ABSTRACT
Submerged weirs are low head hydraulic structures that span the full width of the channel for limiting excessive bed degradation and for bed stabilization. However, in alluvial rivers their presence in the flow also results in local scour which may undermine the structures themselves. A preliminary study on the scouring process at submerged weirs under live bed scour conditions is presented. It is observed that the average maximum scour depths upstream of the weir are found to be strongly dependent on the steepness of the approaching bedforms, and inversely dependent on weir height. The flow transitions from a surface flow regime to an impinging jet flow regime as the water level difference across the weir increases to a certain threshold; two different scour mechanisms downstream of the weir are observed corresponding to these two different flow regimes. The normalized downstream average maximum scour depth increases with increasing weir height.
