ABSTRACT
The Unazuki dam and the Dashidaira dam, which are constructed in the Kurobe River basin with a large amount of sediment yields, have conducted the coordinated sediment flushing for the purpose of maintaining the function of the dam, preventing the degradation of the downstream riverbed and reducing coastal erosion. However, riverbed degradation and shortage of sediment with large diameters have been still in progress. In this paper, we develop the riverbed variation model by floods that can reproduce the sediment movement from and in the Unazuki dam reservoir by using the cross-sectional data before and after the coordinated sediment flushing during the flood. It was clarified that considerable amounts of large sediments such as 100mm and 50mm which contributes to the stability of the downstream river channel pass through a sediment flushing gate from the coordinated sediment flushing analysis.
