Bangkok is sinking - slowly but surely

The floods besieging Bangkok now could just be a foretaste of the sinking Thai capital's grim future as climate change makes its impact felt, experts say.

The low-lying metropolis, built on swampland, is just 30km north of the Gulf of Thailand, where, experts forecast, the sea level will rise by 19 to 29cm by 2050 as a result of global warming.

Water levels would also increase in Bangkok's main Chao Phraya river, which already overflows regularly.

If no action is taken to protect the city, "in 50 years... most of Bangkok will be below sea level", said MrAnond Snidvongs, a climate change expert at the capital's Chulalongkorn University.

Groundwater extraction

But global warming isn't the only threat. Years of aggressive groundwater extraction to meet the 12 million-strong city's growing needs have also been blamed for Bangkok's gradual sinking.

The city was sinking by 10cm a year in the late 1970s, according to a study published last year by the World Bank, the Asian Development Bank (ADB) and the Japan Bank for International Cooperation.

That rate has since dropped to less than 1cm annually, they said, thanks to government measures to control groundwater pumping.

But Mr Anond disputed their projections, saying the capital was still sinking at "an alarming rate" of 1cm to 3cm a year.

While scientists may argue over the exact figures, they agree about what lies in store for Bangkok.

"There is no going back. The city is not going to rise again," said the ADB's lead climate change specialist David McCauley.

Given the combined threats facing Bangkok - land subsidence, rising temperatures and rising sea levels - the World Bank has predicted that the city's flood risk will increase four-fold from now by 2050.

And the Organisation for Economic Cooperation and Development has classified the Thai capital among the 10 cities in the world facing the biggest potential impact from coastal flooding by 2070.

For now, Bangkok is relying on a complex system of dykes, canals, locks and pumping stations to keep the rising waters at bay.

But the flood protection efforts failed to prevent an onslaught of run-off water from the north from swamping at least a fifth of the capital.

The murky flood waters, triggered by three months of heavy monsoon rains, are edging in on Bangkok's glitzy downtown area, threatening luxury hotels, office buildings and shopping malls.

Rapid urbanisation is one reason the rains are affecting the sprawling megacity so badly, experts say.

As the area that needs flood protection gets larger and more built-up, the water "has fewer places to go", said Dr Francois Molle, a water management expert at France's Institut de Recherche pour le Developpement.

Bangkok will eventually be underwater. "The only question is when," said Dr Molle.

Experts say Thai authorities must address the capital's land use and consider relocating factories or industrial parks in flood-prone areas.

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