Reasons for Exceptionally Heavy Rainfall on 20 July 2023

Mr Melvin Yong Yik Chye asked the Minister for Sustainability and the Environment with regard to the heavy rainfall observed on 20 July 2023, which nearly equalled the average rainfall recorded for July (a) whether this is caused by a particular weather phenomenon or tropical storm; and (b) whether it has exposed certain areas of Singapore that require further drainage works to prevent flash floods from occurring due to freak weather incidents.

Thunderstorms are common occurrences in our warm and humid climate and can be intense under certain atmospheric conditions. The heavy rainfall on the morning of 20 July was due to widespread intense thunderstorms over many parts of Singapore. Nearly half a month’s worth of rainfall fell within one hour. The heavy rainfall on that morning resulted in a localised flash flood that occurred along Dunearn Road. PUB issued early flood risk warnings about 20 minutes before the flash flood occurred and the flash flood subsided within 15 minutes. The Public Utilities Board (PUB)’s Quick Response Team was also on site to render assistance and the road remained passable to traffic.

Dunearn Road is a known hotspot for floods. We completed the upgrading of the Bukit Timah First Diversion Canal in 2019. Longer-term measures, including widening and deepening a 900-metre stretch of the canal from Rifle Range Road to Jalan Kampong Chantek, are expected to complete by 2026. Since 2021, PUB has carried out interim works to alleviate flood risks in the Dunearn Road area. These include raising a 450-metre stretch of Dunearn Road and deepening the adjacent Bukit Timah Canal.

Over the years, we have reduced the flood-prone areas in Singapore from over 3,000 hectares to less than 30 hectares today. PUB has also been planning and carrying out similar drainage improvement works for areas with higher flood risks, subject to land and other site constraints. In planning for flood resilience, PUB takes into account the long-term impact of climate change, which could potentially lead to more extreme rainfall events observed in our region and beyond.

It is not sustainable to rely solely on drainage works in land-scarce Singapore for flood resilience. With more intense weather events arising from climate change, we will need to be prepared for and be used to occasional short incidences of flash floods, such as the one on 20 July 2023.

I strongly encourage members of the public to use PUB’s communication channels to receive alerts on flood warnings so that they can adjust their plans accordingly. Managing flood risks is a collective effort.