booklet 4

• Where does coastal sediment come from?

  - rivers and streams (fluvial)

  - cliff erosion

  - longshore drift

  - wind

  - glaciers

  - offshore

  - biological origin - incl shells, coral and skeletons of marine organisms
• sediment movement


  - research suggests movement occur in distinct areas or sediment cells within which inputs and outputs are balanced

  - 11 have been identified on coastline of england and wales
• sediment cell definition


  distinct area of coastline separated from other areas by well - defined boundaries, eg. headlands and stretches of deep water
• sediment cells systems


  - can be regarded as closed systems

  - however is easy for fine sediments to find way around headlands and into neighbouring cells
• sediment cells - inputs

  source of sediment

  - cliff erosion

  - fluvial sediment

  - eroding depositional features

  - beach recharge

  - offshore bars and sediment

  - erosion of wave cut platform
• sediment cells - transfers / processes

  transportation

  - LSD

  - currents

  - saltation
• sediment cells - stores

  sinks / permanent storage

  - estuary

  - submarine canyon

  - offshore bar / bank

  - dredging

  sub sinks / temporary stores

  - sedimentary features
• sediment budget


  - balance between sediment being added to and removed from the coastal system
• positive budget


  - more material added to cell than removed

  - net accretion of material

  - shoreline builds towards sea

  - surplus of material
• negative budget


  - more material removed from cell than added

  - deficit in sediment supply

  - shoreline retreats landward
• positive budget examples

  - sea level rise

  - creation of groynes

  - rockfall in upland

  - deforestation along coast

  - building of coastal port (sediment trap)

  - creation of campsite
• negative budget example


  - dam built along rivers course

  - dredging a river

  - creation of sea wall

  - sea level rise

  - building of coastal port