Erosion Process of Multiple Debris Flow Surges Caused by Check Dam Removal: An Experimental Study

Abstract

Debris flows are one of the most serious natural disasters on Earth and cause great losses in human life and property each year. Check dams have been widely utilized in debris flow hazard mitigation, and over time, some control projects have exceeded their designed service lifetime. However, the processes of stored sediment erosion with multiple surges of debris flows after check dam removal are unknown. Here, the stored sediment erosion processes associated with different reductions in the dam height (i.e., the removed height) were revealed by physical experiments. The results showed that erosion was concentrated on the stored sediment scarp formed by dam removal and that the erosion process mainly included undercutting and widening. The erosion efficiency of the debris flow gradually decreased with the development of erosion and was positively correlated with removed height, negatively correlated with the accumulated debris flow volume, and proportional to the remaining potential volume of sediment to be eroded. The erosion volume development process was well described by an exponential function model, and the physical meanings of the parameters in the model and their empirical values were clarified. Moreover, the distribution of the erosion volume along the flume was shown to satisfy the Weibull distribution, and the distribution parameters were related to the removed height, erosion volume, and sediment volume fraction of the debris flow. We anticipate that our results will serve as a starting point for the demolition and reconstruction of debris flow hazard mitigation engineering in mountainous areas.

Bank Retreat Mechanisms Driven by Debris Flow Surges: A Parameterized Model Based on the Results of Physical Experiments

“…During this period, the debris flow's ability to remove sediment from the toe exceeds the supply of sediment from bank failures. The rapid removal of supplied sediment was observed in the experiments (video data in Wang et al, 2024, such as Case 1-S4 and Case 1-S10), which is attributed to the strong sediment transport capacity of debris flows (Cui et al, 2013;Garcia-Martinez & Lopez, 2005) and the steep channel bed. Consequently, the rate of bank retreat is primarily controlled by the erosion rate of in-situ soil at the toe by debris flows.…”

“…The mean and standard deviation of peak h for each surge were 6.4 and 0.7 cm, respectively. The Fr corresponding to peak h ranged from 3.2 to 4.2 (Figure 3b), which was considered reasonable based on Fr from field cases (Du et al, 2023;Guo et al, 2020;Wang et al, 2022;Zhou et al, 2019). Moreover, the erodible banks were prepared through the following steps: bank soils were paved in a layer-by-layer manner (not compacted), and each layer was approximately 20 mm in thickness.…”

“…Substituting M = tanα/b 0 , a parameter characterizing the geomorphological characteristics of the erosion section channel, into Equation 9 yields the following: ) and b 0 3 is a volume scale (Wang et al, 2022).…”

“…The widening of the channel bed resulting from bank retreat reduced the flow depth of the debris flow, which contributed to the gradual decrease in the increase rate of the V ero value, as shown in Figure 7. To further explore the relationship between bed widening and the erosion efficiency of debris flows, the bed widening was quantified by the relative bed widening width: According to previous research (Sawaske & Freyberg, 2012;Wang et al, 2022), the erosion efficiency with respect to erosion length was defined as follows:…”

Preliminary Investigation on the Kinetic Characteristics of the Glacial Debris Flows in Tianmo Valley, Tibet Plateau, China

“…(2020) used this method to systematically analyze glacial debris flow deposits along the Sichuan‐Tibet railway. Some empirical methods have also been proposed to predict the velocity and run‐out distance by considering various factors (C. Chang et al., 2011; Q. Fang et al., 2019; X. Wang et al., 2022). These methods are important for conducting quick risk assessments.…”