Coastal transportation is an important coastal process that involves the movement of materials along the coast by the action of waves and winds. With the constant movement of waves, different materials are picked up and are transported to other areas, and can travel thousands of kilometres. This coastal process helps maintain balance in marine environments as this continuously changes our ocean’s layout.
Various external factors greatly influence coastal transportation, such as weather patterns, climate, and other hydrometeorological events. For example, as weather patterns become more intense, materials and sediment can be transported farther distances. In general, aggressive weather events play an important role in the intensity of the ocean’s transportation activities.
Coastal landscapes continuously change because of these transportation events. For one, transportation can lead to the deposition and build-up of sediment along coastlines, thus forming different depositional landforms. In other instances, transportation usually follows the erosion and removal of materials along coastlines. For us to gain a better understanding of the other coastal processes, we must first look into what coastal transportation is.
What is Coastal Transportation?
Coastal transportation is the movement of different sediment and materials through the interaction between land and sea. Waves are the main drivers of coastal transportation; however, different hydrometeorological events such as storms and typhoons also impact this coastal process. As the wind blows and forms waves, the friction between the water and the sediments allows for the movement of these materials across the oceans. These natural interactions subsequently continue to change our coastal landscapes. However, coastal transportation works not only on its own, but in tandem with other coastal processes such as deposition, erosion, and weathering.
Coastal areas experience the interaction of different energies and forces that greatly influence how sediment is moved. Gravity and friction, in particular, are some of the main forces that drive transportation activities. Because of the large amount of force these exert, sediment and other particles are able to travel significant distances.
Competence and capacity are two important terms used to describe coastal processes and the sediment they carry. Competence refers to the biggest size of material that an agent can transport. On the other hand, capacity refers to the maximum load an agent can transport. Both concepts help us describe the type and amount of sediment that can be transported by this coastal process.
In coastal areas, the swash, or forward movement of waves, and the backwash, or the backward movement of waves significantly contribute to the transportation of sediment along coastlines. The longshore drift, in particular, is the process of moving sediment along the coastline through waves that hit the shore obliquely. This process combines the swash and backwash of waves that form a zig-zag movement across shores, which is mainly due to the direction of the prevailing wind.
The ocean consists of different layers where sediment is suspended or settled. On the seabed, there are significantly concentrated layers of sediment that are very sensitive to the movement of water. As waves begin to form, some sediment is suspended and carried away to other areas of the sea. Furthermore, the seabed’s thickness plays an important role in determining the impact of the movement of water.
A suspension layer normally occurs over an extensive area on top of the saltation level. This layer usually contains a high concentration of sediment molecules that stay here for a long time. This sediment normally only moves during a return current. Not all sediment, however, remains suspended, depending on its size and physical characteristics, some sediment floats above the water’s surface or simply settles down on the seabed. Depending on the energy exerted, different sediment is eventually picked up and transported.
As mentioned, coastal transportation is not an independent process. Usually, after transporting materials to coastlines, wave energy is lost and thus, some sediment is deposited and begins to build up in a process called coastal deposition. Furthermore, after coastal erosion events, the removed sediment is then transported to different locations. The different types of waves that carry the sediment also help determine how far up the coastlines they will travel.
Many types of coastal transport allow the coastal processes to occur, and many different physical changes happen to the sediment for the different types of coastal transport to occur. Aside from the longshore drift, let us look at the other types of coastal transportation.
Types of Coastal Transportation
As mentioned, coastal transportation happens because of the movement of material on the seabed. The various waves cause the creation of longshore drift, but a lot of elements help contribute to the transportation of this sediment during a longshore drift. The different elements and physical changes that form part of the longshore drift include the following:
Solution
Solution happens when minerals are dissolved in seawater and are carried in a solution. Usually, the load here is not visible, since the sediment becomes incorporated with the seawater. Salt, for example, is a material that dissolves in water, which gives rise to the ocean’s high salinity.
Saltation
Saltation is the process wherein materials bounce along the seabed. This usually consists of small pebbles and large sand grains that currents cannot keep afloat for long periods of time.
Suspension
Suspension occurs when sediment remains suspended in the water. This sediment is not so heavy that it settles on the ocean floor, and not too light that it remains afloat. Because this sediment remains suspended, it flows along with the waves, resulting in its transportation.
Traction
Traction occurs with heavy sediment that settles down on the ocean floor. Because of its weight, it usually just rolls along the bottom of the ocean floor. However, this type of coastal transportation is often slow given the size of the sediment that is transported.
Read more about Coastal Landscape Development
Frequently Asked Questions
Why do we need coastal transportation?
To allow for the build-up processes to continue, the ocean constantly needs to move material around. Some transportation events result in the break-down of the coastal areas, and removed material is transported to different areas. The movement of sediment, rocks, and materials plays a key role in our coastal processes.
What are the key elements in the coastal transportation process?
The key elements include the energy from waves, wind, and the sizes and physical characteristics of the sediment and different materials to be transported.
What types of material normally become transported by the sea?
The materials transported by the sea include large boulders or rocks, refined material for example clay or sand, small particles and pebbles. Depending on their size, these materials are transported through different means.
Where does the sea transport the material to?
Depending on the type of material transported and the availability of space in coastal areas, waves can either transport these materials to beach areas on the bottom of the ocean.
What happens to material collected by the waves?
Materials collected by the waves are transported and deposited in other spaces. These include the beach areas or other places on the seabed or layered spaces. The build-up and deposition of this sediment results in the formation of depositional landforms that shape our coastal areas.
References
- 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
- Sawczyński, Szymon & Kaczmarek, Leszek. (2014). Sediment transport in the coastal zone. Technical Sciences. 17. 165-180.
- Wigley, R. 2011. Geohazards in coastal areas. Council for Geoscience Report Number: 2011-0066
- https://pmel.noaa.gov/pmel-theme/oceans-and-coastal-processes-research