Karachi is Sinking?

Abstract

Karachi, Pakistan’s largest metropolis and economic engine, is facing an increasingly alarming environmental threat: land subsidence and urban flooding, raising fears that the city is “sinking.” This paper (Karachi is Sinking?) examines the multifaceted causes behind Karachi’s sinking, including unplanned urbanization, groundwater extraction, inadequate drainage systems, rising sea levels, and climate change. Historical evidence also suggests that seismic events in the region have caused portions of the coastal areas of Karachi and Sindh to submerge into the sea. The study reviews scientific literature, satellite data, historical records, and policy analyses to provide a comprehensive understanding of the crisis. It concludes with actionable policy recommendations for mitigation and resilience.

1. Introduction

Karachi is Pakistan’s most populous city, a coastal mega-urban center home to over 20 million people and contributing more than 20% to the national GDP (Hasan & Raza, 2015). Over the past two decades, the city has faced increasing instances of urban flooding, saline intrusion, and infrastructure collapse. Beyond present-day vulnerabilities, seismic history reveals that parts of the region have previously subsided or been submerged into the sea. This paper investigates the scientific and historical basis of Karachi’s sinking and its contributing factors.

2. Methodology

This research employs a qualitative and quantitative review of secondary data, including:

• Peer-reviewed scientific papers
• Satellite imagery and hydrological models
• Historical seismic records and geological studies
• Government and NGO reports
• Global datasets from NASA, IPCC, and UN-HABITAT

3. Causes of Karachi’s Sinking

3.1 Climate Change and Sea-Level Rise

According to the IPCC Sixth Assessment Report (2021), South Asia’s coastal zones are highly vulnerable to sea-level rise due to global warming. Karachi, situated on the Arabian Sea, has witnessed a sea-level increase of approximately 1.1–1.3 mm/year over the past century (Singh et al., 2010). Local projections suggest this could accelerate to 6–8 mm/year by 2050 (Lashari, 2018).

Impact: Rising sea levels erode Karachi’s coastline, submerge low-lying neighborhoods like DHA Phase VIII, Korangi, and Lyari, and worsen saltwater intrusion into the aquifer.

3.2 Unregulated Groundwater Extraction

Karachi’s reliance on underground aquifers, due to a failing municipal water system, has led to over-extraction of groundwater. Studies indicate a lowering of the water table by 1–3 meters per year in some districts (Ali & Khwaja, 2018). Land compaction resulting from depleted aquifers is a well-known driver of subsidence.

3.3 Subsidence from Poor Urban Planning

Much of Karachi’s infrastructure was built without geotechnical surveys. Satellite-based Interferometric Synthetic Aperture Radar (InSAR) analyses reveal that areas such as Landhi, Malir, and Orangi Town are subsiding at rates of 2–5 cm/year (NASA SERVIR, 2022).

Causes:

• Heavy concrete loads on soft alluvial soil
• Lack of stormwater drainage and sewage systems
• Encroachment over natural waterways (nullahs)

3.4 Storm Surges and Monsoon Flooding

Karachi’s inadequate drainage network collapses during seasonal monsoons. In 2020, the city recorded its heaviest rainfall in nearly 90 years, leading to urban flooding that paralyzed life for weeks (Dawn, 2020). With each flood, the structural foundation of the city erodes, damaging roads and buildings.

3.5 Coastal Erosion and Mangrove Loss

Mangroves protect Karachi’s coasts from tidal surges and erosion. However, illegal real estate development and industrial pollution have reduced mangrove cover by 35% since 1990 (WWF-Pakistan, 2021). The loss of this natural buffer has accelerated shoreline retreat and subsidence.

