A heavy rainfall from the 12th typhoon in 2011 produced huge sediment in the Kumano river basin. The sediment may induce the severe influences such as the increasing of the reservoir sediment and the river bed aggradation. Therefore, the sediment management in this watershed supposedly becomes more severe. In this study, the sediment runoff model considering the sediment production and supply due to the landslide was applied in order to discuss about the sediment management in the next 100years. To obtain the spatial distribution of the initial grain size distribution, two stages of pre-calculations were em-ployed. As a result of application, the sediment management combining the control of the amount of sediment passing through the dams and the control of the sediment supply from the tributary rivers was turned out to be effective.