Displacement of sediment caused by deformation of the flow pattern, causes scour and depression at the bottom of the rivers and bridge piers. This phenomenon is considered as one of the reasons of demolition and unsustainability of the bridges. During the past decades, various methods of confronting, controlling and scour reducing are proposed. In addition to the bed characteristics of the ben that is one of the important factors in erosion, hydraulic factors also play a significant role in the occurrence of this phenomenon. In this research, simultaneous usage of roughness and collar in local scour reduction in different experimental conditions was evaluated and studied. The experiments were conducted under clear water scour and a constant discharge of 21 L/S for a period of 8 hours for the experimental piers which included piers with usage of roughness and collar in different conditions. All experiments were done in a flume of 8 m length, 0.4 m width and 0.6 depth at the Hydraulics Laboratory of the Isfahan University of Technology. Plastic circular piers with diameters of 3 cm were used. Scour pattern was studied and its local depth was measured and results were also verified. Results were shown that using roughness is actually effective in scour depth reduction. Also studying the collar with diameters of 2, 2.5 and 3 times the diameter of the base pier individually and simultaneously, shows a tremendous impact on scour reduction due to simultaneous usage of roughness and collar. The results was also shown that simultaneous usage of collar with diameter of 2.5 times the pier diameters and also 15 mm roughness as the optimal case, was improved the scour depth reduction from 55 to 96 percent. Also using of the collar with diameter of 3 times pier wasn’t shown a significant difference with the selected optimal case and was not considered. Further analysis of the velocity profiles and the stress around the pier revealed the existence of horseshoe vortex and downward flow simultaneously at the upstream of pier. In addition, the existence of wake vortex in the downstream caused serious fluctuations in flow structure. Quadrant analysis further revealed that Ejection and Sweep are the dominant phenomena in the process of scour. Keywords: Local scouring, Scouring depth reduction, Roughness and Collar, Flow structure, Quadrant analysis