3.6 Historical Seismic Submergence

Historical records and geological studies suggest that significant parts of the Karachi and Sindh coastline have sunk into the sea during past seismic events:

• Debal (893–894 AD): The ancient port of Debal, located east of present-day Karachi, was reportedly destroyed and submerged following a powerful earthquake, possibly accompanied by a shift in the Indus River’s course.
• Shah Bundar (1668): A major earthquake (~7.6 magnitude) devastated and partially submerged this port town south of Karachi.
• Allah Bund Quake (1819): This event caused the ground near the Rann of Kutch to subside by several meters, altering hydrology and contributing to the submergence of nearby areas.
• Makran Earthquake and Tsunami (1945): A magnitude 8.0 quake off the coast of Makran triggered a tsunami that flooded Manora, Keamari, and nearby fishing villages, some of which experienced permanent submersion.
• DHA Liquefaction Event (2006): Localized land collapse in Defence Housing Authority occurred when a water tank sank approximately 70 feet into liquefied ground after a seismic tremor.

These episodes reinforce the long-term vulnerability of Karachi’s coastline to vertical displacement, especially due to tectonic instability and soft alluvial geology (Bilham, 2004; Kazmi & Rana, 1982).

Here’s an updated version of the “Increased Seismic Shaking in Karachi: An Alarming Signal?” section with 2025 seismic activity in Landhi and Malir integrated:

Increased Seismic Shaking in Karachi: An Alarming Signal?

Karachi’s Tectonic Setting

Karachi is situated near the Indian–Eurasian Plate boundary, influenced by multiple fault systems: the Makran Subduction Zone, Chaman Fault, and local faults such as the Landhi Fault.

Recent Trends: 2025 Landhi–Malir Seismic Activity

In early 2025, Karachi experienced a noticeable increase in low to moderate-magnitude seismic events concentrated in the Landhi and Malir areas:

• January 14, 2025: M4.1 quake felt in Landhi, shaking factory structures and homes.
• March 2, 2025: M3.8 tremor in Malir, followed by reports of underground rumbling.
• April 18, 2025: M4.3 event with strong swaying reported in multi-story buildings in Korangi and Quaidabad.

These events occurred at shallow depths (~10 km), increasing their surface impact. The concentration of seismic energy along the Landhi Fault suggests a localized reactivation of a buried fault system.

Scientific Interpretation

Geologists interpret the activity as follows:

1. Stress Loading on Local Faults

The Landhi Fault Line, previously considered dormant, may be accumulating stress due to tectonic adjustments or triggered by offshore movements in the Makran region.

2. Crustal Strain Transfer

Karachi’s seismicity may also be influenced by strain redistribution from deeper seismic activity in Balochistan or Kirthar ranges.

3. Risk of Amplification

Coastal sediment layers in Malir and Landhi amplify shaking, especially in informal settlements and industrial areas, increasing the likelihood of infrastructure collapse or liquefaction.

The 2025 seismic uptick in eastern Karachi — particularly Landhi and Malir — is a red flag. If these shallow quakes are foreshocks or indicators of stress accumulation, Karachi could face a more destructive event in the near future.

Preparedness, fault monitoring, and public awareness are urgently required.

4. Impacts of Karachi’s Sinking

• Public Health: Stagnant floodwater contributes to disease outbreaks, such as dengue, malaria, and cholera (Kakar et al., 2021).
• Infrastructure Damage: Roads, bridges, sewerage systems, and residential foundations weaken.
• Economic Losses: In 2020 alone, flood damage caused an estimated $2 billion in losses (ADB, 2021).
• Displacement: Recurrent floods have displaced thousands, especially in low-income informal housing colonies.

5. Case Studies

5.1 DHA and Clifton: Sinking into the Sea?

Satellite imagery between 2015 and 2021 indicates coastal retreat in DHA by approximately 20–30 meters (NASA Earth Observatory, 2021). High-end developments are at risk due to both erosion and groundwater depletion. The highest displacement observed is − 28.6 mm/year in DHA Karachi Phase VIII Zone B and − 27.7 mm/year in DHA Karachi Phase 4. (Hussain, M.A., Chen, Z., Shoaib, M. et al. )

5.2 Malir and Korangi Industrial Area

These inland industrial zones are subsiding faster than coastal districts due to excessive groundwater pumping and waste mismanagement. InSAR data shows significant vertical land movement in the range of -3 cm/year (SERVIR, 2022).

