How do waves shape the coast through erosion, transport and deposition?
Constructive and destructive waves, the processes of marine erosion, transportation by longshore drift, and deposition (AO1).
A focused CCEA GCSE Geography guide to coastal processes. Covers constructive and destructive waves, the four processes of marine erosion, transportation by longshore drift, and why deposition occurs, as the foundation for coastal landforms.
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What this dot point is asking
CCEA wants you to explain how waves shape the coast, the difference between constructive and destructive waves, the four processes of marine erosion, how sediment is moved along the coast by longshore drift, and why deposition happens. These processes are the foundation of the whole Coastal Environments theme: every coastal landform is produced by them, so learning them well makes the landforms much easier.
How waves form and the role of fetch
As a wave reaches shallow water near the shore it breaks. The water that rushes up the beach is the swash; the water that drains back down is the backwash. Whether the swash or backwash is stronger decides whether a wave builds or erodes the beach.
Constructive and destructive waves
The same coast can have both at different times: gentle weather brings constructive waves that build the beach, while storms bring destructive waves that strip it.
The four processes of marine erosion
The sea erodes the coast by the same four processes as a river.
- Hydraulic action. The force of waves crashing against the cliff compresses air in cracks, which then expands and breaks the rock apart.
- Abrasion (corrasion). Waves throw sand and pebbles against the cliff, wearing it away like sandpaper. This is a major process at the cliff foot.
- Attrition. Rocks and pebbles carried by the waves knock together and break into smaller, rounder, smoother pieces.
- Solution (corrosion). Acids in the seawater dissolve soluble rock such as limestone and chalk.
Transportation by longshore drift
Longshore drift is the key transport process. It explains how beaches are fed with sediment and how depositional features such as spits are built further along the coast.
Worked example: explaining wave action
Common mistakes
Examples in context
Example 1. Why a sheltered bay has a wide beach. In a sheltered bay, waves arrive with less energy and tend to be constructive, so the strong swash deposits sand and the beach grows wide. On an exposed headland nearby, destructive storm waves dominate and erode the rock. This contrast between deposition in bays and erosion on headlands is the basis of the next dot point on coastal landforms, and CCEA rewards students who connect the wave type to the landscape.
Example 2. Reading the prevailing wind from a spit. Because longshore drift moves sediment in the direction of the prevailing wind, the direction a spit points along the coast tells you the direction of drift, and therefore the prevailing wind direction. Being able to read this from a map or photo is a higher-order skill that links the transport process to a real landform and to ordnance survey map work.
Try this
Q1. What three factors control the size of a wave? [3 marks]
- Cue. Wind strength, how long the wind blows, and the fetch (distance of open water).
Q2. Which type of wave builds up a beach? [1 mark]
- Cue. A constructive wave, with a strong swash and weak backwash.
Q3. In which direction does longshore drift move sediment? [1 mark]
- Cue. Along the coast, in the direction of the prevailing wind.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA Unit 1 (style)4 marksDescribe the differences between constructive and destructive waves.Show worked answer →
Four marks for two clear differences, each contrasting the two wave types.
Energy and frequency: constructive waves have low energy and are less frequent (around 6 to 8 per minute); destructive waves have high energy and are frequent (around 10 to 14 per minute).
Swash and backwash: constructive waves have a strong swash and weak backwash, so they build up the beach; destructive waves have a weak swash and strong backwash, so they drag material away and erode the beach.
Markers reward differences that contrast the two types directly, especially the swash and backwash and their effect on the beach.
CCEA Unit 1 (style)6 marksExplain the process of longshore drift.Show worked answer →
Six marks for a sequenced explanation, ideally with reference to a diagram.
Waves approach the beach at an angle, because of the prevailing wind direction.
The swash carries sediment up the beach at that same angle.
Gravity pulls the backwash straight back down the beach at a right angle to the shore.
This zig-zag movement transports sediment along the coast in the direction of the prevailing wind.
Over time large amounts of sand and shingle are moved along the shore, which can build features such as spits.
Markers reward the angled swash, the right-angle backwash, the zig-zag path, and the link to the prevailing wind direction.
Related dot points
- The formation of headlands and bays, caves, arches, stacks and stumps by erosion, and beaches and spits by deposition (AO1, AO2).
A focused CCEA GCSE Geography guide to coastal landforms. Covers how headlands, bays, caves, arches, stacks and stumps form by erosion, and how beaches and spits form by deposition, linked to the processes that create them.
- The causes and effects of coastal flooding, the threat of rising sea levels, and the conflicting ways people use and value the coast (AO1, AO2).
A focused CCEA GCSE Geography guide to coastal flooding and human pressures on the coast. Covers the physical causes of coastal flooding including storm surges and rising sea levels, the social, economic and environmental effects, and the competing demands people place on coastlines.
- Hard and soft engineering strategies for managing the coast, their costs and benefits, and how to evaluate the most sustainable approach (AO2, AO3).
A focused CCEA GCSE Geography guide to coastal management. Covers hard engineering such as sea walls, groynes and rock armour, soft engineering such as beach nourishment, dune regeneration and managed retreat, and how to evaluate the most sustainable approach.
- A case study of coastal erosion and management on a named coastline, its causes, the strategies used, and their effects (AO1, AO2).
A focused CCEA GCSE Geography case study of coastal erosion and management, using the Holderness coast as a worked example. Covers why the coast erodes so fast, the management strategies used, their effects downdrift, and how to deploy a case study in an exam answer.
- The processes of fluvial erosion, transportation and deposition, and how they change from the upper to the lower course (AO1, AO2).
A focused CCEA GCSE Geography guide to fluvial processes. Covers the four types of river erosion, the four ways a river transports its load, why and where deposition happens, and how the balance of these processes changes from the upper to the lower course.
Sources & how we know this
- CCEA GCSE Geography specification — CCEA (2017)
- CCEA GCSE Geography (2017) Unit 1 past papers and mark schemes — CCEA (2024)