Coastal Landscapes

• Formation of coastal landscapes

  • Waves, tides and sea levels all change the development of coastal landscapes
  • Modern coasts are shaped by the energy balance between tides and waves
  • Sea level and geology create boundary conditions, as do estuary’s where rivers meet the sea
• Wave dominated coasts - Profiles

  • Experience a seasonal change in profile
  • Summer = depositional
  • Winter = erosional
  • During the winter sand is eroded from the coast and during summer it returns under low wave action
• How waves are generated

  • Waves are generated through wind blowing on the surface of the sea, these pressure fluctuations are the main driver of wave formation.
  • The height of waves is dependent on the fetch area of wind (area that the wind blows over), wind speed and duration of wind
  • The longer the duration of wind = higher waves
  • Waves in transitional and shallow water are affected by bottom friction. As they are affected, they steepen, slow down and then compress. DRAW?
• Wave dominated coasts - Swash Zone

  • cross shore transport which is perpendicular to the shore
• Depositional characteristics of wave dominated coasts

  • Beach ridges – no aeolian sediment, elevation close to storm surge, coarser sediments
  • Dunes – aeolian over marine, no close relationship to swash zone, vegetation
  • These dunes are transgressive and can often infringe onto rivers and estuaries  
  • Wave dominated estuaries receive their sediments from marine and fluvial sources. Therefore, they are influenced by wave tides
• Wind, sediment transport - Wind dominated coasts

  • Wave dominated coasts have a surplus of sediment supply, with winds that need to be around 8m/s to transport this sediments, but there are also plants present to hold these sands down
• Tide Dominated Coasts

  • Where strong tidal currents redistribute sediments along the path of transgressing and regressing tidal currents
  • This leads to the formation of tidal flats, channels or ridges which are often composed of fine sediments
  • Tide dominated estuaries are coastal embayments that have been partially infilled by sediments from the catchment and marine sources, in this case tidal currents are influential in shaping the geomorphology of the estuary
• Rocky Coasts

  • Morphology of a rocky coast is dependent on the competency of lithology and rate of weathering
  • Cliffs and shore platform features are formed through erosion
  • Due to this they preserve evidence of past sea levels
  • Erosion by wave action is primarily concentrated in pre-existing fractures, bedding planes and weaker rocks (as these are points of weakness where the effect of erosion is easier and more pronounced)
• Rocky Coasts- Weathering


  • Different regions of rocky coasts experience different levels of weathering or abrasion. E.g., Weathering is primarily concentrated at the rock face whereas the wave attack zone experiences higher abrasion
• Cycle of Headland Erosion (1-5)

  1. Cracks at base -> exposed due to fluvial action, wave action pressurises the air, forcing the crack to widen
  2. Weathering such as wet drying, widens the crack
  3. Overtime the crack becomes a wave cut notch. Further abrasion and weathering deepen the notch to form a cave
  4. Refraction of waves inside the cave cause the strength of waves to carve out the sides
  5. Wave refraction affects all three sides of the headland, if caves are aligned on two sides, then the waves break through to from an arch
• Cycle of Headland Erosion (6-9)

  • 6. Vertical joints are exposed by tall destructive waves
  • 7. Overtime the arch become unstable and collapses to form a stack
  • 8. The stack is further eroded at its base, creating new notches
  • 9. The stack eventually collapses to form a stump, broken material is further eroded away
• Erosional Coastal Landforms

  • Sea stacks: Formed as a result to headland erosion
  • Cliffs: The shape and form of coastal cliffs in rocky coasts, is dependent on the erosion experienced via wave and wind action
  • Wave cut platforms: When waves erode a cliff and leave a flat platform. in rocky coast environments, wave cut platforms experience high levels of hydraulic weathering and sediment abrasion. The development of the notch occurs in the wave attack zone and as the notch deepens, the cliff above collapses to leave a flat platform. DRAW
• Depositional coastal landforms

  • Beaches: formed from the deposition of sand through waves or wind. Beaches include other forms influenced by the deposition of sediments, such as dunes or ridges