Monitoring,Identification And Risk Assessment Of Landslides In Gongshan Section Of Nu River Basin Based On Time-series InSAR

Landslides not only pose a serious threat to human life,but also cause damage to natural resources,ecological environment and economic development.Nu River Basin is characterized by complex landform,active geological structure,high vegetation coverage,strong concealment of geological disasters and typical characteristics of high-level long-distance chain disasters.After the high-level remote landslide occurs,loose material flushes the pull groove along the slope and easily turn into debris flow,resulting in serious disasters.The identification and risk assessment of landslide hazards is the main measure to reduce landslide disasters.Therefore,it is of great practical significance to carry out monitoring,identification and risk assessment of landslides in Nu River Basin.The monitoring and identification of landslide hazards is one of the important tasks of disaster prevention and mitigation in recent years.Interferometric Synthetic Aperture Radar(InSAR)has the characteristics of all-day,high precision and wide range.It is widely used in urban subsidence,earthquake and geological disaster monitoring,etc.,becoming a popular research method to monitor surface deformation.Taking the Gongshan section of Nujiang Basin as an example,this paper uses InSAR technology to monitor surface deformation and identify potential landslide hazards.With the support of GIS technology,the landslide risk and vulnerability evaluation indexes are selected from the aspects of engineering geology,topography,soil conditions,hydrological environment,human engineering activities and social economy in the study area,so as to evaluate the landslide danger and vulnerability.The conventional landslide danger assessment is optimized by using InSAR monitoring results.Based on the above two evaluation results,the landslide hazard risk evaluation in the Gongshan section of the Nu River Basin is completed.The research results enhance the sensitivity to terrain,improve the rationality of regional landslide danger and risk assessment,and supplement the areas where landslide data is missing.The main conclusions are as follows:(1)Surface deformation monitoring and identification,and analysis of landslide hazards in the Gongshan section of the Nu River Basin.The results of the radar line-of-sight deformation rate in the Gongshan section of the Nu River Basin are-80.59-93.31mm/y in the ascending orbit,-119.87-84.83mm/y in the descending orbit.The deformation rate in the ascending slope direction is-364.86-364.21mm/y,and the deformation rate in the descending slope direction is-372.75-356.85mm/y.A total of 57 active slopes were found in this study,including 7 known landslides.The active slopes are mainly distributed along the banks of the Dimaluo River,a tributary of the Nu River,Gongdu Highway and around towns.(2)Landslide danger assessment and optimization.The research shows that the assessment results of Certainty Factor(CF),Frequency Ratio(FR)and Maximum Entropy(Max Ent)models are similar,and the medium and high danger areas are mainly distributed on both sides of the Nu River.The AUC values of the three models were 0.941,0.936,and 0.960,respectively.From the aspect of verification accuracy,the Max Ent model was finally selected as the initial landslide danger assessment result.In the optimized danger assessment results,the medium-danger area increased from 75.841km~2to 100.401km~2,and the high-danger area increased by 43.02km~2.The areas with medium-high danger are mainly the distribution area of moraine and the accumulation of loose material along the highway.Landslide hazard evaluation based on InSAR results can be used to evaluate the regional deformation state in real time and correct the incompleteness of historical landslide disaster data sets.(3)Landslide vulnerability assessment.The results show that the middle and high vulnerable areas of landslides in the Gongshan section of the Nu River Basin are mainly distributed on both sides of the Nu River River.Divided by township boundaries,the highly vulnerable areas are concentrated in the central part of Cikai Town,where the government of Gongshan County is located.There are no high vulnerable areas in Bingzhongluo Township,Pengdang Township and Pladi Township,but only extremely low,low and medium vulnerable areas.(4)Landslide risk assessment.The assessment results show that the medium and high risk areas are concentrated in areas where human activities gather.Among then,the high-risk areas are mainly concentrated in Cikai Town and Bingzhongluo Township,and the distribution of Pengdang township and Pladi township is relatively fragmented.In the high-risk areas,there are strong human activities,high density of buildings and cultivated land,abundant water resources,good economic development,perfect transportation facilities,and complex topography,so they suffer from a high degree of landslide risk,which will cause large losses.