Seawall

Adapted from : Wikipedia 

A seawall (also written as sea wall) is a form of coastal defence constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation and leisure activities from the action of tides and waves.^[1] 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.^[2]

The coast is generally a high-energy, dynamic environment with spatial variations occurring over a wide range of temporal scales.^[3]The shoreline is part of the coastal interface which is exposed to a wide range of erosional processes arising from fluvial, aoelian and terrestrial sources, meaning that a combination of denudational processes will work against a seawall.^[4] Given the natural forces to which seawalls are constantly subjected, maintenance (and eventually replacement) is an ongoing requirement if they are to provide an effective long term solution.

The many types of seawall in use today reflect both the varying physical forces they are designed to withstand, and location specific aspects, such as: local climate, coastal position, wave regime, and value of landform. Seawalls are classified as a hard engineeringshore based structure used to provide protection and to lessen coastal erosion. However, a range of environmental problems and issues may arise from the construction of a seawall, including disrupting sediment movement and transport patterns, which are discussed in more detail below.^[5] Combined with a high construction cost, this has led to an increasing use of other soft engineering coastal management options such as beach replenishment.

Seawalls may be constructed from a variety of materials, most commonly: reinforced concrete, boulders, steel, or gabions. Additional seawall construction materials may include: vinyl, wood, aluminium, fibreglass composite, and with large biodegrable sandbags made of jute and coir.^[6] In the UK, sea wall also refers to an earthen bank used to create a polder, or a dike.

Advantages and Disadvantages 

Seawall type	Advantage	Disadvantage	Global example
Vertical	The first implemented, most easily designed and constructed type of seawall. Vertical sea walls deflect wave energy away from the coast. Loose rubble can absorb wave energy.	These are partial to a lot of expensive damage in a short period of time. Vertical design can be undercut by high-wave energy environments over a long period of time.	Vancouver Seawall
Curved	Concave structure introduces a dissipative element. The curve can prevent waves from overtopping the wall and provides extra protection for the toe of the wall Curved seawalls aim to re-direct most of the incident energy, resulting in low reflected waves and much reduced turbulence.	More complex engineering and design process. The deflected waves can scour material at the base of the wall causing them to become undermined.	Torcross UK andSeagrove Bay UK.
Mound	Current designs use porous designs of rock, concrete armour. Slope and loose material ensure maximum dissipation of wave energy. Lower cost option.	Less durable. Shorter life expectancy. Cannot withstand or protect from high-energy conditions effectively.	Central Waterfront, Seattle

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                                     ( Short video on how a Seawall looks like) 

Seawall in Singapore : http://wildshores.blogspot.com/2011/10/construction-at-changi-east-seawalls.html