Most bridges over waterways are susceptible to the local scour of the piers. Methods have been developed to control, reduce or eliminate the local scour. These methods have been mainly categorized in two groups. The first group involves techniques to increase the bed material resistance against scouring. The second one is to change the flow patterns and reduce the power of the existing vortices; i.e., using collars or slots. A collar is a plate attached to the bridge pier to delay the formation of the vortices. In this work, new shapes for collars have been proposed and compared with the...