Abbas Torabizadeh - PhD candidate, Faculty of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.
Ahmad Tahershamsi - Associate professor, Faculty of Civil and Environment Engineering, Amirkabir University of Technology, Teh-ran, Iran
Mohammad Reza Majdzadeh Tabatabai - Assistant professor, Faculty of Water and Environmental Engineering, Shahid-Beheshti University, Tehran, Iran.

Step-pools, which are composed of sequential steps and pools, are common features in steep and narrow channels. Steps are developed by large rock masses, while pools are formed because of the scouring energy of the tumbling flows in upstream of the steps. Morphology of step-pools and cascades reflect the geological and climatic factors affecting channels in mountain watersheds. Data analysis indicated that flow resistance is a function of geometric, bed material size, longitudinal slope and hydraulic radius characteristics. In this study using the data obtained from other researchers, the effect of these factors is separately evaluated on Chezy coefficient.

Step-pool, Flow Resistance, Mountain Streams, Chezy Coefficien.