S'pore's coastal guardians against the rising sea

Crowned by glittering skyscrapers, Singapore also wears a "necklace" of green, brown, blue and grey - a mosaic of colour and texture.

From seawalls and mangroves to sandy beaches and rocky shores, these coastlines separate the Republic from the rising tides.

But this coastal patchwork also means there is no one-size-fits-all approach to protecting the country's coastlines from rising sea levels, said Professor Robert Nicholls, a coastal engineering expert who has advised the Singapore Government on adaptation strategies.

"Different coastlines lead to different responses of the coast to sea-level rise and also different consequences if disaster unfolded," Prof Nicholls, who is director of the Tyndall Centre for Climate Change Research at Britain's University of East Anglia, told The Straits Times.

"So when we assess a coastline we examine the hazard, exposure and vulnerability and how these might change to understand the scale of the problems and identify the range of potential solutions," he added.

About 70 per cent of Singapore's coastline is currently protected by hard structures, said Ms Hazel Khoo, director of the coastal protection department at national water agency PUB. These include concrete seawalls and stone revetment walls, as well as hard infrastructure like the Marina Barrage and dams such as the ones in Kranji and Yishun, she said.

Nature dominates the rest.

About 16 per cent of the coast are mangroves and mudflats, 12 per cent are sandy beaches, and less than 1 per cent are rocky shore habitats, noted Mr Lim Liang Jim, group director for conservation at the National Parks Board (NParks).

But the impact of climate change, including sea-level rise, could affect the people and places here. Already, the Meteorological Service Singapore assessed last year that the country's average sea level today is 14cm above pre-1970 levels.

And with human activities emitting more heat-trapping gases into the atmosphere, causing water to expand and ice sheets to melt, the situation looks set to worsen.

In 2019, a major United Nations report found that if emissions remain high, sea-level rise in the centuries ahead could exceed rates of several centimetres per year, instead of the current increase measured in millimetres per year.

In response to this threat, new developments such as the Tuas Port will be built at least 5m above sea levels. But Singapore is also looking at ways to protect its coastlines, and whether it can combine man-made structures with nature to keep out the rising tides.

Mangroves, for instance, can help to prevent coastline erosion, protecting coastlines during storm surges and shielding seagrass beds and coral reefs from siltation, said NParks' Mr Lim. Mangroves also play a role in soaking up the planet-warming carbon dioxide that is driving climate change, with the ability to capture more than three times the carbon in dryland tropical rainforests, he added.

PUB's Ms Khoo said the efficacies of hybrid solutions combining hard and soft measures will need further study. "Upcoming site-specific studies will examine them and determine their suitability at specific segments of the coastline," she said.

Singapore had earlier identified four areas as being vulnerable to rising sea levels - the City-East Coast stretch, Lim Chu Kang, Sungei Kadut and around Jurong Island.

Studies at the coastlines of the City-East Coast stretch and Jurong Island will start this year, while studies in the remaining areas in the north-west are expected to commence next year.

Ms Khoo said PUB divided Singapore's coastline into different segments, knowing that different strategies will be needed to protect each of them. "Site-specific studies to develop coastal protection measures for the various coastlines will be conducted in phases progressively, starting with the more critical segments," she said.