Laboratory study on the characteristics of large wood and debris flow processes at slit-check dams

Abstract

Large wood (LW) in debris flows during flooding can cause significant damage to check dams, bridges, and other major infrastructure in its flow path. When LW accumulates and forms logjams, large volumes of sediment can be deposited, resulting in increased backwater. The logjams can then suddenly collapse, with the deposited sediment and accumulated water increasing the magnitude of debris-flow peak discharge. To better understand the characteristics of debris flow discharge caused by LW accumulation and collapsed logjams, as well as the associated magnitude amplification effects, a series of experiments was carried out in a laboratory experimental channel. The main purpose of this study was to analyze the process of LW accumulation and collapse and to determine the magnitude amplification ratio of the debris flow peak discharge with LW. The results revealed three types of debris flow movement with LW: flow with no clogging or breakage, flow with clogging but without breakage, and flow with both clogging and breakage. The results indicated a significant effect on the magnitude amplification ratio caused by LW clogging and breakage. The maximum magnitude amplification ratio was 1.60 in the experiments, with a relative LW length and volume of 0.875 and 0.75, respectively, during the clogging and breakage process.