A day after flash floods ground morning rush-hour traffic to a halt on the Ayer Rajah Expressway (AYE), national water agency PUB has come up with an interim plan to solve the problem in that area.
It will build a tidal gate at the Sungei Pandan Kechil canal within six to nine months. The 2m-tall steel gate near West Coast Road prevents high tide from the sea from flowing into the canal, by creating a temporary storage area.
"If we can cut out the influence of the tide, it helps buy some time during severe rain," PUB's director of catchment and waterways Tan Nguan Sen told The Straits Times.
A city-bound stretch of the AYE shut down for 40 minutes on Thursday morning, as the combination of heavy rain and high tides "stressed out" the area's drainage system, said Mr Tan, with water overflowing onto all four lanes of the major artery. The problem was compounded by the fact that the AYE sits atop a junction where three drains meet, before they channel out to the canal.
Because each drain carries water from a different direction, the intersection at which they meet faces a lot of resistance. This slows down the speed at which water can flow through, said Mr Tan.
PUB will also widen culverts at the intersection to allow a higher volume of water to pass - a process that will start by the end of this month and be completed by the end of the year.
The agency intends to widen and deepen the canal, but that would "require more thorough investigation" and upgrading works will take place only in 2015, said Mr Tan.
PUB will also consider building a barrage - a larger version of a tidal gate - in the long term.
"But we'll try to push forward these plans as fast as we can; that's our priority," said Mr Tan.
Heavy rain continued yesterday morning, although no flash floods were reported.
The National University of Singapore, where several facilities were flooded in Thursday's downpour, said it is looking at solutions to mitigate floods.
The highest total daily rainfall recorded on Thursday was 122mm at Holland Road. That is more than the amount of rain that fell for the whole of last September - 107.6mm.
The rain was particularly heavy on Thursday due to "the convergence of winds over the region", said the National Environment Agency.