Plumb depths of Singapore floods for good solutions

One year on, no one seems any wiser on the cause of recent floods
Tan Dawn Wei Straits Times 13 Jun 11;

NEARLY one year after flash floods rained on Singapore's proudest parade Orchard Road, some were surprised that there would be a replay of the baffling waterworks last Sunday.

After all, the national water agency, PUB, had vowed to do all it could to protect businesses and buildings in the area, and elsewhere, after last year's flood.

In the one year since two bouts of intense rain got dumped along the shopping avenue one morning, submerging the Scotts and Orchard Road junction, PUB had dived right into raising 1.4km of roads from Orchard Parade Hotel to Cairnhill Road to the tune of $26 million.

Yet, last Sunday, shoppers found themselves splashing about in ankle-deep water in Tanglin Mall while their groceries floated by. The Tanglin area has been spared floods for the past 25 years; last Sunday's washout surprised even PUB head Khoo Teng Chye.

So what happened? And why was it that the PUB's best efforts a year ago did not prevent more floods in Orchard Road?

Depending on who you talk to, everyone - from the agency to academics to angry coffee shop conversationalists - has a point of view.

Some say the weather is at fault. Perhaps weather patterns have changed, suggested Dr Vivian Balakrishnan, just two weeks into his job as Minister for the Environment and Water Resources. It's time to relook Singapore's drainage system to cope better with this phenomenon, he added.

But geographers demur that it's still too early to tell if weather patterns have changed. One terrible thunderstorm does not a climate trend make.

Indeed, statistics from the National Environment Agency (NEA) show no discernible trend in rainfall patterns over the last 30 years.

From 1980 to last year, the total annual rainfall has gone up and down, with the highest recorded in 2007 at 2,886mm and the lowest at 1,119mm in 1997. Last year, it was 2,075mm.

Rainfall intensity has also tended to fluctuate over the years and does not display a clear trajectory.

In other words, there's no data to support the theory that there is more rain these days, or that the rain is falling more intensely than decades ago.

Another common explanation for the floods is urbanisation. A concretised built-up environment spells the end of green spaces which formerly absorbed water run-offs. Now, all that water has nowhere to go, argued engineers and even greenies. These people want to see more green areas preserved or created to absorb or slow down the surface run-off.

In a post on Dr Balakrishnan's blog, one netizen who works in the construction industry, fingered jet grouting as the culprit. Used to treat and stabilise soil, this process makes the soil impermeable to water, a problem compounded by the density of buildings in Orchard Road.

'So in effect, we have a bowl-shaped, rock-hard valley with Orchard Road in the middle,' he described.

New developments have come up along Orchard Road, which some say contribute to the floods in heavy rain. After all, the mammoth Ion Orchard mall was once a 1.86ha green lung.

A third group blames the Marina Barrage, and says water accumulating there simply wasn't pumped out fast enough into the sea, causing a backflow.

The Government has been quick to pooh-pooh both theories. In Orchard Road, it says, drainage capacity had been factored in before the first bricks for Ion were even laid. It did concede that with Orchard Road nearly completely urbanised, the drains designed to service it have also maxed out.

As for the barrage, the Government says it has helped keep Chinatown, Boat Quay and other low-lying city areas free from flash floods. In any case, the upper end of Orchard Road is too far to have any impact on the barrage, PUB said.

Perhaps that exercise to raise roads after last year's floods channelled water to the Tanglin and Cuscaden stretches, the Orchard Road Business Association contended.

No, the situation could be far worse if not for the raised roads, countered PUB. Cuscaden also sits on a higher plane, so water should be flowing down to Orchard Road instead, it added.

PUB has since said that this year's flood was caused by a smaller drain at Grange Road that overflowed. It also said there were inadequate drainage pumps in buildings such as Tanglin Mall and Liat Towers, failing to keep the water out.

After last year's floodings in Orchard Road, PUB had first said it was a clogged drain. Then, it conceded that the 4km long Stamford Canal simply couldn't cope with all that rain that came pouring down in two hours.

The truth is that one year after the first spate of Orchard Road floods, no one - not even the experts in government - seems able to give a conclusive answer on what led to the floodings.

Was it because rainfall patterns had changed? While the Government said the rain last week was unusually intense, it has also admitted that rain intensity fluctuates and there is no clear pattern.

If there was no discernible change in rainfall patterns, were the floods due to urbanisation?

Due to unfortunate isolated incidents of a drain that got choked?

Or because drains and canals criss-crossing Orchard Road are too small to cope with sudden downpours?

So far, straight answers are not forthcoming - maybe it is impossible to pinpoint one single reason among the confluence of factors.

Meanwhile, PUB is ramping up its drain and road improvement works. These are mitigation measures that will probably be useful - but they may or may not prevent future floods.

This is why it is vital that this new panel of local and overseas experts that Dr Balakrishnan is appointing to review Singapore's flood-protection measures provide the answers that people are looking for.

It is important to plumb the depths of the floods and be as clear as possible on the root problem - what is causing these floods? Only then can good solutions be put in place.