Wednesday, 7 February 2018

Not feasible to build drains for all extreme rainfall events: Environment and Water Resources Minister Masagos Zulkifli

No history of flash floods in most areas hit on Jan 8
Very costly to build and expand drains to accommodate every extreme rainfall event: Masagos
By Audrey Tan, Environment Correspondent, The Straits Times, 6 Feb 2018

Only two of the nine locations in eastern Singapore that suffered flash floods on Jan 8 had a history of flooding, Minister for the Environment and Water Resources Masagos Zulkifli said yesterday.

He also said that with climate change, Singapore can expect intense rainfall to be the norm in future. This means flash floods could occur in areas with no record of flooding.

But he cautioned that it was not feasible to build and expand drains to accommodate every extreme rainfall event, as that would be very costly and require setting aside large tracts of land. For instance, Bedok Canal is being widened at a cost of $128 million and the space can accommodate a 10-lane expressway.

Mr Masagos made these points in Parliament to five MPs, including Mr Murali Pillai (Bukit Batok) and Non-Constituency MP Dennis Tan, who had asked about the floods.

On Jan 8, the nine places were inundated with rain - the heaviest recorded total rainfall that morning was 118.8mm, half of Singapore's average rainfall for January - with submerged cars, flooded bus cabins and some businesses being disrupted.

Although eight of them are low-lying and susceptible to flash floods, only two had a history of flooding.

They are Tampines Road, opposite Jalan Teliti, and Arumugam Road in the Ubi area. Between 2015 and this year, five flash floods took place in Tampines Road and three in Arumugam Road.

"The flash floods were caused by the intense rainfall temporarily exceeding the existing design capacity of the drains," Mr Masagos said.

"Although the flood waters affected only certain stretches of the roads, and subsided within 15 to 60 minutes, we acknowledge that members of the public were inconvenienced and a number of cars had stalled," he added.

Every year, since 1980, heavy rain has been pouring down more often. Also, the annual maximum hourly rainfall has risen. It was about 80mm in 1980 and 90mm in 2016.

It has led the Government to invest in drainage infrastructure.

Since 2012, drainage improvement works have been carried out at 327 locations and such upgrading is still going on at 73 other places, with 22 more planned for this year.

On the Jan 8 case, he said drainage improvements are being carried out in eight of the nine affected areas, "to enable the drains there to discharge more water in a shorter time when completed".

In the ninth location in Tampines Avenue 12, the building of an unauthorised road had intensified the flash flood.

The PUB has worked with the developer to improve the drainage, Mr Masagos said, adding that it is now working on a long-term measure of installing a permanent drainage system. It will be built in tandem with the upcoming development project at an adjacent worksite.

Singapore saw floods on 14 days last year, compared with 10 in 2016, and six in 2015. This year, four flash flood days were recorded last month.

But there is a limit to how many drains can be built or upgraded.

Mr Masagos cited the Bedok Canal, which takes in water from four of the nine places hit by the Jan 8 flash floods. It is being widened from 38.5m to 44m, by the first quarter of next year.

With the expansion, the canal will be wide enough to accommodate an expressway of 10 lanes. But to deal with extreme rainfall, it would have to be widened to at least 62m - a 16-lane expressway.

Such a move would displace the Bedok Park Connector and community spaces adjacent to the canal, and possibly even affect the surrounding residential areas, Mr Masagos said.


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