Computation of the main channel and flood plains discharges using new methods of optimization

Due to momentum exchange between main channel and flood plains, the flow hydraulic in compound channels is complicate. Most studies in this area are focused on prediction of the average cross sectional velocity and total flow discharge, while distribution of flow rate in the main channel and the flood plains is also important. In flood conditions and during the spill of water onto the flood plains, the bed load and suspended sediment load are transported mainly by the main channel flow discharge and floodplain flow has very little effect. Moreover, for simulation of river morphology, the individual velocity and shear stress in the main channel and floodplains are needed and utilizing the average cross sectional velocity led to erroneous results. In this study, using 102 laboratory stage-discharge data from canals with compound channel sections, the individual flow discharges in the main channel and floodplains are calculated with aid of two new optimization methods of Genetic Programming and Decision Tree Model and then compared with one-dimensional empirical methods. Results show that these two new methods with mean error of 2.1 and 6 %, respectively, have appropriate ability for main channel’s flow discharge prediction. Among the empirical methods, the vertical divided channel method with mean error of 19% has the largest error in this regard. For floodplain’s flow discharge prediction, in addition to Genetic Programming and Decision Tree Models, the vertical divided channel method has considerable accuracy.