Field experiments on coarse-sediment displacement upstream of flood mitigation dams

This study deals with the transport behavior of the coarse-sediment at Masudagawa flood mitigation dam (FMD), Japan. Radio frequency identification system (RFID) was used to trace the displacement of the IC tagged particles following major flood events since June 2011. Through this, the relationship between recovery rate of the tagged particles and distribution of shear stress over the FMD bed was investigated. Moreover, this study attempts to provide a primary concept for sediment transport processes within the FMDs and to identify a linkage between governing morphological characteristics within the FMD and the transport behavior of coarse-sediment. This study shows that recovery rate of the RFID tagged particles is closely associated with hydro-morphological characteristics of each sub-zone upstream of FMDs. The upstream retention area of Masu-dagawa FMD was classified into three hydro-morphological regions. It was found that the characteristics of tractive force during a flood event within these three regions are different, resulting in transport behavior of the coarse-sediment. In addition, it was found that a small flood event may cause a larger volume of sediment deposition within the FMD compared to a major flood event.