Human activity and coastal recession

• What human actions have influence of coastal recession?

  Dredging, dams and coastal management
• What is dredging?


  The removal of sediment from rivers or the sea.
• How does dredging impact coastal recession?

  It impacts the amount of sediment being deposited at the coast.
• What are dams?


  The construction of dams, traps river sediment behind the dam wall.
• What is the estimated amount of sediment stores behind the worlds dams?

  100 billion tones
• How do dams impact coastal recession?

  It staves the coast of sediment.

  Causing beaches to decrease in size as they aren't being supplied with sediment.

  Destructive waves have more impact increasing the rate of erosion.
• Name an example where a dam has reduced sediment transport.

  In Spain the river Ebro- 93% reduction in sediment downstream.
• How does coastal management impact the rate of recession.

  Coastal defences like Hornsea's sea walls and rip rap reduce the amount of erosion- slowing recession of the coast.
• How can coastal management have a negative impact on the rate of coastal recession?

  Groynes at Hornsea on the Holderness coast reduces longshore drift.

  Starving areas down the coast e.g. Mapleton (terminal groyne syndrome).
• Why is dredging performed?

  Sand/gravel removed is used by the construction industry.

  Dredging of estuaries maintains navigable channel for shit transport.
• Name an example of how dredging impacted coastal erosion.

  Village of Hallsands, Devon
• What was Hallsands village like before the dredging?

  Fishing village

  100-96 people living there

  Used to have a 30m beach
• Describe the dredging at Hallsands village coast with dates.

  1895- dredging starts for 5 years

  1897- locals complaining

  1905- storm and spring tides destroyed parts of village

  1900s- dredging put to a stop but its too late, its being eroded away
• How did dredging impact Hallsands village?

  The beach was eroded away then the village was engulfed by the water.
• What other geological factors impact coastal recession?

  Geological - lithology(rock type, bond, porous) and geological structure (joints in rocks, dipping, faults)

  Marine - fetch and longshore drift
• How does human activity increase coastal recession?

  By interrupting the operation of the sediment cell.