Why some coastlines are vulnerable

Eduqas asks you to explain why some coastlines are at greater risk of erosion and flooding than others. The main influences are:

• Geology — soft rock (e.g. boulder clay) erodes far faster than resistant hard rock (e.g. granite).
• Fetch and waves — a long fetch gives powerful destructive waves that erode more.
• Relief — low-lying coasts (e.g. much of eastern England) are exposed to flooding from storm surges.
• Rising sea level — climate change raises sea level, so waves reach further inland.

Key term — fetch: the uninterrupted distance of open sea over which the wind blows. A longer fetch (plus stronger, longer-lasting wind) makes bigger, more powerful waves.

Constructive vs destructive waves

A wave has a swash (water rushing up the beach) and a backwash (water draining back down). Two kinds of wave shape the coast in opposite ways:

Misconception: the constructive wave is the one that builds beaches (its swash is stronger than its backwash). Don't assume big, dramatic waves build up the coast — the tall destructive ones tear it down.

Which wave builds a beach?

Four ways the sea erodes

Weathering (breakdown of rock in place, e.g. freeze–thaw) weakens the cliff. Then moving waves erode it by four marine processes:

• Hydraulic action — the sheer force of water (and trapped, compressed air) pounding into cracks blasts the rock apart.
• Abrasion (corrasion) — waves fling pebbles and sand against the cliff, sandpapering it away.
• Attrition — rock fragments carried by the sea knock against each other, becoming smaller and rounder over time.
• Solution (corrosion) — slightly acidic seawater dissolves soluble rock such as limestone.

Watch out: attrition wears down the sediment itself (making rounder pebbles); abrasion uses that sediment to wear down the cliff. Don't mix them up.

Match the process to its meaning

Tap a process on the left, then tap its correct description on the right.

Which process?

Longshore drift moves the sediment

The sea moves eroded material along the coast. The key process is longshore drift:

Misconception: longshore drift moves sediment along the shoreline, not straight out to sea. It's the sideways, zig-zag transport of material — not the loss of a beach offshore.

Your turn — longshore drift

Cave → arch → stack → stump

Where hard and soft rock meet the coast, soft rock erodes into bays and resistant hard rock is left jutting out as headlands. On a headland, erosion attacks lines of weakness in a famous sequence:

Where the sea attacks a cliff, it erodes a wave-cut notch at the base; the rock above collapses and the cliff retreats, leaving a wave-cut platform.

Getting the order right

Deposition: beaches and spits

When waves lose energy — in sheltered bays or where the coast changes direction — they deposit sediment, building beaches, spits and bars.

Erosion or deposition landform?

Tap a landform, then tap the box it belongs in.

The threat of coastal flooding

Low-lying coasts face flooding as well as erosion. A storm surge is a temporary rise in sea level caused by low air pressure and strong onshore winds during a storm.

• Rising sea level (climate change) means surges reach further inland and defences are overtopped more often.
• Small Island States (e.g. the Maldives, Tuvalu) are extremely vulnerable — whole islands may be lost, creating environmental refugees.
• Forecasting by the Met Office and the Environment Agency gives flood warnings so people can prepare or evacuate.

Exam link: Eduqas expects you to link coastal flooding to sea-level rise and to know its impact on vulnerable communities, including Small Island States.

Hard vs soft engineering

Coasts are managed to reduce erosion and flooding. Two broad approaches:

• Hard engineering — sea walls reflect waves; groynes trap sediment moved by longshore drift and widen the beach; rock armour (rip-rap) and gabions absorb wave energy.
• Soft engineering — beach nourishment adds sand to build up the beach; dune/marsh planting stabilises sediment naturally.

Hard or soft engineering?

Tap the correct type of engineering for each defence.

Choosing a defence

"Hold the line" vs "managed retreat"

Shoreline Management Plans choose a policy for each stretch of coast, balancing the cost of defences against the value of the land:

• Hold the line — keep defending the existing coastline with hard/soft engineering (used to protect towns and valuable land).
• Managed retreat (managed realignment) — deliberately allow low-value land to flood or erode, often creating new salt marsh that absorbs wave energy.
• Do nothing / no active intervention — allow natural processes where defending is not worthwhile.

Misconception: managed retreat is a deliberate decision to stop defending a stretch of coast and let it flood/erode naturally — it is a chosen strategy, not a failure or an accident. It is often used on low-lying coasts (e.g. parts of Essex and North Norfolk).

Your turn — evaluating defences

Case study: the Holderness Coast, UK

The Holderness Coast in East Yorkshire is one of the fastest-eroding coastlines in Europe, retreating on average about 1.5–2 metres every year.

• Why so vulnerable? The cliffs are made of soft boulder clay (glacial till), which slumps easily when saturated. Powerful destructive waves have a long North Sea fetch.
• Impacts: around 29 villages have been lost to the sea since Roman times; farmland, homes and roads continue to be lost.
• Management: the town of Mappleton is protected by two rock groynes and rock armour (built 1991), which trap sediment and shield the cliff — "holding the line".
• Conflict: the groynes trap sediment, so the coast down-drift (e.g. Great Cowden) is starved of beach material and erodes even faster — a source of conflict between residents.

Exam tip: a good case-study answer names the place, gives facts/figures (e.g. ~2 m/yr, 29 lost villages, Mappleton groynes 1991) and explains a conflict between different users of the coast.

Understanding the case study

The key ideas to know

You've covered Eduqas Theme 4 — Coastal Hazards and their Management. Press Finish to see your score.