DEVELOPMENT OF NUMERICAL MODEL ON TRANSPORT PROCESS OF REPLENISHED SEDIMENT AND ITS APPLICATION

As a method of countermeasure to bed degradation and armoring phenomena of bed material in the downstream are of dam reservoirs, sediment augmentation has been carried out in many Japanese rivers.However, the effect of sediment augmentation on the bed elevation, sediment size and habitat in the downstream reach of the sediment augmentation has not been studied well because of the small amount of the replenished sediment. In this study, one dimensional bed deformation analysis is developed to simulate the sediment transport process of the replenished sediment in the Nakagawa, Tokushima. Here, the Japanese largest scale sediment augmentation has been performed in the Nakagawa.The results show that the developed model is able to simulate the sediment transport process from sediment augmentation. Furthermore, sediment deposition areas of each sediment size class are simulated. The coarse sediment is transported only within 3-4km. On the other hand, the fine material is transported to the downstream area from 10km to 20km. As a result, bed material from 4km becomes finer more than that near the replenished sediment area.