The Chao Phraya river delta in Thailand is one of the fastest-sinking regions in the world, according to a recent analysis of satellite data. This sinking phenomenon is not unique to Thailand, as river deltas around the world are experiencing a similar trend, putting millions of people at risk of flooding.
Researchers at Virginia Tech, led by Manoochehr Shirzaei, studied 40 river deltas, including the Mekong, Mississippi, Amazon, Zambezi, Yangtze, and Nile, to determine the rate at which they are sinking. The data, collected from 2014 to 2023 using the European Space Agency’s Sentinel 1 satellite radar, revealed that more than a third of each delta is sinking, with some areas experiencing subsidence rates exceeding global sea level rise.
In many cases, the sinking of river deltas poses a greater threat to the communities living on them than sea level rise itself. This is because as the deltas sink, the combined effect of sinking land and rising seas leads to accelerated sea level rise in these regions. For example, the Chao Phraya delta in Thailand, where Bangkok is located, has an average subsidence rate of 8 mm per year, twice the current global mean sea-level rise.
The main drivers of subsidence in these deltas are groundwater extraction, sediment alteration, and urban expansion. Groundwater extraction was found to have the strongest overall influence on subsidence, but some deltas are more impacted by sediment changes and urban expansion. Shirzaei emphasizes the importance of addressing human-driven subsidence through measures like groundwater regulation, managed aquifer recharge, and sediment management.
One concerning factor highlighted in the study is the impact of water-intensive facilities, such as data centers, on groundwater extraction and subsidence in vulnerable regions like river deltas. Shirzaei warns that data centers relying on local water supplies can worsen the risk of rapid land subsidence in these areas, leading to infrastructure instability and increased flooding.
Policy-makers and stakeholders are urged to consider the local factors contributing to subsidence in river deltas and prioritize mitigation measures. By addressing issues like groundwater extraction, sediment management, and urban expansion, communities in these at-risk regions can better prepare for the challenges posed by sinking land and rising seas. It is essential to take a holistic approach to adaptation efforts and ensure that all stakeholders are involved in sustainable solutions for the future of river deltas worldwide.
