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30 December 2021 by Aurecon Hong Kong Ltd
Singapore’s sea levels are projected to rise between 0.25 metres and 0.76 metres between 2070 and 2099, according to the country’s Climate Action Plan. With about 30 per cent of Singapore sitting less than 5 metres above sea level, coastal protection is understandably one of the government’s top priorities. In fact, the government is investing S$100 billion over the next 100 years to safeguard the city state against rising sea levels and temperatures, with an initial injection of S$5 billion set aside for its new Coastal & Flood Protection Fund.
Although the need is becoming more urgent, tackling rising sea levels is not new for the country. Back in 2011, Singapore raised the minimum reclamation level from 3 metres to 4 metres above sea level. This strong, proactive approach was exactly the right thing to do too, as data showed that between 1993 and 2009, the local sea level increase was almost double that globally. Singapore’s sea level rise reached up to 4.6 millimetres a year during the period compared to a global annual increase of 2.8 millimetres.
Among the many initiatives the country is looking to implement, one of the most keenly watched will be the plan for Singapore’s East Coast Park. This communal area regularly bustles with thousands of people, serving as a local community to live and play. It has a mix of residential housing and recreational developments, but the area faces challenges because it is located on relatively low land. If extreme weather events occur in combination with rising sea levels, the residential and recreational areas could be subjected to higher chances of flooding.
For warding off the threat of rising sea levels, there are three main coastal strategies for reducing flood risk and erosive forces:
For East Coast Park, some exciting concept ideas have been put forward. One of which is the “Long Island Project”. This project explores reclaiming a series of new islands in front of East Coast Park; while this area is developed to house recreational areas, a large reservoir and housing estates, it will also help protect the country against sea level rise and provide an alternative source for Singapore’s drinking water supply.
These types of large-scale plans will in turn encourage smaller scale nature-based solutions – including eco-designs – to be explored and used for both coastal protection and CO2 absorption (carbon sink). This helps to minimise environmentally destructive impacts by integrating alongside living processes. The great benefit of eco-design solutions is they not only ensure coastal protection, but also promote marine biodiversity preservation, increase the marine and terrestrial habitats and helps with the overall carbon absorption agenda.
A good example of a successful eco-design coastal defence is the Staten Island Living Breakwater project in the U.S. The innovative coastal green infrastructure project increases physical, ecological and social resilience along the waters in lower New York Harbour.
The Living Breakwater project comprises a series of nine ecologically enhanced breakwater segments off the southwestern tip of Staten Island. Made of a combination of hard stone and ecological concrete units, the breakwaters are non-traditional rubble mound structures. It was designed to reduce or reverse erosion and reduce coastal storm risk through wave attenuation.
The project integrates ecological[1] enhancements like “reef streets” and “reef ridges” and water retaining elements, into the breakwater’s physical structure. The use of bio-enhancing concrete also helps increase biodiversity and improves the ecosystem services the structures provide. It also helps with the active restoration of oysters on and within the breakwaters.
For East Coast Park, the eco-design explored could be a balance between hard structures, such as rock armour revetments and soft structures, such as planted mangrove forests. With the presence of rock armour revetments – potentially coated with eco-slurry to promote biodiversity growth[2] – these structures will provide an excellent habitat for corals, algae and other marine life to settle and grow. In turn, coral reefs help to protect and foster a conducive marine environment that promotes local biodiversity.
These hard and soft structures should be embedded in the design of a waterfront promenade to improve the overall landscape and potentially boost civic engagement in mangrove and local species restoration.
Land reclamation activities could further re-shape the coastline along East Coast Park. The natural effects of currents, swell, tides and waves will impact the coastline through erosion and sedimentation and overtime, C- or J-shaped beaches will be naturally formed. As such, designing and creating a series of new coastal coves that are close to nature’s own design, will help to bring a new coastline back into its natural equilibrium.
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An additional natural defence option for protecting the East Coast Park shoreline from erosion could be promoting the active growth of seagrass beds.
Seagrass is nature’s only marine flowering plant and the species is good at stabilising the seabed with their roots. Further, the plants act as a natural water filter by trapping suspended matter in their roots and letting clean water flowing out. Seagrass can store as much as 83,000 tons of carbon per square kilometre: an impressive amount considering the same area of forest can store only around 30,000 tons of CO2. Hence, seagrass plays an important part in CO2 absorption (i.e. acting as a carbon sink).
Seagrass also provides a conducive habitat for mammals like dugongs to thrive and serve as nurseries for marine life, such as juvenile fishes, crustaceans, cuttlefishes and seahorses. The good news: seagrass is already found around Singapore, for example along Labrador Park and just off the man-made beaches along Sentosa.
Mangrove forests could present a strong option as the line of defence for East Coast Park. Mangroves thrive in Singapore’s sediment rich marine waters and can be found around Kranji, Mandai, Pulau Tekong, Pulau Semakau, Pulau Ubin and other parts of the country’s southern coasts and islands.
While mangroves do not directly protect the land from sea level rise, they can protect the hinterland from the impact of waves, winds and extreme weather effects. In addition, they offer excellent environmental credentials. Their trees are able to store more carbon than normal terrestrial trees at around twice the rate according to some studies. In addition, they absorb carbon dioxide (CO2) and store this in their roots and underwater in the waterlogged soil between the roots, and are able to trap it there for millennia, provided no mangrove deforestation happens.
Currently, East Coast Park does not have any existing mangrove forests, so the challenge will be to nurture young mangrove trees as there are less mature trees around to shield the young seedlings. Fortunately, Singapore’s seas are relatively calm and the coast rarely experiences strong waves. However, if a design was to be implemented with mangrove trees integrated with smaller scale concrete open-faced tetrapods with holes at the side for the roots to grow, this will give the mangrove trees a good chance to stabilise and flourish.
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Situated behind the mangrove forests can be protective structures, such as rock armour revetments that play a vital role in absorbing the impact of wave energy especially during storms, whilst protecting the coastline from the effect of erosion. In Singapore, the gaps between the outer layer of armour rocks are filled with concrete to provide a smooth finish and prevent mosquito breeding.
While the challenges Singapore is facing in relation to rising sea levels are significant, it is heartening to know that the government is already showing strong leadership and commitment in facing them head on. One of the biggest challenges when dealing with climate change is understanding the risks and here Singapore is already ahead of the curve.
In 2018, Singapore’s Building and Construction Authority (BCA) commissioned the first-of-its kind study to form the national framework for coastal protection measures. Singapore’s BCA also understands the need for the framework to be flexible and dynamic to accommodate both future needs and the latest around climate science.
As Singapore continues to invest in coastal protection over the next century, the key to success will be to harness intelligent and innovative engineering solutions to deliver the most effective protection over the long-term.
In recent history, Singapore’s approach to urban planning and infrastructure has served as an inspiration to other countries, both across South East Asia and worldwide. With climate change in the spotlight like never before, the country has an exciting opportunity to set new standards for sustainable and resilient design that enables both the local economy and community to prosper.
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