| Due to the rapid development of society and the impact of tectonics,the surface deformation has become a frequent phenomenon in recent years.The resulting land subsidence,house tilt and other problems have affected people’s production and life and the sustainable development of economic society.The current monitoring of surface deformation mainly relies on traditional methods such as leveling,which cannot achieve monitoring in large areas.However,the SBAS-InSAR method based on satellite remote sensing technology has the advantage of wide monitoring range and being able to monitor the surface 24/7.Due to insufficient research on surface deformation in the Lijiang River Basin,this article conducted an experiment using SBAS-InSAR technology to monitor surface deformation in the Lijiang River Basin.The reliability of this technology in surface monitoring in the Lijiang River Basin was explored,and the spatiotemporal characteristics and influencing factors of surface deformation were analyzed,in order to provide scientific data reference for landscape protection and sustainable development of cities in the basin.The main work content and achievements of the paper are as follows:(1)In response to the current lack of research on surface deformation in the Lijiang River Basin,this article uses 81 Sentinel-1A satellite images covering the Lijiang River Basin and conducts surface deformation research experiments using SBAS-InSAR technology from 2017 to 2018 and 2019 to 2021.For the different landforms in the upper,middle,and lower parts of the watershed,the watershed is divided into three parts for processing: upper,middle,and lower,Different phase unwrapping methods are adopted for different parts,and the image processing effects of various filtering methods are compared.The output deformation results under different coherence thresholds are compared.In order to determine the accuracy of the obtained deformation results,a typical area of Yangjiao Mountain was selected for analysis.The analysis results showed that the surface deformation situation in the Yangjiao Mountain area was consistent with the surface changes presented in optical images.(2)A spatiotemporal statistical analysis was conducted on the deformation results of the Lijiang River Basin,276 deformation areas within the basin were circled and counted.The administrative zoning map of the watershed was overlaid with the deformation results to obtain the number of deformation areas within each administrative region in the watershed.The average deformation rate of the designated deformation points in the deformation area was calculated,and the deformation rate was graded.The changes in deformation intensity in the two result maps were compared.The results show that there are only 22 deformation areas in the main urban area of Guilin City,while there are 236 deformation areas in administrative regions with rapid urbanization development such as Lingchuan County,Xing’an County,Lingui District,and Yangshuo County.In terms of changes in deformation intensity,there are a total of 113 deformation areas in the watershed that have transformed from deformation to no deformation.The average deformation rate of 31 deformation areas is decreasing,and the deformation intensity of 30 areas has not changed,indicating that the deformation trend in the Lijiang River Basin is generally stable.(3)Based on the surface deformation situation in the Lijiang River Basin,the causes of surface deformation in the basin are analyzed by considering factors such as terrain slope,surface land type,groundwater extraction and precipitation,and urban development.The analysis results show that as the terrain slope increases,the deformation intensity is also more likely to change;Due to the different coherence,compared with other land cover types such as forest land and cultivated land,the artificial surface has the most deformation areas,up to 186;Due to excessive exploitation of groundwater by human production activities,changes in the pore structure of soil layers can have an impact on the formation of surface deformation in the watershed;With the urbanization development of various districts/counties within the watershed,the expansion of cities can easily lead to changes in surface morphology and the impact on surface loads,leading to the occurrence of surface deformation. |
