ANALYSIS AND FUTURE PROJECTION OF REGIONAL SEDIMENT TRANSPORT PROCESSES IN THE TENRYU WATERSHED AND THE ENSHU-NADA COAST

Abstract

  Regional sediment transport processes were investigated on the Tenryu River and the Enshu-nada coast. A numerical river sediment model was developed, which involved sediment dynamics in reservoirs and riverbed vegetation. The model was verified by the mineral properties of surface sand particles sampled in a wide area, which were identified by image processing technique based on a digital microscope. It was found that the spatial and temporal variation in sand properties reflected the local geology and the interruption of sediment movement by dam construction. Shoreline model was combined with the river sediment model and improved to account for individual movement of sediments from different sources. The model indicated that the interruption of sediments in reservoirs would eventually change sediment properties around the river mouth and degrade the beach durability against erosion unless effective countermeasures are introduced.