The Effects of Added Vegetation on Sand Bar Stability 1 and Stream Hydrodynamics 2

Vegetation was added to a fully-developed sandy point bar in the meander of a 5 constructed stream. Significant changes in the flow structure and bed topography were observed. 6 As expected, the addition of vegetative resistance decreased the depth-averaged streamwise 7 velocity over the bar and increased it in the open region. In addition, the secondary circulation 8 increased in strength, but became confined to the deepest section of the channel. Over the point 9 bar, the secondary flow was entirely outwards, i.e. towards the outer bank. The changes in flow 10 led to changes in bar shape. Although the region of the bar closest to the inner bank accumulated 11 sediment, erosion of the bar and the removal of plants by scouring was observed at the interface 12 between the planted bar and the open channel. 13