modeling laboratory-scale unsteady flow hydrographs: bed shear stress and sediment transport on rough surfaces

Hydroelectric dams represent the primary source of renewable energy in France but have a significant impact on the proper functioning of aquatic ecosystems by disrupting the ecological continuity of rivers. Indeed, these structures interfere with sediment transport by reducing sediment availability in downstream sections and causing major disruptions to the morphology and ecology of the environment. To offset this deficit, spawning ground restoration operations can be carried out to replenish sediments. Predicting sediment transport, particularly the remobilization of these sediments, is of paramount importance in order to accurately assess the durability of the inputs and their ecological effectiveness.

To better understand and quantify these phenomena, which are often difficult to measure in reality, experimental laboratory models are developed to replicate the hydrodynamic and sedimentary conditions observed in the field through scaling techniques. This development of the experimental model relies on preserving the Froude number (hydraulic) and the Shields parameter (sedimentary). These parameters enable the reproduction of flood hydrographs, river roughness, and the size of recharging sediments at the study site on a laboratory scale. A characterization of the hydrodynamic parameters on a rough bottom was then carried out using Particle image velocimetry (PIV), enabling the bottom shear stress to be estimated and compared with the displacement of localized sediment input.