Empirical analysis of backwater level due to skewed bridge constriction

A simple empirical method is proposed for computing the backwater level for different bridge shapes and crossings in compound channels. A series of parametric studies was conducted on the influence of the Froude number, opening ratio, discharge and roughness coefficient on the backwater depth. The results of the parametric studies, along with multiple regression analysis, were used to derive a simple accurate mathematical model for computing backwater depth. The proposed method was first compared with the energy method for different skew angles and roughness cases. Comparison of the results of the proposed method and the energy method showed good correlations. The proposed method was also validated by comparing its results with experimental data for normal and skewed crossings at 30° and 45°. The overall absolute average percentage difference between the proposed method and the experimental data was found to be 5.1%, while the overall root mean square error was found to be 0.008.