Dynamics of internal bore migration within turbidity currents under variable dam slopes

Reservoir sedimentation and turbidity currents present persistent challenges to water resources management by reducing storage capacity, degrading water quality, and increasing risks to hydraulic infrastructure. This study provides a spatiotemporal investigation of submerged muddy lake deformation, focusing on estimating the travel time of turbidity current head velocity between the plunge point and the dam. Such estimates are critical for optimizing sediment venting operations and mitigating sediment-related hazards. Additionally, the run-up height of forward-propagating turbidity currents and the dynamics of upstream-migrating internal bores are examined to evaluate the effects of dam slope and the temporal evolution of muddy lake deformation. A series of laboratory experiments was conducted using three dam slopes, three inflow discharges, and three turbidity current concentrations, during which turbidity current head velocity and internal bore velocity were systematically measured. The results indicate that, for a given concentration and dam slope, the dimensionless bore velocity is largely insensitive to variations in inflow discharge and dam slope. The bore velocity decreases with increasing upstream distance and is consistently approximately 50% lower than the corresponding turbidity current head velocity. Furthermore, the square root of the dimensionless propagation distance is identified as the key governing parameter controlling both the relative bore velocity and the run-up height. Regression analysis demonstrates that the inflow densimetric Froude number, current thickness, and dam slope dominate the flow mechanism of upstream-migrating internal bores, yielding coefficients of determination (R²) exceeding 0.70. These findings advance fundamental understanding of muddy lake deformation processes and offer practical insights for managing turbidity currents and reservoir operations. By improving the prediction of turbidity current dynamics and internal bore behavior, this study supports the development of more effective sediment venting strategies. It contributes to the long-term sustainability and safety of reservoir systems.