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Article

Vertical Ground Displacements and Its Impact on Erosion along the Karachi Coastline, Pakistan

1
Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong SAR 999077, China
2
Research Institute for Land and Space, The Hong Kong Polytechnic University, Hong Kong SAR 999077, China
3
Centre for Geo-Computation Studies and Department of Geography, Hong Kong Baptist University, Hong Kong SAR 999077, China
*
Author to whom correspondence should be addressed.
Academic Editors: Paweł Terefenko, Jacek Lubczonek, Marta Wlodarczyk-Sielicka and Katarzyna Bradtke
Remote Sens. 2022, 14(9), 2054; https://doi.org/10.3390/rs14092054
Received: 9 March 2022 / Revised: 10 April 2022 / Accepted: 21 April 2022 / Published: 25 April 2022
(This article belongs to the Special Issue Advances in Remote Sensing of the Inland and Coastal Water Zones)
This study employed remote sensing (optical and synthetic aperture radar) and data analysis techniques to quantify vertical ground displacements and assess their contribution to coastline erosion. To provide evidence from Pakistan, we selected the coast of Karachi—a mega-city located along the dynamic coastline of the Indus River Delta—which has been experiencing severe coastal erosion during the last few decades. Observations from the C-band Envisat/ASAR and Sentinel-1A sensors over the 2004–2010 and 2014–2016 periods, respectively, enabled us to study vertical ground displacements in the study area, providing a long-term assessment during 2004–2016. Results suggest that some areas along the Karachi coastline are subsiding at comparable rates to or even much higher than the relative sea-level rise (SLR, ~1.9 mm/yr), which may amplify the rates of relative SLR in coming years, along with accelerating coastal erosion. Various parts of the study area along the coast are unstable and undergoing displacement. Landsat images from 1989 to 2018 (10-year temporal resolution) were further used to examine the state of coastline erosion using three statistical approaches (i.e., End Point Rate (EPR), Linear Regression Rate (LRR), and Least Median of Squares (LMS)). While the erosion underlaid the majority of the eastern sections of the study area, the ground displacements were spatially heterogeneous across the study area and along the coastline. Erosion rates of ~2.4 m/yr spatially corresponded with ground displacement rates of up to ~−1.4 cm/yr, but not all the coastline segments with high annual mean erosion rates were associated with local mean subsidence. The causes of ground displacements and coastline erosion were analyzed, and results were interpreted by integrating spatial ancillary information. Results indicate that rapid urbanization, construction on reclaimed land, coastline erosion favoring seawater intrusion, failed drainage/sewerage networks, and soil liquefaction are contributing to the site-specific variations in the land displacement in Karachi. View Full-Text
Keywords: remote sensing; coastal dynamics; coastline erosion; vertical ground displacement; InSAR remote sensing; coastal dynamics; coastline erosion; vertical ground displacement; InSAR
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MDPI and ACS Style

Kanwal, S.; Ding, X.; Wu, S.; Sajjad, M. Vertical Ground Displacements and Its Impact on Erosion along the Karachi Coastline, Pakistan. Remote Sens. 2022, 14, 2054. https://doi.org/10.3390/rs14092054

AMA Style

Kanwal S, Ding X, Wu S, Sajjad M. Vertical Ground Displacements and Its Impact on Erosion along the Karachi Coastline, Pakistan. Remote Sensing. 2022; 14(9):2054. https://doi.org/10.3390/rs14092054

Chicago/Turabian Style

Kanwal, Shamsa, Xiaoli Ding, Songbo Wu, and Muhammad Sajjad. 2022. "Vertical Ground Displacements and Its Impact on Erosion along the Karachi Coastline, Pakistan" Remote Sensing 14, no. 9: 2054. https://doi.org/10.3390/rs14092054

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