LAUSR

Abstract A riparian vegetation dynamics model was proposed to consider the mutual influence of hydro-morphology and vegetation dynamics in a sand-bed river. The simulation model consists of four sub-models: river flow and sediment transport, recruitment, growth and expansion, and destruction of vegetation. The numerical simulation was applied to the downstream part of a sand-bed river for predicting the vegetation dynamics over a long period. The model performance is validated by comparison with the field investigation results obtained from analysis of aerial photographs. The simulation results showed that the growth of vegetation starts from the shoreline and the downstream part of sandbars, and the riparian vegetation increases the stability and the relative elevation of the bars. From the good agreements of the temporal tendencies of vegetation recruitment, expansion, and destruction with those obtained from the aerial photographs analysis, the vegetation dynamics model proposed in this study was verified to reproduce the long-term trend of riparian vegetation dynamics fairly well. Finally, the model was applied to different sandbar modes, i.e., alternating bars and multiple bars. The simulation results indicated that the expansion and destruction rates of vegetation show similar tendencies for both bar mode cases, and they were mainly determined by the magnitude of the annual maximum flood. However, the amount of vegetation coverage rate in the alternating bar case was higher than that in the multiple bar case.