IN FOCUS: With 'no place to retreat to', Singapore advances to protect its coastlines

SURROUND SINGAPORE WITH WALLS?

There is no one-size-fits-all solution for Singapore’s 300km-long coastlines with their different typologies, said Prof Yong from NUS.

“New, integrated solutions are site-specific and tailored to complement varied land uses in that area,” he added.

Long Island, for example, will combine land, waterfront housing and leisure amenities with coastal defence, noted Prof Yong, who also chairs PUB’s coastal protection expert panel.

But varied as they are, the same principles apply to Singapore’s plans to tackle rising sea levels, said Ms Sarah Hiong, a deputy director at PUB’s coastal protection department.

“We have to be environmentally sensitive. We will engage our stakeholders to get inputs on some of these measures. We want it to be multifunctional as far as possible,” she said. 

One project exemplifying these principles is the Marina Barrage dam, which took 20 years from inception to actualisation and cost S$226 million. While its primary function is flood control, it has since become an iconic feature in the Marina Bay skyline, attracting more than 16 million visitors since its opening in 2008. The Marina Reservoir also serves as a source of drinking water and adds to Singapore’s water supply. 

Currently, around 70 per cent of Singapore’s coastline is protected by sea walls and stone embankments. These are hard, man-made structures that protect land and infrastructure from erosion and seawater intrusion. 

Other structures such as dykes, dams and tidal gates protect parts of the coastline where there are coastal reservoirs, such as along the Northwest Coast.

Why not simply surround Singapore with more strong barriers then? 

Building only sea walls around the country would protect the land but also end up harming existing marine ecosystems, said the Singapore Management University’s (SMU) associate professor of urban climate Winston Chow. 

“The wave energy is reflected out into the sea,” he explained.

Given Singapore’s push towards being a “city in nature”, putting it within walls would also be less than ideal. 

“Visually speaking, if you have sea walls everywhere … let’s say around East Coast Park, West Coast Park … it is at odds with the prevailing ecological aspects or functions that these parks have,” said Assoc Prof Chow, who teaches SMU’s Master of Sustainability programme. 

“There’s a disconnect which will happen if you decide to ring Singapore around with just sea walls.” Singapore is also adopting ideas from the Netherlands, a country one-third below sea level that has successfully designed systems to keep waters at bay. 

For instance, PUB is studying the feasibility of storm surge barriers for a channel of water between mainland Singapore and Jurong Island. These barriers can be closed during extreme sea level events, but otherwise left open for ships to pass through. If employed, these massive structures can protect parts of the Southwest Coast and Jurong Island.

Singapore may also consider the use of polders on the mainland, following its first project at Pulau Tekong which is on track to finish by end-2024. Polders are tracts of land that lie below sea level and are reclaimed through dykes, drainage canals and pumping stations.

As a further protection, new buildings can also, simply, be constructed at a higher level. That’s what Singapore is doing for Changi Airport’s upcoming Terminal 5, which is being built on a site 5.5m above mean sea level and with an extensive drainage network to minimise flooding. 

Long Island, too, will be reclaimed at a higher level, though authorities have yet to settle on a figure. In 2011, Singapore raised its minimum land reclamation level from 3m to 4m in view of long-term sea level rise.

Singapore has also injected a substantial S$125 million into a research programme and opened a new Coastal Protection and Flood Resilience Institute to consolidate expertise.

The launch of the centre signifies the importance of innovative solutions designed for the local context, said Singapore Institute of Technology’s (SIT) engineering associate professor Tay Zhi Yung. 

It also implies a need for more engineers and experts skilled in coastal protection and flood management, he added.

To come up with solutions, PUB has already been working on a model to simulate both inland and coastal flood risks, enabling it to better assess the impact of climate change on Singapore.

ADDING NATURE TO THE MAN-MADE

Going forward, experts point to “greening” structures – including transplanting organisms onto sea walls – as one possible panacea. Dr Stephen Summers, a senior research fellow from the Singapore Centre for Environmental Life Sciences Engineering (SCELSE), is one scientist looking at how to increase ecological function and diversity on barren sea walls. 

“A lot of the particle filtration is lost if there’s no organisms, no filter feeders, no sponges. They take all the particles out of the water,” he explained.

Without filter feeders to help purify water during seasons of heavy rain, there will be a build-up of particulates and nutrients that can form harmful algae blooms. This will in turn threaten the health of aquatic life and even humans, if consumed.

Dr Summers’ centre is working on a greening method which manipulates biofilm – a slimy layer of microorganisms – on a sea wall to make it conducive and encourage other organisms to settle and colonise. 

This would roughen up the sea wall and also serve to attenuate the force of waves.