Monitoring And Analysis Of Surface Deformation In Dongting Lake Area Based On InSAR Technology And Offset-tracking Method

Dongting Lake is an important flood-regulating lake in the Yangtze River Basin of China.It is distributed in 29 counties and districts in Hunan and Hubei provinces,with a wide range.It is an important commercial grain and oil base,aquatic product and breeding base in the country.The area has abundant rainfall all year round,great seasonal changes,and high vegetation coverage.In recent years,the water area of Dongting Lake has been reduced,and the surrounding surface morphology has potential safety hazards.The causes of surface deformation and landform damage include man-made and natural factors,and the causes and effects of them are complex.In the Dongting Lake Basin,there are dense river swamps and vast river network plains.The dynamic development of the water system is one of the main factors for the change of the regional surface morphology.In this study,radar remote sensing satellite monitoring is carried out for Dongting Lake and its important water system.The monitoring period is from January 6,2018 to September11,2021.Using SBAS-InSAR technology for time series monitoring,the processing steps such as differential interferometric processing of images,removal of interfering phase information,rate inversion of surface deformation,and geocoding are completed.In the monitoring results of 59 Sentinel-1A satellite data for 45 months,time series analysis was performed on 4 areas where obvious surface deformation was found.And combined with historical satellite images and regional information overview,the trend of the development of surface morphology is inferred,and corresponding safety warnings are made.The key areas of surface deformation monitoring include subsidence of roads and bridges,regional irregular surface deformation,beach alluvial and embankment erosion.In addition,using the Offset-tracking method,image registration,filtering,geocoding and radiometric calibration are performed on the SAR images.Then the backscatter coefficient map of the region is obtained by threshold setting and threshold segmentation classification method.In this thesis,more than 36 backscatter coefficient maps are classified and analyzed.In 5 hot spots of change in the waters of East Dongting Lake,continuous time series analysis was performed on 16 backscattering coefficient maps covering the key areas.And make the geomorphological research of key areas and the trend inference of the dynamic development of waters.The hot spots of change include different phenomena such as landform changes and erosion,seasonal changes in water area,submerged beach,and reduction of lake water area.In the monitoring of surface morphology and water area,a stable area experimental control group was set up to conduct a comprehensive analysis of the monitoring of surface deformation and water area changes.Finally,this thesis focuses on investigation and monitoring of flood disasters,encroachment and degradation of wetlands and beaches,sediment deposition and river silting in the Dongting Lake area.Combined with the characteristics of the regional environmental background,the formation mechanism and development trend were analyzed.In this thesis,based on the previous experiments of only ground monitoring or lake monitoring,water and land monitoring are integrated and analyzed.With innovative analysis ideas,take the practical application effect of technology and the safety investigation and protection of surface morphology as the primary goal of research and monitoring.The monitoring results and regional information will be comprehensively summarized in the key monitoring areas,and the prone points of geological disasters and hidden danger areas will be delineated.The supporting data and the research information will be provided for relevant departments.