belfasttelegraph

Monday 29 December 2014

The real Atlantis? Megacities under threat from land subsidence

Venice, flooded in November 2013. Human-driven subsidence has stopped but the ground level is still falling thanks to natural factors.
Venice, flooded in November 2013. Human-driven subsidence has stopped but the ground level is still falling thanks to natural factors.
Tokyo. The centre of the most populous metropolitan area of the world (home to more than 36 million), Tokyo has struggled with subsidence for decades. Groundwater extraction peaked in the 1970s and subsidence was bought down through restrictions to a rate 1cm a year in the early 2000s.
Dhaka. The Bangladeshi capital is home to around 15 million, with 546 water pumps removing around 1.9 million cubic metres of water a day for drinking supplies - this still only meets 85 per cent of demand.
New Orleans. New Orleans may not be a megacity in terms of population (roughly 370,000) but is sinking all the same. Land reclamation in the first half of the 20th century has turned the land into a giant sink, with ground levels falling as low as 12ft below sea level.
Jakarta. The capital of Indonesia and its population of nearly 10 million are expected to sink five to six metres by the end of the century unless groundwater extraction is stopped.
Ho Chi Minh City. The capital of Vietnam, formerly known as Saigon, is expected to grow to a population of 13.9 million by 2025 and is sinking 2cm a year.
Bangkok. Land subsidence has affected the capital of Thailand for more than 35 years, with the ground's soft thick clay only exacerbating the threat from flooding.

A new paper from the Deltares Research Institute in the Netherlands published earlier this month identified regions of the globe where the ground level is falling 10 times faster than water levels are rising - with human activity often to blame.

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