SEDIMENT VOLUME PREDICTION IN THE DIVERSION POOL OF THE KOSHIBU DAM SEDIMENT BYPASS TUNNEL USING BEDLOAD MONITORING IN UPSTREAM REACHES

Abstract

 Sediment bypass tunnel (hereafter SBT) is one of the countermeasures for reservoir sedimentation which bypasses inflow sediment to the downstream directly. For operating SBT efficiently, issues to be known are how and when to switch the inflow both for refilling the reservoir water volume and bypassing high concentration sediment, and to find the appropriate sedimentation height in the diversion pool to minimize the sediment inflow to the reservoir. In order that, it is required to predict sediment transport phenomena during SBT operations. In this study, we analyzed the field data at upstream river to predict inflow sediment discharge and created a sediment diversion model at the SBT diversion pool. Based on the comparison of several SBT operation rules, we have proposed the suitable excavation volume of the diversion pool to minimize the amount of sediment flowing into the main reservoir.