GROUNDWATER DRAINAGE FLOW IN A SOIL LAYER RESTING ON AN INCLINED LEAKY BED

We study subsurface storm flow from a planar hill slope, a problem tha t is similar hydraulically to lateral flow toward drains in landfills. Our analysis is based on the linearized one-dimensional Boussinesq eq uation (Dupuit-Forchheimer approximation), which is extended to allow for leakage through the underlying barrier. This linear advection-diff usion equation has a greater range of validity than the kinematic wave equation. Stating it in terms of the discharge, the variable of prima ry hydrologic interest, we integrate it numerically, using an adaptati on of the Muskingum-Cunge routing scheme. A single-step computation of the outflow hydrograph, which combines the convenience of an analytic al solution formula with acceptable accuracy, is proposed as a design tool and as a means of parameterization of drainage from hill slopes. Depth profiles are determined afterwards by a simple integration of Da rcy's law. Examples of the buildup and recession phases, with and with out leakage, demonstrate the application of the computational method.