A seawall is a man-made structure erected to protect the shore from tidal waves and thus prevent erosion and flooding. Apart from providing coastal defense, a seawall protects human habitation and recreational activities from the sea waves. A seawall reduces the wave energy by reflecting it back to the sea. This greatly reduces the energy and erosion of the existing coastline. Seawalls provide a number of benefits but they also have certain negative features which have to be considered in order to ensure that the construction of the seawall is truly beneficial and appropriate to the costs involved.
Vertical seawalls were among the first to be implemented and were relatively easier to design and construct. Vertical seawalls are constructed in highly exposed settings. They help in deflecting the wave energy back to the sea, thus saving the coast. The loose rubble effectively absorbs wave energy and minimizes the damage to the coast. However, vertical seawalls can be damaged over a period of time by high -wave energy resulting in lot of expenses to repair the damage. The Vancouver seawall is an example of Vertical seawalls.
Curved Seawalls help in breaking the waves and lessen the wave energy. The curved design of the seawalls adequately protects the base of the wall and prevents the waves from reaching the top of the wall. The concave structure of the seawall dissipates incident energy leading to low waves and reduced turbulence. But the biggest disadvantage of curved seawalls is that its design involves complex engineering and high costs. Besides, the deflected wave energy can rub against the material beneath the wall causing damage to the seawall over a period of time. The Torcross and Seagrove bay in the UK are examples of Curved seawalls.
Mound seawalls involve the construction of mound type structures in situations where wave energy is low and less demanding settings which are least exposed use a facing of sandbags, stones or porous rocks that form concrete armor for the embankment. The option of mound seawalls involve lower costs but they may have limited life expectancy.. They cannot withstand high-energy environments and are less durable. The Central Waterfront in Seattle is an example of the Mound type seawall.
Construction of a seawall may be expensive but it can be an effective coastal management solution and can be planned keeping in mind the various positive features compared to other engineering methods. The construction of a seawall provides for increased coastal defense besides providing opportunities for sightseeing and recreation. Seawalls are strong defenses that are durable even in increased energy environments and last longer than other engineering methods. Seawalls effectively control soil erosion and in extreme conditions, seawalls prevent loss of life and property by minimizing erosion.
The construction of Seawalls involves high costs besides dissolving the beaches and making them nonfunctional for beach goers. It is important to determine whether the construction of a seawall is beneficial and worthy of the high costs involved. Seawalls may not be a pleasing sight and ruin the landscape of the sea. The construction of seawalls can destroy the formation of intertidal beaches and wetlands that form naturally near the shoreline.