Effects of vegetation on flow structures and bed profiles in curved open channels

Flow in curved open channels is characterized by a generation of the pressure-driven secondary now and the scour along the outer bank. Tt is expected that the vegetation can control the local scour and accumulation in curved open channels. In this study, three-dimensional mean flow structures were measured in curved open channels with various vegetation arrangements. Furthermore, experiments were conducted in a movable bed and the effects of vegetation on the local scour were examined. The secondary flow is generated only in the region outside the vegetated zones and the lateral scale of the vortex structures in bends are reduced. The main flow indicates complicated behaviors affected by the strong lateral shear, a centrifugal force and the momentum transport by the secondary flow. The vegetated area reduced the scour along the outer bank, but another scour around the vegetated zone was generated.