Analysis of Surface and Sub-Surface Flows
J. Bridget Avendt and Nikolaos D. Katopodes
A finite volume based numerical model for unsteady, two-dimensional shallow water flow and transport over arbitrary terrain is coupled to a finite element model simulating water and solute movement in three-dimensional, variably saturated media. The surface model is capable of simulating wetting and drying of variable topography. The subsurface model solves Richards’ equation for variably saturated flow, and the Fickian-based convection dispersion equation for solute transport by means of Galerkin’s scheme. The two models are coupled using surface boundary conditions and infiltration rates. The two-dimensional grid for the surface model comprises the top layer of the groundwater model. The depths calculated on the surface are incorporated as fixed boundary conditions for the subsurface model. In turn, the vertical velocities found using the subsurface program serve as infiltration rates for the source term in the surface flow calculation.