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.

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

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 the Southeast Asia regional research director for START (global change System for Analysis, Research and Training, a multi-national NGO).[http://start.org/]

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. 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 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.

It is a necessary project, but so far it has not got anywhere because politicians only look at the short-term cost. It is one of a number of measures one 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 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, 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.”

Bangkok er sandsynligvis står over for sådanne alvorlige oversvømmelser i midten af dette århundrede, at dele af den thailandske hovedstad, kan må opgives, medmindre radikal der gribes ind snarest.

Indsynkning og fattige byplanlægning har resulteret i lavtliggende by gradvist synker mellem 2cm og 5cm et år.

Med den ekstra problemer af stigende vandstand, som FN's Internationale Panel on Climate Change skøn på mellem 18 cm og 59cm i 2050, og kysterosion langs bugten i Thailand, kunne Bangkok snart kæmper med regelmæssige oversvømmelser op til 2 m høj.

I årtier har vi vidst, at byen var ved at synke på grund af sediment kompression, men nyere forskning har vist, at Jordskorpen sig selv er også deprimerende her, forårsaget af tektoniske begivenheder, der er helt uden for vores kontrol. Det er en kombination af faktorer, "sagde den sydøstlige Asien regionale forsknings-direktør for START (globale ændringer System for analyse, forskning og uddannelse, en multi-national NGO). [Http://start.org/]

Tidlige advarsler Eksperter første lød advarsler om, at Bangkok var ved at synke i begyndelsen af 1980'erne. En stor del af problemet var forårsaget af vand til industrien udpakkes fra grundvandsresourcerne hurtigere end den kunne erstattes, hvilket jorden til at komprimere.

Ændringer til loven om vandforbruget har bidraget til at mindske antallet af jorden kompression, men forskerne advarer om, at politikerne stadig ikke har givet nok tænkt til omfanget af fremtidige problemer.

Et andet problem er, at mange af Bangkoks kanaler, som engang drog sammenligninger med de Venedig, er blevet cementeret og omdannet til veje, mens huse og fabrikker er blevet bygget på den naturlige flodsletter omkring hovedstaden.

I regntiden, brast kanalerne, der er tilbage ofte er deres banker, hvilket dele af byen under vand. Og mens oversvømmelser på nuværende omfatter regnvand fra nord, bør havet begynder at oversvømme fra syd, vil det sætte store dele af frugtbar landbrugsjord i fare for saltindhold.

Problemet er meget større end selve byen - det påvirker fire eller fem provinser langs kysten, som skal slutte sig sammen og koordinere deres indsats. Der er projekter, der udføres, men der er behov for en holistisk tilgang - i øjeblikket, en provins, for eksempel, er plantning mangrover bidrage til at mindske erosion, hvilket er fint, men det gør ikke meget godt, hvis det naboprovinsen gør noget andet .

En fremgangsmåde vil ikke løse dette - må der være mange løsninger, og der er behov for at være et sted, hvor forvaltninger og akademikere kan samle deres ideer og beslutte, hvad de skal gøre. I øjeblikket har vi ikke noget lignende det, og svaret er fragmenteret.

Dike planer Anond opfattelse er, at folk og industrien gradvist vil blive tvunget til at opgive områder med stor risiko for oversvømmelser og flytte til højere grund, med diger er bygget til at beskytte vitale infrastruktur såsom Suvarnabhumi Airport.

En mere radikal forslag er at bygge en massiv diget, ca 100 km lang, på tværs af bugten Thailand fra Hua Hin til Pattaya. Væggen, der ville være tre gange større end verdens længste diget, den 33 km lange Saemangeum Seawall i Sydkorea, ville koste hundreder af millioner af dollars, men eksperter advarer, at omkostningerne til den thailandske økonomi havvand oversvømmelse landbruget og industrigrunde kan være langt højere.

Det er et nødvendigt projekt, men hidtil har det ikke fået nogen steder, fordi politikerne kun ser på de kortsigtede omkostninger. Det er en af en række foranstaltninger bør man se på, herunder at genopbygge byens kanaler, og handler for at bevare vådområder og forhindre flere bygninger på dem. Den massive diget ville være teknisk muligt, ifølge en hollandsk arkitekt og byplanlægger. "Havet er kun ca 20m dybt i de fleste steder, så teknisk set er det ikke noget problem overhovedet - spørgsmålet er én af omkostningerne," sagde han.

Men, kampagneleder for Greenpeace Sydøstasien, advarede om, at de miljømæssige og sociale konsekvenser ville være vanskeligt at forudsige. "Der er fiskersamfund langs hele kysten, og det ville have en enorm økonomisk og social indvirkning på dem," sagde han. Han dog enige om, at en vis form for koordineret indsats var nødvendig. "Bangkok er blevet identificeret som en af de klimaforandringer hot spots - det vil være en af de hårdest ramte byer i verden ... Klimaforandringer og deres virkning skal være på den nationale dagsorden og gjorde en central del af Thailand's udviklingsplaner - det kan ikke ses som en stand-alone spørgsmål. "