小渋ダム上流河道の土砂動態と排砂バイパストンネル分派堰における土砂管理手法について

Abstract

Countermeasures for reservoir sedimentation are proposed such as dredging, excavation and sluicing. Sediment bypass tunnel (hereafter SBT) is one of those countermeasures which is to bypass inflow sediment to the downstream directly. It is currently operating at the Asahi, Miwa and Matsukawa dams in Japan. It has been also operating at the Koshibu Dam since 2016. Issues for the operation of SBT are how to optimize the operation such as opening and closing of the inlet gate of SBT under considering both the recovery of the reservoir storage and minimizing the sediment inflowing to the dam reservoir. In order that, it is essential to know the timing of sediment transport in the upstream river of the dam. This study shows the dynamics of inflow sediment measured by pipe type and plate type hydrophones and turbidity meter at the upstream river of the Koshibu Dam.