Test-run plan and environmental monitoring plan for reservoir sedimentation control facilities in Miwa Dam Redevelopment (interim report)

Abstract

Sedimentation is progressing in the Miwa Dam due to the inflow of large amounts of sediment resulting from floods. In order to recover storage functions, a redevelopment project has been underway since 1987. In the redevelopment project, the sediment bypass facilities which are sediment bypass tunnel, diversion weir and check dam completed in 2005 whereas additional reservoir sedimentation control facility, which is the first trail in Japan, is still under construction. This facility will dredge and convey sediment, which overflowed the diversion weir during floods and accumulated in the dam reservoir, to a "stockyard" located upstream of the diversion weir. When the sediment bypass facilities go into operation, these sediments will be eroded and discharged to the sediment bypass tunnel by the tractive force of the guided water flow from upstream channel during floods. This paper reports on the test-run plan and the environmental monitoring plan for this additional reservoir sedimentation control facilities.