This paper presents different sediment management techniques of Japanese dams with focusing on sediment bypass tunnels. In Japan, Miwa dam on the Tenryu River and Asahi dam on the Shingu River are good examples for sediment bypass tunnels where routing incoming sediment directly to downstream reaches. These dams are practically using sediment bypass tunnel successfully to realize a sustainable reservoir management. The paper aims at how to select this technique among several other solutions and introducing monitoring techniques to improve sediment bypass operation. The results show that sediment bypass is suitable for medium size reservoirs with steep original river bed slope and effectively functioned for successful reservoir sediment management. The facility proved its effectiveness in mitigating reservoir sedimentation in Miwa dam and turbidity of river water contributing towards restoration of downstream environment.