From Hyporheic Science to River Restoration: The Contribution of Physically-Based Hydrological Models

Abstract:

River managers need practical tools to promote appropriately hyporheic functions in restoration schemes. Hyporheic ecosystems are largely controlled by hydrological processes, which may be simulated through physically-based models. Despite their apparent limitations (sophisticated, data-hungry, and computationally demanding), these models offer substantial advantages that may pertain to the operational level of river management: representation of specific landscapes, process-based sensitivity analyses, and alternative restoration scenario testing. This presentation builds on idealized and field-based studies, as well as literature examples, to discuss how physically-based models of hyporheic exchange can be fully exploited for restoration purposes. Results suggest that these models are best suited to map spatial patterns of exchange at the sediment-water interface, rather than to estimate HEF fluxes and residence times. Because subsurface data are typically unavailable or sparse, an approach combining high-resolution topographic data combined with a sensitivity analysis appears as a promising approach for: (a) delineating potential areas of upwelling and downwelling along longitudinal and lateral channel sections; and (b) highlighting potential differences in HEF characteristics between reaches. To achieve satisfactory simulations, however, the challenge lies in the topographic representation of the channel and the discretization of the mesh. Here, common pitfalls are identified, and guidance to overcome these is provided.