21 March 2010

SiReNT, coastal erosion and mangroves

SiReNT (Singapore Satellite Positioning Reference Network) is an ultra-precise satellite navigation network that can be used, among others, to study coastal erosion and natural habitats.
Pulau Semakau will host the sixth and latest point on the system. It will also be used to"study the environment around the southern tip of Singapore, measuring coastal erosion, natural habitats and tidal activity in the area."

Is this a big deal?

According to media articles, Professor Peter Ng said the system will enable researchers to better understand the changes to the environment in areas around Pulau Semakau and St Johns Island, and devise methods to conserve biodiversity such as mangroves more quickly.

In beaches, only a few centimetres of sand are eroded every year, so tracking a trend over time is needed to devise the appropriate protection measures such as building sea walls, said TMSI research fellow Durai Raju.

Prof Ng said the new system could add 50 per cent to efficiency and save costs.

How serious is the erosion problem?
Erosion is a serious problem on many stretches of our shores. Along the reclaimed shores of the East Coast erosion is affecting structures there and there have been on going shoreline restoration and repairs to seawalls to deal with it.
Similarly at Pasir Ris recreational beaches, with repairs to the seawalls. Such repairs have their own impact on the shores.
Erosion on the shore

Elsewhere, on natural shores and mangroves, erosion can also be severe.

At Sungei Buloh, erosion is extensive and severe. The ground is literally being lost beneath the mangrove trees near the Main Bridge.
Erosion at the Main Bridge
While I recently saw this huge and seemingly healthy Perepat tree fallen over at the Mangrove Boardwalk.
Perepat (Sonneratia alba)
It is believed that erosion here is due to the loss of silt that was usually carried down the Kranji river. Since it was dammed to create the Kranji Reservoir, the input of silt is much reduced.

With the building of dams across our other rivers such as at Punggol, will the mangroves there also suffer the same fate? While Singapore is now touted as a City of Waterways, sadly, our re-engineering of natural waterways affect our natural coastal habitats as well.

At Chek Jawa, there also seems to be a loss of silt.
Erosion at the mangroves of Chek Jawa

Why save mangroves?
From Studying mangroves to save Singapore's coast Amresh Gunasingham, Straits Times 14 Nov 09, researchers at the Singapore-Delft Alliance highlight these points:
  • Mangroves produce nutrients that support offshore fish farms.
  • Mangroves can mitigate sea level rise. Mangroves left as they are could complement man-made sea walls to minimise the damage. "Building concrete sea walls can fulfil a certain function, but by promoting biodiversity, we can also use nature to reinforce the engineering function."
In addition, mangroves and the marine life they shelter also filter and improve water quality. Thus possibly helping to reduce situations which resulted in the recent mass fish deaths near Pasir Ris and Pulau Ubin.

As we learn more about the roles of mangroves, and how to conserve them, Singapore can also share this knowledge to protect mangroves in the region. Elsewhere vast tracts of mangroves provide a livelihood to many people, mitigate the impact of storms and provide other important ecological services.

In Southern Thailand, the economic benefits the mangroves provide include: collected wood and other forest products; cultivation for off-shore fisheries; and coastal protection against storms, a total of $12,392 per hectare over the course of nine years.

There are also efforts to look at mangroves in carbon capture, as part of the Blue Carbon concept.

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