Dams are important water infrastructure whose main purposes can be compromised by sedimentation. This causes loss of storage volume, affecting river sediment fluxes and morphology. However, sediment management strategies can be implemented to reduce these impacts. Our goal is to characterize and quantify key processes of an idealized and reduced physical model of water injection dredging, applicable as a sediment management technique. Three sets of experiments were conducted, varying the following parameters: (a) jet discharge; (b) jet angle; (c) bed angle. The spatio-temporal evolution of the main physical processes (scour hole formation, sediment suspension development, and downstream deposition) was analyzed using images of profiles acquired during the experiments. We identified two distinct transport modes depending on how the jet flow connects with the turbidity current, each associated with different stages of scour hole development. In our experiments, the bed-perpendicular component of the exit velocity (momentum) of the jet is the primary driver of the morphological evolution. We demonstrate self-similarity in the longitudinal profiles of the scour hole and downstream deposit. Finally, we discuss practical implications of this study, such as the net displacement of the material, scaling, and limitations. This research contributes to the development of innovative sediment management strategies for water reservoirs and other hydraulic structures.

A revision of the popular equation of Richardson and Zaki (1954a, Transactions of the Institute of Chemical Engineering, 32, 35–53) for the hindered settling of suspensions of non-cohesive particles in fluids is proposed, based on 548 data sets from a broad range of scientific disciplines. The new hindered settling equation enables predictions of settling velocity for a wide range of particle sizes and densities, and liquid densities and viscosities, but with a focus on sediment particles in water. The analysis of the relationship between hindered settling velocity and particle size presented here shows that the hindered settling effect increases as the particle size decreases, for example, a 50% reduction in settling velocity is reached for 0.025 mm silt and 4 mm pebbles at particle concentrations of 13% and 25% respectively. Moreover, hindered settling starts to influence the settling behaviour of sediment particles at volumetric concentrations of merely a few per cent. For example, the particle settling velocity in flows that carry 5% silt is reduced by at least 22%. These observations suggest that hindered settling greatly increases the efficiency of natural flows to transport sediment particles, but also particulate carbon and pollutants, such as plastics, over large distances.