The study of vegetation evolution is essential for further understanding of biogeographic feedback and ecological restoration. In this paper, a vegetation evolution model based on velocity threshold (scaled by the average flow velocity of the bare bed) was established to simulate the vegetation evolution process in compound channels. In this model, the effect of vegetation on water flow was generalized as equivalent Manning coefficient, and the velocity field was obtained by solving two-dimensional shallow water equations. The model defined that new vegetation was added in areas where the velocity was less than the velocity threshold, and conversely, vegetation was destroyed in areas where the flow velocity exceeded the velocity threshold. The model was used to explore the effect of velocity threshold, initial vegetation coverage, and relative water depth (the ratio of the flow depth in the floodplain to that over …