Water solution

BLAME it on the (blocked) drain. Oh wait, it's the heavier rain. Climate change upsets weather patterns.

That's why some parts of Orchard Road get flooded during intense storms, some people say.

Is it the Stamford Canal? Maybe it can't cope. Perhaps urbanisation is at fault, others maintain.

So what really hurt Singapore's shopping mecca? The answer, it seems, is all of the above.

Heavier rain

Data shows that more frequent and intense rain fell over Singapore during the last 30 years.

While sensors and SMS alerts give advance warning of impending flooding, they can't minimise it.

And it's not just water; extreme weather like prolonged drought wreaks havoc, too.

Topography

The stretch between Cuscaden and Cairnhill Roads (including Orchard Road) is like a basin.

Low-lying buildings at the bottom of a slope (such as Liat Towers) or those with open basements (Liat Towers and Lucky Plaza) are particularly vulnerable to water pooling onsite.

While sandbags, flood barriers and raised platform levels can reduce the effects of flooding, their impact is localised.

Last year, 12 flood experts were appointed by the Government to look into the problem.

The panel recommended the building of water-retention ponds, porous pavements, rain gardens, water-storage tanks and flood plains to slow down and reduce water run-off.

Modelling tools simulating the drainage system's flow and water levels would also aid future flood-protection plans. A digital map showing Singapore's land height is in the works.

Stamford Canal

The 4km channel from Tanglin Road to Raffles Avenue is maxed out. It can't drain more intense run-off.

Authorities initially blamed a choked section of the canal for causing the June 2010 floods that affected Liat Towers, Lucky Plaza and Delfi Orchard.

Then their stance shifted. Indeed, national water agency PUB estimated the canal had to be widened and deepened by almost a third to cope with heavier rains.

But upsizing the canal would be too disruptive and costly, Minister for the Environment and Water Resources Vivian Balakrishnan argued. Better to build a diversion canal, costing up to $400 million, to divert excess flow, experts added.

Urbanisation

The loss of green spaces leads to an increase in storm water run-off.

Building rooftop gardens and retention ponds can delay overflow and retain water upstream. But setting aside land two to three times the size of a football field for these ponds is something that land-scarce Singapore can ill afford, said Dr Balakrishnan.

A PUB spokesman said density is factored in when the drainage system is planned. It "will review its methodology to better estimate the impact of urbanisation", she added.

This article was first published in The New Paper.