The Formation Environment And Disaster Trend Research With Debris Flow In Bingzhongluo-Pihe Of Nujiang River

The Nujiang Alpine Gorge area is one of the most serious debris flow disasters in my country.The frequent occurrence of debris flow disasters poses a huge threat to the local ecological environment and the safety of residents' lives and property.As a sudden geological disaster,the occurrence and development of debris flow are affected by a variety of environmental conditions.Therefore,it is the theoretical basis for scientific prediction and disaster prevention to clarify the correlation between various environmental condition factors and debris flow disasters.Provide an important foundation.At present,there are few related studies on debris flow in the Nujiang Canyon area,and most of them stay at the stage of qualitative analysis.In the related research,only historical debris flows are taken as the research object,but as debris flow hazards in the Bingzhongluo-Pihe Township section of the Nujiang River are prone to be prone to debris flow hazards,the impact The development of environmental conditions has been neglected,so it is urgent to carry out related research.Through the interpretation of remote sensing images,on-site identification and quantitative discrimination of area-elevation integrals,the spatial distribution and historical disaster profiles of various types of debris flows in the Gongshan and Fugong Canyon areas of the Nujiang River were basically ascertained,and preliminary exploration was made using GIS spatial analysis and statistical methods The environmental conditions for the development of historical debris flow ditches and active debris flow ditches in the study area were discussed,and the development characteristics of debris flow in different river sections were discussed in combination with the spatial differences of the environmental conditions.Finally,the debris flow disaster trends were analyzed based on the principle of extenics.The main results are as follows:(1)A total of 191 debris flow ditches with a hazard line density of 0.9/km and a total of 94 active debris flow ditches with a disaster line density of 0.44/km were developed in the Bingzhongluo-Pihe Township area.The development of debris flow disasters in the watershed has obvious differences in time and space,and also has certain regularity.In terms of time,debris flow disasters in the study area show unstable periodicity of inter-annual activities,seasonality and concentration of intra-annual activities,night-time and periodical characteristics of intra-day interactions,and are often accompanied by other disasters.Spatially,debris flow ditches are relatively concentrated in the river section of Puladi-Shiyuexiang Township,active flow ditches are mainly concentrated in the area north of Shiyuexiang Township,and large-scale and extra-large debris flows are relatively north of Puladi Township and south of Shiyuexiang Township.Concentrated development;different active debris flow ditches are selective to the shore,and active debris flow ditches develop on the left bank;vertical,historical debris flow ditches have relatively little difference in relative elevation distribution,and active debris flow ditches are mostly concentrated in channels with a relative height difference greater than 2000 m.(2)Due to the debris flow fluid structure and composition,the main stream vertical ratio drop,the original terrain of the accumulation area and the erosion of the main river,the integrity of the fan body of the entire river section is poor,and it exhibits a variety of fan shapes,lens shapes,irregular shapes,etc.form.The debris flow accumulation fan in the area has a blocking effect on the main river,which is positively related to the size of the fan body.The scale of the accumulation fan is related to a certain development stage of the gully watershed.The volume of the fan body is related to the watershed area as a power function with V=2.42x0 The change of.55 is related to the exponential decrease of the ditch-bed ratio,with a change of V=38.19 e 0.01 x,and a power function of the length of the main ditch,with a change of V=3.761x0.55.(3)Focus on selecting factors such as slope,average specific descent of the main ditch bed,and gully density for in-depth analysis.Judging from the relative probability of the occurrence of debris flow among various factors,the spatial distribution of debris flow is greatly affected by the topographical conditions,structural conditions and rainfall conditions,mainly distributed in the mountainous area with a slope of 25?45° accounting for about 60%?70% The bed aspect ratio is reduced to 150‰?350‰,and the channel has a higher fault density and abundant rainfall;the development of active debris flow is obviously affected by structural faults,which is related to the extent of erosion,lithology,human engineering activities and vegetation coverage It is closely developed in the trenches with strong channel erosion(gully density greater than 2.0km/km2),weak rock mass properties,strong human engineering activities and low vegetation coverage.(4)From the perspective of time,the debris flow in the area has been formed since the late Pleistocene.With the increase of the undercut rate of the valley,the frequency of debris flow has increased.Since the Holocene,it has entered a period of high incidence of debris flow development.Since modern times,engineering activities have gradually become An important factor influencing the occurrence of debris flows.In addition to providing abundant sources of debris flows,engineering activities also intervene in complex climate systems on a long-term scale,leading to the occurrence of extreme climates.The annual rainy season debris flows and the disasters they cause may become more serious.Spatially,the Bingzhongluo-Puladi area will remain the most prone to debris flow hazards and will be concentrated in the Gongshan county area;the Puladi-Shiyue Township area will be the high prone to debris flow hazard,and the overall occurrence of debris flow The scale is relatively small,and the hazard risk is relatively lower than the upper reaches.The Shiyue-Pihe Township area is a relatively low risk of debris flow hazards in the area,and the left bank debris flow is more likely to occur than the right bank.