Throughflow

In hydrology, throughflow, a subcomponent of interflow, is the lateral unsaturated flow of water in the soil zone, where a highly permeable geologic unit overlays a less permeable geologic unit, and which returns to the surface, as return flow, prior to entering a stream or groundwater. Once water infiltrates into the soil, it is still affected by gravity and either infiltrates to the water table or travels downslope. Throughflow usually occurs during peak hydrologic events, and flow rates are dependent on the hydraulic conductivity of the geologic medium.