Why Sinkholes Must Be Treated as a Serious Urban Threat in Karachi
Mohammad Ehsan Leghari
A Warning from Shanghai’s Sudden Collapse
The recent sinkhole incident in Shanghai China, should be read not as an isolated accident but as a structural warning for rapidly urbanizing coastal cities across Asia. On 11–12 February 2026, a large sinkhole suddenly opened at the intersection of Qixin Road and Li’an Road in Shanghai’s Minhang District, close to an active metro construction site for the Jiamin Line. Within hours, a section of the roadway collapsed, adjacent infrastructure was undermined, and groundwater flooded the cavity, turning an ordinary urban junction into a hazardous void. While no casualties were reported, traffic paralysis and emergency stabilization works followed immediately, exposing how fragile even “engineered” urban ground can be under certain conditions (CNA, 2026; SCMP, 2026).
For cities such as Karachi, this episode is not a distant spectacle but a mirror. The geological processes that triggered Shanghai’s collapse, soft alluvial soils, groundwater disturbance, infrastructure leakage, and construction-induced stress are deeply familiar to Karachi. The difference lies not in geology, but in governance preparedness. Ignoring these warning signs risks turning minor surface failures into life-threatening urban disasters.
Understanding Sinkholes: Science beneath the Collapse
Sinkholes are manifestations of subsurface failure, occurring when underground material loses its load-bearing capacity and the surface collapses abruptly or progressively. In urban contexts, two forms are particularly relevant. Dissolution sinkholes typically occur in karst landscapes where limestone dissolves over time, forming cavities. More relevant to deltaic megacities, however, are cover-collapse sinkholes, where erosion within unconsolidated soils creates underground voids that suddenly fail under surface load (USGS, 2023; BGS, 2022).
Deltaic cities such as Shanghai and Karachi (partly) are built on thick layers of unconsolidated silt, clay, and sand. These sediments are inherently weak and highly sensitive to water movement. When groundwater flows through them, whether due to natural fluctuation, pipe leakage, or excavation, it can wash away fine particles through a process known as internal erosion or piping, gradually hollowing the subsurface until collapse becomes inevitable (ICE, 2023; Phys.org, 2013).
Human activity significantly accelerates this process. Deep excavations, tunnelling, and piling disturb stratified soil layers and can intersect pressurized aquifers. Aging water supply and sewerage systems leak persistently, saturating soil and removing structural support. Excessive groundwater extraction lowers the water table, causing soil compaction and regional subsidence, further destabilizing already fragile ground conditions (Penn State Extension, 2021; PreventionWeb, 2024). Climate stressors like intense rainfall, storm surges, and saline intrusion in coastal aquifers, compound these vulnerabilities.
Shanghai’s Collapse: A Textbook Case of Urban Ground Failure
The Shanghai incident exemplifies a classic cover-collapse sinkhole in a non-karst environment. A crater estimated at 10–15 meters in diameter and depth formed rapidly, engulfing road surfaces, footpaths, and landscaped areas. Investigations indicated that groundwater leakage during metro excavation was detected a day earlier, suggesting a failure to fully contain subsurface water inflow. Once erosion reached a critical threshold, surface collapse followed abruptly.
Shanghai’s broader geological context is crucial. The city rests on Quaternary alluvial deposits of the Yangtze River Delta, that is, soft, compressible soils with limited bearing capacity. Over the past century, excessive groundwater extraction caused the city to subside by up to three meters in certain districts, weakening subsurface integrity despite later regulatory controls (Wu, 2022). Combined with intense construction density and stressed underground utilities, even minor disturbances can trigger disproportionate failures. Importantly, this was not Shanghai’s first such incident. Similar road collapses linked to pipe failures and construction works were reported between 2023 and 2024, underscoring a systemic issue rather than a singular engineering error (SCMP, 2024). The city’s response, immediate site stabilization and review of construction safety protocols, reflects institutional capacity that many South Asian cities lack.
Karachi’s Structural Exposure: A Crisis Waiting to Escalate
Karachi’s vulnerability is, if anything, more acute. Like Shanghai, it is a coastal megacity built on deltaic alluvium, this time deposited by the Indus River system including Malir, Liyari and other rain fed river systems of Khirthar range. Satellite-based InSAR studies show that Karachi is subsiding at rates reaching 10–17 mm per year in several districts, including Korangi, Landhi, Malir, Defence, and parts of North Karachi (Khan et al., 2022; MDPI, 2023). Unlike Shanghai, however, this subsidence occurs amid weak regulation, fragmented institutions, and chronic infrastructure neglect.
