Numerical simulation of surface runoff with coupled two-dimensional overland flow and one-dimensional stream network flow

摘要

In the surface flow component of a physically based watershed model, the complete two-dimensional Saint Venant equations and their approximations are applied for overland flow simulations, while a one-dimensional counterpart is used for river/stream network flow. A suite of options including full dynamic wave, diffusive wave and kinematic wave models is included. When the wave propagation in surface runoff is dominated by inertial forces, the fully dynamic wave model is mandated. If the inertial forces are negligible, diffusive or kinematic wave models are appropriate. In the latter case, pressure forces are also neglected. For fully dynamic wave model, the method of characteristics (MOC), which is best suited for hyperbolic equations, is applied to approximate the governing equations. The simplified diffusive wave model is solved by either the Galerkin finite element method or semi-Lagragian method. Since the kinematic wave model represents the pure advec-tion of wave phenomena, it is suitable to use a semi-Lagrangian method. The hydraulic structures, river junctions and other internal boundary conditions are also completely incorporated into each option. The internal coupling at the interface of overland flow and stream flow are considered. Several numerical experiments are used to test the accuracy and stability of the new numerical model.