Land subsidence risk assessment due to groundwater level reduction (Case study: Mahidasht Basin)

Land subsidence is increasingly recognized as one of the most significant geomorphological hazards in arid and semi-arid regions worldwide, primarily driven by the compaction of subsurface layers resulting from excessive groundwater extraction and the overexploitation of aquifers. This phenomenon presents substantial challenges to sustainable water resource management and environmental protection, as it leads to deformation of the ground surface, structural damage to infrastructure, reduction in aquifer storage capacity, disruption of natural drainage systems, and threats to ecological stability. Understanding the mechanisms, spatial distribution, and temporal trends of subsidence is essential for developing effective mitigation strategies and ensuring long-term water security in vulnerable regions.



The present study investigates land subsidence in the Mahidasht plain, with a particular focus on the role of declining groundwater levels as a primary driver of surface deformation. To achieve this, piezometric data collected from observation wells over a six-year period (2017–2022) were integrated with high-resolution Sentinel-1 radar imagery and the Interferometric Synthetic Aperture Radar (InSAR) technique. This combination enabled a comprehensive spatiotemporal analysis of subsidence patterns and allowed for precise quantification of both the magnitude and rate of surface settlement across the plain. Results indicate a substantial decrease in groundwater levels, with the piezometric surface dropping by approximately seven meters during the study period. The InSAR analysis revealed annual subsidence rates ranging from 3 to 14 centimeters, with the highest rates observed in the central and northwestern areas of the plain. Spatial correlation analysis further demonstrated a strong, direct relationship between groundwater depletion and the intensity of land subsidence, confirming that anthropogenic groundwater withdrawal is the dominant factor driving surface deformation in the region.



Further investigations suggest that geological and hydrogeological conditions, such as sediment composition and the thickness of unconsolidated alluvial layers, modulate the severity and spatial variability of subsidence. Regions characterized by loose, unconsolidated sediments exhibited higher susceptibility to settlement, whereas areas underlain by more consolidated deposits or bedrock experienced comparatively lower rates of subsidence. The observed patterns indicate that areas subject to intensive groundwater extraction are particularly vulnerable, and without proper management interventions, continued subsidence could exacerbate structural and environmental risks. Beyond direct impacts on infrastructure, subsidence also has significant environmental and socio-economic consequences, including disruption of natural drainage patterns, increased flooding risk, soil degradation, decreased agricultural productivity, and long-term ecological imbalance.



The study highlights the effectiveness of integrating remote sensing technologies, such as InSAR, with ground-based hydrogeological measurements for monitoring land deformation over time. This integrated approach not only provides a detailed understanding of the magnitude and distribution of subsidence but also offers a valuable tool for identifying high-risk zones, evaluating temporal trends, and informing decision-making processes related to urban development, infrastructure planning, and water resource management. Continuous monitoring using advanced remote sensing techniques is critical for early detection of emerging subsidence hotspots and for the implementation of timely mitigation strategies.



The findings emphasize the necessity of adopting sustainable groundwater management practices to reduce subsidence rates and mitigate associated risks. Potential interventions include controlled and regulated groundwater extraction, artificial recharge of aquifers, soil compaction management, land-use planning, and the establishment of protective policies for critical infrastructure. In addition, the development of early-warning systems, risk maps, and adaptive management frameworks can facilitate proactive responses and prioritization of interventions in areas most affected by subsidence. The results underscore that a multidisciplinary approach combining hydrogeology, remote sensing, geotechnical analysis, and environmental management is essential for addressing the complex challenges posed by land subsidence in semi-arid regions.



In conclusion, land subsidence in the Mahidasht plain is predominantly driven by anthropogenic activities, particularly excessive groundwater extraction, while geological characteristics influence the severity and spatial distribution of the phenomenon. The integration of InSAR with piezometric measurements provides a robust methodology for detecting, quantifying, and mapping subsidence patterns, offering critical insights for policymakers, water resource managers, engineers, and environmental planners. The study reinforces the importance of sustainable groundwater management, continuous monitoring, and the application of advanced remote sensing technologies to mitigate subsidence risks. Furthermore, the implications of this research extend beyond the Mahidasht plain, offering valuable lessons for other semi-arid regions around the world facing similar challenges of water scarcity, intensive groundwater use, and land subsidence. By understanding the mechanisms, drivers, and consequences of subsidence, decision-makers can implement more effective, evidence-based strategies to protect infrastructure, maintain agricultural productivity, preserve ecological systems, and enhance the resilience of human and natural systems to ongoing environmental change.



Ultimately, this study demonstrates that proactive, integrated management of groundwater resources, combined with cutting-edge monitoring technologies, is critical for reducing land subsidence, safeguarding environmental and socio-economic assets, and promoting sustainable development in arid and semi-arid regions globally. The findings contribute to a deeper scientific understanding of subsidence processes, provide a foundation for policy development, and emphasize the need for coordinated efforts between scientists, planners, and decision-makers to ensure the long-term sustainability and resilience of vulnerable landscapes.