Journal of Agronomy1812-53791812-5417Asian Network for Scientific Information10.3923/ja.2006.536.540MoghadamM. Fathi-3200653To evaluate effects of flow rate and flow depth on friction factor, tree models of pine and cedar were subjected to a series of flow rates at different flow depths. To include effects of land slope on the analyses in this study, boundary shear approach (instead of direct drag force measurement) and dimensional similitude were used to develop a relation between flow velocity and land slope. Results showed that friction factor was considerably decreased, thus flow was less retarded with increase of land slope as a result of increase in flow velocity and streamlining of the vegetation. Also, friction factor increased with increase of flow depth due to submergence of more rough elements with flow depth.]]>Einstein, H.A. and R.B. Banks,195031603610Fathi-Moghadam, M.,19961996Fathi-Moghadam, M. and N. Kouwen, 19971235157Fathi-Moghadam, M. and A. Sharify,20052005Jarvela, J.,20021st Edn.,pp: 311-318pp: 311-318Jarvela, J.,20032003pp: 845856Jarvela, J.,200426170Kouwen, N. and M. Fathi-Moghadam,2000126732740Petryk, S. and G. Bosmajian,1975101871884Rautiainen, M.P., T. Stenberg, A.K. Nilson and H. Smolander,200329314323Ree, W.O. and F.R. Crow,19771977Stenberg, P., T. Nilson, H. Smolander and P. Voipio,200329363370Stephan, U. and D. Gutknecht,20022692743Stone, B.M. and H.T. Shen, 2002128500506USDA Handbook of Channel Design for Soil and Water Conservation, 19541954