A model for lateral hyporheic flow based on valley slope and channel sinuosity

The meandering of rivers results in head gradients across point bar deposits leading to hyporheic exchange: the flow of groundwater from and back to the stream. Two models for predicting horizontal fluid flux through the hyporheic zone, one based solely on valley slope and another that uses both valley slope and channel sinuosity, are presented in this article. Both models require knowledge of aquifer hydraulic conductivity. The models are developed via a suite of groundwater flow simulations with boundary conditions taking a variety of channel geometries, idealized as sinusoidal, and valley slopes that we assume are similar to that of the water table. Functional predictive models are developed by fitting a line or surface to discrete model output which covers the spectrum of most natural meandering rivers. Since the fitted models only require channel slope and/or sinuosity (plus hydraulic conductivity), they are amenable for regional estimation of hyporheic flux using digital terrain data.