Impact of Sediment Siltation Height on the Flow Characteristics of Spillways in Check Dams

To precisely determine discharge capacity and spillway flow characteristics in check dam systems with severe siltation on China's Loess Plateau, a theoretical framework was established and complemented with scaled physical modeling to systematically investigate sediment deposition impacts on discharge processes and velocity profile alterations. The experimental findings revealed that sediment accumulation height critically governs spillway discharge stability, where heightened siltation levels induced amplified flow turbulence, whereas increased discharge rates demonstrated turbulence mitigation effects. Within the spillway transition zones, silt deposition was found to exacerbate turbulent flow conditions, consequently magnifying velocity gradient fluctuations and dynamic pressure oscillations. The discharge coefficient displayed an inverse relationship with siltation elevation, with particularly marked reductions observed under low head conditions at the weir crest.A novel discharge prediction model incorporating siltation correction factor CS was derived from the classical broad-crested weir equation. Benchmarking against field data yielded maximum relative deviations under 5%, validating the model's precision in quantifying discharge rates under extreme siltation scenarios. These outcomes establish a methodological foundation for optimizing discharge estimation protocols and implementing risk-informed reinforcement measures in siltation-prone check dam systems.