Extreme subsidence in a populated city (Mashhad) detected by PSInSAR considering groundwater withdrawal and geotechnical properties

Abstract

Ground deformation can cause serious environmental issues such as infrastructure damage, ground compaction, and reducing the ground capacity to store water. Mashhad, as one of the largest and most populated cities in the Middle East, has been suffering from extreme subsidence. In the last decade, some researchers have been interested in measuring land subsidence rates in the Mashhad valley by InSAR techniques. However, most of those studies were based on inaccurate measurements introducing uncertainties in the resulting subsidence rates. These researches used a small number of EnviSat data with long perpendicular and inhomogeneous temporal baseline. This paper seeks to determine the subsidence rate in urban areas of Mashhad in recent years, the threat that was neglected by the city managers and decision-makers. For this purpose, the Persistent Scatterer inSAR technique was applied in the study area using two time-series of descending and ascending Sentinel-1A acquisitions between 2014 and 2017. The results demonstrated the maximum line-ofsight deformation rate of 14.6 cm/year and maximum vertical deformation (subsidence) rate about 19.1 cm/year which could have irreversible consequences. The results were assessed and validated using piezometric data, GPS stations, and geotechnical properties. This assessment confirms that the main reason for subsidence in the interested area is groundwater over-extraction. Also, investigation of geotechnical properties shows that thick fine-grained layers in the northwest of the city could strongly affect the results. At the end of this paper, a new simplified method was proposed to estimate specific storage in special cases to predict the subsidence rate. Ground deformation has been reported as one of the severe geological hazards around the world 1. It is mainly due to the fact that anthropogenic activities such as fluid extraction or injection, underground excavations, and expanding construction have been increased in many regions as a forthcoming problem 2-5. Multiple studies have reported that several areas are suffering from land subsidence as a result of fluid overextraction. These areas include but are not limited to cities in

Comparative Study of Groundwater-Induced Subsidence for London and Delhi Using PSInSAR

“…Satellite interferometric techniques, such as persistent scatterer interferometric synthetic aperture radar (PSInSAR), provides the means for less tedious, cost-effective, large spatial coverage (basin level) mapping of ground movement without compromising on accuracy and precision [15][16][17][18]. This technique was first introduced by Alessandro Ferretti in 2000 [19] and has been developed and applied for mapping surface deformation associated with groundwater change [14,[20][21][22][23]. While PSInSAR can provide accurate land deformation information, it can only be calculated on permanent scatterers that maintain stable scattering with respect to time.…”

Estimation of Ground Vertical Displacement in Landslide Prone Areas Using PS-InSAR. A Case Study of Bududa, Uganda

“…This advantage is attributed to the ascending and descending trajectory of the SAR satellites [29]. InSAR, however, does not directly measure displacement in the vertical direction but the Line of Sight (LOS); therefore, it requires projection of the LOS displacement to the vertical direction [30]. Several algorithms have been developed to ensure that the projection to both the vertical and horizontal directions is reliable enough to achieve accuracy comparable to Global Positioning Systems (GPS) and Levelling [28] [30].…”

“…Several algorithms have been developed to ensure that the projection to both the vertical and horizontal directions is reliable enough to achieve accuracy comparable to Global Positioning Systems (GPS) and Levelling [28] [30]. In this study, we employ a technique where a combination of ascending and descending satellite tracks of significantly different geometrical properties are used to derive vertical displacement [30]. We here, however, put emphasis on the vertical displacement that is well estimated by InSAR and used PS-InSAR to derive displacement points in the vertical, which points are more comparable with GPS points in contrast to if we had used Small Baseline Subset (SBAS) advanced In-SAR algorithm.…”

Land Subsidence in Beijing’s Sub-Administrative Center and Its Relationship with Urban Expansion Inferred from Sentinel-1/2 Observations

“…In urban areas, abundant PS points can be obtained to characterize regional land subsidence based on PS-InSAR data. Many studies have applied this method to successfully monitor urban land subsidence (Roque et al 2014;Minh et al 2015;Jiang et al 2016;Aslan et al 2018;Khorrami et al 2020).…”