SINGAPORE — If you were out on the roads across Singapore last Saturday (18 April), you would have experienced widespread floods triggered by the heavy downpour.
On that day, western Singapore experienced one of the heaviest daily rainfall records in 40 years, according to national water agency PUB.
Apart from unpredictable weather, there is one other development that could make low-lying Singapore more susceptible to flooding in the decades to come: rising sea levels. As a result of climate change, the sea level around Singapore is also predicted to rise by more than 1m by 2100.
The urgency of the situation was first underscored by Prime Minister Lee Hsien Loong at the National Day Rally in 2019, when he announced that $100 billion or more would be needed to shore up Singapore's coastal defences in the coming years.
At last year's Budget, Deputy Prime Minister Heng Swee Keat also announced an initial injection of $5 billion to the Coastal and Flood Protection Fund.
And just last month, PUB announced that it will soon award tenders for coastal protection studies, which will take a few years to complete.
"Without timely action to protect our coastlines, parts of Singapore could be submerged, impacting our homes and livelihoods," the agency said.
In this first of several stories on the environment by Yahoo News Singapore in commemoration of Earth Day on 22 April, we take a look at the impact of the climate crisis on Singapore's shores.
More flooding in low-lying areas
About 30 per cent of Singapore lies less than 5m above the mean sea level and these areas will be susceptible to flooding as the sea level rises, along with tides and storms, experts told Yahoo News Singapore.
"Places like East Coast Park or Sungai Buloh, some of our low lying areas, may get flooded during high tide," said Associate Professor Adam Switzer, who is a principal investigator with the Earth Observatory of Singapore (EOS) at Nanyang Technological University.
"So we will see an increase in what we call nuisance flooding," he added.
Secondly, infrastructure may also be affected, he noted. "What happens when we have rainfall that is falling into our canal systems and it can't go anywhere because the sea levels are already high?"
Similarly, director of the EOS Professor Benjamin Horton noted the increasing "vulnerability of cities and associated infrastructure that line many of the coastlines in Southeast Asia because of higher extreme sea levels (and flooding), coastal erosion, salinisation of surface and ground waters, and degradation of coastal habitats."
As flooding and rising sea levels sweep the region, Prof Horton predicts that hundreds of millions of people are likely to lose their homes in coastal and low-lying areas in Asia.
He pointed out that 19 of the 25 cities most threatened by a 1m sea-level rise are in Asia, with seven in the Philippines alone.
"Sea-level rise and flooding will have serious economic consequences. Global flood losses are expected to increase to US$52 billion per year by 2050 from US$6 billion in 2005. These estimates do not consider the ecological consequences of sea-level rise on coastlines of Asia," he said.
Additionally, mass migrations cannot be ruled out in the coming decades, as those living in cities that may be severely affected by rising seas could relocate altogether, he added.
Strengthening coastal defences
So how can Singapore protect its shores from the rising sea level?
At the 2019 National Day Rally, PM Lee said new developments have to be built at least 4m above sea level, up from 3m previously. Critical infrastructure such as Changi Airport Terminal 5 and Tuas Port are being built at least 5m above sea level.
But as large parts of Singapore are low-lying, including the East Coast stretch from Changi to the City, encompassing the Central Business District, other solutions have to be found.
Lee suggested in his speech that polders such as those in the Netherlands could be one possibility, where a seawall is built and water behind the seawall continually pumped out; a small polder is being built at Pulau Tekong. Another alternative he raised is to have barrages like the one at Marina Bay.
On the tenders for the coastal protection studies, PUB last month said, "Examples of potential measures include sea walls, earthen bunds, empoldering and nature-based enhancements such as mangroves."
Natural, green infrastructure
Noting how Changi Airport's Terminal 5 is being elevated above sea-level, Prof Horton suggested that existing houses can be elevated and new ones built on stilts. "We can further think about engineering advances that will enable Singapore buildings to float," he proposed.
Singapore Management University's Associate Professor of Science, Technology and Society Winston Chow said that in addition to protecting Singapore's coasts with 'hard' infrastructure like seawalls, dykes, or polders along its exposed coasts, natural forms of defence should also be deployed.
"We can also accommodate for sea-level rise using 'natural' coastal features, such as managing mangrove coasts that can potentially adapt to rising sea levels 'naturally' to protect against erosion," he said.
Prof Horton said mangroves, oyster beds, corals and coastal dunes can be tapped to increase coastal resilience. "Natural infrastructure, also referred to as 'green infrastructure', mimics natural systems or restores natural processes to provide a service, such as shoreline protection."
Reducing carbon emissions
Experts said that given the long-term impact of climate change and the coastal-protection infrastructure that will be put in place in the decades ahead, careful planning and execution is of paramount importance.
Assoc Prof Chow pointed out that some projects have to take place sooner rather than later, taking into account the parts of Singapore that require more protection.
Meanwhile, Prof Horton noted that robust and accurate projection of sea-level rise is necessary before Singapore spends considerable time, effort and money on its adaptation measures.
"Ultimately, the best way to mitigate rising sea levels is to slow down climate change by implementing the commitments laid out in the Paris Agreement," he added. Among other things, the agreement aims to keep the rise in global average temperature to well below 2 deg C above pre-industrial levels by reducing carbon emissions.
The Singapore government aims to halve 2030 peak greenhouse gas emissions by 2050 and achieve net zero emissions in the second half of the century.
If countries meet their commitments, Earth will warm by about 2 deg C by the end of the century compared with its pre-industrial average, said Prof Horton. Scientists believe that a rise of between 2 and 3 deg C will be the tipping point at which the Antarctic ice sheet will slip into rapid collapse, with catastrophic consequences for cities around the world, he added.
Singapore's natural assets should be fully harnessed with coastal forests or mangroves acting as carbon sinks, Assoc Prof Switzer explained. "They contribute to removing carbon from the atmosphere, which is the source of the problem that is generating the sea level rise. And so having mangroves that are perhaps behind sea walls or in the right places are going to contribute to our efforts to reduce carbon in the atmosphere."
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