Coastal Erosion
What is Coastal Erosion?
Coastal erosion is when the shoreline gradually wears away because of the sea’s force. Over time, this can lead to loss of land, damage to properties, and changes to our coastline.
The cliff erosion seen in this image occurred in Pembrokeshire.
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A large section of the Wales Coast Path gave way which meant the path had to be diverted around the hazard.
​Coastal erosion occurs when the energy from water and wind interacts with sediment and rocks making up the coastline. Sediments are removed from beaches, cliffs, or dunes, often transported to other areas along the coast. Depending on the type of coastline—whether sandy beaches, rocky shores, or estuarine environments—the rate of erosion and the mechanisms involved can vary significantly.
Types of Coastal Erosion
A variety of natural and human-induced factors, known as "forcings," drive coastal erosion. Understanding these forcings is key to predicting and managing erosion.
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1. Wave Action
Waves are one of the primary forces driving coastal erosion. As waves break on the shore, they exert pressure that can dislodge and transport rocks and sediments. Strong, high-energy waves, particularly during storms, can cause rapid erosion. Long-term wave action shapes coastlines through processes such as abrasion, hydraulic action, and attrition.
The Green Bridge of Wales was formed over millions of years through erosion from wave action. Initially, two caves either side of the outcropping would have been formed and these gradually eroded to create this dramatic rock arch. Eventually the bridge section will collapse leaving two sea stacks.
2. Tidal Forces
Tides contribute to coastal erosion by affecting how far waves can reach up the shore. High tides can lead to greater erosion as they allow waves to reach farther inland, particularly during storm surges. Over time, the ebb and flow of tides can transport sediments alongshore or offshore, influencing both erosion and deposition patterns.
The River Severn has one of the largest tidal ranges in the world. During Spring tides, the difference in water levels between high and low tides can be as much as 15 metres.
With rising sea levels this tidal range is set to increase and could see many communities on the banks of the Severn experiencing severe flooding during extreme weather events.
The River Severn has one of the largest tidal ranges in the world. During Spring tides, the difference in water levels between high and low tides can be as much as 15 metres.
3. Wind and Aeolian Transport
Wind plays a significant role in shaping coastal dunes and beach profiles. Wind can blow loose, dry sand inland, depleting beach areas and weakening natural coastal defenses like dunes. In exposed coastal areas, strong winds can significantly accelerate erosion, particularly when combined with storm conditions.
This dune system serves as a barrier between the sea and Swansea University's Bay Campus. Increasing frequency and intensity of storms could see dune systems start to retreat inland, causing issues for any infrastructure or settlements behind them.
4. Sea-Level Rise
As global temperatures rise due to climate change, sea levels are increasing. This rise results in more frequent and prolonged inundation of coastal areas, leading to higher rates of erosion. As the sea encroaches inland, the natural buffer zones between the land and sea are diminished, making coastal environments more vulnerable to wave action.
The village of Fairbourne is one of the most vulnerable in the UK to sea level rise. Built on a low lying flood plain an increase in sea level could see severe flooding and potentially the abandonment of protection for the town by 2054. It might become one of the first villages in the United Kingdom to be "decommissioned" with residents moved away and buildings and infrastructure removed to prevent pollution when the sea overwhelms the area.
5. Storms and Extreme Weather Events
Intense winter storms can dramatically accelerate coastal erosion on the Welsh coastline. During these events, large waves, storm surges, and strong winds can remove vast amounts of sediment in a short period, cause damage to coastal defences and cause flooding. The impact of these storms can be especially devastating in areas already vulnerable to erosion.
Cliff falls are common in many parts of Wales. This image shows a cliff fall near Saundersfoot which occurred overnight whilst Storm Ciaran was passing through the area.
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Increasing frequency and intensity of storms is likely to increase the number of cliff falls especially on softer cliffs.
6. Human Activities
Human activities such as coastal development, deforestation, and the construction of sea walls or groynes can alter natural sediment transport processes, leading to increased erosion in some areas. For example, coastal armoring might protect a specific area from erosion but can exacerbate erosion downstream due to the interruption of sediment flow.
Groynes are a type of sea defence which are common across Wales. These are designed to interrupt the process of longshore drift and trap sand on a beach in order to try and prevent erosion in that location.
7. Geology and Coastal Composition
The type of rock or sediment that forms a coastline plays a significant role in its susceptibility to erosion. Soft sedimentary rocks like sandstone and clay erode more quickly than harder rocks like granite. Sandy beaches are more vulnerable to erosion than pebbly or rocky coasts. Understanding the local geology is crucial for assessing erosion risks.
Much of the coastline in Ceredigion is composed of a very soft sediment which is a remnant from when Wales was covered by glaciers during the ice ages.
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These types of cliffs are particularly vulnerable not only to wind and wave action but also rain and overland flow which can form large gullies contributing to further instability.