LAND SUBSIDENCE: GEOGRAPHY
NEWS: The roof overhead and the ground beneath their feet, crumbled
WHAT’S IN THE NEWS?
The land subsidence in Belgachia, West Bengal, caused by unregulated dumping and poor urban planning, disrupted basic services for hundreds of families. It highlights the urgent need for scientific landfill management, groundwater regulation, and accountable urban governance to prevent such man-made disasters.
Context: Belgachia Land Subsidence Crisis, West Bengal
• What happened: In Belgachia, an urban area in north Kolkata, West Bengal, a major land subsidence event occurred at an old municipal dumping ground.
• Immediate consequences:
• Collapse of underground infrastructure led to the disruption of electricity and water supply.
• Hundreds of families in surrounding slums and residential areas were affected, losing access to basic services.
• Wider significance: This is not an isolated accident but a symptom of man-made urban mismanagement, especially in waste disposal and unregulated development.
What is Land Subsidence?
• Definition: According to the National Oceanic and Atmospheric Administration (NOAA), land subsidence is the sinking or downward settling of the Earth's surface, caused by movement of underground materials.
• Types of causes:
• Natural causes: Tectonic movements, karst topography (dissolution of limestone), earthquakes.
• Man-made causes: Groundwater depletion, mining, and poor land use practices.
• Global relevance:
• Cities like Jakarta (Indonesia) and Manila (Philippines) are sinking several centimeters per year due to over-pumping of groundwater.
• Other affected cities include New Orleans, Vancouver, and Mexico City.
Recent Indian Example: Joshimath Land Subsidence (2023)
• Location: Joshimath, a pilgrimage and military town in Uttarakhand.
• Extent: Around 65% of houses were reported to be damaged due to land subsidence.
• Causes: Construction of roads, hydroelectric tunnels, poor drainage, and fragile geology.
• Lesson: Shows how natural fragility and unscientific development lead to irreversible urban crises.
Major Causes of Land Subsidence in Urban India
a) Over-extraction of Groundwater
• Why it happens: Cities extract massive amounts of groundwater for drinking, irrigation, and industrial uses without recharge.
• Impact: Water removal reduces underground pressure, causing aquifer compaction and surface sinking.
• Example: In Delhi and Chennai, land subsidence has been linked to unsustainable groundwater extraction.
b) Unregulated Dumping of Solid Waste
• How it contributes: Landfills create vertical load on weak soil, especially if waste is dumped on wetlands or marshy land.
• In Belgachia, decades of unscientific dumping altered the land profile, eventually leading to collapse.
• Waste degradation also produces methane and leachate, further weakening the ground.
c) Rapid and Unscientific Urbanization
• Nature of problem: High-rise buildings, flyovers, and metro tunnels are often constructed without proper soil testing or respect for load-bearing capacity.
• Result: Added weight and underground vibrations cause the land to gradually sink or crack.
• Observation: Urban planning often ignores geotechnical surveys, especially in slum areas and near water bodies.
d) Natural Geological Factors
• Karst regions: Areas where underground limestone dissolves over time, leaving behind voids that collapse.
• Seismic activity: Earthquakes and minor tremors can destabilize the soil, especially in flood-prone or low-lying urban regions.
• These factors often combine with man-made stresses to accelerate subsidence.
5. Consequences and Urban Impact of Land Subsidence
a) Damage to Public and Private Infrastructure
• Cracks appear in roads, bridges, buildings, and pipelines.
• Municipal costs increase due to recurring repairs and emergency restorations.
• In Belgachia, subsidence caused collapse of electricity poles and pipelines, disrupting essential services.
b) Displacement of Vulnerable Populations
• Slum communities, often located near dumping grounds and low-lying areas, are forcibly displaced.
• Temporary shelters lack sanitation, clean water, or health facilities, creating humanitarian distress.
• Families face loss of housing, livelihoods, and security.
c) Public Health Emergencies
• Waterlogging and flooding become common in sunken areas, breeding mosquitoes and pathogens.
• Exposure to chemical sludge, methane, and foul gases leads to:
• Respiratory infections (asthma, bronchitis).
• Gastrointestinal diseases (diarrhoea, cholera).
• Skin disorders due to toxic contact.
Way Forward: Comprehensive Solutions
a) Scientific Landfill Management
• Segregate and process waste at the source (dry, wet, hazardous).
• Promote composting, recycling, waste-to-energy plants.
• Restrict the height, weight, and expansion of landfills.
• Use sloping guidelines and geo-synthetic covers to stabilize dump sites.
b) Soil Testing and Predictive Modelling
• Conduct geotechnical and hydrological studies before any major construction.
• Use GIS-based simulation models to predict stress points and land sinking trends.
• Establish early warning systems to detect shifts and vibrations in real-time.
c) Revival of Local Governance and Urban Planning
• Empower elected municipal representatives with:
• Urban planning authority.
• Budget control for disaster management.
• Regular audits of:
• Landfill sites.
• High-risk constructions.
• Encroachments near water bodies.
d) Inclusion of Ragpickers in Urban Waste Management
• Ragpickers are integral to recycling and waste segregation.
• Formalizing their work through:
• ID cards, safety gear, and training.
• Linking them to urban employment schemes.
• Involving them in municipal solid waste planning.
Conclusion
• The Belgachia land subsidence episode is a wake-up call for India's cities to address the hidden dangers beneath urban surfaces.
• Cities must move beyond firefighting and embrace sustainable urban planning, scientific waste management, and inclusive governance.
• Preventing future disasters requires integrating technology, local knowledge, and community participation to make urban areas resilient, equitable, and safe.
Source : https://www.thehindu.com/news/national/west-bengal/the-roof-overhead-and-the-ground-beneath-their-feet-crumbled/article69415952.ece