Major River Deltas Sinking Worldwide

New research published in the journal Nature Geoscience shows that 73% of the world’s major river deltas, formed when rivers deposit sediment on their way out to sea, are sinking. This has major implications for the 500 million people who live in or near river deltas.

Results show that sediment delivery to the deltas has been reduced or eliminated at the majority of deltas, of which much can be attributed to upstream damming and a reduction in the number of distributory side channels. The creation of reservoirs, floodplain engineering and extractive activities are also factors, causing sediment compaction. The Po Delta in Italy, for example, subsided by 3.7 metres in the twentieth century, with 81% of this attributable to methane mining.

The reduction in sediment delivery is causing the deltas to sink, exacerbating the risk of flooding around the delta, caused by an increase in sea level rise under climate change. Population growth and development around the delta will also further exacerbate flood risk. Overall, the surface area of deltas vunerable to flooding could increase by 50% under the Intergovernmental Panel on Climate Change (IPCC) projections for sea level rise in the twenty first century.

Research paper: Syvitski, J.P.M., Kettner, A.J., Overeem, I. et al. (2009). Sinking deltas due to human activities. Nature Geoscience. Doi: 10.1038/NGE0629
Original source: Science for Environment Policy, European Commission