Hydraulic Flood Routing Using Dynamic Wave Method and Comparison with Linear and Nonlinear Hydrologic Muskingum Routing Methods (Case Study: Lighvan-Chai)

Flow routing is a mathematical procedure for predicting volume change, speed, and shape of a flood wave in a channel as a function of time which is of great importance in river engineering, flood control and hazard reduction, river conservation, and modeling of flow in weirs and reservoirs. The solution of flood routing can be carried out using hydrologic or hydraulic procedure depending on conditions and existing information. In this research, hydraulic routing was carried out using 4-point finite difference Muskingum method based on St Venant dynamic wave equations. Furthermore, Muskingum linear and nonlinear hydrological approaches were applied for the purpose of comparing results of the methods and the parameters of Muskingum models were estimated using least square errors procedure. Along the reach of Mehranrood between Lighvan and Hervi hydrometer stations using upstream input hydrographs (Lighvan station) and downstream output hydrographs (Hervi station) 3 flood events were selected for flood routing. In hydraulic routing procedure, output hydrograph was obtained using input hydrograph and hydraulic characteristics of the reach. Hydraulic characteristics used in this method were longitudinal slope, side slope, bottom width and length of reach. In hydrologic routing procedure, one of the input flood hydrographs associated with the related output one were used for estimation of linear and nonlinear Muskingum models parameters. The resulted parameters then were used to evaluate the goodness of fit of the models by application of the two other input and output flood hydrographs. Results showed that hydraulic flood routing using dynamic wave method (4-point finite difference Muskingum method) was more compatible with the observed output hydrograph than Muskingum hydrological methods. Weak efficiency of the linear Muskingum model was also observed in comparison with the nonlinear one.