Does a coast just 'happen'? Do the landforms appear overnight? Of course not! Coastal processes are the different ways that sediment is moved around the coastal system. Some processes take sediment away from the coast, others add sediment to it, and the rest just move sediment around. Have you ever visited the coast? If you have, the chances are you will have seen evidence of some or all of these types of processes! Sitting on a sandy beach and watching waves crash against the rocks are just two examples of you seeing the result of coastal processes. How? What are the effects? Stay tuned to find out!
Coastal processes definition
First things first, it's time to do some defining. In geography, the coastal process definition is as follows:
A coastal process is a way in which sediment is moved around the coastal system. This can be through removing and/or breaking down sediment (erosion and weathering), moving it around (transportation) or adding sediment (deposition).
From this definition, it is clear that there isn't just one coastal process behind the shaping of coastal environments. In fact, there are four main types of coastal processes. Each of these four processes can happen in slightly different ways, giving us different types of coastal processes. Confused? Don't worry. Let's break it down.
Types of coastal processes
There are four main types of coastal processes: erosion, weathering, transportation and deposition. Erosion and weathering both break down the material, transportation moves it around, and deposition adds material to the landscape.
If you need help remembering, think of the processes like this...
- If something is eroded or weathered, it is worn out or broken down!
- If something is transported, it is moved about.
- If something is deposited, it is added or left somewhere else.
Coastal erosion processes
Coastal erosion is the breaking down and transporting away of material. This typically occurs because of interactions involving the sea itself. As we mentioned earlier, there are different types of coastal erosion. The main ones we are going to concern ourselves with are abrasion, hydraulic action, attrition and solution, all actions that take something away from the coast.
| Coastal erosion processes |
|---|
| Coastal process | Explanation |
| Abrasion | Coastal abrasion happens when a rock is carried along by the water and smashes into a cliff, causing a piece of that cliff to break off. Abrasion breaks down the material and then transports it away. |
| Hydraulic action | Hydraulic action is a type of coastal erosion done by the sea itself. Have you seen waves crashing against the rocks along the coast? These waves can be so powerful that they can cause the rock to break apart. The broken-down rock is then carried away by the waves. |
| Attrition | When it comes to coastal processes, attrition is the coastal process that involves the breaking down of rocks by other rocks. While you might confuse this with abrasion, the two are actually somewhat different. Attrition happens when pieces of broken rocks that are floating in the sea crash into other broken pieces of rock in the sea. Over time, those pieces erode, leaving smooth pebbles behind. |
| Solution | In coastal processes, solution is the process of a rock being dissolved by the sea and then transported away. While limestone and chalk are very susceptible to dissolving after coming into contact with seawater, not all rock types will be affected by seawater. |
Table 1
Coastal weathering processes
Coastal weathering is a type of coastal process that also involves the breaking down of rock. So, how is this any different from erosion? Where erosion involves the breaking down and transporting away of rock, weathering breaks down the rock in-situ (aka where it is found).
Erosion happens if a rock is broken down and transported away by the sea. Weathering happens if a rock is broken down and left where it is.
There are 3 types of coastal weathering: mechanical, chemical and biological. Essentially, this means that weathering can be done by physical factors (e.g. the climate), chemical factors (e.g. acid rain and seawater) and/or biological factors (e.g. animals burrowing into rocks). You can read all about these different subprocesses in our explanation on Weathering.
Fig. 1 - Animal burrows are a type of biological weathering
Did you know? While most people think of coastal processes happening in or near the sea, weathering often happens on land and above sea level. We call this subaerial weathering.
Coastal transportation processes
In the same way that you can be transported by your feet, bike, scooter, cars, bus, boat, plane and countless other forms of transport, sediment can be transported by a range of coastal transportation processes. In the same way that money or convenience might help you choose your mode of transport, the type of coastal transportation happening is often determined by the size of the sediment or material being transported. Will it be solution? Will it be suspension? Will it be saltation or traction? What do all of these words mean? Let's take a look.
