Coastal Processes

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Coastal Processes

Coastal zones are dynamic areas of the earth that experience the influence of both marine and atmospheric activities, also known as coastal processes. These processes involve different events that build-up, breakdown, and transport materials in these coastal zones. Waves, wind, and tides for example impact these coastal areas and change their landscapes through continuous processes that happen all year round. Coastal processes are important as these help change landscapes and maintain natural balance in our ecosystems.

Coastal processes usually impact coastal zones within at least 5 kilometers of the coast. Different areas are impacted by coastal processes. Examples of these include dunes, beaches, barrier islands, and deltas. These processes help us understand their impact on different habitats, organisms, ecological systems, and animals that can be found in these coastal zones. To better understand how these processes affect our environment, let us look at the different examples of coastal processes that we experience.

The following sections will focus on key coastal processes namely waves, constructive and destructive waves, coastal erosion, coastal transport, and coastal deposition. So, what are these coastal processes we continue to refer to?

What are coastal processes?

As mentioned, coastal processes include all of the processes that work on our coastal zones to change their landscapes. To identify these coastal processes, scientists and researchers typically look for physical indicators of transport and erosion through the different sediments and materials we find in these coastal zones.

Waves, wind, and tides are some of the driving forces that shape our coastal zones. These processes involve significant use of energy for coastal processes to occur. Some of the main impacts that influence beach and marine areas involve deposition, erosion, and transportation.

Transportation happens when tides and waves transfer pieces of material to different areas. Deposition occurs when tides and waves lose their energy and lose the ability to transport varied materials, thus depositing these materials. Erosion, on the other hand, refers to the removal of sediments and materials from these coastal zones. As mentioned, waves and wind play a significant role in maintaining these coastal processes

Waves 

Waves are one of the main driving factors of coastal processes. Waves carry the energy of the oceans that allows for the transportation of different materials to different areas. Without waves, the natural transportation of sediments may not happen, and thus, the formation of different landforms will not occur. In reality, waves provide more than half the energy required for coastal processes to occur.

Waves occur on the surface of bodies of water as swells. These features are created through pressure and friction from wind forces that blow over the surface of the sea. The energy in waves are some of the most significant forces involved in coastal processes. These waves are key factors in the development of our marine environments and the subsequent breakdown thereof.

Waves are affected by a variety of factors. Wind, in particular, greatly affects how strong a wave is and how far a wave can travel. The different forces that work on waves such as gravity and friction significantly affect the strength and rate of transportation of waves. Understanding how these waves work helps us understand the mechanisms involved in coastal processes.

Aside from wind, other hydrometeorological events increase the intensity of waves. Such events include storms, typhoons, and storm surges. With the onset of climate change and changing weather patterns, waves have become increasingly more intense and aggressive, which pose a problem for communities along coastlines.

Waves can be classified into two types: Constructive and Destructive waves.

Destructive and Constructive Waves

Constructive waves build up beaches as they deposit sediments and other materials along coasts. Their low energies and long wavelengths help develop depositional landforms during calm weathers. In contrast, destructive waves are aggressive waves that break down and erode coasts. Their strong backwashes and high energies help remove material along coastlines during aggressive weathers. Destructive waves have much greater height than constructive waves

Both types of waves are significant in the different coastal processes as they help transport materials to different areas, causing varying in our marine environments.

Tides happen because of gravitational attractions by the moon or the sun, and they play a significant role in managing constructive and destructive waves. Additionally, tides help determine if a coastal area will experience high tide or low tide.

Aside from these constructive and destructive waves, different waves exist, and they, too, play a key role during coastal processes. These waves include the following: 

Open Ocean Wave

These waves come around and allow for particles to rise and move with the wave until the peak relaxes. As these waves pass, water molecules rise up and move forward in the direction of wave motion. This results in water molecules that move through orbital paths as waves pass

Waves at the Shoreline

These happen when a wave reaches the shore and slows down. The waves come closer to each other and also grow taller. The orbital paths of water molecules become increasingly elliptical, most especially at the base of these waves. Breakers eventually develop that result in the collapse of the wave as it reaches its peak height.

Coastal Sedimentation

When waves dominate the shorelines, fine sediments remain suspended and are carried away, while the larger, coarser sediments are left behind. The fine sediments that are carried away are eventually transported by waves to different locations.

