Drainage network has to be ‘future-proofed’

SINGAPORE — Minister for the Environment and Water Resources Vivian Balakrishnan said the drainage network will have to be “future-proofed” to cope with intense thunderstorms that may hit the island, similar to the one that caused yesterday morning’s flash floods in several parts of Singapore.

Speaking on the sidelines of an event at the National University of Singapore (NUS), Dr Balakrishnan laid out immediate and long-term plans for the two rivers, Sungei Pandan Kechil and Sungei Ulu Pandan, which overflowed as a huge amount of rainwater fell yesterday morning.

The walls near the opening of the culvert below the Ayer Rajah Expressway, near NUS, will be widened to improve water flow. Work will start this month and be completed by the end of the year. The Sungei Pandan Kechil canal would be extended to make sure it has sufficient capacity to deal with the increased run-off.

Construction work will commence in first half of 2015, said national water agency PUB. Beyond these moves, the authorities are also examining if a barrage is necessary in the future to deal with the tidal influence.

As for Sungei Ulu Pandan, the area around Commonweath Avenue is undergoing drainage improvement works but the culvert underneath Clementi Road will have to be examined in the long term. These works are “a major operation” as the drainage system is inter-connected, said Dr Balakrishnan.

Engineering experts TODAY spoke to said even though more can be done to ensure that significant flooding does not happen again, it will be unrealistic to eliminate it forever.

Engineer Chong Kee Sen, who is the Vice-President of The Institution of Engineers in Singapore, said the works will “take time”. “We must be realistic, the whole problem cannot be eliminated and we can never say there will never be a temporary build-up of water at all. But the authorities will have to look into areas of serious flooding and they will have to relook what other measures can be done, those with significant flooding have to be re-looked at as flooding on major infrastructure can cause significant inconvenience,” he added.

Dr Chiew Yee Meng, who is Head of Environmental and Water Resources Engineering at Nanyang Technological University, noted that the scale of the area affected yesterday was “quite extensive”, spanning from the Tanglin area to Chinatown and to the southwest of the island.

“The authority is trying its best to overcome the problem, but the flow of flood water has to be tackled holistically because fluid is a continuum and cannot be solved individually as interfering in one area may bring about unexpected effects both upstream or downstream of the initial problem area,” said Dr Chiew, who is a Professor in Civil and Environmental Engineering.

He called for greater studies to be conducted. “While the authority has carried out certain large drainage works in the country in the past, how this affects the overall drainage pattern in the whole country should be carefully studied.

“This will allow one to come up with a holistic mitigation approach. The issue of climate change, or changes to rainfall intensity, is another topic that remains unresolved presently,” said Dr Chiew.