BMA takes baby steps to drain waters
City Hall tries its best to stem flash flooding as monsoon downpours leave the capital in chaos, writes Supoj Wancharoen
The Bangkok Metropolitan Administration (BMA) is improving the city’s ability to withstand flash floods with new facilities, tools and manpower, a crucial move given the capital can now see up to 60mm of rainfall in 24 hours and monsoon rains cause canal levels to rise.
Two recent episodes highlight the problem as Bangkok was beset with deluges and thunderstorms last week that hit a crescendo last Wednesday and Thursday.
Some 23 parts of the city where submerged on those two days including a section of Ratchadaphisek Road in front of the Criminal Court which disappeared under 20cm of water.
The heaviest rainfall was measured in Wang Thonglang district, when the maximum rate hit 169mm per hour or three times what the city’s drainage system can handle.
Deputy Bangkok governor Chakkaphan Phewngam, who is responsible for flood control, said yesterday the BMA is building two drainage tunnels to help out — one measuring 6.4km in Bang Sue district and another 9.4km one near Bung Nong Bon in Prawet district.
The former has been completed and will open for a test run in August. The second tunnel should be finished by 2019, Mr Chakkaphan said.
“We believe they will definitely help ease conditions during t he annual floods as they will both drain water from the heavy rains directly into the Chao Phraya River,” he said.
He declined to give details about how much water the tunnels could accommodate or siphon off.
Mr Chakkaphan said the BMA’s seven drainage tunnels have played an instrumental role in containing flooding. Their combined capacity stands at 155.2 cubic metres per second, he said.
Bangkok is home to two giant tunnels that drain floodwater into the city’s main river: one is near Bung Makkasan and the other is beneath Rama IX Road. The former measures 5.98km and 4.6m in diameter. The latter is 5.11km and 5m in diameter, the deputy governor said.
Five other drainage tunnels are located on Sukhumvit sois 26, 36 and 42, near Klong Prem Prachakorn, and in Phaya Thai district. But these are less able to mitigate flooding as they drain the water into nearby canals, he added.
Other facilities include a 77km flood wall along the Chao Phraya and dykes built under projects initiated by the late King Bhumibol Adulyadej. Over half the city’s 6,400km of drainage pipes are now being cleaned up, Mr Chakkaphan said.
Bangkok is famous for its polluted klongs (canals). There are 1,682 in the city and 121 are being cleared of weeds and other blockages so the water can run freely, officials said.
City authorities have installed 176 pumping stations, 232 floodgates and 271 deep wells to handle flash floods. Special areas set up to collect rainwater — known affectionately here as gaem ling or “monkey cheeks” — can receive 13 million cu/m of water, the BMA said.
As a further safety measure there are flood-prevention centres and three radar sites in Nong Chok, Nong Kham and Nong Bon to monitor rainfall and alert authorities when needed.
Other weapons in the city’s arsenal include portable pumps (the BMA has 2,514 of these at its disposal), sand bags (3.6 million) and mobile vehicle-mounted electricity generators (17), Mr Chakkaphan said. Over 700 officials at 108 disaster relief units are also on hand.
The deputy governor earlier raised concern over sanitation. He blamed some of the flooding in the city on poor waste disposal, saying city officials must unclog drainpipes to allow floodwater to flow more easily into natural water sources.
The situation would be helped if the public was responsible and stopped dumping waste into canals, he said.
Houses and other obstructions can also hinder efforts to help the floods subside, he said, pointing by way of illustration to the 3,000 or so houses along Klong Lat Phrao which have been found to encroached into the canal, blocking the waterway.
About 500 residents have agreed to relocate, he said.