Frictional Coefficient for River with Exreme Large Rock Bed.

Abstract

The paper consists of three parts. I) Estimation model for projecting rock height distribution on the river bed; To normalize the figure of the bed which is extremely varies with river location, the projecting height distribution is calculated by astocastic model. II) Similitude for roughness coefficiant; To keep the kinematical similitude, it is necessary to satisfy, the following five restic condions, t_r=x_rh_r^-1 (Froude rule)(1), Q_r=x_rh_r^3/2 (discharge rule)(2), l_b=h_rx_r^-1 (geometric rule)(3), τ_or/ρ_r=R_rh_rx_r^-1 (boundary shear stress rule) or n_r=R_r^2/3x_r^-1/2 (Mannings rule)(4), α_r=1 (velocity distribution rule)(5), (r is the.ratio of the model to the proto type, ) If F_r, I_br and n_r are satisfied, it was substantiated to get Manning's n for the prototype. III) Hydraulic stracture of roughness: To estimate the represent roughness length forthe distributed diameter, a hydraulic stracture of the roughness was discussed.