Bangkok's flood defences losing battle with heavy rain

City Hall has blamed unusually heavy downpours for causing the flood woes and traffic chaos in Bangkok on Monday night. The city's single giant drainage tunnel can't cope.

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Tunnel takes flak for traffic chaos

Supoj Wancharoen 
Apinya Wipatayotin  

City Hall has blamed unusually heavy downpours for causing flood woes and traffic chaos in Bangkok on Monday night as its much-touted giant drainage tunnel was criticised for failing to ease the city's flooding.

Flash floods caused by heavy rains triggered traffic chaos on Bangkok streets, drawing a barrage of complaints from motorists stuck in traffic gridlock for several hours.

Deputy Bangkok governor Amorn Kitchawengkul met the directors of five district offices in northern Bangkok – Don Muang, Sai Mai, Laksi, Chatuchak and Bang Khen – to discuss ways to cope with flood problems in these areas.

The five districts have experienced heavy rain over the past week. Floods in the areas can only be drained into the Premprachakorn canal. But the canal is now filled to capacity and canal water cannot be drained out to the Chao Phraya River, Mr Amorn said.

On Oct 1, rainfall on Chaeng Watthana Road in Laksi district was measured at 144mm – the highest ever recorded in Laksi district.

City Hall explained that its 2.2-billion baht tunnel under Rama IX Road can't prevent flooding in the whole city area.

On Monday night, rain amounts were recorded at 107mm in Laksi, 90.5mm in Klong Toey and 90mm in Saphan Sung, whereas City Hall's drainage systems can only cope with 60mm.

In northern Bangkok, which borders Pathum Thani, there are low-lying areas such as a section of Phahon Yothin Road near the National Memorial and the Lam Luk Ka intersection, which experience persistent flooding caused by heavy rains.

Efforts are being made to drain floodwater in Klong Premprachakorn into the Chao Phraya River via other connecting canals, Mr Amorn said.

Mr Amorn also said that the Meteorological Department has predicted a combination of a low pressure front and a monsoon trough from the southwest which will affect the Central region and Bangkok from now until Friday, after which conditions are expected to improve.

He said that City Hall is working to drain off water in several canals and instal water pumps in flood-prone areas to prevent inundation.

Adisak Khantee, a former director of the department of drainage and sewerage under the Bangkok Metropolitan Administration (BMA), explained why the BMA's existing giant drainage tunnel under Rama IX Road had failed to ease flooding for the whole of Bangkok.

Opened in 2011, the 2.2-billion-baht tunnel was touted as a solution to flash floods that usually come after torrential downpours. He said the drainage tunnel is the only one in the city, out of four planned, so its drainage capacity cannot cover all areas of the capital.

The tunnel has a drainage capacity of 60 cubic metres per second and cannot handle excessive floodwater caused by heavy rains, he said.

Next year, another drainage tunnel will be open under the Bang Sue canal, which will help improve flood drainage in Bangkok, Mr Adisak said.

"I assure you that the tunnel is in full operation. But it is the only tunnel and it cannot ease flooding in the whole city. The tunnel can drain floods covering 50 square kilometres, but Bangkok covers more than 1,600 square kilometres," the Bangkok governor said previously.

He also said that plans are being drawn up to build three more tunnels at Klong Bang Sue, Bung Nong Bon and Don Muang to boost efficiency in flood drainage.

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