Constructive and Destructive Waves

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Constructive and destructive waves will determine whether a beach is built up or eroded

Waves are a significant factor in coastal processes as they allow for the build-up or breakdown of beaches. The intensity of a wave is dependent on the amount of energy it carries. Increased energy in waves allows for significantly higher waves and for more frequent coastal erosion events.

Wave intensity and power are highly dependent on wind and tidal conditions. Wind strength significantly impacts how waves operate within coastal processes. In particular, the friction between the ocean floor and the wind creates observable swells. The circular movements within waves require energy to ensure their continuous rotation, for this energy allows waves to progress and move forward until they reach the shoreline.

The different characteristics of constructive and destructive waves help us understand how they are able to collect or deposit sediment in the form of sand and rock particles. Both of these play an important role in keeping the natural balance of our oceans. However, with the increased onset of hydrometeorological hazards such as storms, typhoons, and tsunamis, the wave function is significantly altered. Humans and biodiversity experience the threat of losing their habitats because of these occurrences, and increased erosion can become dangerous to coastlines.

There are two different types of waves – constructive and destructive. These waves form part of the coastal processes and are important in the development of coastlines and beach areas. Before we look at the difference between these two waves, let us first understand the different terms that are used when discussing waves.

Read more about Waves: Formation, Types, Summary

What are Swash and Backwash?

We first need to understand the push and pull of waves, also referred to as swash and backwash activities. The energy of the swash and backwash help determine the type of wave that occurs.

Swash refers to when waves travel towards the beach, pushing sediment up the shoreline. This progressive activity allows the development of beaches and other landforms through a process known as coastal deposition.

Backwash on the other hand refers to how waves move back down the beach, and back into the ocean. During this process, sediment and other materials on the beach are carried away back into the sea. This process is an important concept in coastal erosion, as backwash returns material to the ocean. When waves get stronger, the more likely it is for destructive natural phenomena such as coastal erosion to occur.

What are Constructive Waves?

Constructive waves help build up and develop coastal areas. These waves are characterised by a strong swash and a weak backwash, and the dominating presence of the swash is what brings and deposits sediment onto these coastlines, thus forming depositional landforms such as spits, tombolos, and bars. These waves are characterised by low height in proportion to their length and have relatively low energy.

These waves usually predominate in calm weather conditions when less energy is transferred to the water. Thus, these waves are more common in summer than in winter. Additionally, these waves typically occur in sheltered bays and spits, where they help build up and develop depositional landforms along the coastlines.

Constructive waves have long wavelengths and low frequencies since only about eight to ten waves occur per minute. This low frequency is what helps prevent intensive erosion from taking place since it hinders the removal of sediment from the coastline. Because constructive waves lack a breaker component, these waves can simply move up beaches and deposit material at the beachfront. The weak backwash and suppressed wave gradients prevent any sediment from being carried back into the sea after deposition.

What are Destructive Waves?

Destructive waves, in contrast to its counterpart, help erode and remove sediment such as sand and rock particles from coastlines. These waves are characterised by a strong backwash and a weak swash. The dominating backwash helps remove material from the coastline, taking it back into the sea. These waves are characterised by their vast height in proportion to their length.

These waves are created in aggressive weather conditions such as storms and typhoons where high energy is transferred to these waves. Destructive waves are thus more common in winter than in summer and usually occur in exposed bays. Because of changing weather patterns and climate change, destructive waves have become more apparent on coastlines, which poses a threat to the landscape and biodiversity that is present there.

Destructive waves have short wavelengths and high frequencies since around 10 to 14 waves can occur every minute. Because of the presence of a breaker, these waves will eventually plunge towards beaches after reaching a certain height. Because of this, destructive waves do not usually travel far up the shoreline. Furthermore, the high frequency allows the erosion of materials and sediment to return to the ocean since there is usually increased water to transport these materials out to sea.

The outcome, therefore, is a destructive phenomenon that erodes beaches and sometimes damages coastal landscapes. Less sediment, sand and geological material becomes available to build up the beach due to the increased erosion brought about by destructive waves.

Frequently Asked Questions?

How do waves affect coastal landscapes?   

Waves play an important role in the coastal processes that help shape coastal landscapes. Depending on the weather and wave type, waves can be involved in processes that either build up or destroy shorelines.

What drives constructive and destructive waves?  

Energy is the main factor that drives both constructive and destructive wave types. Higher energy found in waves results in the occurrence of destructive waves. In contrast, lower energy found in waves results in the occurrence of constructive waves.

What is the role of frequency in waves?

Frequency helps determine the coastal processes that occur on shorelines. Destructive waves generally contain a higher frequency, and with more waves that occur per minute, erosion is usually the end-product. Constructive waves, on the other hand, have lower frequencies, and this allows a more gentle approach that helps deposit materials.

What are the impacts of destructive waves?

Destructive waves cause significant coastal erosion in the coastal areas. For example, cliff landscapes continue to lose sediment through erosion due to the action of destructive waves. When erosion occurs, humans and animals alike are greatly affected by this event.

What are the impacts of constructive waves?

Constructive waves cause significant coastal deposition in coastal areas These waves help deposit sediment and sand materials. These constructive waves allow the formation of different depositional landforms along the coastline such as beaches, spits, bars, and sand dunes.

Are waves influenced by climate change?

Global warming and changing weather patterns greatly affect how waves function. For example, in the case of an earthquake, tsunamis can sometimes occur. These powerful waves become destructive and can easily destroy a shoreline because of the damaging effects of erosion. For these specific reasons, scientists continue to study the earth’s changing climate conditions to formulate plans and steps that will help mitigate the damaging effects of these waves.

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://senior.stpauls.br/geography/form-3/1-coasts/3-what-are-the-differences-between-constructive-and-destructive-waves
  3. http://www.geography-site.co.uk/pages/physical/coastal/waves.html 
  4. Sweeting M. M., Wave – Trough Experiments on Beach Profiles, 1943, The Geographic Journal, Vol. 101 (4), pp. 163 – 168.
  5. Yoshida J, etal., 2014, Framework for Proper Beach Nourishment as an adaption to Beach to beach erosion due to sea level rise, Special Issue No. 70. Proceedings of the International Coastal Symposium 2014, pp. 467 – 472

Cite/Link to This Article

  • "Constructive and Destructive Waves". Geography Revision. Accessed on March 29, 2024. https://geography-revision.co.uk/gcse/coastal-landscapes/constructive-and-destructive-waves/.

  • "Constructive and Destructive Waves". Geography Revision, https://geography-revision.co.uk/gcse/coastal-landscapes/constructive-and-destructive-waves/. Accessed 29 March, 2024.

  • Constructive and Destructive Waves. Geography Revision. Retrieved from https://geography-revision.co.uk/gcse/coastal-landscapes/constructive-and-destructive-waves/.