Beijing Regional Land Subsidence Monitoring And Risk Assessment Studies

Land Subsidence, a kind of main urban geological disasters which has occurred in our country and all over the world, is a loss of environment and resources which is unable to be compensated. The land subsidence in Beijing area that occurred about fifty years is developing continuously and deeply affects the sustainable development of social economy.The lack of observational data has made it difficult in the past to accurately define the extent of the deforming areas, the magnitude of the surface displacements, and the seasonal land-surface motion with higher temporal resolution and spatial resolution. Persistent scatterers (PS) interferometry, which is an extension of conventional differential synthetic aperture radar interferometry (D-InSAR), it can reduce the temporal and spatial decorrelation and weaken the error that occurred by atmospheric delay,enhance temporal and spatial resolution, therefore,the Persistent scatterer (PS) technology is a useful method for monitor the land subsidence . In this paper, I have used ASAR data to derive detailed maps of the time-varying surface displacement fields over the Beijing city from 2003 to 2006 with PS-InSAR techniques.Based on the land subsidence retrieved by PS-InSAR techniques using ASAR data, I establish a hazard assessment model of land subsidence in Beijing using the AHP—Fuzzy method. The AHP-Fuzzy model index system is composed of 3 first-grade factors and 9 second-grade factors, and the evaluation method is based on Remote Sensing and GIS technology. PS-InSAR techniques were used to retrieve the parameters of land subsidence by using ASAR data. The parameters are as the factors in the AHP—Fuzzy evaluation model. The AHP—Fuzzy assessment model was analyzed by using a GIS-based modeling approach. Finally, a case study was carried out in Miyun-Huairou-Shunyi area of Beijing. The more detailed results include: firstly, the risk index value of each study area was extracted by means of the AHP—Fuzzy method. Second, the risk degree of land subsidence was analyzed using the dimensional analytical method based on GIS technology. Third, combining with the present situation of groundwater overexploitation and the thickness of compressive layer, the hazard level of land subsidence can be divided into three grades: the less risk area, the middle risk area, the higher risk area. It indicates that the risk of land subsidence in Beijing is indispensable. This result is reasonable and useful for land subsidence disaster prevention and reduction.