SINGAPORE - To better protect parts of Singapore's coastline from extreme sea-level events, barriers resembling large metal "arms" could be deployed in the future.

Storm surge barriers have been successfully utilised in countries such as the Netherlands to protect areas from flooding. Hinged on the coast, they "hug" the coastline to allow ships to pass, but can swing outwards in the open waters before extreme high tide events hit.

National water agency PUB is studying the feasibility of deploying such structures to protect Singapore's south-western coastline from storm surges - higher-than-usual tides caused by storms brewing offshore.

With mean sea levels expected to rise due to climate change, storm surges could contribute to extreme sea level events and cause coastal flooding in low-lying areas.

The local coastline is vulnerable to storm surges at varying degrees, depending on the orientation of the coast, depth of water, wind speed and tide levels.

The south-western coast supports various waterfront activities, including offshore and marine, logistics, and the energy and chemical sector, said Ms Hazel Khoo, director of PUB's Coastal Protection Department, on Wednesday (March 16) in response to queries from The Straits Times.

"Coastal barriers could be an effective solution against extreme sea level rise and will be assessed to ensure that our maritime traffic and operational activities of the waterfront industries are not adversely affected," she added.

PUB called for a tender last Friday (March 11) to study the feasibility of coastal barriers, such as storm surge barriers, and raising the ground level of mainland industrial estates as an alternative solution.

The narrow channel of water between the south-western coastline of mainland Singapore and Jurong Island makes the deployment of storm surge barriers feasible, as they could fully enclose the channel as needed and be left open for sea craft to pass through otherwise.

The study will examine three areas: the northern coast of Jurong Island, the Jurong coastal area including West Coast Park and Pasir Panjang Terminal, and part of Tuas, which includes the Tuas Water Reclamation Plant and various shipping yards.

Other than storm surge barriers, the study will also look into barrages - dam-like structures - with navigational locks.

These locks are openings that allow ships and other sea-going vessels to pass through, but can be shut to protect against high tides and storm surges.

Barrages such as Singapore's Marina Barrage, on the other hand, are permanent barriers with gates that can be opened to discharge excess stormwater. They can also be equipped with navigational locks to allow vessel movements between two bodies with different water levels.

The study will also include preliminary analysis on various coastal adaptation solutions, including the possibility of raising the ground levels of JTC's estates during redevelopment. By studying this option, PUB will be able to determine the extent of protection it could provide.

Singapore has already moved to protect itself from future sea-level rise, by lifting upcoming infrastructure such as the Tuas Port by 5m above mean sea level rise.

The Centre for Climate Research Singapore has projected that climate change could cause a mean sea level rise of up to 1m by 2100.

Taking into account extreme high tides and coastal surge, mean sea levels could go up by 4m to 5m.

But PUB said it was taking a longer-term view of coastal protection, examining how to protect these areas against possible inundation at a mean sea level rise of 2m.

"Given the uncertainty of climate change projections, it is important that Singapore have in place plans and strategies in the event actual or projected sea levels are higher," it added.

The two-year study, which is expected to commence by the second half of this year, will be conducted concurrently with JTC's site-specific study of Jurong Island, and PUB will integrate the findings of both studies to assess the appropriate coastal protection options for the south-western coast.

The JTC study is one of eight site-specific studies that PUB will be calling for in phases to see how different parts of Singapore will be protected from sea-level rise. The City-East Coast study is already ongoing, while the Jurong Island and north-western coast studies are expected to start this year.

Factors such as costs (constructability, operations, and maintenance of the barriers) and existing and long-term land use plans, will be considered for the coastal barriers study, said PUB. 

The study could cost up to $3 million.

"The impact to maritime traffic and operational activities of the waterfront industries along the affected navigational channel will also be assessed," it added.

Throughout the course of the study, PUB and the appointed consultant will work closely with other government agencies, including the Urban Redevelopment Authority, the Maritime and Port Authority of Singapore, JTC and waterfront companies within and around the study area, to seek their feedback, said the agency.