Sea walls are used to protect coastlines from destructive waves. They are made from concrete reinforced with steel. Their walls are curved in order to deflect the breaking wave back onto the next incoming wave. This reduces the energy of the incoming wave and makes it less likely to breach the top of the protective wall. Sea walls are used in the coastal town of Lahinch in Co. Clare to protect businesses built along the coast.
Gabions
Gabions are steel mesh cages that are filled with stones. They are used to reduce the energy of incoming waves. When a wave hits a line of gabions, it is broken up as the wave filters through the stones in the mesh. As the wave’s energy is spread out, its erosive power is reduced. Although gabions are effective, they are not long-lasting as the mesh wire can break during storms and the stones can be washed away. Sea walls are seen as a better choice as they require less maintenance.
Groynes
Groynes are low walls made of cement or wood that are built at right angles to the shore. They are used to trap sediment being moved along the coast by longshore drift. This allows material to accumulate and prevents the erosion of beaches. Several groynes have been built along Youghal Beach in Co. Cork. A negative effect of groyne construction is that this deprives nearby coastal areas of natural deposition. This can lead to increased erosion in those areas.
Rock Armour
Rock armour is a basic but effective form of coastal protection. Large boulders are placed along a coastline to reduce sea erosion. When waves crash off these boulders, their energy is reduced, preventing erosion from occurring. Although they are effective, rock armour is not a popular choice of coastal defence as it is bulky and takes up too much space on the beach.
: Fig. 11.26 Rock armour PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT 215 : Fig. 11.23 A sea wall
