Forestation in rivers generally causes reduction of river flow capacity. Therefore, we have to manage a vegetation condition in the river properly. The object of this study is to forecast the vegetation condition with enough accuracy for effective management tasks. We had conducted a field observations of an annual vegetation growth rate, hydraulic conditions of wash out and lodging of vegetation, and bed deformation at Ohara area in the Asahi River from 2008 to 2013. Then, we developed a vegetation dynamic model based on the field observations. We simulated the vegetation condition at Ohara area in 2013 by using this model, and also examined the model by comparing the simulation results with an aerial photograph taken at Ohara area. The simulation results showed that the model can basically reproduce vegetation condition in Ohara area.