Φ-indices approach and multivariable regression analysis for prediction of discharge in asymmetric straight compound open channel flows

The measured discharges were compared with the predicted ones obtained from the Φ-indices methods with vertical, horizontal and diagonal interface planes; FI-V, FI-D and FI-H, respectively, with the use of three well-known methods for the computation of the apparent shear stress acting on the interface perimeter, τa, and the multivariable regression model for discharge prediction. At lower relative depth values, almost all the tested methods predict discharge with acceptable accuracy. In addition, as the relative depth increases, the results demonstrate a suitable accuracy of the FI-V with the vertical division lines and the multivariable regression model method. The multivariable regression model presented has been identified as the best-fit model in 26 cases out of 29 through minimization of the mean squared errors.