Pages: 43-55

Abstract

Through studding open channel hydraulics with rigid bed, roughness coefficient could be assumed unchanged and after assigning one of the flow resistance formulas could be directly used for calculating of longitudinal slope and channel depth. Butt in river hydraulic the bed is mobile and the resistance against the current or on the other word roughness coefficient is changeable. In this case, we cannot use flow resistance formulas directly and without knowing of changing of resistance coefficient through different condition of flow and sediment. According to Mahpoor research (1385), none of parametric models has a suitable engineering attention to predict roughness coefficient. Hence in this research by using some of USA rivers data a new parametric model will be extended. Mix of geotechnical and hydraulic parameters and by using a nonlinear regression models will be assess and finally a new comprehensive model create.