Act now to stop Bangkok sinking, urge scientists

Irin News 13 Jan 10;

BANGKOK, 13 January 2010 (IRIN) - Bangkok is likely to face such severe flooding by the middle of this century that parts of the Thai capital may have to be abandoned unless radical action is taken soon, experts warn.

Subsidence and poor urban planning have resulted in the low-lying city gradually sinking between 2cm and 5cm a year, according to researchers in Thailand.

With the added problems of rising sea levels, which the UN International Panel on Climate Change estimates at between 18cm and 59cm by 2050, and coastal erosion along the Gulf of Thailand, Bangkok could soon be contending with regular flood waters up to 2m high.

“For decades we have known that the city was sinking because of sediment compression, but recent research has shown that the crust of the earth itself is also depressing here, caused by tectonic events that are totally outside our control. It is a combination of factors,” said Anond Snidvongs, the Southeast Asia regional research director for START (global change System for Analysis, Research and Training, a multi-national NGO).

Early warnings

Experts first sounded warnings that Bangkok was sinking in the early 1980s. Much of the problem was caused by water for industry being extracted from underground aquifers faster than it could be replaced, causing the soil to compress.

Changes to the law on water use have helped reduce the rate of soil compression, but researchers warn that policy-makers are still not giving enough thought to the scale of future problems.

Another issue is that many of Bangkok’s canals, which once drew comparisons with those of Venice, have been concreted over and turned into roads, while houses and factories have been built on the natural floodplains surrounding the capital.

During the rainy season, the canals that are left frequently burst their banks, causing parts of the city to flood. And while the floods at present comprise rainwater from the north, should the sea start to flood from the south, it will put large swathes of fertile farmland at risk of salinity.

“The problem is much larger than the city itself – it affects four or five provinces along the coast that need to join together and co-ordinate their efforts,” Anond said.

“There are projects being undertaken, but there needs to be a holistic approach – at the moment, one province, for example, is planting mangroves to help reduce erosion, which is fine, but it does little good if the neighbouring province is doing something different.

“One approach will not solve this – there need to be many solutions, and there needs to be a venue where administrations and academics can pool their ideas and decide what to do. At the moment we do not have anything like that and the response is very fragmented.”

Dike plans

Anond’s view is that people and industry will gradually be forced to abandon areas prone to flooding and move to higher ground, with dikes being built to protect vital infrastructure such as Suvarnabhumi Airport.

A more radical proposal is to build a massive dike, around 100km long, right across the Gulf of Thailand from Hua Hin to Pattaya.

The wall, which would be three times bigger than the world’s longest dike, the 33km-long Saemangeum Seawall in South Korea, would cost hundreds of millions of dollars, but experts are warning that the cost to the Thai economy of sea-water flooding agricultural and industrial land could be far higher.

“I think it is a necessary project, but so far it has not got anywhere because politicians only look at the short-term cost,” said Seree Supharatid, director of the Natural Disaster Research Centre at Rangsit University.

“It is one of a number of measures we should be looking at, including rebuilding the city’s canals, and acting to preserve the wetland areas and prevent any more building on them.”

The massive dike would be technically feasible, according to Cor Dijkgraaf, a Dutch architect and urban planner. “The sea is only around 20m deep in most places, so technically it is no problem at all – the issue is one of cost,” he said.

However, Tara Buakamsri, campaign manager for Greenpeace Southeast Asia, warned that the environmental and social consequences would be difficult to predict.

“There are fishing communities all along the coast, and this would have a huge economic and social impact on them,” he said.

He agreed, however, that some form of coordinated action was necessary.

“Bangkok has been identified as one of the climate change hot spots – it will be one of the most affected cities in the world... Climate change and its effect needs to be on the national agenda and made a central part of Thailand’s development plans – it cannot be seen as a stand-alone issue.”