STUDY ON THE GENESIS OF RAINFALL-GLACIER MIXED TYPE DEBRIS FLOW OF HAIBALO GULLY IN NORTHWEST YUNNAN ON JULY 28, 2019

The Haibalo Gully located in the Hengduan Mountain region in northwest Yunnan, where a debris flow broke out at 2:40 am on July 28, 2019. In order to scientifically and accurately carry out debris flow monitoring, early warning and comprehensive prevention work in this area and guarantee the construction and operation safety of Xiangli(Shangri-La to Lijiang) highway in the middle and lower reaches of Haibalo Valley, this paper studied the characteristics and genesis of this debris flow according to the field survey, UAV aerial photography and remote sensing, combined with indoor experimental analysis and calculation. For this debris, the maximum bulk density was 16.77 kN·m^-3, so it belonged to low-viscosity debris flow, with flood-peak discharge about 528.16 m³·s^-1. Under the influence of geological and climatic conditions, there are 3 types of source in Haibalo Gully, landslide mass on side bank of gully in valley area, moraine and frozen weathered debris in the high position. The debris flow occurred at the tail of the main rainfall process from the evening of the 27^th to the early morning of the 28^th. According to the monitoring of 9 rainfall processes in Haibalo Gully Basin from August to October in 2019, we found that the main process of rainfall in this area is 6 hours, and the precipitation increases significantly with the elevation. The heavy rainfall that triggered the debris flow concentrated in the peak ridge area of 4200~4800 m in the west of Haba snow mountain, and the average rainfall was 60.43 mm in the main rainfall process of 6 h. In addition to the rainfall, the excitation factors also contain glacier melt water in the peak ridge area. According to calculation, the average melting water equivalent of the glacier is 17.29 mm during the 6 h rainfall. The achievements of this study can provide a reliable scientific basis for the monitoring, early warning and prevention of the rainfall glacier-malt-water mixed type debris flow in the Hengduan Mountain region of northwest Yunnan.