Hydrologic flood routing, in branched river systems via nonlinear optimization

The Muskingum method is one of the common hydrologic flood routing methods for rivers. The method is simple but its application is restricted to single reach problems. In order to apply this method for a certain reach two basic parameters should be determined first. These parameters are usually estimated by using trial and error combined with a curve-fitting technique. In this study, a method is proposed in which the calibration is performed by using a nonlinear optimization technique, which is capable to solve problems with more parameters. The proposed method is applied for (1) one river reach, (2) three branches in which six parameters must be determined, and (3) a river with an unknown intermediate catchment hydrograph. These problems were also solved by a sophisticated numerical hydraulic model applying the de Saint Venant equations. The comparison of the results indicated good agreement between the methods.