Effect of Climate change on subsidence in Eastern Gangetic Plain, India: A Correlation of untrodden factors

Globally, the land subsidence (LS) calamity crisis has intensified, adversely affecting the infrastructure, ecology and population. The Instability in climate intensifies the extreme weather conditions and impacts the natural cycles leading to various natural/human made calamities. LS process is instigated due to aquifer compaction, peat decomposition, permafrost degradation, earthquake etc, which results due to extreme climate interplay. Inversely, some LS events also release the greenhouse gases accelerating the climate change. This study seeks to explore the intricate dynamics of the Eastern Ganga Plain (EGP) and the complex relation between climate change and LS. The EGP is a geomorphologically dynamic region featuring deltas, estuaries, wetlands, and floodplains shaped by fluvial and depositional processes. In the current study remote sensing based radar interferometry is applied to understand the evolution of LS scenario in Kolkata Urban Area (KUA) of EGP, Interferometric SAR can assess the ground deformation with high precision by analyzing phase differences using multi-temporal images, suggesting potential subsidence region and infrastructure stability. The hydro-climatic parameters of the EGP are analyzed for long-term climatic behavioral patterns for understanding the feedback of climate driven LS in conjunction with interconnected anthropization and significant climate variation. The interpretation of groundwater level data (2013 to 2023) and groundwater storage data (2004 to 2023) for the KUA reveals distinctive results that diverge significantly from previous studies, suggesting additional factors contributing to subsidence beyond partial aquifer compaction. The presence of wetlands and swamps in the Eastern Kolkata Region presents a high potential for earthquake-induced liquefaction, given the area's association with various tectonic features. Organic deposition in the Bengal Basin, associated with Holocene sediments as confirmed by borehole lithology, contributes to land subsidence through peat decomposition, as evidenced by methane emissions detected using Sentinel-5P TROPOMI data. Climatic variables significantly contribute to subsidence in the Kolkata Urban Area (KUA), beyond the effects of partial aquifer compaction, particularly through liquefaction, peat decomposition, and seismicity. Multi-temporal analysis of 192 Sentinel-1A SAR scenes (2017–2023) and GRACE data (2004–2023) identifies 13 potential subsidence hotspots, with rates ranging from -2.9 to 5.1 mm/year. Time-series GPM and GRACE data reveal increasing groundwater storage in the EGP alongside abrupt precipitation changes. Geotechnical and borehole analyses reveal that peat decomposition and liquefaction significantly impact the eastern Kolkata Urban Area (KUA). Geotechnical and borehole lithology analyses indicate a significant interplay between peat decomposition and liquefaction potential, predominantly affecting the Eastern Kolkata Region of the KUA. Climate change and extreme weather accelerate subsidence, requiring proactive, interdisciplinary strategies to mitigate and reverse human-induced impacts. Comprehensive surveys and expanded in-situ data are crucial to assess contributing factors and subsidence severity.