It is important that both of the hard and soft counterplans function well for the prevention of sediment disaster. However, the hard counterplans, for example, sabo-dams are not exactly understood about their role and effect. The author tried to make clear the role, the effect and the limit of sabo-dam for the prevention of disaster with the manual made by the Ministry of Construction and some case studies. From the case studies, the followings became clear. In the northwestern district of Hiroshima Prefecture, where the author had investigated and collected the data, the catchment area of torrent, where debris flow had occurred, and the sediment discharge of unit area were common. However, the proportion of the sediment gradient to the original bed gradient was smaller than the standard arranged by the Ministry of Construction. Though the sabo-dams functioned according to the plan, the number and the scale of the sabo-dams were not enough for the prevention of sediment disaster.