The Living World
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Factors Influencing Coastal Erosion

Coastal erosion is the process of land wearing away along the coastline. Over hundreds, and thousands of years, erosion can dramatically transform the coastline of an area.

Erosion is influenced by many factors and being aware of its causes is important to understanding broader coastal landscapes in the UK.

Geology

Rock type

The type of rock present along a coastline plays a significant role in determining erosion rates. Different rock types have varying levels of resistance to erosion caused by destructive waves, the primary cause of erosion on coastlines.

  • Hard Rock – Rocks such as granite or limestone are strong and dense. Therefore, they are more resistant to erosion than other types of rock. This slows down the wearing away of material along the coastline, which can help protect distinct features. Typically, you’ll see features such as headlands in areas that have harder rock.
  • Soft Rock – Sedimentary rocks like clay or sandstone are softer and more prone to erosion, leading to faster rates of coastal retreat. Where there are areas of softer rock, features such as bays, or lower cliff profiles are more likely to form.

Rock structure

The structure of rock layers also influences erosion rates. If the rock layers are inclined or folded, it can create weaknesses that accelerate erosion.

Wave Type

Wave energy

Waves are the primary agents responsible for coastal erosion. The energy carried by waves determines their erosive potential. The waves with higher energy levels will have greater erosive effects, while the opposite is true for waves with lower energy levels.

The main cause of erosion on the coastline is a type of wave called a destructive wave. Destructive waves are powerful waves with high energy levels and strong backwash. They have a more erosive impact on coastlines by removing sediment and eroding the land more rapidly.

Destructive waves mainly erode the landscape through hydraulic action. This is when the waves smash against the cliff with great power. Air is trapped within cracks in the rock, which breaks the rock apart.

Waves can also help to strengthen coastal features through constructive waves. These weaker waves have lower energy levels and a stronger swash which tends to deposit sediment, building up coastal features rather than eroding them.

Fetch

The distance over which waves travel across open water, known as fetch, also affects erosion rates. Longer fetches allow waves to gather more energy, leading to increased erosion.

Local Climate

Storms

Intense storms, including hurricanes and cyclones, dramatically accelerate coastal erosion rates. These storms generate powerful destructive waves and storm surges, causing significant land loss and damage.

Rainfall and Runoff

Excessive rainfall can increase runoff, carrying sediment from inland areas into coastal environments. The sediment has an abrasive effect on the coastal landscape, and a large amount can contribute to higher erosion rates.

Sea Level Rise

Rising sea levels increase erosion rates by exposing more land to wave action. Greater numbers of destructive waves, and an amplification of their effectiveness can dramatically affect the coastline. Valuable coastal habitats and infrastructure can be destroyed, and houses positioned on the coastline are equally at risk.

Human Activity

Coastal Development

The construction of buildings, roads and other structures along coastlines can disrupt natural sediment flow, and alter wave patterns. This can lead to localised erosion or sediment accumulation, affecting nearby areas.

Deforestation

Clearing coastal vegetation removes natural barriers that stabilise the sand and soil. This makes the coastline more vulnerable to erosion and sediment accumulation.

Sand Mining

The extraction of sand from beaches or dunes for construction disrupts natural sediment cycles and natural processes of migration for animals. The removal of sand leads to less natural protection against the causes of erosion in those areas.

Climate Change

Human-induced climate change, through greenhouse gas emissions, contributes to rising sea levels and altered weather patterns. These changes increase the rates of erosion along vulnerable coastlines, which visibly alters landscapes across the world.

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