We will describe a physically-based distributed catchment-scale model for the simulation of coupled surface runoff and subsurface flow. The model is based on coupling Richard’s equation for variably saturated porous media and a diffusion wave approximation for surface water dynamics. The numerical scheme uses a finite element Richard’s equation solver, FLOW3D and a surface DEM-based finite difference module, SURF-ROUTE. Retardation and storage effects due to lakes or depressions are also implemented, to give a complete description of the catchment flow dynamics.
