Experimental study on the sediment deposition upstream of open check dams in trapping debris flows

Open-type check dams, used in debris-flow control can intercept and reduce flow energy, but their function is an urgent problem to address. Flume experiments were designed to understand sediment deposition and trapping performance of open-type dams against debris flow. Sediment deposition varied with opening form and size due to structural configuration and blocking performance. The process was influenced by slurry discharge and hydraulic jump. The study revealed the sediment entrapment mechanism, involving banked-up, backwatering, and dewatering, influenced by dam structure and blocking performance. Evaluation of permeable sediment barriers’ sediment-retention capabilities showed a closed dam’s efficiency was generally higher. Sediment retention was influenced by debris flow bulk density and scale, and relative opening degree of the barrier. Barriers with different opening configurations had varying retention rates when intercepting high-concentration debris flow. The open-type check dam’s sediment-trapping efficiency showed an overall negative correlation with relative opening and a positive correlation with sediment volume concentration. For different check dams with varying opening forms, the difference in sediment-trapping efficiency increased as relative opening increased, especially when intercepting debris flows with higher sediment concentration. This conclusion can provide a theoretical basis for scientific design of permeable sediment barriers and improve the debris flow prevention and control system.