LONG-TERM EVOLUTION OF SAND AND GRAVEL BEACHES ON THE MIYAZAKI COAST

Shinji Sato, Shun Kishimoto, Haruna Hiramatsu

Abstract


Long-term evolution of Miyazaki Coast was investigated in terms of four aspects, geology and geography,
comparison of shoreline in available maps and photographs, sediment retention analysis in watershed scale and sediment size as well as luminescence measurements of foreshore sediments. Geological and geographical analysis revealed steep topography in northern part and fluvial plain on the southern part. The total rate of sediment retention in reservoirs was found to be as much as 1.9 million m3/year. Historical shoreline retreat in the recent 200 years was significant in the northern region whereas severe erosion was developed in the last decades on the southern region close to the rivermouths of the Hitotsuse River and the Ooyodo River. The sand grain size and the thermoluminescence intensity were both found to decrease from north to south, implying the dominant direction of longshore sand transport is from north to south.

Keywords


long-term morphology; longshore transport; thermoluminescence

References


Liu, H., S. Kishimoto, T. Takagawa, M. Shirai and S. Sato. 2009. Investigation of the sediment movement along the Tenryu–Enshunada fluvial system based on feldspar thermoluminescence properties, J. Coastal Research, 25, 5, 1096–1105.http://dx.doi.org/10.2112/08-1065.1

Liu, H., A. Hamamoto and S. Sato. 2010. Investigation on the nourished sand movement in terms of luminescence measurements, J. Coastal Engineering, JSCE, 66, 1, 666–670 (in Japanese) .

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