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  Straits Times 24 Jun 07
Is S'pore ready for the next big flood?
In Part 2 of our special on climate change, Arti Mulchand goes back to the past for clues on what rising sea levels could do to Singapore

RAIN did not fall on Feb 9, 1974, yet 'mystery floods' swept through Singapore, bringing life to a virtual standstill.

Seawater 1m high covered large tracts of the island. Nicoll Drive, which now hugs the Changi Beach coastline, was under 1.5m of water, threatening the malnourished children at the Singapore Children Society's convalescent home nearby. The police were called in to move the children to higher ground.

Merchants in Boat Quay lost thousands of dollars in goods such as rice, coconut and oranges; the breakwater off Collyer Quay was submerged and traffic came to a standstill.

The reason: a worldwide high tide surge between Feb 7 and Feb 12, which went beyond the usual 1m to 2.4m here.

On Feb 9, the tide stood at 3.9m, a record for Singapore.

So, for a few hours, Singapore got a taste of what a sea-level rise of over 1m might be like, said Professor Wong Poh Poh of the department of geography at the National University of Singapore, who has been studying Singapore's coasts since the 1960s.

A recent United Nations report by more than 2,000 scientists from more than 100 countries studying climate change had warned that global warming - largely caused by human carbon dioxide emissions - could cause sea levels to rise by 18cm to 59cm by 2100.

The 1974 high tide provides a good opportunity to study how a rise in sea level would affect Singapore's coastlines.

Prof Wong, who studied first-hand the havoc wreaked by the 1974 big flood, came to this conclusion: A 1m rise in sea level could lead to a greater impact of waves on the shores, coastal erosion and flooding, and pools of water getting left behind in low-lying areas.

The remaining mangrove swamps on the west and north coasts and the coral reefs fringing the offshore islands would also be submerged. Erosion would affect beaches in the south-east, west and north coasts, and cliffs and slopes on the north and west coasts.

His findings were compiled into a report in 1992 in which he also suggested that Singapore's coastal reservoirs, such as Kranji, Sarimbun and Seletar, could be under threat.

The former tidal estuaries were dammed up by dykes built across river mouths to make them into reservoirs. But an increase in sea level could lead to salt water entering these reservoirs, making the water undrinkable.

It can take up to two years for the sea water in the reservoirs to be flushed out completely and be replaced by rainwater, said the Public Utilities Board (PUB).

Professor Wong's report was cited in 2000, when Singapore made its first report to the United Nations Framework Convention on Climate Change, a platform for countries to work together to avert the threat of global warming.

The document outlined some of Singapore's key vulnerabilities and acknowledged that climate change could aggravate problems such as erosion and flooding.

It stated that some of Prof Wong's proposed solutions - including docks and dykes, better tide gates and pumping systems to redirect water - should be considered and more research done.

Already, a formal 'vulnerability' study is under way. It was kicked off earlier this year and is being led by Professor Liong Shie-Yui, principal research fellow at the National University of Singapore's Tropical Marine Science Institute.

His 14-member team is examining climate data, such as rainfall and temperatures from the 1960s onwards, and will also study the implications of saltwater intrusion into the ground, canal systems and reservoirs, as well as the stability of slopes both inland and along the coasts. Preliminary findings will be released next year and the study completed in 2009.

Some groundwork already appears to have been laid by Prof Wong.

Back in 1992, he pointed to areas that appeared to be more vulnerable than others, because they are less than 2m in height above sea level.

They included some of the commercial areas around the Singapore River, parts of the industrial land on the west coast, parts of Changi Airport and a major part of the recreational land along East Coast Park.

Many of these areas were reclaimed before 1991, when the PUB imposed rules for the height of new reclaimed land, which now has to be 125cm above the highest recorded tide, allowing it to cope even if sea levels rise by the maximum of 59cm by 2100.

Prof Wong also pointed to the south-western coastline, where West Coast is, which could be most vulnerable to wave attacks if the sea levels rise because of the incidence of 'Sumatra squalls'.

