Abstract
Comprehensive sediment management in reservoirs is required to preserve the capabilities of water resources facilities and to conserve the environment in rivers and coastal areas downstream of the reservoir. As one means of achieving the goals, ‘sediment replenishment’ has been carried out to excavate some of the sediment deposited in reservoirs, transport it to downstream of the dam, and discharge it into downstream rivers and finally into the sea with floodwater. This paper identifies the characteristics of sediment deposited in the Sakuma Dam reservoir in the Tenryu River and discusses the effects of ‘sediment replenishment’ on river bed changes. One dimensional numerical simulation shows that appropriate sediment excavation from the upper part of the Sakuma Dam reservoir and sediment supply to downstream rivers will contribute to maintaining both reservoir and river bed levels, and mitigating the armoring of river bed materials in rivers downstream of the Akiha and Funagira Dams. Consensus building among several stake-holders should be necessary to continue sediment replenishment for a long time successfully.