| Coastal transportation processes |
|---|
| Transportation process | Explanation |
| Solution | As mentioned above, solution happens when a rock dissolves after coming into contact with seawater and is then transported away within the water.Imagine putting a sugar cube in your cup of tea. The sugar cube is transported around the cup via the tea. The same thing happens with material (e.g. limestone) and seawater. Remember: A big part of coastal erosion is transporting the material away from where it was broken down. This means that a lot of coastal transportation processes are also involved in coastal erosion! |
| Suspension | Suspension transports material by carrying it along with the water's flow. For this to work, the material often has to be quite light in weight. Silt is a great example of something often transported via suspension.Silt is a fine type of material (particles that are bigger than clay but smaller than sand) that is often transported through suspension. |
| Saltation | In simple terms, saltation describes transportation that happens when material is bounced along the seabed. The type of material is often larger in size and weight than those transported by suspension. This is because it is too heavy to be transported, and the waves do not have enough energy to move the material by carrying it. Some examples of materials that are transported via saltation are large sand particles and small bits of shingle. |
| Traction | Traction is a transportation type usually saved for the largest and heaviest materials in the water. These materials are rolled along the floor. |
Table 2
Coastal deposition processes
So we know how material is broken down and how it is transported around coasts, but how is it added to certain areas? The answer is, of course, coastal deposition. Almost acting in complete opposite to coastal erosion, coastal deposition happens when sediment being transported around is dropped. Over time, this can cause material or sediment to build up. This is how we get our beautiful sandy beaches. So, how does this happen?
- When waves lose their energy, they drop the material they were carrying. This can happen as waves slow down or when the water gets more shallow, or even when there is not much wind keeping the wave's energy up.
Our explanation of Waves describes the different types of waves we encounter on our seas. Constructive waves are lower-energy waves behind coastal deposition. By contrast, destructive waves are higher-energy waves that drive certain processes of coastal erosion. Be sure to check out our explanation for more detail on these waves and how they are different from each other!
Effects of coastal processes
Ultimately, the major effects of coastal processes are quite obvious. Either they break down the material, transport it away or deposit it somewhere. This can result in the coastline retreating or being built up with extra sand and other material. As well as influencing the coastline as a whole, these processes can result in the most amazing Coastal Landforms. In fact, the landforms you see along the coast can tell you whether an area of the coastline is dominated by erosion and weathering or deposition.
Fig. 2 - Arches are created by coastal erosion; beaches are created by coastal deposition
Beyond shaping the environment, erosion and weathering can have devastating effects on people. Homes and entire villages can be destroyed, causing people to lose their jobs and livelihoods. Deposition can make gorgeous sandy beaches that entice tourists, which can boost the local economy and create lots of jobs for locals.
Transportation can have a mix of effects. It can starve areas of sediment while providing it to others. Therefore, you should consider the effects of transportation on both the area from which it is transporting material and the area it is transporting it.
Coastal processes examples
Here are a few quick-fire examples of coastal processes to use to boost your exam answers:
Coastal erosion is happening at the fastest rate in Europe along the Holderness coast in NE England. Erosion, alongside weathering, is causing the coastline to retreat at around 2m every year.
Fig. 3 - The Holderness coast is the fastest-eroding coastline in Europe
Coastal deposition is found on the other side of the UK (NW) at Formby beach. This beach is known for being gloriously sandy and even having lots of sand dunes. This is an example of a classic landform formed by lots of coastal deposition.
Coastal Processes - Key takeaways
- The main types of coastal processes are erosion, weathering, transportation and deposition.
- Coastal processes can influence the shape of the coastline, as well as the people living on or near the coast.
- Coastal processes are evident all along the coast, including the UK, where erosion dominates in some places (e.g. Holderness), while deposition dominates in others (e.g. Formby).
References
- Fig. 1: biological weathering (https://commons.wikimedia.org/wiki/File:Uca_tangeri_-_burrow_entrance_-_Cabanas_de_Tavira,_Portugal.jpg) by PePeEfe (https://commons.wikimedia.org/wiki/User:PePeEfe) Licensed by CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/deed.en)
- Fig. 2: Arch created by coastal erosion (https://commons.wikimedia.org/wiki/File:Durdle_Door_Overview.jpg) by Saffron Blaze (https://commons.wikimedia.org/wiki/User:Saffron_Blaze) Licensed by CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/deed.en)
- Fig. 3: Holderness coast, the fastest eroding coastline in Europe (https://commons.wikimedia.org/wiki/File:Looking_north_along_the_Holderness_Coast_-_geograph.org.uk_-_2745952.jpg) by Ian S (https://www.geograph.org.uk/profile/48731) Licensed by CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0/deed.en)
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