How are coastal landscapes shaped, why do they change, and how can the resulting risks be managed?
Coasts as systems within sediment cells, the marine and sub-aerial processes that create erosional and depositional landforms, the causes of coastal recession and flooding, and how coastal risk can be managed sustainably.
An Edexcel A-Level Geography answer to coastal landscapes and change, covering the coast as a system within a sediment cell, marine and sub-aerial processes, erosional and depositional landforms, the physical and human causes of coastal recession and flooding, and sustainable coastal management approaches such as holding, advancing or retreating the line.
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What this dot point is asking
Edexcel wants you to treat the coast as a system within a sediment cell, explain the marine and sub-aerial processes that produce erosional and depositional landforms, explain the physical and human causes of coastal recession and flooding, and evaluate how coastal risk can be managed sustainably.
The answer
The coast as a system within a sediment cell
England and Wales are divided into eleven major littoral cells (for example Cell 2, Flamborough Head to The Wash, which contains the rapidly eroding Holderness coast). Treating the coast as an open system with inputs, throughputs, stores and outputs is the foundation of the whole topic: it explains why defending one place can damage another, and it underpins Shoreline Management Plans (SMPs) that are written cell by cell rather than property by property.
Coasts are classified by geology as concordant (rock bands parallel to the coast, producing cove coastlines such as Lulworth Cove, Dorset) or discordant (bands at right angles, producing headlands and bays such as Swanage Bay and the chalk headland of The Foreland). They are also classified by energy as high-energy (exposed, long-fetch, destructive waves, net erosion) or low-energy (sheltered, short-fetch, constructive waves, net deposition), and by sea-level history as emergent or submergent.
Marine and sub-aerial processes and the landforms they create
Erosion works by hydraulic action (compressed air in joints), abrasion (sediment thrown at the cliff), attrition (rounding of particles) and solution (carbonate dissolution). Transport is by traction, saltation, suspension and solution, and along the coast by longshore drift, which moves sediment in the dominant wave-approach direction (southward along Holderness).
Sub-aerial processes are weathering and mass movement acting on the cliff face from the land side. Mechanical weathering (freeze-thaw, salt crystallisation), chemical weathering (carbonation) and biological weathering weaken rock; mass movement (rockfall on resistant cliffs, rotational slumping on weak clays) then delivers material to the foot of the cliff. At Holderness the soft glacial till slumps after winter rain saturates it, which is why recession there is episodic, not steady.
Coastal recession and flooding
Recession rates depend on lithology and structure (Holderness till retreats over a hundred times faster than Cornish granite), wave energy and fetch, sediment supply and sea-level rise, which lets waves attack the cliff for longer at higher levels. Coastal flooding results from storm surges, low atmospheric pressure (a hPa fall raises sea level by roughly cm), high spring tides and human factors such as subsidence and the removal of natural defences. The 1953 North Sea flood killed over 300 people in eastern England and drove the construction of the Thames Barrier (completed 1982). Both recession and flooding threaten people, infrastructure and ecosystems, and climate change raises the risk through rising seas and stormier conditions, with consequences felt most by low-lying and low-income communities.
Managing coastal risk sustainably
Shoreline management plans choose between four policies: hold the line, advance the line, retreat (managed realignment) or no active intervention. Hard engineering (sea walls, groynes, rip-rap, gabions) resists the sea but is costly and can starve downdrift coasts. Soft engineering (beach nourishment, dune regeneration, managed realignment) works with natural processes. Integrated Coastal Zone Management (ICZM) coordinates the whole cell and balances players with conflicting attitudes, a synoptic link to the human geography units: residents and businesses want their property held, while environmental groups and cost-conscious agencies may favour managed retreat. The chosen future for a stretch of coast is therefore a contested decision, not a purely technical one.
Examples in context
Example 1. The Holderness coast, East Yorkshire. Holderness is the fastest-eroding coastline in Europe, retreating at an average of about m per year and having lost some 30 villages since Roman times. The cause is a combination of weak glacial till cliffs, a long North Sea fetch generating high-energy destructive waves, and a narrow beach that gives little protection. Defences at Mappleton (a rock revetment and two groynes installed in 1991 to protect the village and the B1242 road) trap longshore drift, so the cliffs immediately to the south are starved of sediment and erode faster, a clear case of terminal groyne syndrome and a sediment-budget deficit shifted downdrift. The SMP for most of the coast is no active intervention, reflecting the high cost of holding the line against the value of farmland, and pitting residents (who lose homes) against the Environment Agency (which weighs cost-benefit at the cell scale).
Example 2. Medmerry managed realignment, West Sussex (2013). At Medmerry the Environment Agency deliberately breached an old, expensive-to-maintain shingle bank and let the sea flood low-lying farmland, creating around ha of new intertidal salt marsh. The scheme cost roughly £28 million but better protects the nearby town of Selsey and the Bracklesham caravan parks than the failing defence did, while creating habitat that itself absorbs wave energy. Medmerry is the standard A-Level example of soft engineering / retreat the line delivering both flood protection and environmental gain, illustrating how an ICZM, whole-cell approach can be more sustainable than holding a hard line everywhere.
Try this
Q1. Explain how a wave-cut platform forms. [4 marks]
- Cue. Waves erode a notch at the cliff base; the cliff above collapses and retreats, leaving a gently sloping platform exposed at low tide.
Q2. Suggest why managed realignment may be more sustainable than a sea wall. [4 marks]
- Cue. It works with natural processes, creates habitat, reduces long-term cost and avoids starving downdrift coasts.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel Paper 1 (style)12 marksAssess the relative importance of physical and human factors in causing coastal recession.Show worked answer →
AO1 credits accurate process knowledge; AO2 credits applying it to recession and reaching a judgement on relative importance. Physical factors drive much recession: high-energy destructive waves, rock type and lithology (the weak glacial till at Holderness erodes far faster than the chalk further south), structure (concordant versus discordant coasts), sub-aerial weathering and mass movement, and rising sea level that lets waves attack higher up the cliff. Holderness, eroding at roughly m per year, shows weak geology meeting a long North Sea fetch.
Human factors can accelerate recession: dredging and dams cut sediment supply, while coastal defences in one place starve beaches downdrift (terminal groyne syndrome), as the groynes and sea wall at Mappleton (1991) starved the cliffs immediately south. A balanced AO2 judgement might argue physical factors set the baseline rate while human interference, especially disruption of the sediment budget, often tips a stable coast into rapid recession. The strongest answer links the chosen factors to a located example with figures.
Edexcel 20198 marksStudy Figure 3 (a sediment cell diagram). Explain how the concept of the sediment budget helps to predict whether a stretch of coast will erode or accrete.Show worked answer →
This is an AO1/AO3 resource question: read the figure, then apply the budget concept. Define the sediment budget as the balance of inputs (rivers, cliff erosion, longshore drift in, offshore bars) against outputs (deposition, longshore drift out, offshore loss). Where inputs exceed outputs the coast tends to accrete (a positive budget, building beaches and spits); where outputs exceed inputs it tends to erode (a negative budget). Reward use of the figure: candidates should read off arrows showing the dominant longshore drift direction and identify updrift sources and downdrift sinks. A strong answer notes the cell tends towards dynamic equilibrium, so a sustained negative budget (for example after dredging cuts a river input) predicts recession, while interrupting drift with groynes shifts the deficit downdrift.
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Sources & how we know this
- Pearson Edexcel A-Level Geography (9GE0) specification — Pearson Edexcel (2016)