These are thunderstorms that develop over Sumatra or the Malacca Strait, and move in over the west coast of Singapore and Peninsular Malaysia during the south-west monsoon season from June to September.

Today, those winds already generate waves that are more than a metre high, said Prof Wong. Rising sea levels could mean a stronger attack on the shores when such squalls develop.

Some of the reclaimed islands south of Singapore are also about 2m above sea level as well, he said.

Prof Wong's scenarios throw up visions of destroyed coasts, submerged areas and undrinkable water.

But work to avoid such catastrophes have been put in place over the years. Beyond minimum heights for reclaimed land, some $2billion has been poured into drainage infrastructure in the past 30 years.

The completion of Marina Barrage and other flood-alleviation projects, including raising roads and enlarging drains, is likely to cut down the 124ha of flood-prone areas by more than half in 2011.

This means only a combined area about twice the size of the Singapore Zoo would risk inundation during high tide and heavy rainfall.

Singapore is also getting some outside help, especially from the Dutch, the world's foremost dyke builders.

Dykes are used extensively in Holland, more than half of which lie below seawater level. Delft Hydraulics, a Dutch water research and consulting organisation, has tied up with Singapore to create the Singapore Delft Water Alliance, and a research centre has been set up with NUS and the PUB.

It is probably easier to conjure up images of battered coastlines and flooded roads than another thing that could come as the world gets warmer: diseases.

While no conclusive studies have been done in regions where diseases like dengue, for example, are endemic, what is known is that small changes of 1 to 2 deg C in temperature could have an impact, said the National Environment Agency.

Warmer temperatures at this time of the year, for example, favour the breeding of the Aedes aegypti, which has contributed to the current dengue surge. There is still some debate on the effect large temperature changes have on diseases.

Changing climate could also have a major impact on coastal ecosystems and biodiversity.

Singapore's corals, already stressed out by sediment-filled waters, could be under threat, for example. Warmer sea temperatures cause the corals to have a 'stress' reaction and throw out the algae that they usually house within their flesh and which give corals their colour, said Tropical Marine Science Institute's Prof Chou Loke Ming.

The algae, called zooxanthellae, photosynthesise and pass on sugars, among other things, to the corals. In turn, the corals offer the algae protection, shelter and carbon dioxide for photosynthesis.

The bleached corals - so called because they lose their colour - can survive without the algae for about two to three weeks, but if sea temperatures stay up for much longer than that, they will die, said Prof Chou.

A 1998 mass bleaching incident that affected reefs all over the world at an unprecedented level demonstrated just that. The incident, which coincided with a strong El Nino year, saw sea water temperature rising by close to 4 deg C. The corals here were bleached by between 50 and 90 per cent and up to a depth of 6m. About a quarter of the corals were finally lost.

Singapore now has about 190 species of hard corals, with at least two lost species on record, said Prof Chou. Some 60 per cent of corals have been lost since the 1960s.

Recent coral reef analysis indicates that between 24 and 30 per cent of reefs in Asia is likely to be lost in the next 30 years due to climate change and other stresses.

About 50 per cent of Asia's biodiversity may also be at risk due to changes in temperature and rainfall patterns. Professor Peter Ng, director of the Raffles Museum of Biodiversity Research, suspects the effects of climate change are already being felt here.

But because no reliable baseline data going back 30 or 40 years exists, and new species are still being discovered, there is 'no smoking gun', he said.

But like Prof Wong and numerous other scientists who have been trying to warn the world about the effects of climate change and the way human beings are contributing to the problem, Prof Ng said that the time to act to avert an ecological disaster is now.

'We know climate change is happening, and right now, the changes are gradual, but there will be a breaking point, and when you get to the edge of that cliff, you go straight down. Until you get to the edge though, you can still backtrack,' he said.

'If all the available indicators say that something is going wrong and will have consequences, you should be super kiasu and try not to get to that point.

'The end-game is otherwise catastrophic.'

Were you caught up in the 1974 floods? Send your photographs or memories of the event to 75557@stomp.com.sg with the subject header 'Flood'.
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