Friday, 18 November 2016

Polder Development: New land reclamation method for Pulau Tekong

Pulau Tekong to get extra land the size of two Toa Payoh towns using new reclamation method
Extra land to be used for military training will free up space on main island for other uses
By Yeo Sam Jo, The Straits Times, 17 Nov 2016

A plot of land the size of two Toa Payoh towns will be added to the north-western tip of Pulau Tekong using a land reclamation method that is new to Singapore.

The 810ha space, to be used for military training, will be created by empoldering - a method which involves building a dyke around the area to be reclaimed and draining water from it.

Compared with the traditional technique of filling a water body with sand, this method is expected to cut construction costs and the amount of sand required, and could be used for other projects in future.

National Development Minister Lawrence Wong told reporters during a site visit yesterday that Singapore is "always in need of more land".

"This particular expansion, it's going to be used for Singapore Armed Forces (SAF) training. But the needs for land continue to grow, whether it's for military, for housing, for commercial uses," he added. "We are always looking at options to expand. And by expanding Tekong, providing SAF with more space for their training needs, which are growing, we can free up land on the main Singapore island for other developmental purposes."

Singapore has been studying the empoldering method for some time, he said. It has visited the Netherlands, where the practice is prevalent, and consulted experts from the country. The technique will create a low-lying tract of land, known as a polder, about 1.2m below sea level.

Water levels in the polder will be controlled by drains and pumps, and a 10km-long dyke standing about 6m above sea level will buffer the reclaimed area from the sea.

"This is really a project not just about expanding our physical space but also about building up capabilities and making ourselves a more resilient nation in the longer term," Mr Wong said, referring to challenges such as disruptions in Singapore's sand supply and rising sea levels due to climate change.

"The experience that we gain in learning how to build dykes, in learning how to manage coastal areas, this will be very important for us as we deal with the threat of climate change in the longer term."

Mr Wong said empoldering is expected to lead to "significant" cost and sand savings, but did not reveal any figures. He added that he would "not rule out" adopting empoldering for future reclamation works here.

The Housing Board, the appointed agent for the project, will call for tenders by the end of this year. Construction will commence at the end of next year, and the reclamation is slated for completion around 2022.

Thereafter, the Defence Ministry will maintain the polder plot, while the drainage system, dyke, water pumping stations and canals will be maintained by national water agency PUB. The land will also come with 21km of roads - the length of East Coast Parkway - and 29km of drains.

HDB said an environmental study carried out found the polder's impact on surrounding marine life and the environment would be "minimal". Surrounding areas with mangroves and other plant life will be conserved and protected.

Dutch experts give advice on Tekong land reclamation
By Yeo Sam Jo, The Straits Times, 17 Nov 2016

A popular tale by American author Mary Mapes Dodge tells of a Dutch boy who saves his country by putting his finger in the hole of a leaking dyke. The Dutch have had a long history with dykes - embankment barriers - given how the Netherlands is prone to flooding.

It may come as little surprise then that Singapore's latest land reclamation venture on Pulau Tekong, which will use a 10km-long dyke, is being done in consultation with Dutch experts.

To ensure that the project is cost- effective, safe and environmentally sensitive, Singapore is working closely with Professor Kees d'Angremond from the Netherlands, a longtime adviser to the Republic on reclamation. He is also an authority on polder development - the reclamation method that will be used to create 810ha of extra land on the offshore island.

This involves building a dyke around the area to be reclaimed and draining water from it. It will result in a low-lying tract of land, known as a polder, that is buffered from the sea by the dyke. Water levels in the polder are then controlled by a network of drains and pumps.

While polders may be new to Singapore, Prof d'Angremond said they have been built in the Netherlands for the past 2,000 years. These polders started out as primitive ones built by farmers who wanted to protect their land against flooding, and were often a matter of trial and error, he said.

With modern technology today, safety of the polders is ensured using advanced methods. These include the building of strong dykes to ensure water does not flow in, determining the dyke's height in relation to expected sea levels and wave action, and having a grass cover on the inner dyke slope to ensure it does not erode, Prof d'Angremond said.

A stone revetment, similar to a sea wall, will protect the dyke from the sea waves, said the Housing Board, the reclamation project's appointed agent. Meanwhile, either a cement bentonite screen or a diaphragm wall will minimise the seepage of sea water through the dyke.

The professor acknowledged that Singapore has "more severe" rain than the Netherlands, which might make draining water from the polder more challenging. But he said that this could be solved with a proper pumping system.

He added: "We will do a lot of research in polders together to see whether we can make further improvements that are really dedicated to the conditions in Singapore."

Building expertise for land reclamation
Editorial, The Straits Times, 30 Nov 2016

Dyke construction and coastal management will play an essential role in the evolution of Singapore's land reclamation efforts. This is to be expected as the effects of rising sea levels, a consequence of climate change, will be felt on islands and littoral states in general. Thus, it is useful to gain experience in the use of seawalls for reclamation when a plot of land, the size of two Toa Payoh towns, is added to the north-western tip of Pulau Tekong - a method that is novel here.

The development of Pulau Tekong was forecast in the Land Use Plan of 2013. Reclamation, chiefly around Tuas and Tekong, was cited then as a key plank of Singapore's attempts to accommodate a larger population by 2030. Works around those areas would increase the country's land area by some 5,200ha by 2030. That expansion is equivalent to nine Ang Mo Kio towns. The scale indicates the level at which Singapore has to peg its efforts to overcome land constraints if it is to provide a quality of life in the future commensurate with what it offers now. The building of new towns and the redevelopment of golf courses will complement reclamation efforts. Given that the plan's target date is only 14 years away, it is imperative to begin work well on time so that the reclamation process is sustainable. Tekong's expansion is for Singapore Armed Forces training, but it also will free up land on the mainland for housing and other developments.

Technological advances are making a crucial contribution to reclamation efforts. Pulau Tekong will benefit from empoldering, a method that involves building a dyke around the area to be reclaimed and draining water from it. This will be an improvement on the traditional technique of filling a water body with sand, because it could lower construction costs and will decrease the amount of sand required. The latter advantage is a substantial one since dependence on sand imports, which is subject to various constraints, could have narrowed Singapore's room for manoeuvre on reclamation one day. The use of the Dutch empoldering method offers a way to create space more viably.

A larger issue is the steps which Singapore has to take to deal with rising sea levels, as climate change is irreversible. Dykes and flood-control measures will need to become habitual for the population of an island city-state whose only ecological hinterland is what is produced by its expertise, ingenuity and determination. Here, there is a lesson to be learnt from the Dutch, who have built polders for the past 2,000 years. These have evolved, through trial and error, from primitive forms into their modern incarnation as a part of the Netherlands' environmental security. Singapore would do well to continually study best practices elsewhere to shore up its own ecological defences.

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