Effects of proximity of the sediment mining pit on riverbank stability.

Unregulated sediment dredging near riverbanks considerably increases the risk of bank failures. This study examines how the proximity of sediment mining pits influences riverbank stability by conducting controlled laboratory flume experiments on three riverbank slopes: 25°, 31°, and 40°. The analysis considers three scenarios-upstream pit, instream pit, and no-pit conditions while evaluating key hydraulic parameters, including mean streamwise velocity, Reynolds shear stress (RSS), and turbulent kinetic energy (TKE). These measurements provide insights into flow dynamics, turbulence characteristics, and morphological changes. The results indicate that steeper slopes experience higher erosion risks. The 40° slope exhibits velocity increases of up to 35% and TKE peaks reaching 40% above baseline levels when a pit is in close proximity, leading to severe toe scouring and sediment detachment. In contrast, the 25° slope maintains hydraulic equilibrium, limiting velocity increases to 15% and experiencing minimal turbulence-induced erosion, making it the most stable configuration for reducing mining-related impacts. The 31° slope, corresponding to the angle of repose, strikes a balance between sediment mobility and stability but requires localized reinforcements to mitigate erosion. These findings highlight the need for well-regulated sediment mining practices and targeted riverbank stabilization strategies to reduce the growing risk of bank failures.