Sand mining raises risk of Asian deltas sinking

Reuters: Sand mining from rivers is depriving many low-lying Asian deltas of the sediment they need to maintain themselves, raising the risk of worsening land loss to sea level rise, researchers say.
Combined with losses of soil-holding mangroves and accelerating groundwater extraction, which can lead to land sinking, the mining is increasing climate-related threats for those living in low-lying coastal areas, they said.
“We have created a recipe for climate disaster,” said Marc Goichot of the World Wildlife Fund (WWF).
Deltas dependent on the Ganges-Brahmaputra-Meghna, Mekong and Yangtze rivers are now sinking and shrinking, according to research carried out by WWF – a situation worsened by climate-related warming and rising sea level.
That is a problem not only because the deltas are home to millions of people but because they produce a significant share of the region’s food.
The Mekong delta, for instance, home to 17 million people, is a major source of rice for the region and underpins a quarter of Vietnam’s GDP, Goichot said.
“It is 40,000 square kilometres – larger than many countries – and most of it is sinking,” he said.
At the heart of the problem, Goichot said, is a lack of enough sediment moving down the rivers – and much of that is the result of mining of sand as a construction material and for other uses, he said.
In some major rivers in Asia, such as the Mekong, Yangtze and Ganges-Brahmaputra-Meghna, as much as 90 per cent of the sediment that once travelled down the system is now collecting in reservoirs or being mined, WWF’s research showed.
That means much less material is arriving in delta areas to replace soil lost to coastal erosion and other natural processes.
For those living in the deltas, it can mean growing risk of floods, inundation from coastal storm surges and worsening salt contamination in drinking water.
Kusum Athukorala, former chair of the Sri Lanka Water Partnership, said the loss of sand also means less water-storage capacity in rivers, and less water flowing in to restore aquifers.