| The Xiangxi River and Zhaxi River basins in the Three Gorges Reservoir Area are located at the junction of the second and third terraces of China’s terrain.Due to the erosion of the Yangtze River and its tributaries,the area has high mountains and deep valleys,and complex geological environment conditions.At the same time,due to the periodic rise and fall of the water level in the Three Gorges Reservoir and the strong impact of human engineering activities,landslide disasters in the area occur frequently,seriously threatening the lives and property of local people and the safety of water and land transportation.For this reason,based on Arc GIS software,this paper takes Xiangxi River and Zhaxi River basins as the study area,establishes a landslide disaster spatial database according to field survey and data collection,builds a landslide disaster evaluation index system and quantitative evaluation model,and carries out landslide disaster vulnerability assessment,risk assessment and vulnerability assessment with slope unit as the basic evaluation unit,Based on this,a quantitative risk concept model(R=H)is used for comprehensive risk assessment and vulnerability assessment × V)A landslide hazard risk assessment was conducted,and the research results obtained are as follows:(1)Establish a spatial database of landslide disasters and analyze the distribution law of landslide disasters.According to the field survey and data collection,the spatial database of landslide disaster is established based on Arc GIS software.From a spatial perspective,landslides are generally distributed in strips along the Xiangxi River and Zhaxi River,mainly within 2km of the river.The density of landslide points in the north section of Xiangxi River is significantly higher than that in the south section.There is a huge difference between the two sides of the south section,that is,landslides are mainly distributed on the right bank,and there are almost no landslides on the left bank,while the density difference of landslide points on both sides of Zhaxi River is relatively small.From a temporal perspective,the occurrence of landslides is largely influenced by rainfall and reservoir water storage,and the number of landslides is highly positively correlated with rainfall.Based on the distribution pattern of landslides and the disaster characteristics of typical landslides in the area,11 influencing factors were preliminarily selected,including elevation,elevation difference,slope,aspect,engineering geological rock group,slope structure,wading degree,water system distance,road distance,rainfall,and land use.(2)Establish a landslide hazard susceptibility evaluation system,divide slope units,and conduct landslide hazard susceptibility evaluation.The frequency ratio method was used to analyze the sensitivity of various factors and grading intervals to landslides,and its causes were explored.Through Spearman correlation analysis,the two factors of higher collinearity elevation and distance from the road were eliminated,and the vulnerability evaluation system was established with the remaining nine factors.458 slope units were divided using hydrological analysis method,and slope units were used as evaluation units.The coupling model of information quantity and logistic regression was used to evaluate the susceptibility of landslides.The results indicate that susceptibility is closely related to rivers and human engineering activities.The accuracy of the evaluation results was tested using the ROC curve,and the area under the curve AUC=0.840,indicating that the model has good prediction results and can accurately predict the development of landslides in the study area.(3)Conduct landslide hazard assessment under different rainfall return periods using rainfall as the triggering factor.Through correlation analysis between annual rainfall and historical landslide data over the past 60 years in the research area,the results showed a strong positive correlation between rainfall and the number of landslides.Using the Pearson-III distribution model to fit and obtain the rainfall frequency curve,the extreme values of rainfall were obtained for 5-year,10-year,20-year,and 50-year return periods.Then,combined with the landslide disaster catalog database,the landslide area induced in each prone zone under each rainfall return period was calculated,and the spatial and temporal probabilities of landslides were further calculated.Finally,the risk assessment of landslide disasters under different rainfall return periods was obtained.Taking the hazard zoning map under a 5-year rainfall return period as an example,the results show that:(1)in the same prone zoning,the spatial probability of landslides also increases with the increase of rainfall return period,but the temporal probability is exactly the opposite,constantly decreasing,resulting in no obvious pattern of hazard values;(2)Under the same rainfall recurrence period,as the susceptibility level increases,the spatial probability of landslides induced by rainfall continues to increase,resulting in an increasing risk value.The final risk zoning results are roughly similar to those of susceptibility zoning.(4)We conducted a vulnerability assessment of landslide disaster bearing bodies.A vulnerability evaluation system was established based on the actual situation of the disaster bearing body in the research area,including population density,GDP density,road density,and farmland density.The weights of each indicator were determined using the Analytic Hierarchy Process,and a vulnerability comprehensive index model was used to conduct vulnerability evaluation.The results indicate that the vulnerability level of Zigui County in the southern part of the study area is significantly higher than that of Xingshan County in the northern part.The extremely vulnerable areas in the southern part are mainly distributed in the northwest of Shuitianba Township,east of Xietan Township,northeast of Guizhou Town,and central part of Guizhou Town.Only Zhaojun Town in the northern part is the extremely vulnerable area.(5)Based on the results of hazard and vulnerability assessments,a quantitative risk concept model(R=H × V)Conduct landslide hazard risk assessment.The results show that:(1)The total area of high and extremely high risk areas is 39.5146 km2,accounting for 9.17% of the total area of the study area.There are a total of 42 slope units,accounting for 9.17% of the total slope units in the study area.This area needs to be included in a professional monitoring and warning system for key monitoring and prevention.(2)The area of the medium risk area is20.2704 km2,accounting for 4.70% of the study area.It consists of 23 slope units,accounting for 5.02% of the total slope units in the study area.Regular monitoring through group measurement and prevention is sufficient The total area of low and extremely low risk areas is371.3617 km2,accounting for 86.13% of the study area.There are 393 slope units,accounting for 85.81% of the total number of slope units in the study area.Most of these areas are high altitude and less affected by rivers.Only pay attention to prevention in rainstorm season. |
