Abstract

Hydraulics of open channels studies and analyzes the flow in rivers. Resistance to flow is one of the important and effective issues in open channels. Flow resistance in hydraulics of open channels is considered by using roughness coefficient of channel. Thus, determining this coefficient precisely is one of the important factors in the study of open channels. This coefficient is a function of various factors including soil type, shape of soil section, irregularity of path and so forth. Vegetation effect is one of the most important factors in determining the effect of vegetation coefficient which was studied in this article. To this end, Jarvela's method, Fathi Moqadam's method and Velzen's method were used. Sensitivity of roughness coefficient of vegetation to parameters contained in these methods was studied. Results showed that Fathi Moqadam's method overestimates and Jarvela's method underestimates roughness coefficient of vegetation. Therefore, Fathi Moqadam's method can be used for estimating roughness coefficient of important and valuable lands which need considering higher confidence coefficient of and Velzen's method and Jarvela 's method can be used for lands with lower importance.