Factors Affecting Sediment Cells

• What is a sediment cell?

  Closed system where sediment moves between sources (inputs), transfers (processes) and sinks (outputs) to maintain dynamic equilibrium
• How is sediment transported in a sediment cell?

  Longshore drift to maintain a balance in the system
• What is a sediment sink?

  Sand dunes and a spit, where material accumulates and is stores
• What effect does this natural equilibrium have on the beach?

  Ensures beach remains stable and coastal features e.g dunes and spits can continue to develop
• What happens if the balance between sediment input, transport, and deposition is broken?

  Coastal erosion
• If a dam has been constructed on the river, what effect would this have?

  Sediment blocked from reaching the coast

  Reduces supply of sand and silt

  Causes beach depletion as less material available for deposition

  Reduction in input of river sediment will make the marine erosive processes more active and may lead to erosion of coast in downdrift direction
• If groynes have been installed, what effect would this have?

  Sediment trapped locally but prevents long shore drift from distributing material further along coast, leading to increased erosion down-drift, as areas beyond the groynes receive less sediment replenishment (terminal groyne syndrome)
• If a seawall has been built, what effect would this have?

  Protects infrastructure but prevents natural cliff erosion, cutting off another sediment source

  Sea wall protects town but also starve down drift areas of sediment which may also contribute to reduction in sizes of landforms e.g spit and narrowing of beaches
• If there is less input from offshore bars, what is the effect?

  Marine erosional processes more active and beaches may be depleted
• What is the effect of beach depletion and reduced longshore drift on the stable sediment sink (the spit)?


  Weaken it, causing erosion and possible breakdown of the landform
• If the coast loses sediment, what is it more susceptible to?

  Storm damage, potentially leading to flooding and further coastal retreat
• What effect will rising sea levels have?

  May cause permanent sediment loss, reducing beach stability
• Without intervention e.g beach nourishment, what happens to the system?


  System may not recover, leading to permanent changes in beach morphology