Impacts of approach bedforms on live-bed scour at rock weirs

Rock weirs are river restoration structures used for grade control, raising upstream water level and restoring river habitat. This paper presents an experimental study of local scour at rocks weirs under live-bed scour condition. The effects of approaching bedform, flow intensity, weir height and void ratio on the scour depth at rock weirs are analyzed and discussed. Under clear-water scour condition, scour occurs only at the downstream of rock weirs; the equilibrium scour depth increases with increased flow intensity and weir height, but decreases with increased void ratio. Under live-bed scour condition, scour occurs both upstream and downstream of rock weirs. The equilibrium upstream scour depth increases first and then decreases with increased flow intensity, decreases with increased weir height, and has a complex relationship with increased void ratio. The equilibrium downstream scour depth decreases first and then increases with flow intensity, increases with increased weir height, and decreases with increased void ratio.