farhang forghanparast - Master student in Civil Engineering - Hydraulic Structures, Faculty of Engineering, University of Mohaghegh Ardabili, Ardabil, Iran
farid mohammadi - BS in Civil Engineering from the University of Tabriz, Iran
ghazal mohammadi - BS in Civil Engineering from the University of Guilan, Iran

The Roughness coefficient has a decisive role in determination of hydraulic parameters such as flow velocity and boundary shear stress which adds to the importance of this Issue.Despite all the research which has been going on, on the roughness coefficient there is no certain relation to calculate the exact value of it and it is only experimental methods which are being used.This paper attempts to provide a better understanding of some relations as well as using relations to estimate the roughness coefficient passing in open channels using Software (HEC-RAS). to achieve that we will study the simulation of the hydraulic behavior in the flood zones of different return periods and The height of the water at various points along the river ‘Siahrood’, in Guilan Province ,Iran and sensitivity analysis of parameters influencing roughness coefficient

Manning roughness coefficient, turbulent flow, laminar flow, fixed bed, moving bed