SINGAPORE: It would be impractical to expand Singapore’s drains to accommodate all instances of extreme rainfall as this would require “massive land take and much higher costs”, said Minister for Sustainability and the Environment Grace Fu.
Speaking in Parliament on Monday (May 10), Ms Fu noted that drainage design standards were raised a decade ago to cater for higher intensity rainfall, in line with national water agency PUB’s efforts to address the impact of climate change.
The Government has invested almost S$2 billion in drainage works since 2012, and will invest another S$1.4 billion over the next five years to enhance Singapore’s flood resilience, she said.
PUB will implement “cost-effective measures” to minimise flood risks and better manage flood events, said Ms Fu.
She gave the example of the water agency’s rainfall forecasting radar, which is being upgraded to help improve the prediction of areas where heavy rainfall might occur and improve response time to possible flash floods.
Ms Fu's comments come after flash floods were reported across the island on Apr 17 due to heavy rains, with flood risk warnings for more than 20 locations including the Bukit Timah and Ulu Pandan canals as well as Sungei Pandan Kechil.
Ms Fu noted the highest rainfall that day was at Ulu Pandan, with 170.6mm of rain.
“This is the highest daily rainfall recorded in April since 1980 and is equivalent to 110 per cent of Singapore’s average rainfall for the whole month of April, falling in a single day,” she said.
This resulted in flash floods occurring at Bukit Timah and Dunearn Roads near Sime Darby Centre and a stretch of the park connectors along Ulu Pandan Canal, she added.
High water levels in the Bukit Timah Canal prevented discharge from roadside drains along Dunearn Road and Bukit Timah Road from flowing into the canal, she said.
The minister noted that the upgrading of the Bukit Timah First Diversion Canal between Bukit Timah Road and Clementi Road was completed in September 2019 at a cost of S$300 million.
Water level sensors installed along the upgraded stretch of Bukit Timah Canal - just upstream of the expanded Bukit Timah First Diversion Canal - showed that the section of the canal was 50 per cent full on Apr 17, with no flash floods along that stretch despite the heavy rainfall, said Ms Fu.
She added that PUB has also started upgrading works on the section of Bukit Timah Canal between Rifle Range Road and Jalan Kampong Chantek, where flash floods occurred, which is expected to be completed by 2024.
Ms Fu noted that a low-lying 300m stretch of the park connector next to the Ulu Pandan canal was also flooded last month, even though major roads near the canal did not experience flooding.
“PUB will raise this low-lying section of the park connector when PUB reconstructs the Ulu Pandan Canal in tandem with future developments,” she said.