Vegetative filter strips-Effect of vegetation type and shape of strip on run-off and sediment trapping

Vegetative filter strips (VFSs) are a common type of off-site method used to enhance the sustainability of catchment systems by promoting desirable soil and landscape functions. The transport of water run-off and sediment to downstream reaches can be restricted by VFSs in the flow path. The adoption of VFSs is increasing because they have been demonstrated to be effective for trapping run-off and sediment. Thus, an optimized design procedure for developing VFSs is required. To further understand the roles of both vegetation type and geometric size in the design of VFSs, global sensitivity analysis (GSA) within the Vegetative Filter Strip Modeling System was conducted using a traditional elementary effect test and a novel density-based method called PAWN. The analysis involved both a uniform and a concentrated flow scenario. The GSA outcomes indicated that the inputs related to vegetation type were vital for the VFS design, especially in terms of the run-off reduction function of the VFS, irrespective of the scenario that was used. The vertical saturated hydraulic conductivity was the main input responsible for the influence of vegetation type. The inputs related to vegetation type had limited influences on the sediment trapping performance of the VFS, which was shown to be mainly controlled by the length of the VFS. The role of vegetation type in the design of VFSs must be fully considered, especially in cases in which VFSs are established primarily for flood control or run-off reduction purposes.