Constructive and Destructive Waves

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Destructive Waves

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

Wave intensity and power is 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 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 sediments such as 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 way waves 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.

What are Swash and Backwash?

Before we move into the meanings of constructive and destructive waves, 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 peach, pushing sediments up the shoreline. This progressive activity allows for 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 oceans. During this process, sediments and other materials on the beach are carried away back into the sea. This process is an important concept in coastal erosion, as backwash aims to return 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 and develop coastal areas. These waves are characterized by a strong swash and a weak backwash, and the dominating presence of the swash is what brings and deposits sediments on to these coastlines, thus forming depositional landforms such as spits, tombolos, and bars. These waves are characterized by low heights in proportion to their lengths, and have relatively low energies.

These waves usually predominante in calm weather conditions when less energy is transferred to the water. Thus, these waves are more common in summer than in the 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 sediments from the coastlines. 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 sediments from being carried back into the sea after deposition.

What are Destructive Waves?

Destructive waves, in contrast to its counterpart, help erode and remove sediments such as sand and rock particles from the coastlines. These waves are characterized by a strong backwash and a weak swash. The dominating backwash is what helps remove material from the coastline, bringing them back into the sea. These waves are characterized by their tall features in proportion to their lengths.

These waves are created in aggressive weather conditions such as storms and typhoons where high energy is transferred into 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 in coastlines, which poses a threat to the landscape and biodiversity that is present here.

Destructive waves have short wavelengths and high frequencies since around ten to fourteen 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 shorelines. Furthermore, the high frequency allows for the erosion of materials and sediments back into the ocean since there is usually more water to transport these materials out to sea.

The outcome, therefore, is a destructive phenomenon that erodes beaches and can sometimes damage 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 the occurrences of 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 in 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 for a more gentle approach that helps deposit materials.

What are the impacts of destructive waves?  

Destructive waves cause significant coastal erosion in the coastal zone 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 the coastal zones These waves help deposit sediment and sand materials. These constructive waves allow for 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 easily destroy a shoreline because of the damaging effects of erosion. For these specific reasons, scientists continue to study the earth’s changing climate condition in order 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