Experimental Study on Riverbed Scouring Downstream of Weirs in River Channels with Alternating Bars

A large amount of gravel was dredged from riverbeds for use as construction materials and for enlargement of cross-sectional area of flood flow. In many cases, this resulted in the riverbeds being further worn away, and localized scouring downstream of weirs has caused problems. In order to analyze the configuration and depth of such scouring, we had to consider the following two important viewpoints: the formation of alternating bars on the riverbed and the degree to which the riverbed was lowered. In our experimental study, we used experimental channels in which alternating bars and meandering water flows were simulated. The experimental results clarified that the shape and depth of a scoured riverbed vary greatly according to the positioning of the alternating bars and weirs relative to each other. The riverbed suffered considerable scouring downstream of the weir located along a winding riverbank against which flood water collides. We also found that a riverbed suffers deeper scouring if the amount of water flowing is increased.