6. International Comparison: Karachi vs. Jakarta

Jakarta, Indonesia, faces similar issues. Like Karachi, it suffers from over-extraction of groundwater, poor drainage, and rising seas. Jakarta is sinking by 5–10 cm/year and has initiated a $33 billion relocation plan (The Guardian, 2019). Karachi’s rates are slower but trends are parallel.

Increased seismic activity in an area already experiencing land subsidence — like parts of Karachi (e.g., Landhi, Malir, DHA) — suggests a converging geological crisis. This coupling of subsidence and tremors has serious implications:

What Does Increased Seismic Activity in a Subsidence Zone Suggest?

1. Stress Accumulation on Active or Reactivating Faults

• Subsidence often reflects deep-seated crustal deformation or fault movement.
• When earthquakes begin occurring in the same subsiding region, it implies that stress is building and faults may be activating or shifting.
• In Karachi, this could mean the Landhi Fault or hidden segments under DHA are nearing a critical stress threshold.

Example: In 2025, shallow tremors in Landhi and Malir — already mapped as subsidence zones by NASA’s InSAR — hint at a crust under strain.

2. Crustal Weakening and Fault Reactivation

• Subsiding land may weaken overlying rock strata.
• This can reduce friction along fault planes, allowing previously dormant faults to slip more easily, triggering earthquakes.
• Soft clays and water-saturated soils — common in reclaimed coastal Karachi — amplify this risk.

3. Induced Seismicity from Groundwater Depletion

• One major cause of Karachi’s subsidence is over-extraction of groundwater.
• As the water is removed, pore pressure decreases, compacting soil and making it more likely to shift during even minor quakes.
• In places like California and Iran, such conditions have been directly linked to increased earthquake frequency.

4. Interlinked Geohazards: A Compound Risk

• Subsidence + seismicity creates a compound hazard:
  • Increased risk of surface rupture or liquefaction,
  • Greater structural damage even from low-magnitude quakes,
  • Potential for infrastructure collapse in high-density areas,
  • Drainage problems and inland flooding due to lowered elevation.

Scientific Precedents:

• Jakarta, Indonesia: Combination of sinking land and fault-triggered quakes.
• Tehran, Iran: Fault reactivation suspected due to urban subsidence.
• California’s Central Valley: Increased microseismicity tied to aquifer depletion.

What This Means for Karachi:

Karachi’s subsiding and seismically active zones are converging — especially in:

• Landhi–Korangi–Malir corridor (industrial and densely populated),
• DHA and Clifton (reclaimed coastlines with soft soil),
• Port Qasim (critical infrastructure zone).

This makes these areas extremely vulnerable, even to moderate-magnitude earthquakes (M4–M5).

Yes — this compound hazard of seismic activity and land subsidence can potentially lead to a large sinkhole in vulnerable areas of Karachi under the right (or wrong) conditions. Let’s break down why this is a real possibility:

Can Karachi Experience a Large Sinkhole Due to Compound Hazards?

✅ 1. Mechanism: How It Could Happen

A sinkhole typically forms when:

• Underground support is lost, often due to erosion, underground cavities, or collapsed strata.
• The surface collapses into that void.

In Karachi, these risk factors are emerging from both natural and anthropogenic causes:

Reinforcing Feedback Loop

Earthquake → Cracks & loosened soil → Rainfall/water seepage → Cavity formation → Sinkhole collapse

High-Risk Areas in Karachi

1. DHA Phase VIII & Clifton Block 2–5
   • Built on reclaimed land
   • History of liquefaction (2006, 2010 events)
   • Weak drainage systems
2. Landhi & Malir Industrial Zone
   • Heavy groundwater pumping
   • Subsurface factory tanks and piping may corrode or collapse
   • Recent shallow quakes in 2025 raise the risk of sudden collapse
3. Korangi Creek Zone
   • Underlying karstic or clay-rich sediments
   • Close to fault lines + subsidence zones

Supporting Case Studies

• Guatemala City (2010): A massive sinkhole swallowed a building after heavy rain followed by tremors.
• Florida, USA: Earthquakes + groundwater pumping have triggered multiple sinkholes.
• Tehran, Iran: Slow ground deformation followed by sinkhole formation in heavily extracted zones.