Coastal Erosion

Coastal erosion refers to the coastal process that involves the removal of sediments and materials along coastlines. These eroded materials are eventually transported by the action of waves to new locations. In particular, destructive waves are the main cause of coastal erosion as they break down landforms along coastlines.

Tides and waves can erode coastlines in a number of ways. These include:

  • Solutions: acid in seawater corrodes and dissolves sediments on rocks and surfaces along the coastline
  • Abrasion: the action of waves causes pieces of sand or rock to hit the surrounding landscapes, causing a scratching motion.
  • Attrition: the action of waves causes small pebbles to grind with each other, causing them to become smaller, smoother, and rounder
  • Hydraulic action: when waves break and hit surfaces, compressed air found in the crevices of these landscapes expands and exerts pressure on the surrounding rock

Coastal Transportation

The build-up and break down of coastal zones only happen with the help of transport activities. Waves are the key factors that drive coastal transportation. The following are events and actions that result in coastal transportation.

  • Saltation: sediments that cannot be carried by the currents are transported by bouncing on the ocean floor. This usually occurs for small pebbles and large sand grains that are too heavy to be carried by currents
  • Suspension: sediments here remain suspended and are transported by the flow of currents. Sediments here are not too heavy, and thus they can be carried along by the currents.
  • Traction: heavy sediments roll along the seabed. Sediments here are usually heavy, and cannot be carried by currents, thus they settle at the bottom of the ocean and can only be moved by means of rolling.
  • Solution: minerals in sediments may get dissolved in the ocean water and become part of a solution. These are usually not visible given that they have dissolved and have incorporated into the sea water.

Coastal Deposition

Coastal deposition is the coastal process that involves the settling of sediments and materials, causing the build-up and development of different coastal landscapes. In contrast to coastal erosion, these are usually caused by constructive waves that help bring and deposit sediments and materials along coastlines.

When waves fail to overcome the forces of gravity, sediments are usually dropped off and begin to settle in coastlines. Because of the low energy in constructive waves, gravity usually dominates, and causes the build-up of different sediments along coastlines. Other factors can affect the rate of deposition such as climate change, weather patterns, and rate of transportation.

Because coastal deposition involves the build-up of materials, different depositional landforms may develop along coastlines. Examples of these features include beaches, spits, bars, tombolos, and lagoons.

Frequently Asked Questions

What are Coastal Processes? 

Coastal processes allow for the build-up, transportation, and breakdown of sediments in coastal areas. These processes ensure that constant change is being made through the use of energy found in waves, wind, and tides.

What drives the Coastal Processes? 

The key drivers in coastal processes involve wind, tides, and waves that carry large amounts of energy. These play a significant role in the transport of the different sediments and materials to different areas.   

What do we mean by the transportation of sediment?  

Transportation of sediment happens when the waves, for example, pick up the particles and transport them to different areas. This happens when waves have enough energy to pick-up and carry these sediments. 

What is Coastal Erosion?  

Coastal erosion happens when waves, wind, or tides breakdown pieces of rock. For example, the constant crashing of the waves against a cliff causes the removal of materials, returning them back to the sea. These materials are eventually transported to different locations by the action of waves.

What role do Climate Change and Weather Patterns play in coastal processes?  

Climate change and changing weather patterns can increase the onset of different natural hazards such as storms and typhoons. These events increase the intensity of waves, and can cause damage to our coastlines in the form destructive waves that result in excessive erosion. If not addressed, climate change can pose a serious threat to the biodiversity and communities that exist near these coastlines

References  

  1. Frost Gregory, 2011, Review of Coastal Processes and Evaluation of the Impact of the Constructed Groynes along Lady Robinsons Beach, Botany Bay, New South Wales, Australia, University of Wollongong, pp. 1 – 109.
  2. http://thebritishgeographer.weebly.com/coastal-processes.html
  3. http://www.columbia.edu/~vjd1/coastal_basic.htm 
  4. Healy T.R. (2005) Coastal Wind Effects. In: Schwartz M.L. (eds) Encyclopedia of Coastal Science. Encyclopedia of Earth Science Series. Springer, Dordrecht
  5. Dingler J.R. (2005) Beach Processes. In: Schwartz M.L. (eds) Encyclopedia of Coastal Science. Encyclopedia of Earth Science Series. Springer, Dordrecht