Giant drains ‘will not prevent floods’

EVEN with 20 giant drainage tunnels, Bangkok will never be safe from floods, predicts a respected university lecturer. 
Thanawat Jarupongsakul, who teaches at Chulalongkorn University’s Department of Geology, made this prediction when the city administration began touting these structures as a way to improve the capital’s flood problems. 
The city’s administration has already built four giant tunnels at great cost, and there are four others under construction and at least one more being proposed. 
“I personally think these tunnels are a waste of money,” Thanawat said, adding that not only did they cost a lot to build, maintenance costs were also very high. 

Thanawat
He pointed out that Bangkok was sinking, which means the level of the Chao Phraya is rising higher than the city’s canals and its drainage system. 
“This means you have to use pumps to push the water into the river, but when these devices break down, Bangkok can get easily submerged,” he said. 
On June 7, several parts of Bangkok were under water after just a few hours of rain, leaving many Bangkokians stranded in nightmarish traffic for hours and prompting them to lambaste the Bangkok Metropolitan Administration (BMA). 
The city authorities later admitted that there had been some hiccups with an overwhelmed fuse, which disrupted the operations of the Bang Sue Tunnel.

 “Water from these tunnels has to be pushed high so it can flow into canals and then it has to be pushed even higher so it can flow into the river. It’s a difficult task,” Thanawat said. 

He also said this drainage system was implemented several decades ago and many of the pipes must be clogged. 
“Also you can’t expect this system to handle 60 millimetres of rainfall, when just 40mm to 50mm of rain floods the capital,” he said, adding that Bangkok’s urban expansion was also the cause of growing flood risks. 
Bangkok residents use up to 6 million cubic metres of water daily and the wastewater from one big condo project in the heart of the capital is enough to fill up a canal, he said, adding “so when it rains, the city’s canals can be overwhelmed easily”. Instead, he suggested, the BMA should follow Shanghai’s system of requiring that all big buildings construct an underground water bank. 

Former Bangkok Governor MR Sukhumbhand Paripatra

This way, wastewater can be kept underneath the building and released gradually,” he said. 
Visnu Charoen, a senior official at the BMA Drainage and Sewerage Department, said some BMA facilities have underground water banks, like the one along the Srinakharin-Krungthep Kreeta Road, which can hold about 10,000 cubic metres of water. There is also one at the mouth of Soi Suttiporn on Din Daeng Road, which can handle up to 1,200 cubic metres. However, Thanawat said, these water banks were not enough to deal with the flood risks. 

Confessing that the BMA still hasn’t made it mandatory for the private sector to build underground water banks, Visnu added, “we will offer incentives if they agree to prepare areas for water retention”.

Professor Suchatvee Suwansawat, president of the Council of Engineers, said underground water banks would be an innovative flood-prevention solution, and that a couple can be developed right away around the big pond in the compound of the Tobacco Thailand Authority and the Chatuchak Park. 

“These should help ease flooding in Lat Phrao, Bang Sue, Vibhavadi-Rangsit, Ramkhamhaeng and Sukhumvit,” he continued. 
Suchatvee also recommended the use of sensor technology to monitor the state of pumps and water jets.
Thanawat, meanwhile, suggested that canals and waterways be dredged and pumps installed at the mouth of canals to push water into the river as a short-term measure. For the medium term, he said the size of the drainage pipes should be enlarged. 
“For the long term, the government should make it mandatory for all condo projects to build water banks and if possible, Bangkok residents should be charged for water draining,” the academic said. 
He added that water-drainage fees will possibly encourage people to save water, thus cutting down on the water to be drained. 
For now though, Visnu said the BMA was doing its best to keep Bangkok dry by dredging waterways, cleaning drainage pipes and enlarging them where possible. He also pointed out that floods have been draining away more quickly over the past few years. 
“We can’t say drainage tunnels will prevent floods, but at least the water is drained away more quickly,” he said.