Debris Flow Generation Based on Critical Discharge: A Case Study of Xiongmao Catchment, Southwestern China

Abstract

A debris flows generation related to a poorly sorted mixture of soil, catchment topography and rainfall characteristic. Runoff of some depth on valley resulting from intensive rainfall can incur the sediments movement of beds or adjacent banks. The fluid flow in channel affected by rainfall parameters combinations, such as duration, intensity, cumulative rainfall, etc., is the key factor for debris movement. In this paper, the rainfall characteristics and occurrence conditions of debris flow in Xiongmao gully on July, 26th, 2016, have been explored, combined with field survey and indoor simulation experiment on the collected critical discharge parameters of debris movement. Further, debris distribution and the critical discharge characteristics have been analysed, by means of investigation on the catchment topography and occurrence cause of the debris flow, analysis of the critical discharge parameters on which the channel debris began to move, and K value clustering analysis method to characterize the rainfall pattern of the studied area, the discharge calculation of debris flow occurring in different rainfall patterns. The results have shown that, for the debris flow occurrence in Xiongmao gully, the debris initiation on the middle reaches of the gully provide the majority of solid particles for the disaster on July, 26th, 2016, and the upstream confluent provided catchment. Based on the relationship obtained from laboratory test, in which the calculated critical discharge was 43.8m3/s, less than the peak discharge (Qc =66.7m3/s), calculated by morphological method. In addition, it has been indicated that the dominated rainfall patterns of the studied area are first-quartile and second-quartile, that is, the rainfall is primarily at earlier or middle to preliminary stage of this time rainfall event. The critical discharge for the occurrence of debris flow on July, 26th was achieved 20a rainfall frequency, the larger runoff volume generated on shorten heavily rainfall. Based on individuality characteristics, such as distributed hydrological analysis, critical discharge and rainfall pattern of debris flow, the forewarning could be more efficient.

The Use of Rain Gauge Measurements and Radar Data for the Model‐Based Prediction of Runoff‐Generated Debris‐Flow Occurrence in Early Warning Systems

“…Such approach initially used in sediment transport for determining the incipient motion condition (Bathurst et al., 1987) has been extended to DF initiation by Tognacca et al. (2000), and nowadays, it is widely used for determining the triggering conditions of DFs (Berti et al., 2020; Gong et al., 2020; McGuire & Youberg, 2020; Pastorello et al., 2020; Raymond et al., 2020; Tang et al., 2019; Wei et al., 2018) rather than the rainfall‐intensity thresholds.…”

Constructing rainfall thresholds for debris flow initiation based on critical discharge and S-hydrograph

“…A critical discharge approach has been used to define the initiation conditions of debris flows caused by hydrodynamic forces (Gregoretti and Dalla Fontana, 2008;Gong et al, 2020;Pastorello et al, 2020), and the concept of critical discharge is extended to bed failure using a solid-liquid critical discharge process proposed by Tang et al (2019). Takahashi (1978) proposed an equation to calculate the critical water depth that causes channel bed failure, and this critical water depth can be transformed into critical discharges by considering channel characteristics (channel width, channel slope and roughness).…”