What are the impacts of coastal barriers on sediment transport?

Coastal barriers significantly alter sediment transport, leading to changes in beach morphology and potential coastal erosion.

Coastal barriers, such as seawalls, groynes, and breakwaters, are structures built to protect the coastline from the destructive forces of waves and currents. However, these structures can have a profound impact on the natural processes of sediment transport, which is the movement of sand and other materials along the coastline by waves and currents.

One of the primary impacts of coastal barriers is the disruption of longshore drift, a natural process where sediment is transported along the coastline by wave action. This can lead to changes in beach morphology, or the shape and form of the beach. For instance, a groyne, which is a barrier built perpendicular to the shoreline, can trap sediment on one side, causing a build-up of sand and a widening of the beach. On the other side of the groyne, however, the beach may become narrower due to a lack of replenishing sediment.

Another significant impact of coastal barriers is the potential for increased coastal erosion. Seawalls, for example, are designed to protect the land behind them from wave action. However, they can also reflect wave energy back towards the sea, causing the waves to pick up and carry away more sediment. This can lead to a steepening of the beach profile and a loss of beach area, which can further increase the vulnerability of the coastline to erosion.

Furthermore, coastal barriers can also affect sediment transport in offshore areas. Breakwaters, which are barriers built to break the force of waves, can cause sediment to accumulate in their lee, forming a tombolo or a spit. This can alter the seabed morphology and potentially impact marine habitats.

In conclusion, while coastal barriers are important for coastal protection, their impacts on sediment transport can lead to significant changes in beach and seabed morphology and increase the risk of coastal erosion. Therefore, the design and placement of these structures need to be carefully considered to minimise their impacts on natural coastal processes.