Study on the Formation and Initial Transport for Non-Homogeneous Debris Flow

An Shu,Le Wang,Guo Ou,Shu Wang,Xin Zhang

doi:10.3390/w9040253

Abstract

Non-homogeneous debris flows generally occur during the rainy seasons in Southwest China, and have received considerable attention in the literature. Regarding the complexity in debris flow dynamics, experimental approaches have proven to be effective in revealing the formative mechanism for debris flow, and quantifying the relations between the various influencing factors with debris-flow formation and subsequent transport processes. Therefore, a flume-based and experimental study was performed at the Debris Flow Observation and Research Station of Jiangjia Gully in Yunnan Province, to theoretically analyze favorable conditions for debris-flow formation and initial transport by selecting the median particle size d50, flow rate Q, vertical grading coefficient ψ, slopes S, and the initial soil water contents W as the five variables for investigation. To achieve this, an optimal combination of these variables was made through an orthogonal experimental design to determine their relative importance upon the occurrence and initial mobilization behavior of a debris flow and to further enhance our insight into debris-flow triggering and transport mechanisms.

Highlights

Debris flows are some of the most widespread and prevalent hazards in mountainous environments [1]
The factor would exert a stronger influence on the formative duration ∆Tdff, velocity u, and Froude number Fr of the non-homogeneous debris flows when R is larger, and the maximum R value corresponds to the dominant factor
Analysis of variance (ANOVA) was performed to identify whether the errors mainly resulted from the variables or experimental operation, which will enable a better understanding of the impact on the results from the influencing factors and reduce any errors being introduced in the analysis [47,48,49,50,51]

Summary

Introduction

Debris flows are some of the most widespread and prevalent hazards in mountainous environments [1]. In China, much of its mountainous terrain, with complex geological environments and variable monsoon climates, is favorable for the occurrence of debris flows during intense rainy seasons and poses a great threat to the safety of human lives and infrastructure. For this reason, the disasters associated with debris-flow events have drawn considerable attention. A detailed understanding of the formative process and initial transport of debris flows is crucial for gaining insights into the debris-flow mechanism, and for predicting and avoiding debris-flow hazards It is well-known that debris flows are commonly triggered by a combination of three essential factors: sufficient solid loose materials, ample water supply, and steep terrain [2,3]. Giannecchini et al [4] obtained critical rainfall input thresholds for debris flows that hit the southern Apuan area in Italy with a deterministic approach; Zhuang et al [5,6]

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Results

Discussion

Conclusion