Hydraulic Model Investigation of Sediment Deposition Control near Bottom Outlets Using Pressure Flushing

Abstract

As reservoir sedimentation exceeds original design assumptions, the risk of functional degradation of bottom outlets for flood control has increased, creating an urgent need for sustainable sediment management measures. This study focuses on pressure flushing, a sediment removal technique that operates without reservoir drawdown, and reviews structural measures that have been proposed to improve flushing performance. Such measures can be regarded as sediment control approaches near the bottom outlet. From this standpoint, we propose an auxiliary structure that can be retrofitted to existing dams by installing it on an auxiliary gate. Hydraulic model experiments were conducted to examine the influence of its geometry and arrangement on sediment deposition and erosion patterns. The results demonstrate that the configuration of the auxiliary structure significantly affects sediment deposition and erosion patterns near the bottom outlet. These findings indicate that appropriate structural design can effectively control local sediment accumulation, suggesting the feasibility of this approach as a practical sediment management measure for existing dams.