High-performance approach for estimating stage-discharge curves in the open channels

The stage-discharge relationship is one of the frequently used methods for continuous river flow measurement. In the management of water resources and flood control, the accuracy of the rating curve is a key priority. Various methods have been proposed for estimating the stage-discharge curves in open channels, including the model of Ahmadi et al. (2017) in which the rating curve was identified by utilizing the information of discharge at a referenced water level. In the present study, a novel approach was taken to improve that model by modifying its basic assumptions and employing multi-objective optimization. To this end, multivariate relationships were presented to determine the actual mean velocity in the flow cross-section. The unknown exponents of the proposed relationships were obtained by using the second version of the Strength Pareto Evolutionary Algorithm (SPEA2), and the appropriate equation was selected by applying the TOPSIS (Technique for Order Preferences by Similarity to an Ideal Solution) approach. The validity of the proposed method was assessed across 6 artificial and 6 natural hydraulic cross-sections. Results showed a close agreement between the estimated and observed data. In the next step, the results of the proposed method were compared with those of the previous model using the Mann-Whitney U test. The results demonstrated that the proposed model was more efficient than the previous one.