Coastal Erosion

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Coastal erosion

Coastal erosion is one of the coastal processes that allows for the removal of sediment such as different rocks, particles, and limestones, along the coastline. The eroded sediments then experience transportation by waves to other coastal areas. This coastal process serves as a challenge to communities, since the eroded materials are hard to replace.

In the past, coastal erosion helped maintain balance in coastal areas. However, with the increased onset of storms, typhoons, and tsunamis, increased erosion became detrimental to these coastal areas. In general, the more we experience coastal erosion, the more our coastal zones change and impact biodiversity here..

Coastal erosion constantly shapes the terrain of the earth and the availability of land for humans and other organisms as the ocean continues to remove land and deposit sediments in our oceans. With this in mind, let’s look at what coastal erosion is, and the different factors that contribute to this.

What is Coastal Erosion?

In science, erosion refers to the surface processes that removes rocks, soil, and other sediments from a location, and subsequently transporting these to another location. With this in mind, coastal erosion, thus, is the coastal process that involves wearing away and breaking up rock and sediments along the coast. This process refers to the displacement of land, or the long-term removal of sediments along the coastline. These events can either be a rapid-onset hazard, meaning it occurs very quickly, or a slow-onset hazard, meaning it occurs over many years.

Two key factors play a role in coastal erosion, namely natural factors and human-induced activities. Understanding how these factors work helps society come up with control methods that help mitigate the damaging effects of coastal erosion, since this can become a hazard to communities when people are not able to adapt to its damaging effects

Different factors can cause coastal erosion, but normally, this coastal process happens because of the action of waves, currents, tides, wind-driven water, and other meteorological processes. Coastal erosion can also occur due to subsidence and mass wasting processes on weak slopes. Extreme weather events can also increase the intensity of coastal erosion, in the form of strong winds, tsunamis, and storm surges. For example, heavy rainfall can increase saturation of soils, thus reducing their strength, and increasing the chances of slope failures such as landslides.

Many times, human-induced activities can have an influence on coastal erosion. For example, construction events that occur in coastlines can change coastal sediment transport pathways and can even increase the frequency of coastal erosion. The rapid onset of climate change can also increase the frequency and rates of coastal erosion, which can have many damaging effects on ecosystems and biodiversity in these coastlines. .

The transport of materials plays a key role in the erosion process. Take note that during erosion, no replacement of sediments takes place, since the process only refers to the removal and transport of these sediments to another location. The constant occurrence of coastal erosion events and the removal of sediments results in the development of different geomorphic landforms. Some of these landforms include, but are not limited to, tunnels, bridges, caves, arches, and pillars.

Types of Coastal Erosion 

Waves are the primary drivers or coastal erosion. As materials are broken down by waves, sediments fall into the ocean and are transported to different areas. In particular, destructive waves, or waves that have stronger backwashes than swashes, are the most common types of waves that cause erosion. These waves occur during stormy conditions, and are characterized by big, strong waves that have high energy. In contrast, constructive waves occur during calmer weathers, have low energy, and tend to cause deposition, rather than erosion. Because of their characteristics, destructives waves can erode the coastlines in a number of ways.

Hydraulic Action

Hydraulic action is the first type of coastal erosion that occurs when destructive waves that strike a cliff face compress air found in the crevices of these cliffs. The pressure exerted by the compressed air thus erodes the surrounding rocks, causing sediments and materials to break off.

Abrasion

Abrasion occurs when bits of rock and sand hit the surrounding landscapes, performing a scratching action that causes friction and scratching which results in the chipping and breaking off of pieces of rock from cliff faces.

Attrition

Attrition, on the other hand, is another type of coastal erosion that happens when waves grind rocks and pebbles into each other on the shores, causing these sediments and materials to weather and become smoother, smaller, and rounder.

Solutions

Solutions occur when acids contained in the sea water help dissolve specific sediments that react with these acids. The dissolved sediments are thus eroded and transported to new locations by the action of waves.

Corrosion

Corrosion is a similar process where the sea’s acid components corrode rocks on a cliff face. Examples of sediments that are prone to corrosion are limestones and their derivatives, since these have a relatively high pH, making them susceptible to the corrosive properties of the sea’s acid components.

Frequently Asked Questions 

What is Coastal Erosion? 

Coastal erosion refers to the removal of sediments and rocks from the coastline primarily due to the action of waves, currents, tides, and other meteorological factors. Some of the main factors that induce coastal erosion are natural factors and human-induced activities.

How do waves affect Coastal Erosion?  

Waves break down different pieces of sediments and rocks along the coastline that eventually drop into the ocean floor and are transported to different locations. Waves, in particular, have the capacity of removing sediments and transporting them to significantly far locations. The continued occurrence of waves in beaches, most especially during aggressive weathers changes the landscape of beaches.

What are the drivers of coastal erosion?  

Waves, tides, and wind remain the main drivers of coastal erosion because of the energy they possess. The more we experience powerful storms and changes in weather patterns, the higher the frequency of coastal erosion along our shorelines. Additionally, human-induced activities can also affect the frequency and pathways of coastal erosion.

Is coastal erosion a long-term event?  

Coastal erosion can either have a rapid onset which can last for days to weeks, or a slow onset which could occur for years or even decades. Short-term coastal erosion usually happens during meteorological events such as storm surges or typhoons. Long-term coastal erosion is usually characterized by waves that crash upon the coastline, thus shaping their landscape.

References  

  1. Fourie Jean-Pierre et al., 2015, The influence of wave action on coastal erosion along Monwabisi Beach, Cape Town, South African Journal of Geomathics, Vol. 4 (2), pp. 1 – 14
  2. https://www.ga.gov.au/scientific-topics/community-safety/coastalerosion
  3. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/coastal-erosion 
  4. https://www.gsi.ie/en-ie/geoscience-topics/natural-hazards/Pages/Coastal-Erosion.aspx 
  5. https://www.gsi.ie/en-ie/geoscience-topics/natural-hazards/Pages/Coastal-Erosion.aspx