Factors affecting roughness coefficient in a meandering compound channel are investigated and used to predict Manning’s roughness by dimensional analysis. Factors affecting Manning’s roughness, are considered to be geometric as well as hydraulic, namely relative depth of flow, width ratio, bed slope and sinuosity for a meandering compound channel. An experimental investigation was carried out for the highly meandering channel of sinuosity. Observations of various researchers, on the laboratory study of meandering channels have also been used in the investigation. The proposed equation for predicting composite Manning’s roughness is used to estimate the conveyance of a channel with floodplain flow. The proposed dimensional analysis model is observed to predict the conveyance capacity better than other existing methods of Manning’s n prediction.