During uniform flow in an open channel, the resistance is dependent on a number of flow and geometrical parameters. The usual practice in one dimensional flow analysis is to select an appropriate value of roughness coefficient for evaluating the carrying capacity of natural channel. This value of roughness is taken as uniform for the entire surface and for all depths of flow. However, it is observed that the resistance coefficients for meandering channels are found to vary with flow depths, aspect ratio, slope and sinuosity and are all linked to the stage-discharge relationships. Although much research has been done on Manning's n for straight channels, a last word has not been spoken on the roughness values for meandering channels. An investigation concerning the variation of roughness coefficients for meandering channels with slope, sinuosity and geometry are presented. The loss of energy in terms of Darcy-Weisbach coefficient f is evaluated. A simple equation for roughness coefficient based on dimensional analysis is modeled and tested with the recent experimental data. The method gives discharge results that are quite comparable to that of the observed values as well as with other published data.

Accurate estimation of discharge in any open channel depends on the suitable accounting of the resistance coeffi cients. The energy loss is infl uenced by the channel geometry and fl ow parameters, which are assumed to be lumped into a single value manifested in the form of resistance coeffi cients in terms of Manning's n, Chezy's C, and Darcy-Weisbach f. The fl ow structure for meandering channels is more complex as compared to that of straight channels due to its three-dimensional motion. Consequently, the use of design methods based on straight channels is inappropriate when applied to meandering channels and results in large errors when estimating the discharge. A series of experimental results are presented concerning stage-discharge-resistance relationships for meandering channels with rigid and smooth boundaries. Investigation concerning the loss of energy of fl ows for meandering channels in terms of variation of Chezy's C due to variation of sinuosity, geometry, and longitudinal slope are studied. A discharge predictive method for meandering channel is proposed that accounts for the variation of roughness with depth of fl ow in the channel. The performance of the model is evaluated and is found to compare well with other available models.