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Built along the banks of the Chao Praya river as it nears the ocean, Bangkok has long been vulnerable to flooding. Poor urban planning and careless expansion have made the problem worse. And now, climate change eventually could help swamp the city.
The late rainy season storm sweeps across Bangkok, sending sheets of rain down, forcing traffic to a crawl, and quickly flooding low-lying areas.
Warning: water rising
Flooding is a regular feature of this city of 10 million. Usually the water drains away within a few hours. But some climate experts and city planners say future floods may cause lasting damage because of rising sea waters.
Batteries of reports warn of the threat of rising waters to this city and other low-lying communities. The conservation group WWF lists Bangkok alongside Dhaka, Manila, Jakarta, Calcutta, Phnom Penh, Ho Chi Minh City and Shanghai as some of the most vulnerable to massive flooding.
And the United Nation's Intergovernmental Panel on climate change lists Bangkok among the 20 major cities at risk of being swamped by rising sea levels.
Samith Dharmasaroja is the former head of Thailand's metrological department. He gained fame by warning that Thailand's coasts were vulnerable to tsunamis.
The warnings were ignored until the deadly December 2004 Indian Ocean tsunami. Now Samith warns that rising sea levels could swamp Bangkok within two decades.
He says the issue has received little public attention, and unless something is done, Bangkok could be flooded permanently.
"Yes lost forever. Some try to say well forget it because we will move our capital to somewhere else. But it's not that easy," Samith noted. "Moving a capital with 10 million people somewhere; not only the people [have to be moved] you have many constructions - many universities, many government offices, office building, hospitals, and so on. The old historical building - how can you move everything - it would be underwater?"
Samith says the government should consider building an 80-kilometer long system of dikes at the mouth of the Chao Phraya River basin to hold back rising tides. He estimates it would cost more than $3 billion.
Global warming is contributing to rising sea levels, because of melting ice at the poles and the thermal expansion of the water. The issue will be on the agenda at the global climate talks in Copenhagen next month.
Negotiators at the talks, however, are not expected to reach a binding agreement to limit emissions of greenhouse gases, such as carbon dioxide, which are produced by activities such as burning oil. Nor are they expected to agree on aid to developing countries to protect them from rising sea levels and other effects of warmer temperatures.
Bangkok was once known as the Venice of the East because of its system of canals. To contain floods, the city has a system of flood walls, pumping stations, retention ponds and temporary overflows to the north.
But Samith and other experts say that might not be enough. The city has grown dramatically over the past 30 years, spreading into lower lying areas.
Poor urban planning
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Danai Thaitakoo is a lecturer in the Faculty of Architecture at Bangkok's Chulalongkorn University. He says poor planning and urban development have allowed many canals to be filled to make way for roads and other development.
"The canal structure - they don't see the canals as a critical structure for this kind of drainage," Danai said. "When they talk about water - and refilling the canals - most of the canals disappear. We don't have that structure that used to be able to drain the water out of the area or even to contain the water for a certain period."
Danai says planners need to consider restoring the canal system. He says Bangkok also faces the threat of coastal erosion from the rising seas and storm surges.
Other researchers warn that naturally occurring subsidence of the land under the city will add to flooding problems.
Combination of factors could be lethal
Bhijit Rattakul is a former Bangkok city governor who had to deal with the flooding problem while he was in office in the 1990s. Bhijit says rising sea waters and runoff from the northern regions will combine to overwhelm the city.
"There is the overflow of the waters, because of sea level rise and because we cannot discharge the water from the north out to the sea. So that kind of thing will eventually create a scenario … there will be a flood and it's not a normal flood it will be a long flood … not five hours, not six hours may be days before we can pump it out," Bhijit said.
However, engineers with the Bangkok Metropolitan Authority remain confident that existing flood control methods will protect the city for some years to come.
Bangkok faced severe flooding in 1983 and again in 1995. Since then, the government has built 77 kilometers of flood walls along the river banks. The engineers, who are barred by city policy from giving their names, told VOA the walls are a meter high, and that various studies indicate the water level over the next few decades will rise only about 33 centimeters.
The engineers say they will continue to study the issue, but they will need clear evidence that additional work is justified now before asking the city government for more flood control funds.