According to new research conducted by IIT Bombay experts, Mumbai is sinking at a pace of 2mm per year due to a geographical phenomenon known as land subsidence.
What is Land Subsidence?
- Land subsidence is the gradual settling or sudden sinking of the earth’s surface due to the removal or displacement of subsurface earth materials.
- It is considered a natural-anthropogenic hazard and is irreversible.
- It is estimated that by 2040, land subsidence will affect approximately 8% of the world’s top layer and approximately
- 1.2 billion people live in 21% of the world’s big towns.
- In India areas other than Mumbai like Kolkata and Delhi are also witnessing land subsidence. Areas where the earth matter is made up of thin soil particles, like the alluvial deposits of fertile Gangetic plains, are more vulnerable.
Major causes of Land subsidence
- Natural factors: Land subsidence happens due to gradual or sudden natural compaction or collapse of soils due to reasons like –
- Tectonic activities (e.g. earthquake and faulting).
- Volcanic activities.
- Landslide.
- Formation of sinkholes.
- Thawing of permafrost.
- Anthropogenic causes:
- Compaction of aquifer systems due to extensive groundwater withdrawals: When water is extracted from aquifers, the clay between pockets of water collapse gradually, leading to land subsidence.
- Development of underground infrastructure such as metro, tunnels, etc.
- Excessive underground mining of minerals, oil, and gas.
- High load of constructions such as high-rise buildings
Solution
- Using advanced satellite technology to accurately identify hotspots afflicted by land deformation, can prompt local authorities to carry out ground measurements.
- Understanding the geophysical properties of the subsiding areas to tackle causes.
- For instance, in regions with high groundwater extraction, stricter measures for rainwater harvesting, punishing illegal groundwater mining, etc.
- Implementing solutions to offset the over-extraction of groundwater like- recharging groundwater by rainwater harvesting, managed aquifer recharge, pond revival, curbing illegal groundwater pumping, and planting native species that can help in groundwater conservation.
- Evaluating building conditions in hazard zones to undertake necessary repair and maintenance.
- Incorporating land subsidence in the assessment and modeling of flooding and inundation in urban areas.
- Systematic and continuous monitoring of land subsidence to avoid widespread disasters, especially in areas that are highly populated and prone to other hazards like earthquakes, floods, etc.