A unified depth-averaged approach for integrated modeling of surface and subsurface flow systems

A two-dimensional depth-averaged continuum framework is developed for simulating the interaction of flows outside and within porous media. A unique set of generalized equations applicable to both surface and subsurface systems is derived originating from conservation laws of microscopic variables with first volume-averaging and then integrating vertically. The model is free of ad-hoc coupling as interface conditions are satisfied implicitly owing to the generalized nature of the governing equations. The set of depth-integrated equations (unconditionally hyperbolic) is resolved by employing a Total-Variation-Diminishing MacCormack scheme. The developed model is validated with four one-dimensional experimental test-cases (containing both Darcy and non-Darcy regimes) and applied to a demonstrative two-dimensional scenario having various interface conditions. Results obtained from the proposed framework highlights the potential applicability of the generalized model for diverse time-scales and vertical/ sloping interface conditions.