The management of runoff and sediment discharge in a mountain watershed requires a watershed]management system(WMS)that predicts runoff and sediment discharge in any stream section under given rainfall conditions. As part of this system, a rainfall]runoff model has been developed. As an example, the Sumiyoshi River on Mount Rokko has been selected. This paper discusses a sediment discharge model and a deformation of riverbed model as part of this system. We examined a WMS consisting of a rainfall]runoff model, a sediment discharge model and a deformation of riverbed model. The WMS was used to express almost exactly the movement of water and sediment in a mountain watershed, using the Sumiyoshi River as an example. 1) The mountain watershed was divided into many reaches with0]order basins. Sediment discharge was evaluated as debris flow, not as shallow landslides like it was in most previous models. The discharge rate of landslides did not need to be considered with this method. 2) A rainfall]runoff model based on a kinematic wave method, the model which multilayered the intermediate flow layer in the upper layer and a lower layer was introduced, and the water]holding capacity of mountain land was modeled. 3) Sediment discharge was calculated by assuming erosion or debris flow based on the hydraulic quantity of 0]order basins. 4) The deformation of riverbed was calculated by considering the sediment discharge from the valley part computed by the sediment discharge model. And the influence of sediment passing over a Sabo dam, the change in water level caused by the Sabo dam, and the effect that a sediment discharge has in terms of reducing sediment removal were examined. The results showed that, each model reproduced the sediment transport observations of the Sumiyoshi River satisfactorily.

Key wordsFwatershed]management system(WMS), sediment discharge model, deformation of riverbed model,Sumiyoshi River, Mount Rokko