Monitoring Land Subsidence Using PS-InSAR Technique in Rawalpindi and Islamabad, Pakistan

Abstract

Land subsidence is a major concern in vastly growing metropolitans worldwide. The most serious risks in this scenario are linked to groundwater extraction and urban development. Pakistan’s fourth-largest city, Rawalpindi, and its twin Islamabad, located at the northern edge of the Potwar Plateau, are witnessing extensive urban expansion. Groundwater (tube-wells) is residents’ primary daily water supply in these metropolitan areas. Unnecessarily pumping and the local inhabitant’s excessive demand for groundwater disturb the sub-surface’s viability. The Persistent Scatterer Interferometry Synthetic Aperture Radar (PS-InSAR) approach, along with Sentinel-1 Synthetic Aperture Radar (SAR) imagery, were used to track land subsidence in Rawalpindi-Islamabad. The SARPROZ application was used to study a set of Sentinel-1 imagery obtained from January 2019 to June 2021 along descending and ascending orbits to estimate ground subsidence in the Rawalpindi-Islamabad area. The results show a significant increase (−25 to −30 mm/yr) in subsidence from −69 mm/yr in 2019 to −98 mm/yr in 2020. The suggested approach effectively maps, detects, and monitors subsidence-prone terrains and will enable better planning, surface infrastructure building designs, and risk management related to subsidence.

Non-Linear PSInSAR Analysis of Deformation Patterns in Islamabad/Rawalpindi Region: Unveiling Tectonics and Earthquake-Driven Changes

“…This approach proved especially valuable for our comprehensive, long-term investigation, as it provided a means to quantify and analyze the overall non-linear motion. Moreover, it allowed us to gain new insights into the impact of the earthquake on the deformation zone, revealing previously unobserved phenomena [24].…”

“…However, despite these advancements, conventional PSInSAR techniques typically assume linear deformation over time, which can be insufficient for accurately capturing the complexities of long-term and non-linear deformation processes [23]. This limitation was highlighted in a case study of surface deformation in Islamabad and Rawalpindi, where PSInSAR initially pinpointed water extraction as the main factor, neglecting the region's tectonic movements [24]. Despite the detection of a magnitude 4.6 earthquake in 2017, indicative of tectonic activity, a short-term study from January 2019 to June 2021 failed to capture the earthquake's impact or fully evaluate tectonic influences.…”

Impacts of urbanization, LULC, LST, and NDVI changes on the static water table with possible solutions and water policy discussions: A case from Islamabad, Pakistan

“…The study indicates that the groundwater in Rawalpindi City, which is adjusted to Islamabad groundwater levels, decreased by 10-14 m during 1998-2003 and decreased by 5 m during 2003-2007. Furthermore, the groundwater level reduced dramatically from 58-73 m from 2017-2021 (Abbas et al, 2014;Khan et al, 2022).…”

Time series subsidence evaluation using NSBAS InSAR: a case study of twin megacities (Rawalpindi and Islamabad) in Pakistan

“…Using Sentinel-1 data, this technique has also been applied to ground subsidence in Beijing (Gao et al, 2016;Yang et al, 2018), London (Milillo et al, 2018), Spain (Fernandez et al, 2018), coastal areas of Africa (Khan et al, 2021), and Algeria (Beladam et al, 2019). Khan et al, 2022 applied PS-InSAR to the Rawalpindi-Islamabad region; in comparison to our findings, they used a shorter timespan of data (Jan. 2019 to June 2021) and found a higher subsidence of approximately 90 mm/year without considering atmospheric noise removal or resolving deformation along the satellite's line of sight (LOS) to vertical and horizontal components. In this study, we investigate ground subsidence from 2015 to 2022 using the NSBAS technique (López-Quiroz et al, 2009;Doin et al, 2011) with Sentinel-1 data from ascending and descending orbits over the twin cities of Rawalpindi and Islamabad (Figure 1), taking into account atmospheric noise removal and resolving the LOS deformation to horizontal and vertical components.…”