In this research, the performance of the combination of a cable and a collar and their effect on scouring in single and pier groups in clear water conditions has been investigated. The piers have been tested in 3 groups: a single pier, a double pier group, and a triple pier group. In addition, studies were carried out with and without cables and collars aligned in a linear manner, in the direction of flow. The diameter of the tested cylindrical piers was 3 cm, and the distance between them was three times the diameter. The cable diameter was 15% of the diameter of the piers, and the twisting angle of the cable around the piers was 15 degrees. The collars were 2.6 times the diameter of the pier and 2 mm thick. The synchronous combination of the cable and collar causes the reduction of horseshoe vortices due to the impact of the flow and the decrease of scour depth. The maximum decrease of the final scouring depth related to the single pier with a cable and a collar compared to the single pier without a collar and a cable is 66.82%. In addition, the final scouring depth of the first pier of the triple group compared to the first pier of the double group is 78.61%.
