• Road raising and ongoing improvement works to cater for higher rainfall intensity
• Stormwater retention pond Alkaff Lake on track to complete next year
• Enhanced flood monitoring with additional 400 water level sensors installed
• Additional platform Motorist SG app to provide timely alerts to motorists

PUB, Singapore’s national water agency has completed several drainage improvement and road raising works this year to cater for higher rainfall intensity and reduce flood risks in Singapore. Ahead of the Northeast Monsoon season, we have also enhanced our rainfall forecasting, monitoring and flood response capabilities to keep the community out of harm’s way, in the event of flash flood.

Stormwater management and building flood resilience have always been PUB’s key priorities. Over the years PUB has made significant strides to mitigate flooding and
expand drainage infrastructure, where feasible, in land-constrained Singapore. These efforts have seen flood prone areas in Singapore reduced from 3,200 hectares (ha) in the 1970s to less than 30 ha today. Even as it is not feasible or cost-effective to build bigger drains and infrastructure to cater to every extreme rainfall scenario, enhancing our flood resilience and managing flood risk is ever more important and urgent today as climate change intensifies extreme weather. Sudden and intense heavy storms, even during nonmonsoon periods, can temporarily overwhelm our canals and drains and cause localised flash floods, although most typically subside within an hour.

Continuous drainage upgrading and improvement

Major drainage upgrading and improvement works are ongoing across the island. PUB also actively explores interim solutions such as road raising to strengthen flood
protection at several low-lying and flood hotspots1.

In August 2022, PUB completed road raising works at Commonwealth Lane and Punggol Way (slip road to Tampines Expressway) to reduce risk of flood occurring. These areas had experienced flash floods in the past during intense rainstorms. At Dunearn Road, PUB raised a 450m stretch of the road in November 2021 and deepened the Bukit Timah Canal by 1.5m in April 2022 to mitigate risks of flash floods, while ongoing drainage expansion works at the Bukit Timah area (between Rifle Range Road and Jalan Kampong Chantek) are scheduled to complete in 2026. Dunearn Road is similarly a low-lying area that is prone to flooding when there is intense rainstorm.

At Jurong East Street 32, PUB built a new diversion drain at the junction of Jurong East St 32 and Avenue 1 in August this year to divert runoff and improve stormwater
conveyance. A sump area near the junction was also widened so that water levels in the drain can subside quickly during heavy rain. Works to construct a new culvert drain are ongoing to enhance flood resilience in the long term.

Major drainage infrastructure projects including the construction of Alkaff Lake and the Syed Alwi Detention Tank are on track for completion in third quarter 2023 and 2025 respectively. A first-of-its-kind retention pond integrated within Bidadari Park, the dualfunction Alkaff Lake will serve as a stormwater retention pond to temporarily hold stormwater runoff during heavy rain, and also a recreational space with features such as terraced wetlands and a cascading creek. The Syed Alwi Detention Tank, an underground detention tank with a pumping facility beside Syed Alwi Road, is being built to enhance flood protection in the low-lying Jalan Besar area.

“Climate change is causing more frequent and extreme rain events, and we have seen how torrential rain caused severe flooding in many other parts of the world. While it is not possible to cater for all extreme storm events and prevent floods entirely, the realities of climate change require us to build our flood resilience as a nation. We must continue to invest in flood protection measures and build flood resiliency in our critical infrastructure and our community. Stormwater management and building flood resilience is a shared responsibility, as Singapore is vulnerable to flood risks due to our topography and the effects of climate change. Together we can adapt, increase resilience and lower the flood risk. Building owners, contractors and individuals should ensure proper maintenance of their internal drainage system, keep our drains and canals free flowing, and be prepared for flash floods. As thunderstorms can sometimes come with little or no advanced warning, public should stay informed by subscribing to our channels to receive flood alerts and information on what to do during a flood incident.” said Mr Yeo Keng Soon, PUB Director of Catchment and Waterways department.

Enhancing flood response capabilities

To boost flood response capabilities, PUB recently installed an additional 400 water level sensors across various locations, including Kallang River, Sungei Api Api and
Bukit Batok Canal, adding to an extensive network of close to 1,000 water level sensors. During heavy rain, water levels in drains and canals can rise rapidly. With the ability to monitor real-time site conditions, PUB can provide early warning to the public and activate its mobile crew (Quick Response Team) to these areas to carry out flood management, such as removing chokage, deploying portable flood barriers and traffic management.

PUB provides advance warning to the public on potential floods via multiple platforms3 such as Telegram channel (t.me/sgflood), MyENV mobile application (app),
among others, so that safety precautions can be taken. We are broadening our reach to motorists by partnering automotive app Motorist SG4, to provide its users with location specific alerts based on PUB’s flood-risk warnings and flash flood incidents. The app will also suggest alternate driving routes for users to avoid these areas.

During the monsoon season, PUB steps up checks around the island including drainage systems at critical installations and higher-flood risk locations to ensure that public drains around the sites are unobstructed to convey stormwater. PUB also engages residents in low-lying areas to loan them flood protection devices such as flood barriers and flood bags, which can be deployed quickly during heavy rain. Building owners are reminded to ensure that flood protection measures in their developments remain effective and consider suitable flood barriers to keep out stormwater.