waves

• Wave

  Main source of energy at the coast
• Waves

  • Generated by wind
  • Friction between wind and water surface transfers energy from wind to water
• Wind

  Occurs because of the rotation of the earth and differences in atmospheric pressure when different parcels of air are heated differently by the sun
• Wind

  • Fetch
  • Duration
  • Strength
• Wave characteristics

  • Wave height
  • Wave length
  • Wave frequency
• Wave height

  Distance from the peak to the trough
• Wave length

  Distance from crest to crest
• Wave frequency

  Number of waves which pass a specific point over a given time
• Types of wave

  • Constructive
  • Destructive
• Constructive waves

  • Long wavelength (up to 100m), low, spilling waves, low energy, low wave frequency
  • Strong swash, weak backwash
  • Build up the beach with a gentle beach profile
• Destructive waves

  • Short wavelength (Approx. 20m), high, plunging waves, high energy, large wave height
  • Weak swash, strong backwash
  • Beach is limited. Steeper beach profile is likely in the short term
• Beaches are formed from loose material
• Waves alter the morphology (form/shape) of the beach

  The morphology is also affected by the size and shape of the beach material
• The type of wave in an area

  Can vary depending on the time of year or coastal management
• Beach profiles

  Steeper in summer when there are fewer destructive waves and gentler in winter
• Storm berms

  May develop in winter when large destructive waves carry larger sediment further up the beach than normal
• In winter beaches

  May also have a greater variation in pebble size as larger pebbles are deposited by the destructive waves and smaller pebbles are removed
• Offshore ridges/bars

  Formed due to material being eroded from the beach by destructive waves and deposited offshore
• Erosion leads to the formation of a range of landforms at the coast
• Types of erosion

  • Abrasion (corrasion)
  • Hydraulic action
  • Corrosion
  • Attrition
• Abrasion (corrasion)

  Sediment and stones are picked up by the waves and wear away at the cliff/headland
• Hydraulic action

  The shear force of the waves forcing air at high pressure into cracks in the cliff over time this weakens the rock and causes the joint to widen
• Corrosion

  Weak acids in seawater dissolve the rock particles
• Attrition

  As rocks are moved around by the water they knock into each other gradually becoming smaller and rounder
• Factors affecting erosion

  • Wave type
  • Wave size
  • Lithology
• Wave type and size

  Affects the seasonal changes in the amount of erosion
• Erosion

  Tends to happen more during the winter due to a greater number of destructive waves
• Wave type and size

  Affects the amount of hydraulic action and abrasion
• Lithology

  Influences the rate of erosion
• Wave cut platforms

  Formed at high-energy coastlines by hydraulic action and abrasion, which create a wave-cut notch that eventually leads to the cliff retreating and leaving a wave cut platform exposed at low tide
• Landforms at a headland

  • Caves
  • Arches
  • Stacks
  • Stumps
• Formation of a wave cut platform

  1. Powerful destructive waves attack the base of the cliff at high tide

  2. Hydraulic action and abrasion create a wave-cut notch

  3. Overhang created by undercutting collapses due to weathering and gravity

  4. Cliff retreats, leaving a wave cut platform exposed at low tide
• Formation of erosional landforms at a headland

  1. Wave refraction concentrates wave energy onto the headland

  2. Joints in the headland are susceptible to erosion by hydraulic action

  3. Erosion widens the joints, forming a cave

  4. Cave is enlarged by hydraulic action and abrasion

  5. Erosion cuts through the headland, forming an arch

  6. Roof of the cave collapses, leaving a stack

  7. Stack is eroded by weathering, abrasion, and hydraulic action to form a stump