In June 2010, Singapore experienced some of the worse flash floods it had in recent years when heavy and intense rainfall over the Stamford Canal Catchment overwhelmed the Stamford Canal, resulting in flash floods along Orchard Road.
This caused major traffic disruption and property damage, as water flooded into basements of several buildings such as Lucky Plaza, Liat Towers, and Delfi Orchard. About 21 vehicles and 100 shops in the basement level of Lucky Plaza and Liat Towers were flooded. Another 20 cars and seven buses stalled along Orchard Road.
According to estimates, flood damage amounted to about S$23 million from over 800 insurance claims from business interruptions, property damage, and motor vehicle damage. The uncertainty of flooding also forced estate owners to invest in their own flood prevention system.
A year later in 2011, intense rainfall caused the Stamford Canal to overflow again, this time getting into Tanglin Mall and the basement car park of St Regis Residences. At the same time, other areas such as Cuscaden and Claymore experienced flooding as well, stalling cars and causing impassable traffic.
As public calls began to echo for the Public Utilities Board (PUB) to improve its flood management strategy, then-Environment and Water Resources Minister Vivian Balakrishnan said that Singapore had undertaken several initiatives to protect against flooding.
In an interview with Reuters around November 2011, Dr Balakrishnan explained that this included raising the height of reclaimed land an additional 1m above sea level, widening and deepening drains and canals, and getting building owners to improve their flood defences.
“It will be more expensive, more upfront cost, but you are buying insurance for the future,” he said, citing the several large projects that have already been taken on in the past two decades to control water levels at Marina Bay.
Ahead of the year-end monsoon season, Dr Balakrishnan had said that the Government is doing its best to deal with whatever the weather brings and that December would be a time to “stress test” the country’s systems.
A TV news report noted that he said all agencies were on alert and that he was “confident” that the flood problems could be resolved with intelligent use of technology as well as a more informed public.
The following monsoon season in December 2011 did indeed put stress on Singapore’s drainage systems.
Flash floods once again hit the Orchard Road area, with levels getting up to ankle-deep due to an afternoon of heavy rain. Other affected areas included United Square, Cambridge Road, and Kampong Java Road.
Expert Panel recommendations to improve the drainage system
In January 2012, an expert panel on drainage design and flood protection measures released a report with several recommendations on how Singapore could strengthen flood protection in the face of ever-increasing intense rainfall.
The panel was tasked to look into the cause of the flash floods at Orchard Road in June 2010 and June 2011.
Recommendations by the panel include implementing higher drainage design standards, building new capabilities, and working with stakeholders to improve preparedness and mitigate the impact of flash floods.
Following the release of the report, the PUB said that it accepted the recommendations and subsequently announced a plan to spend S$750 million over five years to carry out 20 drainage improvement projects.
According to data from the PUB, some of the drainage improvement works that have been carried out since 2012 include improvements to the Bukit Timah Canal in 2013, construction of collector drains at Changi Reclamation Area A, and construction of the Stamford Diversion Canal and Stamford Detention Tank in 2018.
This is on top of the many other drainage and improvement works across the island. Between June 2012 and 2021, the PUB has carried out 400 drainage improvement projects to address the issue of increasingly heavy rainfall.
S$227 million spent on Stamford Diversion Canal and Stamford Detention Tank
In 2018, PUB unveiled the S$227 million Stamford Diversion Canal and Stamford Detention tank, built to prevent flooding at Orchard Road during intense downpours.
PUB chief executive Ng Joo Hee said at the unveiling: “The same rains that led to the Orchard Road floods eight years ago should not threaten our famous shopping street again.
“Building bigger and bigger drains to deal with more and more intense rain is not a good method. The SDT and SDC are better ways. By detaining, delaying and diverting storm runoff before it can do serious harm, the SDT and SDC offer long-term flood protection for Orchard Road.”
The two projects were expected to ease the load on Stamford Canal by 30 per cent.
