River Delta Subsidence:
A new global study published in Nature warns that several of India’s major river deltas are sinking at alarming rates placing millions at increasing risk of flooding and displacement.
Key Findings of the Study:
- The research analysed 40 major river deltas across 29 countries, covering areas with over 236 million inhabitants exposed to near-term flood risk.
- In India, the study identifies Ganga-Brahmaputra, Brahmani, Mahanadi, Godavari, Cauvery and Kabani deltas as experiencing significant land subsidence.
- Land subsidence exceeds the global mean sea-level rise (~4 mm/year), with over half of deltas subsiding faster than 3 mm/year during 2014–2023. 35% of total delta area globally is sinking, and in 38 of 40 deltas, more than half the area shows subsidence.
- Brahmani (77%) and Mahanadi (69%) are among the fastest-sinking deltas, with large areas subsiding at over 5 mm per year.
- Nearly 50% of deltas, including the Ganga-Brahmaputra, Brahmani, and Mahanadi, are subsiding across over 90% of their area.
- 7 major deltas, Ganga-Brahmaputra, Nile, Mekong, Yangtze, Amazon, Irrawaddy and Mississippi, account for 57% of global subsiding delta area (~265,000 sq km).
- Major delta cities such as Kolkata, Alexandria, Bangkok, Dhaka, and Shanghai are sinking at rates equal to or higher than surrounding regions, increasing risks of urban flooding.
