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Welcome to our coastal protection blog!
In this blog, you will discover the various coastal protection measures adopted in Singapore's East Coast Park, how they function, and what their limitations are.
Enjoy!


Done by:
Chen Liling, Brenda Pong, Samuel Lee, Ang Pin Yuan, Gokul
Commonwealth Secondary School
Class 3C 2012

Seawalls

Seawalls

The purpose of a seawall is to protect areas of human habitation, conservation and leisure activities from the action of tides and waves. As a seawall is a static feature it will conflict with the dynamic nature of the coast and impede the exchange of sediment between land and sea.

The coast is generally a high-energy, dynamic environment with spatial variations occurring over a wide range of temporal scales.

The shoreline is part of the coastal interface which is exposed to a wide range of erosional processes arising from various sources, meaning that a combination of erosion and natural processes will work against a seawall.Given the natural forces to which seawalls are constantly subjected to, maintenance is  an ongoing requirement if they are to provide an effective long term solution.

The many types of seawall in use today depending on both the varying physical forces they are designed to withstand, and location specific aspects, e.g :local climate, coastal position, wave regime, and value of landform.

Beach Nourishment

Beach Nourishment

Firstly, according to the United States Environmental Protection Agency Office, beach nourishment is, simply stated, the introduction of sediment onto a beach. In most cases, the 

sediment is sand and the beach is in an eroded condition. In other words, in order to counter the effects of erosion (and hence removal) of sand on a beach, the agency takes a ‘soft’ (non-engineering, temporary) solution- replenishing the sand from an external source, in order to counteract the effects of erosion, not decrease erosion.

Beach nourishment suffers from a few great drawbacks- the cost of sand in order to replenish a certain stretch of open beach- for example, Florida’s Miami Beach, costed US $64 million in 1976. Adjusting for inflation, this same stretch of beach would cost $328,477,931.30 SGD. In total, 16 kilometers of beach was nourished. This means that less-developed nations would be unable to afford beach nourishment, as indicated in a UNEP report on coastal management in the African Continent. Just for the nourishment of the Cap Vert Peninsula, “beach nourishment, would cost US$255-US$845 million (0.7-2.2% of the country’s GDP) over a fifty year period.”. This means that in a worst case scenario of many major beaches being eroded at an increased rate due to rising sea levels, African countries would be unable to afford the ‘soft’ measure of beach nourishment in the long run.

Another great drawback of beach nourishment is the stopping of the sediment erosion forming a smooth pattern for waves, waves hit other non-nourished portions of the coast harder, causing severe erosion down the coast. This translates to an inability to nourish portions of the beach for fear of causing other downdrift sections from being eroded.

These combined detrimental effects, along with the impermanence of such a measure, makes beach nourishment only affordable by countries severely reliant on beaches and tourism, or otherwise richer countries.

However, this doesn’t mean that beach nourishment is completely inviable. Nations like the United States, Australia, and the Netherlands, with great quantities of beaches and wealth, can afford to replenish beaches with sand. Note that the sand being used to nourish the area must be equal or greater in particle size- this translates to a usually higher cost than the normal sand, as air is trapped under the sand and sold, leading to an abundance of air and not sand. Smaller sand, used by accident in replenishing Hawaiian beaches in Maui, reportedly “contained excess silt that enveloped coral heads, smothering the coral and killing small animals that lived in and around it.”.

The advantages of beach nourishment include- a preservation of the natural beauty of the area, which ‘hard’ measures like groynes cannot provide, an increase in area for settlement and tourism activities in order to increase income from such beaches. The land, finally, remains stable and is not changed by engineering, possibly increasing stable beach area size.

Hence, we may conclude, from examples like the Northern Gold Coast of Australia (75:1 cost:benefit ratio estimated), beach nourishment remains highly expensive, but retains key factors that other measures like groynes and seawall engineering (hard) cannot provide, such as increasing landmass and retaining beauty. However, due to it requiring more replenishment at rough 10 year intervals in most cases, it remains unaffordable or unprofitable for nations with low GDP or low percentage gain of GDP from tourism.

Groynes

Groynes 

To protect East Coast Park’s beaches from erosion, government has built groynes along the beaches. A groyne is a low wall built at right angles to prevent materials from being transported away by the longshore drift. These structures absorb energy of the sea on the shore, like headlands, reducing the impact of energy on the coast. There are 4 types of groynes: Wooden, Steel, Rubble-mound, sand-filled bag and made of concrete elements. Those found at East Coast Park are made of concrete elements.

(Positive impacts)

It traps sediments from longshore drift, forming a beach which attracts tourists, creating a positive impact on the local economy. Coastal erosion on beach is significantly reduced, as the water can only reach the cliff during high tide.

(Negative impacts)

Groynes prevent beaches down the coast from having sediments deposited there, which can lead to soil erosion. This could also destroy buildings and private land near it, causing property prices to plummet or cliff collapse when coasts are not protected from storm-driven waves which are approaching the shore perpendicularly. Protection of the shore by use of one groyne only is most often inefficient. Therefore, shore protection by groynes are designed as a group comprising from a few to tens of individual structures.

On the other side of the groyne, the beach will not be replenished by materials carried by the longshore drift. As a result, the beach further down the coast may be eroded away. While a series of groynes can help reduce this effect, they spoil the natural beauty of the coastal environment.

Breakwater

Breakwater

Offshore breakwaters are used at East Coast Park for coastal protection. The offshore breakwaters are made of granite. It creates a zone of shallow water between itself and the coast, so that waves will break against it before reaching the coast. When oncoming waves hit the breakwaters, they will impact the breakwaters before flowing towards the coast, causing its kinetic energy to largely reduce. The reduction of the waves’ impact on the coast can help reduce soil erosion along the coast.

The disadvantage of breakwaters is that they are unable to provide complete protection as they still leave areas of the coast unprotected; these unprotected areas will be prone to erosion. Breakwaters are also very expensive, each requiring an estimated cost of S$1 million to build and they may not last very long due to the frequent erosive impact of the waves on it. Careful consideration of local tides if also important before building a breakwater.