Floating vegetation island (FVI) provides an effective way to remove excessive nutrition and pollutants in rivers. The Reynolds stress model (RSM) is employed to investigate the hydrodynamic characteristics induced by varied canopy densities of FVI in an open channel. In longitudinal direction, four regions are subdivided according to the flow development process: upstream adjustment region (L_UD), diverging flow region (L_DF), shear layer growth region (L_SD), and fully developed region. The increasing canopy density accelerates the flow adjustment in the diverging flow region and shear layer growth region, signaling a shorter distance to reach an equilibrium stage, while L_UD keeps a constant. The vertical profiles of the normalized velocity are found to be self-similar downstream of the diverging flow region. In the vertical direction, the streamwise velocity profiles in the mixing layer collapse for all …