Indian Deltas Sinking Due to Human Activity

Context

According to satellite data, significant Indian deltas, such as Brahmani and Mahanadi, are rapidly subsiding under the influence of human factors such as the over-pumping of groundwater and urbanisation, which accelerates the subsidence rate faster than natural and raises the risk of millions of people because of the vulnerability to floods and the threat of livelihoods, and the mitigation measures require urgent intervention strategies oriented at sustainable water management and sediment flow.

The Crisis: Widespread Delta Subsidence

• Cause to Be Concerned: In the recent study carried out by satellites Sentinel-1 (2014-2023) on the planet, there was evidence of serious land sinking in the major deltas with India being a hotspot.
• Important Deltas Affected: Brahmani and Mahanadi deltas are of particular concern, and 77% and 69% of their areas are reporting a rate of sinking of more than 5 mm/ year, which is greater than that due to natural geologic subsidence.
• Human-Caused Point of Acceleration: Although natural compaction takes place, man-made actions are accelerating it drastically to such an extent that the natural geological changes are now causing a severe environmental crisis.

Causes: Human Footprint on Deltas

• Groundwater Depletion: This is mainly caused by over-pumping of ground water to irrigate land, support industries and domestic purposes, leading to soil compaction and land collapse.
• Sediment Starvation: The lesser delivery of sediments to the deltas as a result of upstream dams and other diversions does not allow deltas to accrede at a rate sufficient to keep up with rising sea levels.
• Urbanization & Load: Fast urbanization and the presence of heavy infrastructure exert a lot of weight on deltaic soil which further enhances subsidence.

Impacts: Threat to People and Environment

• Heightened Flood Risk: Sinking land will raise relative sea-level rise and coastal and riverine regions will be prone to floods caused by surges, rivers and heavy rain.
• Risk to Livelihoods: Deltas are home to big populations (more than 340 million in the world) and hence the loss of agriculture, infrastructure and coastal settlements by sinking.
• Sinking Faster than Sea-Level Rise: The subsidence rates in Indian deltas are often faster than is predicted to occur in the sea-level, doubling the burden of these areas.

Solutions & Way Forward 

• Sustainable Groundwater Management: This should have strict regulation, encourage harvesting of rain water and efficiency in irrigation (e.g., drip irrigation).
• Sediment Management: Resolve the issue of water management upstream to permit greater deposition in deltas, which might be by controlled environmental flows.
• Integrated Coastal Zone Management: Design policies to ensure there is a balance in development and environmental sustainability including high resolution monitoring.
• Urban Planning: Limit the high-rise construction in susceptible delta territories and foster green infrastructure.
• Policy & Research: Enhance the use of subsidence data in disaster management strategy and invest in further, high-resolution monitoring.

Source: The Hindu

UPSC Prelims Practice Question

Q. Consider the following statements regarding sinking river deltas:

1. Natural compaction of deltaic sediments is a major cause of delta subsidence.
2. Excessive groundwater extraction accelerates the sinking of deltas.
3. Construction of upstream dams increases sediment supply to deltas.
4. Sea level rise worsens the vulnerability of sinking deltas.

Which of the statements given above are correct?

A. 1, 2 and 4 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2, 3 and 4

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