Analysis of the formation mechanism of debris flows after earthquakes – A case study of the Legugou debris flow

Abstract

By means of the Graphic Method, Gray Correlation Method and Frequency Method, the total amount of loose solid materials, the amount of loose solid materials per unit area in the source area, and the risk degree and critical rainfall of the study area are determined, respectively. On the basis of the calculation results, the total amount of loose solid materials is 57.2 × 104 m3, the amount of loose solid materials per unit area is 0.13 m3/m2 (greater than 0.1 m3/m2), which better meets the initiation conditions for dilute debris flow. The Hazard Evaluation Model of Debris Flow in earthquake areas is established by the gray correlation method and the hazard index H = 0.725 is determined. According to the hazard classification standards for debris flows in earthquake areas, the debris flow in Lecugou was moderate after the earthquake. The critical rainfall value of 1H, calculated by the frequency method, ranged from 17.45 to 22.21 mm (Re = 25 mm) and 8.17 to 13.01 mm (Re = 50 mm). The critical rainfall value at 10 min ranged from 6.23 to 8.44 mm (Re = 25 mm) and 2.92 to 5.13 mm (Re = 50 mm), respectively. The maximum rainfall intensity of 45.5 mm/h was reached between 10:00 and 11:00 on July 29, 2019 and the cumulative rainfall reached 144 mm, far exceeding the critical rainfall of Legugou. Under the influence of earthquakes and human activities, the loose solid source amount and loose solid source amount per unit area increased greatly, and the critical rainfall for debris flow after earthquakes decreased sharply, which induced debris flows under the influence of heavy rainfall. This research will be helpful for the establishment of monitoring and early warning systems based on artificial intelligence methods, and can greatly improve the effectiveness of disaster prevention and mitigation.

Simulation analysis of rockfall movement characteristics with debris slope using Unity3D based on UAV remote sensing DSM: a case study of the G318 Highway on the Tibetan Plateau

“…To investigate the movement characteristics and deposit position of rocks on the debris slope of the Tibetan Plateau and to guarantee that the data is more accurate, images more realistic, and analysis results more reliable, UAV tilt photography was performed to obtain a Digital Surface Model of debris slope; moreover, 3D laser scanning was employed to obtain the position and size of the rocks on the slope in this research (Fu et al, 2021;Xue et al, 2021;He et al, 2022;Li et al, 2023). Then, Pix4D was employed to develop a high-precision simulation model, and Unity3D was employed to examine and simulate the process (Wu et al, 2022).…”

The distribution law and coupling factors of debris flows in the G318 Linzhi–Lhasa section of the Sichuan–Tibet traffic corridor

“…Its structural features are a series of nearly east-west faults and folds, and the structural unit belongs to the Gangdise-Tengchong micro-land block. Under neotectonic movement, there is a strong vertical uplift and horizontal sliding of the block (Mikos, 2011;Zhang et al, 2011;He et al, 2022). Under this complex geological activity and structure, the regional seismic activity is relatively strong.…”

Evaluation of Errors and Uncertainties in Debris Flow Modeling with RAMMS

“…Many factors can cause debris flows or increase their floodplains, such as human activities, deforestation, earthquakes, flash floods, heavy rainfall, etc. (He et al, 2022).…”