Abstract: Aquatic vegetation plays an important role in the flow structure in open channels and thus changes the fate and transport of sediment.This paper proposes a 3D turbulence rmdel,introducing vegetation density and drag force to the control equations of water flow with vegetation.The impacts of submerged vegetation on the vertical profiles of horiwntal flow velocities,the changes of the depth-averaged flow velocities in a compound channel with emergent vegetation in the floodplain,and the bed surface topography changes around and in a vegetation island are calculated by the model.The calculated results show a good agreement the with experimental results.