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article imageMegacities and the risks of sinking land

By Tim Sandle     May 10, 2014 in Environment
Utrecht - The world's coastal 'megacities' face bigger problems from land subsidence than they do from a potential rise in the sea level.
Scientists have raised the concern that, In some parts of the world, the ground is going down 10 times faster than the water is rising. Worryingly, the causes are very often driven by human activity. This is affecting a number of megacities. A megacity is a metropolitan area with a total population in excess of ten million people. The largest of these are the metropolitan areas of Tokyo, Delhi, Mexico City, New York and Shanghai: each of these has a population in excess of 20 million inhabitants.
The latest warnings have come from the recent meeting of the European Geosciences Union General Assembly. Here, Gilles Erkens from the Deltares Research Institute, in Utrecht, in the Netherlands warned that parts of Jakarta, Ho Chi Minh City, Bangkok and numerous other coastal urban settlements would sink below sea level unless action was taken.
In his research paper he writes: "Because of ongoing urbanization and population growth in delta areas, in particular in coastal megacities, there is, and will be, more economic development in subsidence-prone areas. The impacts of subsidence are further exacerbated by extreme weather events (short term) and rising sea levels (long term).Consequently, detrimental impacts will increase in the near future, making it necessary to address subsidence related problems now."
Erkens additionally told the BBC that: ""Land subsidence and sea level rise are both happening, and they are both contributing to the same problem - larger and longer floods, and bigger inundation depth of floods. The most rigorous solution and the best one is to stop pumping groundwater for drinking water, but then of course you need a new source of drinking water for these cities. But Tokyo did that and subsidence more or less stopped, and in Venice, too, they have done that."
In an example of the human driven impact, decades of ground water extraction saw Tokyo descend two meters before the practice was stopped a few years ago.
More about megacities, Land, Sinking, Water
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