Many areas of Bangkok were heavily flooded following heavy rain on Tuesday, as Bangkok Governor Sukhumbhand Paribatra said the giant tunnel does work and floating debris does not obstruct the draining process.
Flooding in Don Mueang (From Patcharee Raksawong's Facebook page)
Traffic police said the flood levels in parts of Bangkok such as Sutthisarn, Din Daeng, Don Muang, Pracha Rat Bamphen and Phaya Thai were as high as 80 centimetres.
The flooding caused heavy traffic congestion in many areas of the capital city.
The Bangkok Metropolitan Administration posted a message on the social networking site Twitter apologising for the delay in its drainage effort.
"All workers are doing their best to alleviate the problem for the people of Bangkok," the BMA said.
Bangkok Grovernor Sukhumbhand said all the water pumps and the giant drainage tunnel in the Rama IX and Ramkhamhaeng areas had been operating at full capacity during heavy rain.
"Even though there are about 20 tonnes of floating garbage and debris each day they don't affect the water draining process because it is screened out before the water enters the tunnel," he said.
MR Sukhumbhand said the giant tunnel is effective in draining water from the city into the Chao Phraya River and the Bangkok Metropolitan Administration (BMA) plans to build three more similar tunnels.
He said this while inspecting the giant tunnel on Tuesday morning.
He said the tunnel, which is five metres in diameter, takes water from Khlong Lat Phrao and Khlong Saen Saep and drains water from Bung Kum, Huay Khwang, Lat Phrao, Wang Thong Lang, Bang Kapi, Chatuchak, Min Buri, Bang Sue, Saphan Sung and Khannayao districts into the Chao Phraya River.
Three of its four water pumps are now running to drain water at a capacity rate of 45 cubic metres per second. All four will be running in the event of heavy rain.
"About 20 tonnes of garbage flows along with water everyday but this does not affect the drainage capacity because it is screened out before entering the tunnel," the governor said.
MR Sukhumbhand said the the tunnel is designed for an area of about 50 square kilometres, but Bangkok covers more than 1,600 sqare kilometres.
Flooding in Sukhumvit (From Chuvit's Facebook page)
Therefore, the BMA plans to build three more tunnels - at Khlong Bang Sue, Bung Nong Bon and Don Muang - to drain water out more effectively to the Chao Phra River.
He insisted that officials of the BMA and the Royal Irrigation Department had coordinated well to install more water pumps at the mouth of the Bang Pakong River to drain water out into the sea.
However, Rak Thailand Party leader Chuvit Kamolvisit said on his Facebook page that the water pumps in the giant tunnel could operate only when the waste-screening equipment is working.
"I've received information from an inside source at the BMA about the giant tunnel," Mr Chuvit said. "The problem is that the waste-screening equipment is broken, so no matter how many water pumps you may have, they're useless."
The different political sides were busy blaming each other while taking the public hostage, he said.
"So when will anyone tell the truth to the people?" the opposition MP asked.
Photos by Weearawong Wongpreedee