Upper Bukit Timah Canal upgrade completed, boosting flood resilience with 30% more capacity

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SINGAPORE: The entire 2.3km Upper Bukit Timah Canal has been upgraded,  boosting its capacity to carry stormwater by 30 per cent and strengthening flood resilience in one of Singapore's most flood-prone catchments.

The completion of works on the final 900m stretch, which began in 2019, marks the end of a series of upgrades to the canal, national water agency PUB said on Friday (Oct 23).

The enhanced drainage capacity will benefit an approximately 1,000-hectare catchment encompassing residential and commercial developments, as well as key transport nodes.

The newly completed stretch runs from Rifle Range Road to Jalan Kampong Chantek, near King Albert Park MRT station. The approximately S$60 million upgrade also included the construction of structural supports for the Bukit Timah-Rochor Green Corridor within the canal.

As part of the works, the canal was widened and deepened, with its original trapezoidal profile converted into a U-shaped drain and box culvert to increase its capacity.

Upgrading works on the upstream section, between Jalan Jurong Kechil and Rifle Range Road, were completed in 2024.

With the entire canal now upgraded, PUB said it is better equipped to handle rainfall intensities comparable to those experienced over the past 15 years.

However, very intense storms could still overwhelm the drainage system, given Bukit Timah's challenging topography, land constraints and increasingly intense rainfall brought about by climate change.

To address these longer-term risks, PUB plans to call a tender at the end of 2026 for a feasibility study into further flood resilience measures across the wider Bukit Timah catchment.

The study will explore options such as underground detention structures, which can temporarily store excess stormwater during heavy rain.

It will also examine how such measures could be integrated with existing infrastructure and future developments, while identifying opportunities to enhance public spaces.

"We need to plan ahead today so that we are ready to implement the right solutions when they are needed," said PUB deputy chief executive for flood resilience Angela Koh.

A LONG HISTORY OF FLOOD MITIGATION

Bukit Timah has long been prone to flooding, with its valley-like topography forming a natural basin that channels stormwater quickly into the low-lying canal.

Urban development has added to the challenge by increasing surface runoff into the drainage network, while space constraints limit opportunities to expand the canal further.

"The completion of upgrading works along Upper Bukit Timah Canal is an important milestone in strengthening flood resilience in one of Singapore's most challenging catchments," Ms Koh said.

Over the decades, PUB has progressively expanded and upgraded drainage infrastructure in the area to reduce flood risks.

Two diversion canals, completed in 1972 and 1990, were built to divert stormwater to other waterways. The first diversion canal was later upgraded between 2012 and 2019, while part of the main Bukit Timah Canal was expanded in 2013.

Despite these improvements, flash floods have continued to affect the area during heavy downpours.

The final 900m stretch of the Upper Bukit Timah Canal upgrade was originally slated for completion in 2024, but the timeline was extended to 2026 to coordinate construction with the Bukit Timah-Rochor Green Corridor.

PUB said construction was further complicated by the narrow working space between Bukit Timah Road and Dunearn Road. Traffic had to be progressively diverted, with replacement lanes provided to create temporary work areas.

Works were also restricted to between 9.30am and 4.30pm to minimise disruption, while the canal's proximity to underground MRT lines added to the challenge. The project was also affected by disruptions caused by the COVID-19 pandemic.

"Collectively, these factors added complexity and affected the pace of construction," said PUB's director of the catchment & waterways department Maurice Neo.

PUB said no drainage system can eliminate flood risk entirely and urged the public to remain vigilant during periods of heavy rain.

Ahead of the year-end Northeast Monsoon season, the agency will also launch its third annual Flood Resilience Campaign to raise awareness of flood risks and encourage people to take practical steps to prepare.