The risks are multidimensional. Sudden road collapses on heavily trafficked arteries threaten public safety in a city dependent on surface transport. Economic disruption from repeated road failures undermines Karachi’s role as Pakistan’s financial hub.
These threats are not hypothetical. Karachi has experienced repeated sink-like failures: road collapses on University Road following water line leaks; a major sewage-line failure near Shaheen Complex in 2022 that created a crater over ten feet deep; and large-scale pavement collapses on Jail Road that swallowed vehicles and required prolonged closures. During the 2025 monsoon, multiple road sinks and open manhole collapses were reported, some resulting in fatalities (Geo News, 2025; The News, 2024).
What is alarming is not the singularity of these events, but their frequency; and how quickly they are normalized and patched without structural investigation.
Small Collapses as Early Warnings, Not Minor Nuisances
Minor road depressions, recurring potholes, cracking pavements, and localized subsidence are often dismissed as routine urban decay. Scientifically, such features frequently indicate active subsurface erosion and void formation that may later propagate into larger failures, particularly during heavy rainfall or additional construction loading (ICE, 2023).
In Karachi’s subsiding zones, a small leak-induced cavity can gradually expand laterally, linking with other weakened pockets until a critical collapse occurs. What begins as a shallow depression can, under favourable conditions, evolve into a Shanghai-scale crater. Satellite monitoring has already demonstrated that Karachi’s subsidence is spatially clustered rather than random, implying systemic underground stress (Khan et al., 2022; Wu, 2022).
Ignoring these precursors reflects not technical ignorance but institutional inertia.
From Reaction to Prevention: What Karachi Must Do
Mitigating sinkhole risk requires a shift from reactive repairs to anticipatory governance. First, groundwater extraction should be monitored, the deep excavations of increasing high rise building should be modelled at larger scale. It is time to do detailed geotechnical surveys of Karachi. Stabilizing aquifers is central to stabilizing ground. Second, Karachi’s aging water and sewerage infrastructure requires phased replacement, supported by modern leak-detection technologies and subsurface surveys using ground-penetrating radar. The current World Bank funded “Karachi Water and Sewerage Improvement Project” may have covered it in bits and pieces that need to be looked at. The comprehensive plan for water and sewerage system should be developed first. This should be done integration of Project Team with the core Karachi Water and Sewerage Board team, which apparently have less synchronization.
Urban planning must incorporate subsidence and ground-risk data into zoning decisions, infrastructure routing, and large-scale projects such as transit corridors. Construction in high-risk zones should be conditional on independent geotechnical assessments. Continuous monitoring through satellite-based InSAR and real-time sensors should be institutionalized, not treated as academic exercises.
Finally, sinkhole risk must be recognized as a governance issue. A dedicated ground-stability and subsidence unit, linked to disaster management authorities, utilities, and planning agencies, is essential. International development partners already supporting urban resilience and climate adaptation can be leveraged, but only if the problem is acknowledged as systemic rather than episodic.
Shanghai’s collapse was contained because institutions acted before disaster escalated. Karachi may not be afforded the same margin of error. Sinkholes in hydraulic structures or any set of road construction or other infrastructure, are not sudden surprises; they are the final act of long-ignored processes beneath our feet.
References
British Geological Survey (BGS) (2022) Understanding sinkholes and karst processes.
CNA (2026) Massive sinkhole swallows road near construction site in Shanghai.
Geo News (2025) Explainer: Karachi manhole and road collapse incidents.
Institution of Civil Engineers (ICE) (2023) What are the causes of sinkholes?
Khan, M. et al. (2022) ‘Monitoring land subsidence in Karachi using Sentinel-1 InSAR’, Scientific Reports, 12.
MDPI (2023) ‘Hazard potential and subsidence patterns in Karachi and surrounding areas’, Remote Sensing, 15(5).
Penn State Extension (2021) Sinkholes and underground cavities due to human activity.
Phys.org (2013) The science of sinkholes.
PreventionWeb (2024) The rise of sinkholes: How to spot risks before disaster strikes.
ScienceDirect (2025) ‘Groundwater depletion and seawater intrusion in Karachi’s coastal aquifers’, Journal of Hydrology.
South China Morning Post (SCMP) (2026) Large sinkhole appears in Shanghai during metro construction.
US Geological Survey (USGS) (2023) What is a sinkhole?
Wu, Y. (2022) ‘Subsidence in coastal cities observed by InSAR’, Geophysical Research Letters, 49.
Read: Governance Crisis: Air Quality Worsens
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Mohammad Ehsan Leghari is a water expert, former Member (Sindh), Indus River System Authority (IRSA), and former Managing Director, SIDA.
