Constructive & destructive waves

Waves are made by wind blowing over the sea. The distance of open water the wind crosses is the fetch — a longer fetch means more powerful waves. There are two types:

• Constructive waves — low, gentle waves with a strong swash (up the beach) and weak backwash. They build up beaches by depositing material.
• Destructive waves — tall, steep, frequent waves with a strong backwash and weak swash. They erode and drag material back out to sea.

Which wave builds a beach?

Erosion & transportation

Destructive waves erode the coast in four ways:

• Hydraulic action — waves force air into cracks in the cliff, weakening the rock.
• Abrasion (corrasion) — waves fling sand and pebbles at the cliff, wearing it away.
• Attrition — rock fragments knock together and become smaller and rounder.
• Solution (corrosion) — seawater dissolves soluble rock such as chalk and limestone.

Material is then transported along the coast by longshore drift: swash pushes sediment up the beach at the angle of the wind, backwash pulls it straight back down under gravity — so material zig-zags along the shore.

Erosion, transport or deposition?

Tap a process, then tap the group it belongs to.

Cave → arch → stack → stump

Where hard and soft rock meet the coast, the sea erodes the soft rock into bays and leaves the hard rock jutting out as headlands. On a headland, waves attack lines of weakness:

Put it in order

Beaches & spits

Where waves lose energy, they deposit sediment to build depositional landforms:

• Beaches — sand or shingle deposited in a sheltered bay. Sandy beaches are gently sloping (constructive waves); shingle beaches are steeper.
• Spits — where the coastline changes direction, longshore drift carries material out across the gap and deposits it as a long ridge with a curved (hooked) end. A salt marsh often forms in the sheltered water behind it.

Why defend the coast? Hard vs soft

Coasts are defended because in most continents many people live near the coast, coasts matter economically (tourism, fishing, ports), and rising sea levels from climate change increase the risk of erosion and flooding.

• Hard engineering: sea walls (reflect waves), groynes (trap sediment moving by longshore drift), gabions (rock-filled cages absorbing wave energy).
• Soft engineering: beach nourishment (adding sand) and managed retreat (letting low-value land flood to create natural defences).

Case study flag: CCEA requires one coastal-management case study from the British Isles (e.g. Newcastle, County Down). Check any specific costs or dates against your class notes before quoting them.

Match each defence to its type

Tap a defence on the left, then its matching type on the right.

Your turn — longshore drift rate

Your turn — cliff retreat

The sustainable option

The big ideas to know

You've covered all of CCEA Theme B — Coastal Environments. Press Finish to see your score.