Give one example of a sea defence and suggest how it helps protect the coastline, also commenting on its effectiveness.

One example of a sea defence structure is a sea wall. Sea walls are used to dissipate and reflect wave energy back into the sea, reducing erosion. The wave energy reaches the sea wall, and due to the solid rigid strict, cannot further encroach on the land. This means the energy is either absorbed by the wall or dissipates. The result is a huge reduction in the amount of energy reaching the land, and hence a reduction in the erosion of the land. Sea walls made of reinforced concrete last a long time, however there are high implementation and maintenance costs involved which means they cannot be effective everywhere. Furthermore, once minor cracks develop in sea walls, this can quickly lead to significant damage to the structure as energy will be focused on this point.