Coastal Landscapes in the UK
UK Coastline Overview
The UK has a diverse coastline shaped by both erosion and deposition. The type of coast depends on rock type, wave energy, fetch (distance wind blows over water), and human activity.
Wave Types
- Constructive waves — low frequency (~6–8 per minute); strong swash and weak backwash; deposit material on the beach; build up beach profiles; associated with calm weather
- Destructive waves — high frequency (~10–14 per minute); weak swash and strong backwash; erode the beach; remove material; associated with storms and long fetch
Processes of Erosion
| Process | Description |
|---|---|
| Hydraulic action | Force of waves compressing air into cracks in the rock, weakening and breaking it apart |
| Abrasion | Waves hurl rocks and sediment at the cliff face, wearing it away like sandpaper |
| Attrition | Rocks carried by waves smash together, becoming smaller and rounder over time |
| Solution (corrosion) | Weak acids in seawater dissolve soluble rocks such as chalk and limestone |
Erosional Landforms
Headlands and Bays
Formed where rocks of alternating resistance (hard and soft) meet the coast at right angles. Soft rock erodes faster, forming bays with beaches. Hard rock resists erosion, jutting out as headlands. Over time, wave refraction concentrates energy on headlands and disperses it in bays.
Cliffs, Wave-Cut Notches, and Wave-Cut Platforms
1. Waves attack the base of a cliff, eroding a wave-cut notch through hydraulic action and abrasion
2. The rock above the notch becomes unsupported and eventually collapses
3. The cliff retreats inland, leaving a gently sloping wave-cut platform at the base (visible at low tide)
4. The process repeats, and the cliff continues to retreat
Caves, Arches, Stacks, and Stumps
1. Waves attack a weakness (joint/fault) in a headland → enlarged into a cave
2. Continued erosion from both sides of the headland → caves meet to form an arch
3. The roof of the arch weakens and collapses → leaving an isolated stack
4. The stack is eroded at the base → collapses to form a stump
Example: Old Harry Rocks, Dorset — a chalk stack and stump on the Isle of Purbeck.
Processes of Transportation
Material is moved along the coast by longshore drift:
1. Waves approach the beach at an angle (determined by the prevailing wind direction)
2. Swash carries sediment up the beach at an angle
3. Backwash drags sediment straight back down under gravity
4. Material zigzags along the coast in the direction of the prevailing wind
Other transport processes: traction (rolling), saltation (bouncing), suspension (carried in water), solution (dissolved).
Depositional Landforms
Deposition occurs where the sea loses energy — in sheltered bays, behind headlands, and where the coastline changes direction.
- Beaches — accumulations of sand and shingle; sandy beaches are gently sloping; shingle beaches are steeper
- Spits — a long, narrow ridge of sand/shingle extending from the coastline across a river mouth or change in coastline direction; curved end formed by wave refraction. Example: Spurn Head, East Yorkshire (5.5 km spit at the mouth of the Humber Estuary)
- Bars — a spit that grows across a bay, sealing it off to form a lagoon behind (e.g. Slapton Ley, Devon)
- Sand dunes — formed when wind blows dry sand inland from the beach; stabilised by marram grass; progress from embryo dunes (youngest, nearest sea) to mature dunes (oldest, furthest inland)
Case Study: Holderness Coast, East Yorkshire
The Holderness Coast is the fastest eroding coastline in Europe, retreating at an average of 1.8 metres per year (up to 10 m in storms).
Why It Erodes So Quickly
- Made of boulder clay (glacial till) — a soft, unconsolidated material easily eroded by waves
- Long fetch across the North Sea (~800 km from Scandinavia) creates powerful destructive waves
- Narrow beaches provide little protection at the cliff base
- Slumping occurs when clay becomes saturated by rainfall
Management Strategies
Hard engineering:
- Sea walls — concrete barriers reflect wave energy (e.g. Withernsea, Hornsea); expensive (~£6,000/metre) but effective
- Rock armour (rip-rap) — large boulders absorb wave energy; cheaper (~£3,000/metre)
- Groynes — wooden or rock barriers trap sediment, building up the beach (but starve beaches further along the coast of sediment — terminal groyne syndrome)
- Gabions — wire cages filled with rocks; absorb wave energy
Soft engineering:
- Beach nourishment — adding sand/shingle to beaches to absorb wave energy; natural-looking but needs regular replenishment
- Managed retreat — allowing the sea to flood low-value land (e.g. farmland); cheapest option; creates new saltmarsh habitats
- Dune regeneration — planting marram grass to stabilise sand dunes
Key conflict: Protecting one area (e.g. Mappleton, where £2 million was spent on groynes) starves neighbouring areas of sediment, accelerating erosion elsewhere (e.g. Great Cowden and Aldbrough).