Experimental study on the self-cleaning behavior of slit dams for debris flow hazard mitigation

Abstract

Self-cleaning is a crucial feature of slit dams, which not only enhances upstream and downstream hydraulic connections but also automatically restores a dam's debris flow storage capacity. In this work, a series of specially designed flume tests are performed to simulate the self-cleaning process. The flow rate, relative opening, bed-slope angle, and number of openings are considered. The erosion process, topographic characteristics, and relative erosion depth are analyzed to gain insight into the self-cleaning details. The current results reveal that when the boulders jamming the openings are removed, erosion occurs in three stages (downcutting, headward erosion, and lateral erosion). Conversely, when the blockage remains stable, only surface armoring occurs. Furthermore, after the self-cleaning process reaches a quasiequilibrium state, the topographic features are summarized, and the differences in the maximum erosion depth at the opening are analyzed for different experimental conditions. This paper proposes a critical criterion (F) for the self-cleaning of slit dams on the basis of dimensional analysis. The critical criterion takes into account the interactions of three parameters (Froude number, relative opening, and opening rate) and can be conveniently applied to existing slit dams. When F is less than 0.25, the opening remains blocked, and only surface armoring occurs; when F is between 0.25 and 0.38, the blockage may be removed; and when F is greater than 0.38, self-cleaning leads to massive erosion, and the blockage is removed. Therefore, the proposed critical criterion can help design the opening dimensions of a slit dam, restoring its storage capacity. Finally, the positive effect of self-cleaning on restoring the storage capacity of slit dams is discussed.