As per Study, Seven major deltas — Ganga-Brahmaputra, Nile, Mekong, Yangtze, Amazon, Irrawaddy and Mississippi — account for about 57% of total subsiding delta area worldwide.
Key Reasons for Sinking of River Deltas
- Excessive groundwater extraction: Driven by unsustainable use for agriculture, industry and domestic supply in densely populated regions.
- Land Subsidence: Between 2014 and 2023, more than half of deltas experienced subsidence rates exceeding 3mm per year globally.
- Brahmani and Mahanadi stood out among the fastest-sinking deltas in India.
- Reduced seasonal silt deposits: It is essential for maintaining their elevation, while natural sediment flow is disrupted by river regulation and infrastructure.
About River Deltas
- A Depositional feature formed as rivers empty their water and sediment into another body of water, such as an ocean, lake, or another river.
- For a delta to form, the flow of a river must be slow and steady enough for silt deposition and build up. Hence, not all rivers form deltas.
- They occupy just 1 per cent of land area, support around 6% of the global population, and host 10 of world’s 34 megacities.
Measures to Protect Deltas
- Integrated approach: Prioritizes subsidence mitigation (for example, groundwater regulation, managed aquifer recharge and sediment management).
- Targeted Interventions: Addressing subsidence as an immediate and localized challenge along with broader efforts to counter climate change-driven global sea-level rise.
- Advanced monitoring: Use of InSAR (Interferometric Synthetic Aperture Radar) for monitoring surface elevation changes, etc.
