EFEECTS OF WEIR WITH AN OPENING ON RIVER BED DEFORMATION

Abstract:

River-crossing structures such as dams and weirs have provided various benefits to people. However, it has been indicated that these structures cause several issues in a river. In the upstream of the river-crossing structure, the flow velocity decreases due to backwater. The river-crossing structures cause decreasing the flow velocity due to backwater. Moreover, river-bed level rise because sediment transport is interrupted by these structures. In this study, we focused on the fact that a weir with an opening activates the fluidity of the sediment compared with conventional continuous fixed one and examined the removal function of the sediment deposited upstream of the weir. Experimental results showed that the weir with the opening increased the fluidity of the sediment deposited upstream of the weir and lowered the riverbed. The scouring section upstream of the weir was divided into a gradually varied flow section and a local flow section based on the bed topography. In the gradual flow section, the descent of water level and river bed increase linearly as the opening depth increases. In addition, it was shown that the local scour shapes upstream and downstream of the weir were similar to each other as a result of normalization on the representative scale of vertical and transverse shapes.