PUB review should re-examine data, models to see if the parameters need to be updated
Grace Chua Straits Times 29 Jun 10;
SINGAPORE hosts the International Water Week conference and trade show this week.
Those irate at the two floods this month are dubbing June the Singapore Water Month. Heavy rain and a choked drain caused bad floods at Orchard Road on June 16, sparking jibes about 'Orchard River - Singapore's newest waterway' and 'GSS: The Great Singapore Sail'.
Last Friday, heavy rain felled trees and caused flash floods and traffic snarls across the island. The causes are not clear, but the national water agency PUB said intense rain overwhelmed the drainage system in some areas.
Some Singaporeans are still baffled by the flooding, perhaps because the rainfall was not evenly intense across the island. Roads in many areas were unaffected by floods, and people carried on as usual. So, not having seen any photos of debris choking a drain leading into Stamford Canal, they cannot understand how even a single chokepoint can cause serious damage.
Yet others are urging the PUB and the National Environment Agency's Meteorological Services Division to post online information on flood-prone areas, the location of floods in the past and even the percentage risk of heavy rain.
Such calls spring from the expectations of people who feel that one flood in super-efficient Singapore - let alone two in nine days - is just too much.
Prime Minister Lee Hsien Loong put the issue in perspective on Sunday when he said that a tropical city like Singapore will always face the prospect of flash floods when it rains heavily.
Rather than set aside land and money to build massive drains that remain empty most times, just to ensure there are never any floods, it would be more realistic to prevent widespread and prolonged flooding, and limit the risk to lives and damage to property, he said.
In other words, when you live in a tropical island-city like Singapore, you enjoy sunshine and clear skies - and face the occasional flash flood. Deal with it.
The Prime Minister has a point. Singapore's floods have been well-contained and nowhere as destructive as those that have occurred across the Causeway or in China. Short of erecting a giant dome over the island, there is no way to guarantee complete protection from floods.
Besides asking what the PUB has done to help them - itself a legitimate question - Singaporeans can also ask what they can do to help themselves.
If there were a severe flood, would Singaporeans be prepared? Would we be ready with a stock of clean drinking water, food, an emergency radio and first-aid supplies, or would we wait for someone to come to our rescue?
The simplest thing Singaporeans can do, which will have a direct effect on the drainage system, is to stop littering.
The public should not toss trash into drains or onto streets. A plastic cup or cigarette stub on the ground gets washed into the drainage system.
Last month, the PUB launched a campaign to discourage the littering of drains. Each day, its contractors remove a mind-blowing average of 14 tonnes of rubbish from Singapore's 7,000km of drains and canals. The debris can choke drains and lead to overflows, which are a cause of flooding.
Tides are another possible cause of floods, but not of this month's inundation. The tide was not high, and the gates of the $226 million Marina Barrage were open.
But even if people take the no-littering message to heart, the fact remains that Singapore roads have been flooded more than 10 times in the past five years.
Besides the inundation in Bukit Timah last year, there have been floods in MacPherson and Paya Lebar (April last year, caused by 97.6mm of rain); at Orchard Road (November 2007, 99mm of rain); and in Commonwealth (August 2007, 143mm of rain over seven hours).
This raises the inevitable question of whether the drainage system is structurally adequate, an issue PUB is reviewing.
It might consider two factors. One is whether its assumptions about the frequency of floods should change.
Some experts think climate change may be contributing to changing rainfall patterns, unleashing floods. If so, it is time to re-evaluate the average frequency of storms and revise models and drainage planning based on those numbers.
For example, when a storm is labelled a 'once in 50 years' occurrence, that is a technical term meaning there is a one in 50 chance a storm that size would happen in any given year. That calculation - used by insurance companies and agencies worldwide, including the United States Federal Emergency Management Agency - is based on historical data of past storms and floods, and statistical modelling of future ones.
But if the frequency of storms is changing, that statistic is not an adequate basis on which to make contingency plans. So the numbers may need updating.
The other factor PUB might review is its assumption of what level of flooding is acceptable in Singapore.
Granted, no tropical island-city can ever be 100 per cent flood-free, but are Singaporeans prepared to live with two floods in one month? Or is the threshold two bad floods in a year, as in last year?
The Orchard Road flood is estimated to have cost millions of dollars in damage to property and merchandise. No lives were lost, but just one misstep that day by someone could have led him or her to trip over hidden obstacles or fall into an open drain obscured by flood water.
Existing infrastructure has served the country well, but the parameters may need to be updated in the light of changing conditions.
Floods occur. They are unavoidable. But are our agencies and ordinary people more ready for them now compared to the past?
