2026 年 19 巻 1 号 p. 8-18
The Joganji River basin has experienced numerous severe sediment-related disasters due to the vast sediment deposits (approximately 0.1 billion m3) originating from a massive mountain collapse triggered by the Hietsu earthquake in 1858. Over the past century, numerous sabo facilities have been constructed, effectively reducing sediment runoff from this mountainous region. Monitoring of bedload and debris flow has been conducted since the 1960 s in this basin. In October 2012, a sabo dam with a movable shutter, i.e., an adjustable gate system designed to regulate sediment discharge during floods, was installed in the middle reaches of the river to control sediment transport. The effectiveness of sediment control operations has been monitored using sensor data collected around dams. Pilot operations have been conducted during flood events since July 2016 using five distinct operational patterns, most recently on 8 July 2020 and 1 July 2023. The performance of the movable shutter system was evaluated through these controlled flood operations. The present study introduces recent examples of applied sediment control using the movable shutter at the Myoju Sabo Dam. Active control of sediment runoff during floods was demonstrated using multiple sensors, including the Japanese pipe-hydrophone, photoelectric sensors (PE), and submerged load cell. Differences in the longitudinal distribution of bedload and wash load were observed depending on the shutter operation method, providing insights into effective flood-time sediment management strategies
