| Guangxi Zhuang Autonomous Region is one of the regions where landslides occur frequently in South China.In the study area,there are a large number of potential landslide hazard points,which are widely distributed.Some of them pose a great threat to important places such as schools and hospitals as well as densely populated areas.In order to prevent many potential landslide hazards,it is necessary to rely on reasonable forecasting model and real-time and effective monitoring and warning system.Rainfall is widely used in landslide early warning system because of its advantages in monitoring cost and difficulty.Therefore,it is necessary to discuss the rainfall thresholds of landslides in Guangxi and subregions.The main contents of this paper are as follows:(1)Based on ArcGIS analysis and screening,lithology,land use type,fault development degree,aspect,slope,normalized difference vegetation index,maximum 24 h average rainfall,average annual rainfall and water system were selected as evaluation indexes.The susceptibility regionalization is carried out by using the information model,and the Guangxi region is divided into very high,high,medium and low susceptibility regions.The superposition verification of 5147 potential landslide points shows that the zoning is reasonable.(2)The temporal and spatial distribution of rainfall and landslides in Guangxi was studied,and the distribution of rainfall monitoring stations in the whole region was discussed.The results show that there is a good correlation between rainfall and landslide in the study area,and the distribution quantity and density of rainfall monitoring stations in Guangxi can meet the requirements of establishing a good correlation between rainfall and landslide and extracting accurate rainfall on the day and in the early stage of landslide.(3)According to the pre-set standard,the rainfall monitoring station associated with the landslide is selected by automatic selection method,the rainfall on the day of the landslide and in the early period is extracted,and then the number of landslide events after analysis and screening is determined.The effective rainfall formula was introduced,and the correlation calculation showed that the landslide in Guangxi had the highest correlation with the rainfall on the landslide occurrence day and the total rainfall of 3 days before the occurrence.Based on this,the attenuation coefficient applicable to the study area was calculated as 0.8.(4)Through the study of the rainfall threshold model,the paper obtained the rainfall threshold curve of the whole region of Guangxi and different categories.Firstly,the rainfall threshold curves of Guangxi under different probabilities are calculated,and the interval is divided into different warning levels of disaster prevention departments.Secondly,the study is divided into 5 types based on lithology,3 types based on seasonal rainfall characteristics and mass landslide events are specially considered,and 3 types based on the regionalization of vulnerability.The rainfall threshold curves of the above categories with different probabilities were calculated and compared.The evaluation results of the threshold curves are proved to be good after later verification.(5)Considering the influence of antecedent precipitation,the bias relation of landslide event to the rainfall of the day of occurrence and the accumulated rainfall of 3 to 20 days before occurrence is analyzed.It was found that with the increase of the number of days,the proportion of landslide induced mainly affected by rainfall on the day of the landslide gradually decreased from 40.1% to 16.73%.The results show that antecedent precipitation plays an important role in the occurrence of landslide in Guangxi. |
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