Coastal Landscapes in the UK
Erosion, deposition, landforms and coastal management strategies
- Explain weathering and mass movement processes
- Describe the four coastal erosion processes
- Explain how erosion landforms form (caves, arches, stacks)
- Describe transportation and longshore drift
- Explain deposition landforms (beaches, spits, bars)
- Evaluate hard and soft engineering strategies
- Apply knowledge to Swanage Bay & Jurassic Coast case study
Rockfall
Very fast (seconds)
Landslide
Fast (mins-hours)
Mudflow
Medium (hours-days)
Rotational slump
Medium (hours-weeks)
Soil creep
Very slow (cm/year)
Key factors increasing mass movement:
- • Heavy rainfall (increases weight, reduces friction)
- • Weathering (weakens rock)
- • Waves eroding cliff base (removes support)
- • Human activity (building adds weight)
Hydraulic action
Wave crashes → air compressed in cracks → pressure shatters rock
Effect: Widens cracks, breaks rock apart
Most effective on: Rocks with many joints/cracks (chalk)
Abrasion (corrasion)
Waves hurl sediment/pebbles at cliff → scratches and chips rock
Effect: Wears cliff back like sandpaper
Most effective on: All rock types (most powerful)
Attrition
Pebbles collide with each other → break into smaller, rounder pieces
Effect: Reduces sediment size over time
Most effective on: Pebbles/boulders (not cliff)
Solution (corrosion)
Seawater (slightly acidic) dissolves soluble rocks
Effect: Gradual chemical dissolution
Most effective on: Chalk, limestone only (Old Harry)
Wave Types & Erosion:
Destructive Waves
High energy, steep, frequent (10-14/min) → Strong erosion
Constructive Waves
Low energy, gentle, infrequent (6-8/min) → Deposition
Stage 1: CAVE
Waves attack weakness in headland (crack, joint). Hydraulic action + abrasion widen the crack into a cave. Often forms on both sides of the headland.
At Old Harry: Caves visible at base of No Man's Land
Timeline: Each stage takes 100s-1000s of years
Four Transportation Processes
Traction
Large boulders roll along seabed
Sediment: Boulders (>256mm) | High-energy storms only
Saltation
Pebbles bounce along seabed
Sediment: Pebbles (4-256mm) | Medium-high energy waves
Suspension
Fine particles carried in water (cloudy)
Sediment: Silt, clay (<0.06mm) | All waves (stays suspended)
Solution
Minerals dissolved in water (invisible)
Sediment: Dissolved salts, calcium | Continuous (all waves)
Longshore Drift
Movement of sediment along the coast in a zigzag pattern:
- 1. Swash: Wave breaks, water rushes up beach at angle (prevailing wind direction)
- 2. Swash carries sediment diagonally UP the beach
- 3. Backwash: Water flows straight back DOWN (gravity)
- 4. Backwash carries sediment straight down
- 5. Net result: Zigzag movement = sediment moves along coast
UK Directions:
- • South coast (Swanage): West → East (SW winds)
- • East coast: North → South
Evidence at Swanage:
- • Sediment builds on south side of groynes
- • Beach wider at north end of bay
Beaches
Constructive waves deposit sediment between high & low tide marks. Sediment sorted by size.
| Type | Sediment | Slope | Example |
|---|---|---|---|
| Sand beach | Fine sand (0.06-2mm) | Gentle (5-10°) | Swanage (north end), Studland Bay |
| Shingle beach | Pebbles (4-64mm) | Steep (20-30°) | Chesil Beach, Swanage (south end) |
| Boulder beach | Boulders (>256mm) | Very steep (30-40°) | North Scotland |
Spits
Longshore drift transports sediment along coast. Where coast changes direction (estuary), sediment deposited in original direction → narrow ridge extends into sea. Curved end from secondary winds.
Spurn Head, East Yorkshire
5.5km long, 50m wide at narrowest. Salt marsh behind (50 hectares).
Bars
Like a spit but extends all the way across a bay, connecting two headlands. Creates a lagoon behind.
Chesil Beach, Dorset (near Swanage)
29km bar connecting mainland to Isle of Portland. Pebbles graded from pea-sized (west) to 6-7cm cobbles (east). Fleet lagoon behind.
Sea Walls
Cost: £5,000-10,000/m
Rock Armour (Rip-rap)
Cost: £1,000-3,000/m
Groynes
Cost: £10,000-50,000 each
Gabions
Cost: £100-300/m
Location
- Region: South coast of England, Dorset
- Specific: Swanage Bay sits on the Isle of Purbeck
- Extent: Jurassic Coast stretches 155km from Orcombe Rocks (Devon) to Old Harry Rocks (Dorset)
Jurassic Coast Significance
- • Only natural World Heritage Site in England
- • Represents 185 million years of Earth's history
- • Complete sequence of sedimentary rocks, rich fossil deposits (ammonites, ichthyosaurs)
Why is Swanage Vulnerable?
Physical factors:
- • Soft geology: Wealden Beds (clay/sandstone) = 2-3m/year erosion historically
- • South-facing: Exposed to English Channel storms (100km+ fetch)
- • Wave height: 1-2m average, 5-7m in storms
Economic factors:
- • Seafront properties: £500,000-£2M at risk
- • Tourism revenue: £30M+/year (90% of jobs)
- • 500,000 visitors/year
1. Which erosion process is most powerful at wearing back cliffs?
2. What type of wave causes erosion?
3. What landform is Old Harry at the end of The Foreland headland?
4. How much sand was used to nourish Swanage Beach in 2005?
5. What type of coastline is the Swanage area?
6. How much did the Swanage coastal management scheme cost?
Processes
- Hydraulic action: Air compression in cracks shatters rock
- Abrasion: Sediment thrown at cliff wears it away
- Attrition: Sediment collides, becomes smaller/rounder
- Longshore drift: Zigzag sediment movement along coast
Landforms
- Wave-cut platform: Flat rock area exposed at low tide
- Stack: Isolated column from collapsed arch (Old Harry)
- Spit: Ridge of sediment attached at one end
- Bar: Ridge connecting two headlands (Chesil Beach)