Grace Chua Straits Times 12 Jan 12;
NATIONAL Environment Agency (NEA) officials, who briefed a panel of drainage experts probing recent floods, were of the view that Singapore's rainfall will show no discernible pattern in the future.
But the experts did not quite believe the weatherman.
'It didn't seem physically plausible,' said panel member Lui Pao Chuen, 69, of the NEA's climate vulnerability study, which was first released in 2010 and is meant to project the climate in the future.
So the panel asked to see the rainfall data. And when they pored over the figures, looking at how much rain fell in different parts of Singapore, and which areas experienced the most intense rainfall in an hour, a different picture emerged.
Professor Lui found that there are significant differences in annual rainfall in different parts of Singapore - as much as 50cm between regions. For instance, Changi got 215cm of rainfall a year on average between 1980 and 2009, but the Central Catchment area received 265cm of rain.
Annual rainfall increased, on average, by 15mm a year between 1968 and 2008.
The number of days when there was at least 40mm of rain per hour - a relatively high intensity - went from 50 in 1980 to 65 in 2010.
And the number of days when there was at least 70mm of rain per hour went from five in 1980 to 13 in 2010.
Prof Lui is adviser to the National Research Foundation and advises several other government agencies. The physicist by training was Singapore's chief defence scientist for 22 years till his retirement in 2008.
He and others on the panel were briefed on the study on July 8 last year, which stated that local rainfall till the year 2100 would show 'no discernible trends'.
The 12-man expert panel, formed last June, was tasked with reviewing Singapore's drainage and flood-prevention measures, after the upmarket prime shopping belt of Orchard Road and other areas suffered floods in 2010 and June last year.
Even updated drainage codes may have to be changed further to account for future rainfall predictions.
'The bible may no longer be valid because things have changed,' Prof Lui said, referring to drainage planning parameters.
In news reports immediately after last June's floods, the NEA had also said that, based on its long-term records, its analysis of the rainfall patterns in Singapore showed no significant trend.
But from its data analysis, the panel believed that weather patterns have already been changing and will continue to do so.
It concluded that higher rainfall intensity, increased urbanisation, and a too-small Stamford Canal contributed to the flooding.
In its recommendations, which were released on Tuesday, it said Singapore needs to tackle rainwater at various points along its flow chain and improve monitoring and data collection to better predict possible floods.
It suggested building detention ponds, green roofs and porous roads, among other things.
While the work of national water agency PUB has cut Singapore's flood-prone areas to 56ha today, Prof Lui raised another concern - that that figure might have bottomed out.
That means that flood-prone areas would increase in future if rainfall intensity keeps growing.
Asked to explain the contradiction between the data provided to Prof Lui and its analyses, and if the data was shared with and used by drainage planners, the NEA did not respond by press time.
The PUB was also asked if it collected its own rainfall data, if this data was used by drainage planners, and if planners were aware that rainfall intensity was increasing.
For its part, the PUB said it will study the recommendations of the expert panel and respond at a later date.
Right data flow critical to flood control
Straits Times Editorial 13 Jan 12;
AN EXPERT panel set up to examine ways in which Singapore can tackle floods has come up with a list of comprehensive recommendations. These range from creating rain gardens to capture and retain rain, and erecting green roofs; to improving drain capacity, building porous pavements to soak up rain water, laying a diversion canal and installing flood barriers. These are valuable suggestions to make life less miserable for people and businesses caught up in sudden floods. A series of them in recent years has made Singaporeans intensely aware of how vulnerable they remain to the vagaries of nature even in a modern city-state.
Looking at the longer term, the panel has recommended that a detention pond - which would hold water temporarily in case of intense rainfall - and a diversion canal could be potential solutions. This is in line with the thinking of the national water agency, PUB. However, this is a classic example of an area in which Singaporeans will have to consider carefully the trade-offs they will need to make between convenience and cost. Protection from floods would require major works of this nature, but the costs could be high in terms of the usage of space and money.
For example, for the pond to be viable, it would have to be the size of two to three football fields - something of a luxury in land-scarce Singapore. The canal in question - which would redirect water from Stamford Canal to the Singapore River - will cost between $300 million and $400 million. That would be a major infrastructural investment which would need to be justified by the extent of its contribution to the overall anti- flooding measures. Singaporeans do not want their country to be the Venice of South-east Asia, but they know that they can never be bone-dry in a tropical region. In the end, difficult choices will have to be made.
There is, however, one issue over which there can be little disagreement. This has to do with the collection and study of topographic and weather data. Going beyond existing drainage data collection - which is limited mostly to water movement within drains and canals - Singapore needs a digital map of the country's landscape and ground surface types to aid prediction of flood-prone areas. These are invaluable tools. The larger point is that, the more data that the Government can share with academics and the media, the better it is for Singapore. Public awareness of scenarios and options is an essential part of public confidence in the country's flood-fighting abilities. The alternative is the kind of shock, followed by anger, that some Singaporeans felt when unexpected floods came their way.