A Numerical Analysis About Suspended Sediment Deposition Around Filter Unit

Protection of the foot of river banks is generally set for the purpose of bank erosion countermeasures. Suspended sediment often deposits around such foot protections over time. The vegetation growing in the sediment area acts as an ecological habitat. This vegetation provides the possibility to increase the resistance of the foot protection from flowing water. This study performed a numerical analysis of suspended sediment deposition around a foot protection "filter unit (FU)" in a hydraulic experiment and a local river. The flow was calculated using a two-dimensional model, and the riverbed change was obtained from the calculation considering bed load and suspended sediment. In the hydraulic experiment case, the flow velocity decreased in the FU area due to the resistance of the FUs. Although the sediment was deposited in a low-velocity area, no deposition was observed in the excessively low-velocity area, because the suspended sediment did not flow into the area. In the actual river case, the sediment was not deposited in a high flow rate period because of the high flow velocity even in the FU area. During the low flow rate period after the flood peak, the flow velocity decreased in the FU area, resulting in sediment deposition.