I. Introduction
Coastal erosion has been a natural process shaping our shorelines for millions of years. However, with climate change and human activities, the impact of coastal erosion has become more severe. In this article, we will explore one primary way waves erode coastlines and how it is affecting our planet and communities.
II. Types of Coastal Erosion
Coastal erosion can take many forms, but three types are most common:
A. Abrasion
Abrasion is the grinding action of waves with rocks and other materials on the shore. As waves break on the shore, they pick up and move particles, such as sand and shingle. These particles, in turn, scrape along the rocks and other materials and gradually wear them down.
Abrasion can enlarge the rock’s surface area, while the rocks break off into smaller rocks and contribute to the sediment. For instance, The Giant’s Causeway in Northern Ireland is a spectacular rock formation that formed from abrasive wave action.
B. Hydraulic Action
Hydraulic action describes the erosion caused by the sheer force of water hitting the shore. When waves surge up onto the shore, they can compress pockets of air within the rocks and materials on the shore, creating stress. This stress weakens the rock and can cause pieces to break off.
Hydraulic action can hollow out cliffs and create overhangs, such as Beachy Head, Sussex, and many other places around the world.
C. Attrition
Attrition is the result of the gradual breaking down of materials on the shore by the incessant action of waves. As waves move material around on the shore, the particles knock against each other and gradually wear each other down.
Over time, this action may reduce the size of materials, creating finer grains of sand as small rocky shores become sandy shorelines. In the UK, Chesil Beach in Dorset stretches for almost 30km and was formed through attrition.
III. The Power of the Waves
Wave erosion does not just depend on the type of erosion but also on the wave’s power. Wave power depends on the wave’s height, frequency, and wavelength. When waves break against the shore, they have the potential to create significant erosion.
For instance, in Hawaii, the pounding waves of the Pacific Ocean created significant erosion on the south shore of Maui and destroyed homes and infrastructure. High energy waves can move sediment offshore and impact the ecological function of ecosystems.
IV. The Role of Geology
Another factor affecting wave erosion is the geology of the coast. When waves meet different rocks, they affect each type of rock differently.
A. Hard and Soft Rock
Coasts are composed of either hard or soft rocks depending on their mineral structure and strength. The hard rock typically resists erosion, creating a headland or cliffs sticking out from the coast. Soft rock, on the other hand, is less durable and is prone to faster erosion, leaving bays and protected areas along the coast.
For example, The White Cliffs of Dover are made of chalk that erodes slower than the soft rock below, forming a headland sticking out from the coast.
V. Human Factors in Coastal Erosion
Human activities like building houses, dams, and ports and dredging activities can significantly increase ocean wave action and accelerate coastal erosion.
A. Building and Dams
The construction of coastal structures like seawalls and marinas can change the natural flow of the waves and even cause them to bounce back and erode other coastlines. Human constructions prevent sediment from reaching other areas, leading to uneven distributions of materials and shifts in the natural balance.
For example, The Venice Lagoon is an artificial channel that was built centuries ago giving rise to sediment blocking the lagoon’s channel while being threatened by coastal erosion today.
B. Dredging Activities
Dredging activities can also alter the natural flow of sediment along coasts. Dredging can create unnatural channels and basins near shorelines, affecting currents and sediment distribution. These channels act as amplifiers to the wave’s energy and can substantially speed up erosion.
The Wadden Sea in Europe shows the effects of human disruption. The construction of a dam was meant to protect the Dutch coastline, but it altered the natural water flow, causing severe erosion along the Wadden Sea coast.
VI. The Impact of Climate Change
The impact of climate change is exacerbating existing erosion patterns due to sea-level rise and increasingly powerful storms and wave events.
A. Sea-level Rise
Global warming is causing sea levels to rise. This rise will cause more frequent and severe coastal flooding, leading to stronger wave actions and erosion. Coastal communities will become more vulnerable to erosion threats, risking their safety and homes.
B. Changing Weather Patterns
The frequency and intensities of weather events are altering as climate change is progressing, including waves. Storm surge and wind waves are becoming more frequent, powerful and their duration is longer. These changes will impact coastlines differently, where some will experience faster erosion rates than others and put particular communities at risk.
C. Mitigating Strategies
Several coastal cities around the world are already experiencing erosion with increasing regularity. Strategies such as Managed Realignment or living with water, which encourage the natural movement of coastlines and ecosystems, are a promising approach to maintaining coastal environments. Other methods include using hard engineering techniques such as seawalls or adaptive barrier islands, but balanced measures need to look good for nature, provide natural ecosystems and function, and be sustainable over time.
VII. Conclusion
Wave erosion is a powerful process that shapes our coastlines and, ultimately, our world. Learning about wave erosion is paramount for coastal residents and governments to mitigate and adapt to the impacts, such as loss of infrastructure, homes and ecosystems. This article has explored some causes of wave erosion, including the impact of human activities and the impacts of climate change.
Our collective actions can slow down the erosion and the consequent damages, and initiating mitigation strategies across the globe that maintain natural ecosystems is critical in creating a sustainable approach.