Conclusion: Is a Large Sinkhole Possible in Karachi?

✅ Yes, it is possible. While karstic rock dissolution (a common sinkhole cause) is rare in Karachi, artificial subsidence + shallow quakes + saturated loose soils are enough to form a large infrastructural sinkhole, especially after monsoon or pipeline failure.

Recommendations:

• Monitor subsiding regions using InSAR (satellite radar).
• Conduct geotechnical drilling in industrial zones.
• Install early warning systems for cavity formation via ground-penetrating radar.
• Avoid building heavy structures over suspected sinkhole-prone zones.

7. Policy Gaps

• Lack of Urban Resilience Planning
• Water Resource Mismanagement
• Inadequate Climate Adaptation Strategy
• Encroachment on Natural Drains

8. Recommendations

1. Develop a Coastal Management Plan
2. Ban Groundwater Extraction in High-Risk Zones
3. Restore and Replant Mangroves
4. Urban Drainage Master Plan
5. Early Warning and Citizen Awareness
6. Strengthen Building Codes
7. Integrate Karachi in National Climate Strategies

What Pakistan Should Do?

1. Zone-Based Retreat and Adaptation

• Relocate only the most at-risk neighborhoods (e.g., parts of Ibrahim Hyderi, Korangi Creek, Lyari riverbanks).
• Use government land further inland to build climate-resilient satellite towns with affordable housing.

2. Coastal Resilience Infrastructure

• Sea walls, surge barriers, and mangrove replantation.
• Green belts to absorb runoff.

3. De-densify Central Karachi

• Incentivize businesses and universities to expand into Hyderabad, Thatta, or Nooriabad.
• Use digital connectivity and rail links to decentralize economic activity.

4. Long-Term Dual-City Strategy

• Begin master planning for a second coastal city (like Ormara or Sonmiani) over the next 50 years.
• Build it green, smart, and elevated — but not as a replacement, rather a redundant buffer.

9. Conclusion

Karachi’s vulnerability to land subsidence is no longer speculative – it is a multifaceted reality with historical precedent. Rising sea levels, excessive groundwater extraction, soft soil, and tectonic instability all contribute to the city’s sinking trajectory. Past seismic activity has caused the submergence of coastal towns near Karachi, showing that natural disasters can accelerate this process. Urgent interventions are needed to reverse the ecological degradation, manage water use, and redesign infrastructure to adapt to present and future risks.

References

Ali, S., & Khwaja, M. A. (2018). Karachi’s Water Woes. SDPI.

ADB. (2021). Post-Disaster Needs Assessment: Karachi Floods 2020.

Bilham, R. (2004). “Earthquakes in Pakistan and Northern India: Historical Review and Risk Analysis.” Seismological Research Letters.

Dawn. (2020). Karachi records heaviest rainfall in 89 years.

Hasan, A., & Raza, M. (2015). Responding to the Urbanization Challenge in Pakistan. UN-HABITAT.

IPCC. (2021). Sixth Assessment Report.

Kakar, A. M. et al. (2021). “Disease outbreaks due to urban flooding in Karachi.” Journal of Public Health (JPH).

NASA SERVIR. (2022). Land Subsidence in Karachi Using InSAR.

Singh, O. P. et al. (2010). Sea level rise in South Asia. Springer.

The Guardian. (2019). Jakarta is sinking: Indonesia to move capital.

WWF-Pakistan. (2021). Mangrove Loss in Sindh: Ecological and Economic Impacts.

Nature (2022), Hussain, M.A., Chen, Z., Shoaib, M. et al.  Sentinel-1A for monitoring land subsidence of coastal city of Pakistan using Persistent Scatterers In-SAR technique. 

Kazmi, A. H., & Rana, R. A. (1982). Geology of Karachi and Surrounding Areas.
This is a print publication, not digitized. You may find it via university geology departments or libraries.
Lashari, A. (2018). Impacts of Climate Change on Karachi’s Coastal Areas.
Not directly available online as a standalone publication. May be cited in environmental policy reports.

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