ABSTRACT
Accurate estimation of roughness in a compound channels is an important aspect in River hydraulics. Researchers have suggested equations for estimating composite roughness of an open channel flow which are good for simple channels and do not incorporate the interaction mechanisms that exist in a compound channel. An experimental investigation is performed to study the dependency of geometry, roughness and flow parameters for predicting composite roughness of non-homogeneous compound channels. Standard methods of predicting the composite roughness of compound channels are reviewed and applied to the new experimental rough compound channels for different flow conditions. Effectiveness of these methods is discussed and modification to the standard method is proposed. The new approach is found to give better results as compared to the other approaches when applied to the experimental data sets, large channel of FCF data sets and some natural river data sets.
Keywords: compound channels; composite roughness; stage-discharge relationship; non homogeneous compound channel; different roughness
