| Debris flow is a major geological disaster in the mountainous areas of southwest my country,especially in southeastern Tibet,and the debris flow in southeastern Tibet is mainly concentrated in the lower reaches of the Yarlung Zangbo River and its tributaries,Palong Zangbo.Floods occur in the form of disaster chains,which not only seriously affect the safety of life and property of the local people,but also often cause huge losses to neighboring countries.The most serious debris flow disasters in southeastern Tibet are glacial debris flow disasters,which are not only reflected in their scale,but also have a relatively large scope of impact,causing large casualties and property losses,and easily forming disaster chains.In this paper,the southeastern part of Tibet specifically refers to the lower reaches of the Yarlung Zangbo River and its tributary Palong Zangbo.Combined with the Xiaqu and lower reaches of the Yarlung Zangbo River geological disaster investigation project,through the analysis of the distribution characteristics of glacial debris flows in the lower reaches of the Yarlung Zangbo River and its tributaries,Palong Zangbo,and the hazard of debris flow disasters The environment and the scale and frequency characteristics of major geological disasters in the study area are studied.This paper mainly analyzes the data through ARCGIS and Origin software.Through statistical data and analysis,the following results are obtained:(1)A database of glacial debris flow disasters in southeastern Tibet was established,revealing the distribution law and main controlling factors of glacial debris flow disasters in southeastern Tibet.There are 178 glacial debris flows in the study area,with a total area of 4859.8 km~2.The scale of glacial debris flows is mainly super large,accounting for 80.90%.The glacial debris flow disasters in the study area are mainly distributed on both sides of the river.Except for Medog,which is at a lower altitude,the other places are more concentrated.The distribution of debris flow is consistent with the direction of fault distribution.The glacial debris flow in the study area mainly occurs from May to September,and its occurrence is cyclical and repetitive,that is,the same glacial debris flow ditch will repeat the glacial debris flow disaster within a certain period of time.(2)The topography,provenance,structure and water source of the study area are very favorable for the eruption of glacial debris flow.There are a large number of glaciers developed in the study area,strong glacial action and freezing weathering,violent neotectonic movements and frequent seismic activities,and high and steep valley slopes make moraine,ice water sediments,debris cones,collapses,landslides and other loose deposits are extremely abundant;the strong and persistent tectonic uplift makes the valleys in the study area deep incised,with large gradients and steep valley slopes,and the huge height difference provides huge energy for debris flows.This has created the characteristics of the special development of glacial debris flows in this region.(3)Every strong seismic activity in Tibet's Bomi region is prone to the outbreak of exceptionally large-scale glacial mudslide disasters.Since the beginning of the 20th century,the debris flow in the study area has formed a period of intense debris flow activity centered on Zhamnonggou,Kagongnongba(Guxianggou),Peilonggou,Tianmogou and Sedongpu.In the 20th century,the study area The period of intense activity of internal debris flows is 30-50 years.Due to global warming and frequent extreme weather,glaciers retreat and the amount of snowmelt(ice)increases.Climate warming and glacier retreat provide water source conditions for debris flow activities,and periodic earthquake activities provide source conditions for debris flow activities.It is concluded that the debris flow activity cycle in the study area will be shortened,and the frequency of outbreaks will show an increasing trend. |
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