Prediction of Manning Roughness Coefficient in Meandering Compound flow

Abstract

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 channels. 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 coefficient for meandering channels are found to vary with flow depths, aspect ratio, slope and sinuosity and are all linked to the stage-discharge relationship. Although much research has been done on Manning’s n for straight channels, its dependence on the different parameters for a meandering channel is necessary to be studied. Factors affecting the roughness coefficient in a meandering compound channel are investigated and used in its prediction, particularly Manning’s roughness coefficient by dimensional analysis. Observations of various researchers, on the laboratory study of meandering channels is used to investigate the factors affecting Manning’ n for large scale as well as small scale channels.