Stamford canal to blame for Orchard Road floods

From ‘Stamford canal a cause of flooding again’, article by Saifulbahri Ismail, 31 Dec 2011, Today

The 4km-long Stamford Canal, cited as a factor in last year’s floods along Orchard Road, has again been traced as the source of flooding at Liat Towers last Friday.

Explaining yesterday why the flooding occurred, national water agency PUB said the “prolonged and heavy” monsoon rain on Dec 23 caused “some parts of Stamford Canal to flow full“. Then, 152.8mm of rain fell on Orchard Road from 2.20pm to 5.20pm – equivalent to about half the average monthly total of 287.4mm of rain recorded for the entire month of December over the last 142 years.

…In its statement, PUB assured the public that it takes “its responsibility for flood management seriously”. “PUB regrets the inconveniences caused by the floods to members of the public and businesses,” said the agency. “

…To improve flood protection during similar storms, Liat Towers will be building a perimeter wall along its internal drain. “This will allow more water to be held within this so-called pond and, with the difference in pressure, we’d be able to drain the water into the canal,” said Liat Towers director of property management Lydia Tjhia.

…Given the constraints in expanding Stamford Canal due to the urbanised development in the area, PUB is studying the feasibility of building a detention pond and a diversion canal for the Stamford catchment in the longer term.

In 1984, the Ministry of Environment responded to a reader’s complaint about Orchard Road flooding by citing ‘extremely heavy rainfall’, exposing the inability of Stamford canal to handle any load exceeding the intensity equivalent to a once-in-5-year storm. In that year, May 21’s freak storm yielded a rainfall of 130mm within the interval of 100 minutes, an intensity matching a ONCE in NINETY YEAR storm according to the Ministry, which would require the canal to expand to more than twice its width to 10m. On Dec 23 2011, within the same time period, we had about 84 mm of rainfall, and since the canal overflowed, the downpour would have been considered AT LEAST a once in 5 year event, though it seems we’ve been having ‘improbable’ weather almost every other week.

I’m particularly interested in how weather experts coin a probability of one-in-ninety years when we have been tracking weather for only 142 years without invoking some form of predictive statistics. According to the NEA’s 142 years-old records, December has constantly been the rainiest month. On a single day in Dec 1978 alone, 512.4 mm of rain fell, almost twice the monthly average. In response to what was known then as the ‘worst floods ever’, Minister of Environment E.W Barker said ‘Singapore’s drains were not designed to cope with exceptional rainfall, and it was impractical and uneconomical’ to build ‘extra-large’ canals to cater to freak weather. Between 1978’s record-breaking storm and 1984’s ‘once in ninety years’ rainfall is only a period of 6 YEARS. To pour more cold water on such doubtful statistics,  then-Minister of Environment Yaacob Ibrahim was ‘told by the PUB’ that the Nov 2009 floods occurs ONCE EVERY 50 YEARS. In that storm, 92 mm of rain fell within HALF an HOUR. But wait a second; 1984’s 39 mm/half hour storm was considered a once every 90 YEARS event, which makes the heavier storm in 2009 a MORE LIKELY event, effectively rendering PUB’s predictions meaningless, a case of our climate folks plucking numbers out of ‘thin air’.

Just last year in June, PUB put the blame on a blocked ‘culvert’ along Stamford Canal and ‘an intense amount of rain within short bursts’ within the space of an hour, stubbornly refusing to consider the possibility that flooding is really the result of poor project management over the years. But let’s look at the history of the Stamford canal and, assuming our rainfall patterns haven’t altered significantly based on NEA’s records, see how much time the authorities  have actually spent tackling the flood problem and ‘regretting the inconveniences caused’. It’s like saying I ‘regret’ that you got bitten by my crazy, unpredictable dog but I’m still not sending him to obedience school or putting a muzzle on him.

Originally known during the days of Raffles as ‘Sungei Bras Bassa’, the early versions of the Stamford canal were in place for over a century and was already being blamed for flooding as early as 1911 (sluice gates’ fault). Millions were subsequently pumped into flood control projects to modify the canal, though you can’t help but feel that however PUB claims to take flood management seriously, expanding the Stamford canal has always been an afterthought to more lucrative developments along Orchard Road. It’s not the weather that the canal needs to catch up with but the rabid urbanisation going on around (and OVER) it. Making dodgy predictions about how often heavy rainfall would occur has also prevented the board from preparing for the worst case scenario, and using ‘extreme’ weather is no longer an excuse given we’ve had experiences with ‘once-in-whatever-years’ deluges for more than a century.

  • 1952: A proposed $750,000 to widen and rebuild, including ‘COVERING part of the canal to make a CAR PARK’.
  • 1970: $250,000 to ‘BEAUTIFY the Stamford canal embankment’, including an ‘exposed footpath of uniform width’.
  • 1973: $1.3 m to COVER the Stamford Canal with a pedestrian mall between Cuscaden and Grange Road.
  • 1978: $32 million on a flood control scheme to reconstruct Stamford Canal by ‘widening and deepening’ it.
  • 1993: Floodgates costing $200,000 built in Ngee Ann City-Lucky Plaza underpass (Floodgates built at a cost of $200,000, 16 Sept 1993, ST)

Given that the authorities were well aware of Stamford Canal’s design flaws for so long, Orchard Road continues to be a hotbed of commercial activity.  A pro-business approach towards retail chain Gap  in 2008 resulted in immovable barriers being replaced by a sliding mechanical floodgate system instead. It’s not certain if this compromised, or indeed left a ‘GAP’ (hurr hurr), in flood control, but it leaves one to wonder if Orchard Road would be ‘high and dry’ if it wasn’t, well, Orchard Road.

It’s also a strange twist of ironic terminology that the PUB is now considering ‘ponding’ areas, a mitigating measure which I’ve described in an earlier post, though they were quick to eliminate the use of the same word to describe ‘flooding’ in this press release. Flood dynamics is no doubt a complex science, and no one will blame the PUB for admitting to lacking the expertise to handle the problem, if only they’d stop fudging storm probabilities and making scapegoats out of bad infrastructure like a  carpenter blaming his tools. To make things worse, their ‘drainage overview’ report following the 2010/11 floods contains a blatant lie:

'Orchard area has been flood free for more than 25 years'

Taking 2010 as the assumed ‘first case of flooding in 25 years’, this implies that we haven’t had any Orchard Road floods since 1984. Wrong (1988) and wrong again(2007).

Happy new year everyone.


One Response

  1. […] to the recent flooding – Singapore Notes: Watered Down Explanations – Everything Also Complain: Stamford canal to blame for Orchard Road floods – [Google Search – define […]

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