Hossein Afzali Mehr - Professor, Faculty of Civil Engineering, Iran University of Science and Technology
Ehsan Shahiri Tabarestani - Ph.D. Candidate in Hydraulic Structures and Water Engineering, Faculty of Civil Engineering, Iran University of Science and Technology
Ali Eidi - Ph.D. Candidate in Hydraulic Structures and Water Engineering, School of Civil Engineering, College of Engineering, University of Tehran
Sanaz Hadian - Ph.D. Candidate in Hydraulic Structures and Water Engineering, Faculty of Civil Engineering, Iran University of Science and Technology

The purpose of this study is to quantify the outer part of the boundary layer by mathematical rules and to investigate the boundary layer characteristics in two directions in order to avoid estimation problems and calculate factors such as erosion initiation and flow resistance. Lasem river field data has been used for comparison. From the results, parabolic law could well parameterize the outer part of the boundary layer, however, the inner part does not comply with this law. A comparison of the frictional velocity from the parabolic law and the boundary layer characterization method yields less than a 30% difference

Boundary Layer, Gravel-Bed River, Parabolic Law, Logarithmic Law, Lasem River