ABSTRACT
Sediment replenishment is one common restoration technique to tackle the sediment deficit problem caused by dam construction. The additional sediment supply from replenishment site is beneficial for recovering downstream morphology and aquatic ecosystem. In this paper, we would like to develop a novel methodological approach for assessment of the riverine system during implementation of sediment replenishment in the Naka River, Japan and the Buëch River, France. Key factors for replenishment (placed volume and transported volume, magnitude and duration of flushing flow), and downstream impacts (habitat structures, flow velocity, water depth, riverbed level and substrates, fish species) are considered. Several indices for replenishment and riverine assessment, such as Transported ratio (TR), GUS (Geomorphic Units Survey), BCI (Bed Change Indicator), and Fish Diversity Index (H Value) are determined to statistically evaluate the replenishment works. The results show that the efficiency of SR erosion of France project is higher than Japanese project due to the different optimization strategies. Moreover, both projects can enhance the downstream morpho-ecology by increasing the numbers of GU and promoting the diversity of fish species. It is recommended to conduct continuous SR with adaptable sediment supply to maintain such positive impacts on downstream reach.
