A new water–sediment separation structure for debris flow defense and its model test

Structural measures, such as the commonly used open dam with a water–sediment separation function, are important in the mitigation of debris flow hazards and disasters. However, the existing open dams often lose their water–sediment separation function over time and/or during a debris flow event because of blockage by sediment and other debris. To resolve this problem, this paper describes a new debris flow water–sediment separation structure. This structure causes the separated sediment to leave the structure automatically and move to a deposit field. In this way, it maintains its water–sediment separation function in a debris flow event. To test the effectiveness of the new structure, model experiments were developed and tested in the laboratory. These showed that the water–sediment separation function was maintained. More than 80 % of the sediment larger than the design sediment was separated, and most of it left the structure automatically with the water–sediment separation functioning throughout the debris flow process.