial sand supply from the Hino River, long-term beach changes of the coast were reproduced using the contour-line-change model considering the change in grain size as a reduction process of the Hino River delta. Then the beach changes triggered by various artificial changes were reproduced. The measured and predicted three-dimensional beach changes were in good agreement. Furthermore, beach changes after the suspension of sand back pass which has been carried out on the Kaike coast and the exhaustion of sand supply from the Hino River were predicted using the contour-line-change model. It was concluded that sand back pass and appropriate volume of sand supply from the Hino River was important to maintain the sandy beach of the Kaike coast.