DID YOU KNOW? The sea level is rising around the world at a rate of 3.2 mm per year. We will learn more about this in Chapter 14.
Coastal protection
Over the years people have developed different ways to protect the coastline from erosion. Here are some of the methods used:
Sea walls
Sea walls break the power of incoming waves, and their curved tops push waves back out to sea. During storms, these concrete walls can be damaged and may need repair. Examples of sea walls can be seen at Salthill in Galway and Strandhill in Co. Sligo.
Rock armour
These are large boulders at the base of a cliff or in front of sand dunes. When a wave breaks, it hits the rock armour and loses energy. This reduces the erosion of the coastline. Rock armour is used to protect the coastline at Tramore in Co. Waterford.
: Figure 10.25 Sea defences – a sea wall Groynes
Groynes are concrete or wooden structures built at right angles to the coastline. They extend down the shore and into the sea. They are designed to trap sediment carried by longshore drift. This ensures that sand builds up on the beach rather than being removed from it. Groynes can have a negative impact, however. If sand is trapped in one place, it means that further down the coastline there is nothing to deposit, and the waves have more power to erode.
: Figure 10.26 Sea defences – rock armour Gabions
Gabions are wire cages filled with small stones. They are placed in front of beaches or sand dunes to break the power of the waves and slow down erosion. Gabions are used to protect the beach at Lahinch in Co. Clare.
