| The geological environment of Jiuzhaigou County is fragile,the topography is very undulating,and the stratigraphic lithology is complex.Under the comprehensive action of the above basic geographical environmental factors,the surface deformation in this area is frequent.In addition,due to the influence of strong geological tectonic movement and rainfall,the landslide geological disasters in this county are more,easier and more frequent in a long period of time.Due to the special topographic and geological conditions,coupled with dense vegetation coverage,the landslide disaster in this area is concealed and sometimes difficult to find.The frequent occurrence of landslide geological disasters will cause large-scale social and economic losses and casualties.Therefore,the research focus of this paper is to accurately and effectively identify the landslide geological hazards in this environment,and carry out susceptibility zoning and susceptibility evaluation.Jiuzhaigou Valley is a typical complex geological environment area with high vegetation coverage.Due to its unique geographical environment and climatic characteristics,this region has formed a relatively stable slope belt with a certain scale.This geological background condition determines that conventional field investigation can not meet the needs of landslide investigation and monitoring in this area.For example,affected by high vegetation coverage and mountain shadow,it is difficult for optical remote sensing landslide identification technology and interferometric radar measurement technology to obtain real terrain information of bare surface,and their recognition and application ability is severely restricted in this region.Compared with the traditional measurement technology,Lidar has certain penetration ability to vegetation,and can obtain information by the method of multiple waves,so as to accurately measure the microgeomorphic parameters in the complex geological background area.Therefore,Lidar technology is of great significance for landslide geological hazard identification in complex environment and dense vegetation area.Under the above background,this paper selects Jiuzhaigou as the research area and uses airborne LiDAR data as the main data source to carry out landslide identification research,which provides a new technical support for the identification,prediction and early warning of landslide geological hazards,and provides theoretical and technical support for the research area to carry out multiple zoning tasks of landslide hazards.The main research contents and achievements of this paper are as follows:(1)Acquisition of airborne LiDAR data in the study area.The 50 square kilometers airborne LiDAR remote sensing survey experiment was carried out in Panda Sea area,the core scenic spot of Jiuzhaigou,and the suitability of airborne LiDAR remote sensing survey point cloud density in Jiuzhaigou area was verified.The optimal average point cloud density of Jiuzhaigou landslide identification and susceptibility experiment was 20 points per square meter,and the image resolution was 0.2 meters.The mathematical accuracy is performed in accordance with 1:2000.(2)High-precision DEM and DOM in the study area are obtained after processing the airborne LiDAR data in the study area.Image data,LiDAR results and 3D terrain results generated by Skyline platform based on high-precision DEM data were used to identify the landslide.Then the identification results are compared with the existing landslide data,and it is found that there are new landslide bodies under dense vegetation,which reflects the superiority of airborne LiDAR technology in landslide identification in areas with high vegetation degree.Then,field verification shows that landslides do exist,which verifies the reliability of airborne LiDAR technology in landslide identification in areas with high vegetation degree.(3)Basic data should be preprocessed before landslide susceptibility evaluation.In this paper,1:50,000 geological map and digital elevation model obtained from laser point cloud data in the study area were collected.Geological factors such as stratigraphic lithology and distance from fault could be extracted from geological map,and topographic and geomorphic factors could be extracted from DEM: Elevation,slope,aspect,curvature,topographic relief and surface roughness index.In addition,this paper also selected hydrological factor(distance from water system),social environment factor(distance from road),a total of four categories of background factors as evaluation indicators.The evaluation index system of the susceptibility of landslide disaster development in Jiuzhaigou Valley was constructed.It is concluded that the landslide in the study area mainly occurs in the height of 2000-2800 meters,slope of 15°-45°,curvature of-3～1,distance from fault of0～1500m and distance from road of 0～500m.(4)The information quantity model was used to complete the classification and mapping of landslide susceptibility in Jiuzhaigou research area,and the susceptibility assessment was carried out on this basis.The identified landslide disaster points were taken as the research map layer,and then superimposed with each evaluation factor map layer,and the total information of each evaluation unit in the study area was calculated by using the information quantity model.In the final evaluation results of landslide hazard susceptibility,the study areas are divided into five categories: very low,low,medium,high and extremely high susceptibility areas.According to ROC curve test,the AUC value was 0.929,that is,the accuracy of the information content model was more than 90%,indicating that the method applied to the study of landslide susceptibility regionalization has a good effect,and the regionalization results are reliable.The areas of extremely high,high,medium,low and very low prone areas accounted for 25.58%,21.95%,19.41%,19.54% and 13.42% of the total area of the study area,respectively.The very low prone area accounts for 25.58% of the total area,but the proportion of landslide is 1.51%,indicating that there are few landslides in this area,and the possibility of landslide is very small.Among them,the extremely prone district accounts for 13.42% of the total area,but the proportion of landslide is 68.18%,indicating that the landslide is very intensive in this area and the possibility of landslide is high,which is consistent with the actual situation. |
