COASTS

• Constructive waves

  • They form beaches, formed by storms far away
  • Waves crest far apart
  • Gently sloping wave front
  • Breaking wave spills forward
  • Strong swash pushes sediment up the beach
• Destructive waves

  • They destroy beaches, formed by nearby storms
  • Waves close together
  • Steep wave front
  • Breaking wave plunges forward
  • Steep beach
  • Strong backwash pulls sediment out to sea
• Disintegration of rocks

  Piles of rock fragments (scree) at the foot of cliffs
• Salt weathering

  • Seawater containing salt evaporates and leaves salt
  • Salt crystals expand in the rocks
  • Pressure on rocks causes fragments to break away
• Chemical weathering


  • Caused by chemical changes
  • Rain water is acidic so dissolves rocks
• Carbonation

  • Rainwater absorbs co2 and becomes acidic
  • In contact with alkaline rocks (limestone or chalk) chemical reactions take place and they dissolve
• Biological weathering

  • Due to conditions of flora and fauna
  • Plant roots dislodge cracks and rocks, animals burrow into weak rocks
• Mass movement

  • Rockfall
  • Mudflow
  • Landslide
  • Rotational slip
• Coastal transportation

  • Solution – dissolved chemicals
  • Suspension – particles carried in water
  • Saltation – particles too big for suspension "hopping"
  • Traction – large pebbles rolled along by sea flow
• Longshore drift


  • Zig zag pattern formed by the movement of sediment
  • Movement of sediment along beach (at 45 degrees)
  • Prevailing wind waves approach at an angle
  • Swash carries sediment up the beach (at an angle)
  • Backwash (perpendicular to beach) carries eroded material along beach
• Spit

  • Result of marine deposition (long shore drift)
  • A long narrow accumulation of sand and shingle, one end attached to mainland other into sea, usually have hooked ends
  • Longshore drift transports sand
  • Bar forms
  • Saltmarsh forms in spit shelter
• Bar

  • Permanent landform, result of marine deposition (long shore drift)
  • Extended spit across a bay, forms a new beach with a lagoon, called barrier beaches, can sometimes form out at sea
  • Longshore drift transports sand
  • Spit grows out into sea
  • Spit reaches headland
• Tombolo

  Similar to bar but formed between mainland and an island
• Hydraulic action

  • Wave power on cliffs push air into cracks
  • Cracks expand and pressure causes rocks to split
  • Cuiration – explosive force of air trapped in rock
• Abrasion


  • Waves pick up rocks
  • Rocks get thrown against cliff surface
  • Sandpaper effect smothes out cliff
• Corrosion

  • Salts or chemicals dissolve the rocks
  • Limestone is dissolved by sea salt
• Attrition

  • Sea picks up angular rocks
  • They rub and become rounded as corners chip
• Headlands and bays

  1. A discordant coastline faces wave attacks

  2. Wave attack causes HYDRAULIC ACTION and attrition causing the cliff to retreat

  3. Less resistant rocks are eroded faster to form bays, more resistant remain to form headlands

  4. During calm period beaches for in bays via deposition
• Caves, Arches, Stacks, and Stumps

  1. Joint of crack in a resistant rock is widened by hydraulic action to form a cave

  2. Cave is made longer until it forms an arch

  3. The arch is eroded until it becomes too heavy and collapses leaving a stack

  4. The stack erodes and collapses to form a stump
• Beaches


  • Found in sheltered bays
  • Made by constructive waves
  • Rocky beaches are of high energy environments and the sand has washed away
• Sand dunes

  • Embryo dune forms over debris
  • These are stabilised by vegetation
  • As vegetation dies it adds nutrience so more plants can grow
  • Wind forms depressions called slack
• Hard engineering strategies

  • Groynes
  • Rock armour
  • Gabions
  • Sea wall
  • Beach nourishment
  • Dune regeneration
  • Dune fencing
  • Managed retreat
• Groynes

  • Wooden or rock fences
  • Trap sediment moving via longshore drift
  • Used to maintain or enlarge the beach
  • £1500 each (at every 200m)
• Groynes advantages

  • Creates larger beach for tourists
  • Useful for fishermen
  • Less expensive (than other methods)
• Groynes disadvantages

  • Interrupt longshore drift – starves other beaches
  • Increases erosion elsewhere
  • Unnatural
  • Unattractive
• Rock armour

  • Piles of large boulders at bottom of cliff
  • Force waves to break
  • Absorb wave energy
  • Rocks brought by barge
  • Protect cliffs
  • £200000 per 100m
• Rock armour advantages

  • Relatively cheap
  • Easy to maintain
  • Provides interest
  • Fishing
• Rock armour disadvantages

  • Foreign rocks
  • Expensive transport
  • Obtrusive
  • Geological outliers
• Gabions

  • Wire cages filled with rocks
  • Support cliffs
  • Buffer to sea
  • £50000 per 100m
• Gabions advantages

  • Cheap production
  • Flexible design
  • Improve cliff drainage
  • Can become vegetated and merge with landscape
• Gabions disadvantages

  • Look unattractive
  • Cages only last 5-10 years
• Sea wall

  • Concrete or rock barrier
  • At foot of cliffs or beaches
  • Curved to reflect waves
  • £5000 - £10000 per meter
• Sea wall advantages

  • Effective
  • Provides walkway
• Sea wall disadvantages

  • Look obtrusive and unnatural
  • Expensive
  • High maintenance
• Beach nourishment

  • Replenish and reprofile sand
  • Creating an angles beach 15o reduces wave energy as water cannot go up the slope
  • The higher and wider the beach – greater protection and more tourism
  • Addition of sand/shingle
  • Locally obtained – natural appearance
  • £500000 per 100m
• Beach nourishment advantages

  • Blends in
  • Increases local tourism
• Beach nourishment disadvantages

  • Needs constant maintenance
  • Expensive
• Dune regeneration

  • Marram grass planted to stabilise dunes
  • Sand dunes are effective sea buffers
  • £200 - £2000 per 100m
• Dune regeneration advantages

  • Maintains natural landscape
  • Relatively cheap
• Dune regeneration disadvantages

  • Time consuming
  • Damaged by storms