Coastal Management Comprehensive Notes

Hard Engineering Seawalls How it is designed to overcome the problem Sea walls are usually built along the front of cliffs, often to protect settlements. A seawall is a structure constructed parallel to the coastline that shelters the shore from wave action. This structure has many different designs; it can be used to protect a cliff from wave attack and improve slope stability and it can also dissipate wave energy on sandy coasts. Challenges /Limitations /Disadvantages  However, a seawall may not protect a coast from erosion in the long run. As waves break against the seawall, the curved sea walls reflect the energy of the waves which is redirected downwards, to the base of the seawall, resulting in a strong backwash. The backwash wears away the base of the seawall, causing it to weaken and eventually collapse. Hence, seawalls have to be carefully maintained. the probable collapse of the seawall may also affect access to the beach by people and tourists. It is expensive to build seawalls. In England, it can cost 1 million pounds ($3 million) to build 1 kilometre stretch of seawall.

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Advantages A seawall provides excellent defence where wave energy is high, reassures the public and has a long life span. It protects the base of cliffs, land and buildings against erosion. and can prevent coastal flooding in some areas. Breakwaters How it is designed to overcome the problem An offshore breakwater is a structure that parallels the shore (in the nearshore zone) and serves as a wave absorber. It reduces wave energy in its lee and creates a salient or tombolo behind the structure that influences longshore transport of sediment. More recently, most offshore breakwaters have been of the submerged type; they become multipurpose artificial reefs where fish habitats develop and enhance surf breaking for water sport activities. These structures are appropriate for all coastlines. Challenges /Limitations /Disadvantages   They are unable to provide complete protection