Comprehensive Detection And Analysis Of Debris Flow Characteristics In The Xiaojiang River Basin

The debris flow happened in the Xiaojiang River Basin,which is known for its wide distribution,large scale,diverse types and violent outbursts.The Xiaojiang River Basin in Yunnan is a famous mudslide development area in the world,known as the Debris Flow Natural Museum.The Xiaojiang River Basin in Yunnan Province is located in the zone of the deep fracture.The old and new structures are criss-crossed,the neotectonic movement is strong,with the frequent earthquakes.The Xiaojiang River Basin has steep terrain,complex lithology,severe fracture,strong erosion.Due to the high terrain which is large,the types of climatic zones are diverse,and local heavy rainfall often occurs,and the ecological environment is relatively fragile.The formation of debris flow in the Xiaojiang River Basin is closely related to the natural conditions of the basin and human economic activities.The topography is the intrinsic factor of the occurrence of debris flow,and the human deforestation and destruction of vegetation are external factors.The debris flow in the Xiaojiang River Basin heavily happened,which is destructive and sudden,and it is the main natural disaster that causes loss of life and property and affects social and economic development.Comprehensive exploration and analysis of debris flow characteristics in Xiaojiang River Basin can help people to improve their understanding of debris flow disasters and reduce the loss of life and property caused by debris flow disasters.It is of great significance for the prediction and prevention of debris flow.All the research in this paper is conducted without considering the influence of geological factors,analyzing the topography and geomorphology of Xiaojiang River Basin based on DEM,using the Landsat8 remote sensing image to interpret the debris flow ditch,and analyzing the vegetation coverage and surface cover of Xiaojiang River Basin,based on the above analysis.The ecological vulnerability assessment was carried out for each element,and three typical small watersheds were selected for comparative analysis.This paper analyzes the debris flow characteristics of Xiaojiang River Basin from three aspects,and the research results are as follows:1.Analyzing the topographic of the Xiaojiang River Basin,the characteristics of the debris flow are as follows:Based on the DEM,the topographical features of Xiaojiang River Basin were quantitatively analyzed,and the elevation,terrain relief,slope and aspect were analyzed.From the elevation point of view,the geomorphological structure types in Xiaojiang River Basin are mountainous landforms,most of which are Zhongshan geomorphology,accounting for 96.3% of the entire Xiaojiang River Basin.Very few landforms are low mountains and high mountainous landforms,accounting for 1.4% and 2.3% respectively,most of the debris flows can occur in the Zhongshan geomorphology area;the terrain relief of the Xiaojiang River Basin is divided into four grades: 0m-20 m is flat undulations;20m-75 m is micro undulations;75m-200 m is the small undulations;200m-600 m is the mid-undulation,most of the Xiaojiang River Basin is dominated by small fluctuations,with emphasis on small fluctuations,and the proportion of small fluctuations is 62%,indicating that the debris flow types in the Xiaojiang River Basin are mainly small and medium-sized debris flows,large and extra-large debris flows are less;In terms of slope,the slope range of Xiaojiang River Basin is distributed from 0°~80°.The slope distribution range is wide,the slope is relatively concentrated at 10°~40°,and the slope ratio of 10°~25° is 44.96%.The erosion is more severe,and the soil erosion is also serious.It is the key area for soil and water conservation.This area provides a large amount of loose solid material for the formation of debris flow,and steep slopes larger than 25°.The area is 37.69%,which is the deep cutting area of Xiaojiang River Basin.It is mainly distributed on both sides of the main stream of Xiaojiang River,which is the middle and lower reaches of Xiaojiang River.From the aspect of slope,the area of west slope is larger than that of east slope,so the east and west directions.The distribution of light and heat resources and surface runoff shows a difference,and the mudslides in the west slope are more than the east slope.Based on the hydrological analysis model,the river network extraction and watershed segmentation are carried out in Xiaojiang River Basin.According to the extracted river network,the density of gully in Xiaojiang River Basin is calculated.The density of gully is 1.96km/km2,which indicates that the density of gully in Xiaojiang River Basin is large,and the erosion of gully.The surface runoff ability is strong,and the basin fragmentation degree is relatively high.The Xiaojiang River Basin is divided into 279 small watersheds,which can be used to obtain the vertical and horizontal staggered valleys in the Xiaojiang River Basin,and the terrain is fragmented,which provides favorable conditions for the formation of debris flow.2.By analyzing the characteristics and vulnerability of the surface cover in the Xiaojiang River Basin,the characteristics of the debris flow in the Xiaojiang River Basin are as follows:Based on the Landsat8 remote sensing image,the vegetation index of Xiaojiang River Basin is calculated.Generally speaking,the vegetation coverage of Xiaojiang River Basin is larger,but the overall density is smaller,the vegetation coverage is generally lower,and the forest cover is less.It can be seen that the debris flow is large.Occurring in areas with less vegetation cover,afforestation is needed to strengthen soil and water conservation work to prevent the occurrence of mudslides.Using the remote sensing images to extract surface cover information from Xiaojiang River Basin,the forest land in Xiaojiang River Basin is less,accounting for only 12.84% of the entire Xiaojiang River Basin.Compared with other land types,there are more grassland,accounting for 39.75% in the total area,indicating Xiaojiang River Basin.The soil erosion is more serious;the proportion of cultivated land is 21.99%,and the ecological environment of cultivated land is relatively fragile.It can be found that the debris flow occurs in areas with more wild grassland and less forest land.Remote sensing images were used to interpret the debris flow valleys in the Xiaojiang River Basin.72 debris flows were interpreted in the Xiaojiang River Basin.It can be seen that the debris flow ditch is mainly distributed in the middle and lower reaches of the Xiaojiang River.The debris flow ditch is distributed along the banks of the Xiaojiang River and the debris flow distribution density is relatively large..Based on the analytic hierarchy process,the vulnerability assessment of the Xiaojiang River Basin was divided into four levels of vulnerability: severely vulnerable,moderately vulnerable,mildly vulnerable and potentially vulnerable.The severely vulnerable areas are mainly distributed in the middle and lower reaches of the Xiaojiang River,and are distributed along the banks of the Xiaojiang River.The distribution is relatively concentrated.The moderately vulnerable areas are widely distributed throughout the Xiaojiang River Basin,indicating that the ecological environment of the Xiaojiang River Basin is relatively fragile and is a high-prone area for debris flow disasters.It is more seriously damaged by debris flow disasters;the distribution of lightly vulnerable areas and potentially vulnerable areas is less,mainly distributed in areas with flat topography and high vegetation coverage,most of which are distributed in the upper reaches of Xiaojiang,indicating that the debris flow is mainly distributed in the ecology.Areas with severe environmental vulnerability.3.With comparing and analyzing the three typical small watersheds,the characteristics of the debris flow valley are as follows:Most of the debris flow valleys in the Xiaojiang River Basin are located between 1500-2500 meters above the sea level.Most of the debris flows occur in steep slopes.The more the slopes are in the range of 112.5°-247.5°,the more mudslides are likely to occur.The debris flows mostly occur in the topography.In areas with large undulations,vegetation coverage also affects the distribution of debris flows.The ecological environment with sparse vegetation is relatively fragile and prone to debris flow disasters.The areas with wild grassland and cultivated land are severely soiled,the soil is loose,and the ecological environment is fragile.It is prone to geological disasters such as mudslides and landslides.