Evaluation And Prediction Of Debris Flow Susceptibility In Liaoning Province

Mud-rock flow is a common natural disaster in mountainous areas,which is characterized by sudden,group,accompanied nature,time period,destructive etc.Liaoning province is a typical province with a high incidence of debris flow in northern China,which seriously threatens the safety of residents' lives and property and causes great damage to all kinds of buildings,roads and other infrastructure.The task of debris flow prevention and control in Liaoning province is very difficult.Debris flow risk assessment and prediction should comprehensively consider the impact of geographical environment,such as topography,underlying surface conditions,hydrological and climatic characteristics.Liaoning province is located in temperate monsoon climate zone.Heavy rainfall is an important part and direct inducement of debris flow.To accurately predict the occurring probability of landslide is rainfall type in Liaoning province,collected the province 1950-2020,538 landslides triggered by heavy rainfall statistics,combined with the provinces and regions in the geographic information data and the daily rainfall data of weather stations on the ground,the methods of GIS spatial analysis,statistical analysis,analysis of debris flow environment factor's contribution to the spatial distribution of the weight,The relationship between debris flow and rainfall factors at different time scales is explored,and the influence of different effective rainfall thresholds on the probability of debris flow occurrence in a short term is studied.On this basis,the spatial differentiation of debris flow is divided into different regions,and the environmental thresholds and rainfall warning thresholds of debris flow occurrence in different regions of Liaoning Province are obtained.In addition,the evaluation of debris flow susceptibility in Liaoning province is carried out,and more reliable prediction and early warning information and comprehensive applicable prevention and control countermeasures are put forward.Research shows that:(1)Spatial and temporal distribution characteristics of debris flow disaster sites,occurrence environment and contribution values of influencing factors: Debris flow is concentrated in the east and south of Liaoning Province,and the terrain is mainly mountainous and hilly.In the early 2010 s,the occurrence frequency of debris flow increased sharply,but decreased in recent 5 years.The areas with high incidence of debris flow in Liaoning province are mainly located in the low mountains and hills with an elevation of 100?700 m and a slope greater than 10°.The soil is sandy,mainly brown loam and brown soil,mainly dry land and forest land.The interaction of rainstorm days with soil type,vegetation type and elevation has the highest contribution value to the spatial distribution density of debris flow in Liaoning Province.(2)The relationship between debris flow and rainfall factors at different time scales: in the long-time scale,the linear relationship between debris flow frequency and rainy season rainfall,annual rainstorm rainfall and annual heavy rainstorm days is the strongest,but the linear relationship with other rainfall factors is not obvious.The correlation degree between the occurrence frequency of debris flow and short-term effective rainfall from high to low is the effective rainfall of the same day,the accumulated effective rainfall of the previous three days,the accumulated effective rainfall of the previous seven days.The probability of debris flow occurrence is different under different early effective rainfall thresholds.When the effective rainfall of the same day is 50 mm,the accumulated effective rainfall of the first three days is 77 mm or the accumulated effective rainfall of the first seven days is 142 mm,there is a 50%probability of debris flow occurrence.The risk prediction of debris flow should consider the geographical environment characteristics such as landform and underlying surface material comprehensively.(3)Environmental thresholds of debris flow occurrence and rainfall warning thresholds in different regions of Liaoning Province: cluster analysis method was used to find that the debris flow points of the first type were low in elevation,gentle in slope,and mostly distributed around water areas and forest land;The second type of debris flow has higher elevation,steep slope and arable land distribution.The third type of debris flow has high elevation,steeper slope and the largest population density.The mean effective rainfall of the first,second and third types of debris flows were 59 mm,90 mm and 110 mm,respectively;the mean cumulative effective rainfall of the first three days were 91 mm,115 mm and 135 mm,respectively;and the mean cumulative effective rainfall of the first seven days were 90 mm,120 mm and 152 mm,respectively.The research results provide theoretical reference for disaster warning and prevention.(4)Evaluation of debris flow prone areas: Debris flow disaster points are concentrated in high and medium danger areas.High danger zone is mainly located in Xiuyan Manchu Autonomous County,the junction of Wafangdian city and Pulandian city,Gaizhou city,Zhen'an district of Dandong city,Moderate risk areas are mainly distributed in the periphery of high risk areas and Kuandian Manchu Autonomous County,Fengcheng in Dandong,Benxi County and Hirayama area of Benxi City,Liaoyang County and Gongchangling District and Dengta City in Liaoyang City.