Low Energy and High Energy Coasts- slides

• Low energy coasts


  • Coastlines where wave energy is low
  • Where rate of deposition normally exceeds rate of erosion
  • Beaches and spits are common landforms there
  • They include many inlets, estuaries and sheltered bays
• High energy coasts


  • Coastlines with strong prevailing winds which create high energy waves
  • The rate of erosion is greater than the rate of deposition
  • Headlands, cliffs and wavecut platforms are common there
• Sources of coastal sediments

  • Streams or rivers flowing into the sea
  • Estuaries
  • Cliff erosion
  • Off shore sand banks
  • Material from a biological origin e.g. shells and coral fragments
• There is dispute as to where the sediments which form the depositional features around the British Isles come from
• Sediment cells


  • Distinct areas of coastline separated by well defined boundaries e.g. headlands or stretches of deep water
  • 11 sediment cells have been identified around England and Wales
  • The Llyn Peninsula in Wales acts as a huge natural barrier that prevents the transfer of sediment
• The processes of erosion, transportation and deposition within the coastal margin is largely contained within the 11 sediment cells or littoral cells
• A sediment cell is generally thought to be a closed system, which suggests that no sediment is transferred from one cell to another
• In reality however, it is unlikely that sediment cells are fully closed
• With variations in wind direction and tidal currents it is inevitable that some sediment is transferred between cells
• There are also many sub-cells of a smaller scale existing within the major cells
• Coastal sediment budget


  • The balance between the sediment being added and being removed from the coastal system within each individual cell
  • Coastal erosion controls the level of deficit as it removes material from the shoreline
  • If more sediment is removed than added the coastline will recede
  • The sediment budget can also be used to identify the sources and the sites where sediment is stored (sinks)
• Calculating the sediment budget for a cell

  1. Identification of all the sediment sources

  2. Identification of all the sediment sinks

  3. An estimation of the amount of sediment added and removed each year
• More material is added to the cell than removed

  • Positive budget or a surplus of sediment
  • Shoreline builds towards the sea
• More material is removed from the cell than added

  • Negative budget or a deficit in sediment supply
  • Shoreline retreats landwards