Recently, the expansions of riparian vegetation on gravel bars have been reported in many Japanese rivers. In this study, a numerical simulation model was proposed to predict the long term variations of the riparian vegetation area and the sediment deposition in the vegetated area in gravel river, in which the bar height was estimated by using an empirical relation obtained from the field data, and the vegetation destruction during floods was taken into account through the bar migration. The numerical simulation was performed under the discharge and the topographical conditions of the Tenryu river. The results of the computation show that the present simulation model can roughly estimate the expansion process of vegetated area and the amount of deposition of fine sediment fairly well.