A case study of flood dynamic wave simulation in natural waterways using numerical solution of unsteady flows



Flood routing has many applications in engineering projects and helps designers in understanding the flood flow characteristics in river flows. Floods are taken unsteady flows that vary by time and location. Equations governing unsteady flows in waterways are continuity and momentum equations which in case of one-dimensional flow the Saint-Venant hypothesis is considered. Dynamic wave model as one of the flood routing methods is used for flooding operations because of its high accuracy. Finding the best numerical methods is the main challenge for optimal modeling of dynamic waves and predicting the flood behavior. In this study, a 78-km reach of Ghare-Aghaj River (between two hydrometric stations) is investigated and in addition to the unsteady flow equations (nonlinear Hyperbolic partial differential equations), Preissman implicit scheme and Mac Cormak explicit scheme which are both based on the finite difference numerical methods have been used. Developed models have also been compared with one of the most reliable Mike series computer program. It is aimed to find the most suitable finite difference scheme by comparing the results of two above schemes with the results of Mike 11 program. The results confirmed the superiority of Preissmann implicit scheme in predicting flood wave characteristics for the studied area.