EXPERIMENTS ON THE EFFECT OF RIVERBANK VEGETATION ON CHANNEL MORPHOLOGY: THE CASE THAT THE ROOTS ARE SHORT RELATIVE TO THE BANK HEIGHT

Abstract

 To understand the influence of shallow-rooted trees on channel morphology and river planforms, we conducted hydraulic experiments using bentgrass as a substitute for shallow-rooted trees, such as willow trees, that commonly flourish along the banks of gravel-bed rivers. The experiment demonstrated a meandering flow progression that maintained a channel planform with curved bank lines. Vegetation did not significantly inhibit bank erosion near the apex points in the meandering channel, where the bed near the riverbank was relatively deep. Conversely, vegetation inhibited bank erosion downstream of the meandering channel, where the bed near the riverbank was shallow. The results suggest that the inhibitory effect of vegetation on bank erosion varies depending on the riverbank height and channel depth, thereby influencing the channel morphology and river planform characteristics.