In August, Singapore saw many days of record-breaking wet weather that resulted in flash floods at many locations.
One of the most memorable was the severe flood at a traffic junction in Tampines on 20 Aug, resulting in submerged vehicles and people being rescued.
National water agency PUB said the incident was due to unauthorised drainage works by a construction firm.
They face a fine, as action will be taken against them.
PUB issued a press release on Saturday (11 Sep), saying that in the morning of 20 Aug, parts of the junction of Tampines Avenue 10 and Pasir Ris Drive 12 were under 500mm of water.
That’s about knee level, they added.
It got so bad that PUB’s Quick Response Team found 13 vehicles partially submerged.
Several motorists also needed help to escape their own vehicles. Traffic was diverted, and stranded motorists and pedestrians were helped.
Thankfully, the heavy rain stopped by around 9am, so the flooding fully subsided at 9.40am.
The incident raised concerns as the area isn’t known for flooding, PUB said.
Similar amounts of rainfall had been recorded at the junction on 2 previous days: 5 Apr 2021 and 22 Nov 2020.
However, no flooding occurred during these 2 occasions, they said.
So why did the flooding occur on 20 Aug?
PUB explained that stormwater from the heavy rain is supposed to flow to Sungei Api Api, which is about 1km away from the junction.
It should go through a roadside drain, which was able to take the amount of rainfall that fell in the area on 20 Aug.
However, Tampines Avenue 10 was being widened. Construction firm Samwoh was carrying out the project, the PUB said.
As part of this project, the contractor built a new drain.
They sought no approval from the PUB to alter the existing drain, but concrete slabs blocked it.
The flow of stormwater was diverted to the new drain, PUB said. However, this new drain was still under construction.
The new drain wasn’t properly connected to the existing drain – it was also partially obstructed by scaffoldings.
Again, the connection between the new and old drains was unauthorised, the PUB added.
The unauthorised works “significantly impeded” the discharge of stormwater into Sungei Api Api.
The PUB also noted that the river was only half-full, which should have been full of stormwater due to the heavy rain.
However, a 200m section of the traffic junction saw severe flooding as it was the lowest point in the area.
Here’s a map of the area with a graphical representation of what happened.
The PUB said it “takes a serious view” of contractors carrying out unauthorised works that interfere with drainage.
PUB Catchment and Waterways Department director Yeo Keng Soon said the flooding was “entirely man-made”, adding,
It would not have happened if the contractor had complied with PUB’s regulations for drainage work.
The PUB has already told Samwoh to rectify the problem immediately by removing all obstructions.
They must also ensure stormwater can flow effectively in the drains.
That’s not all for Samwoh, though. PUB stressed that they would be taking enforcement action against the company.
That means charges will ostensibly be fined under the Sewerage and Drainage Act.
The agency noted that for works that affect the stormwater drainage system, offenders may be fined up to $50,000.
For unauthorised alteration of the stormwater drainage system, offenders may be fined up to $20,000.
The reason for the stern action is that it’s “imperative” that Singapore’s drains are kept free-flowing, Mr Yeo said.
The comprehensive network that carries stormwater into water bodies is important as climate change affects us, meaning we’re experiencing more frequent and heavier rainfall.
As all our drains, canals and rivers are connected, unauthorised alterations may affect how the system functions – as we saw in the Tampines flooding.
Mr Yeo also warned all contractors,
…any construction works carried out must not adversely affect the storm water drainage system.
Singaporeans shocked at the sudden flooding in Tampines would have demanded answers as to why it happened.
Now it’s been revealed that the cause was unauthorised drainage works, hopefully, it’ll bring closure to those affected.
At least we’ve also learnt a bit about how the drainage system works in Singapore. Kudos to PUB for getting to the bottom of the unusual flooding so quickly.
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Featured images adapted from Facebook and PUB.
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