The channel routing in Visual OTTHYMO was tested using a natural channel, 5200 m long, main channel bed slope is 0.001, Manning’s n is 0.03, floodplain bed slope is 0.001, Manning’s n is 0.05, no lateral flow, the cross-section parameters are shown in the figure below.


The simulation results from Visual OTTHYMO-MC are compared with the complete unsteady flow equation (SWMM-EXTRAN) and Visual OTTHYMO-VSC and are shown below in the figure below.


The results show that the Muskingum-Cunge (MC) routing method compares very well with the complete unsteady flow equations of EXTRAN. The peak discharge is attenuated slightly more from EXTRAN than that from the MC method; however, the time to peak for both methods is the same. The difference in peak discharges could be due to the fact that the inertial terms in the complete unsteady flow equations are becoming more dominant when rapidly rising hydrographs are routed through the flat channel, compared to the bed slope, as the channel slope is decreased. The Muskingum-Cunge routing method does not account for the inertial effects, and consequently the method tends to show more diffusion than what may actually occur.


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