Effects of Different Routing Parameters on the Accuracy of the River Flood Routing Using the Muskingum-Cunge Method

Flood routing is a technique to determine downstream flood hydrographs that is important. The Muskingum-Cunge method is one of the flood routing methods. In the present study, the accuracy of the Muskingum-Cunge method is investigated using the river reach located between the Mollasani hydrometric station in the upstream, and the Ahwaz hydrometric station in the downstream of the Karun River. The results indicated that using three different values for the parameters of the Muskingum-Cunge method instead of using a constant value as well as the monoclinal wave equations in calculation of the kinematic wave velocity, the accuracy of the Muskingum-Cunge method in estimation of the outflow hydrograph increased. In the present study, the inflow hydrograph was classified into the start, peak, and end of the flood sections, and different values for the parameters of the Muskingum-Cunge method were calculated for each of the three sections. In addition, using the Particle Swarm Optimization (PSO) algorithm, the time step (Δt) of the three sections was also optimized, which in turn improved the calculation accuracy of the Muskingum-Cunge method in estimation of the outflow hydrograph. The Mean Relative Error (MRE) and Relative Error in estimation of the peak discharge (DPO) by using the conventional Muskingum-Cunge method with constant parameters and a time step of 1 hour was calculated as 6.15 and 7.63 percent, respectively. However, using the proposed method in the present study, the corresponding error values of 1.69 and 4.9 percent were obtained, respectively.