Mumbai ‘sinking’ by an average of 2mm annually
Recent new research warns that Mumbai is sinking at the rate of 2 mm annually.
Researchers analyzed subsidence in 99 countries using InSAR (Interferometric synthetic-aperture radar) data. According to this research, China’s Tianjin will be the fastest sinking coastal city in the world.
- InSAR is a technique to obtain a map of ground deformation. It uses radar images of the Earth’s surface taken by orbiting satellites.
- NASA and ISRO (Indian Space Research Center) are working together on the NASA-ISRO Synthetic Aperture Radar (NISAR) mission.
- The goal of this mission is to measure changes in the Earth’s surface. Earth’s subsidence is the gradual subsidence or sudden sinking of the earth’s surface. It is caused by the removal or displacement of subsurface material from the Earth’s surface.
- This adversely alters the local water system. This causes floods, and damages to civil infrastructure like roads, railways, telecommunications etc.
Causes of subsidence:
- Excessive groundwater exploitation, destruction of natural wetlands, development of underground infrastructure, mining and other ecological constraints.
- It can also be caused by natural compaction or subsidence of the soil.
Soil subsidence includes: sinkhole formation, earthquakes, or thawing of permafrost (permanent frost-land).
Ways to control or prevent land subsidence:
- Discouraging water extraction by pumping,
- Artificial replenishment of aquifers from the land surface,
- Leakage of water into aquifers through wells, or by adopting the above methods in combination.
Earlier, the Central Ground Water Board had signed a MoU with the Indian Institute of Remote Sensing. Its objective was to study the effect of groundwater exploitation on land subsidence in North India.
Source – The Hindu