The diversion canal functions to divert excess rainwater from Holland Road, Napier Road, and Grange Road into the Singapore River instead of the Stamford Canal, later merging with the Marina Reservoir.
The detention tank, on the other hand, was built to store excess waters from drains in the affected areas, with a capacity of 38,000 cubic metres. That’s about 15 Olympic-sized swimming pools.
In March 2019, then-Minister for the Environment and Water Resources Masagos Zulkifli noted that a low-lying island like Singapore is more vulnerable to rising sea levels which can exacerbate flooding problems.
“To enhance our flood resilience, we completed the Stamford Division Canal and Stamford Retention Tank last year. Upgrading works at two major waterways, the Bukit Timah first division canal and Sungai Pandan Kecil, will be completed this year,” said Mr Masagos.
$300 million to upgrade Bukit Timah Forest Diversion Canal
Improvements to the Bukit Timah Forest Diversion Canal were completed in September 2019, which took seven years to complete.
The S$300-million project was described as a “necessary investment” by Mr Masagos, who noted that the diversion canal would help Singapore be better prepared for the inevitable rise in sea levels and extreme weather events precipitated by global warming.
PUB stated that the improvement would allow the 3.2km long diversion canal to convey about 30 per cent more rainwater than before, adding that new tunnels and the deepening and widening of the canal will help alleviate the risk of flash floods along Bukit Timah Road and Dunearn Road.
Have the improvements made a difference?
With all these costly improvements to the drainage system, the question on everyone’s mind is: Has it worked?
We need only to turn on the news to find out.
Earlier on 20 August 2021, heavy downpours caused flash floods and traffic jams in several parts of Singapore.
Videos circulating social media showed that water levels at the junction of Pasir Ris Drive 12 and Tampines Avenue 10 reached nearly 1m, with many cars seen trapped in the flood.
The Singapore Civil Defence Force (SCDF) had to be called in to evacuate motorists and passengers from 13 vehicles. One person was taken to Change General Hospital for leg injuries.
That same day, the PUB had warned that water levels in drains and canals were at 90 per cent capacity in several areas due to heavy rain.
It advised the public to stay away from those areas.
A few days later, residents had to contend with more flash floods at Dunearn Road, Upper Bukit Timah Road, the junction between Woodlands Road and Kranji Expressway, and Sunset Drive and Sunset Way.
Dunearn Road had also experienced flash floods earlier in April when water levels in a number of drains and canals exceeded 90 per cent capacity.
Following the incident in April, Minister for Sustainability and the Environment Grace Fu said that Singapore has been experiencing more intense and frequent rainfall.
Speaking to reporters on the sidelines during a visit to one of the Deep Tunnel Sewerage System (DTSS) sites, Ms Fu said: “It shows us the importance of planning for climate change and also mitigation,” noting the S$2 billion already spent by the PUB on drainage improvement works over the last decade.
She went on to say that another almost $S1.4 billion will be spent in the next five years on such projects, adding that there are 37 ongoing projects, with 10 more due to commence this year, including drainage works in Selatar North Link and Serangoon Avenue 2 and 3.
When asked why flash floods still occurred in Singapore despite investments into the country’s drainage system, Ms Fu pointed to the effect of global warming on changing weather patterns.
“We have already been witnessing pattern changes, and we expect to see even wetter and drier patterns going forward,” she remarked.
While it is inarguable that global warming has led to changing weather patterns which in turn has caused increased rainfall in Singapore, it is noteworthy that increased urbanisation and deforestation are key factors in this issue as well.
According to the 2012 expert panel report, urbanisation has “undoubtedly led to an increase in stormwater runoff in Singapore”.
The panel stated that besides generating higher and faster surface run-off, increased urbanisation could lead to increased heat production, changes in rainfall patterns, and other climate change impacts.
So, while global warming is one factor for the more frequent flash floods plaguing the island in recent years, it would be unwise to side-step the severe impact of urbanisation, and consequently, flash floods.
