A monolithically coupled surface water and groundwater finite element model with fully implicit time stepping using Adaptive Hydraulics (AdH) v5.0 (Kraken)

Simulation of surface water and groundwater interaction is becoming increasingly important for the US Army Corps of Engineer Civil Works and Military Missions. This report details the formulation of a monolithic, coupled approach that combines the Richards equation for variably saturated groundwater flow and a diffusive wave approximation for overland flow. The model is implemented with USACE’s Adaptive Hydraulics (AdH) computational framework and is evaluated for several community benchmark problems. The results indicate that the AdH model is stable with performance similar to existing, well-established codes for surface water and groundwater interaction.