The Erosion Threat

• What is a consequence of rapidly eroding coastlines?

  They can damage property and harm civilian lives.
• What are the physical factors causing coasts to recede faster than others?

  • Long wave fetch and large, destructive ocean waves
  • Soft geology, especially unconsolidated sediments
  • Cliffs with structural weaknesses (seaward rock dip and faults)
  • Cliffs vulnerable to mass movement and weathering
  • Strong longshore drift removing eroded debris
• How do human actions affect coastal erosion?

  They worsen erosion by interfering with coastal sediment cells.
• What is dredging?

  Dredging involves scooping or sucking sediment from the sea or riverbed.
• What is the purpose of dissipation in coastal processes?

  Dissipation describes how wave energy is decreased by friction with beach material.
• What happened to Hallsands in Devon due to human impact on coastal sediment cells?

  • Offshore dredging for construction material
  • 1500 tonnes of sediment removed daily
  • Beach level fell, threatening the village
  • By 1990, Hallsands was under serious threat
  • Dredging stopped in 1902; major storm in 1917 breached defenses
  • Hallsands is now an abandoned 'ghost village'
• How does erosion rate vary over time and space?

  • Over time: peaks of erosion in some seasons; variable recession rates
  • Spatial: some locations experience much less erosion than others
• What is the average annual erosion rate at Holderness Coast?

  Approximately 1.25 m per year.
• What factors contribute to variations in erosion rates along the Holderness Coast?

  • Coastal defenses in locations like Hornsea and Mappleton
  • Starvation of sediment due to groynes and breakwaters
  • Erosion rates increase from north to south
  • Variations in cliff height and susceptibility to erosion
  • Mass movement susceptibility and debris protection
• What are 'ords' in the context of coastal erosion?

  Ords are deep hollows on the beach that concentrate erosion by allowing waves to directly attack cliffs.
• How fast do ord locations erode compared to other locations?

  Ord locations erode four times faster than locations without ords.
• How do erosion rates at Hollym vary from 2003 to 2018?


  Erosion varies from 0 m to 11 m, peaking during biannual spring measurements.
• What are the main causes of erosion at Hollym?

  • Winter storms, especially during high spring tides
  • Rare summer storms lead to lower autumn erosion rates
  • Northeasterly storms due to long wave fetch from the Norwegian coast
• What is the significance of river-transported sediment for coastal maintenance?

  • Maintains dynamic equilibrium between deposition and erosion
  • Interference with sediment flow can cause dramatic coastal changes
• What happened to sediment flow after the construction of the Aswan High Dam?

  Sediment volume fell from 130 million tonnes to about 15 million tonnes.
• What dramatic effect did the Aswan High Dam have on erosion rates at Rosetta?

  Erosion rates increased from 20-25 m/yr to over 200 m/yr.
• What are the consequences of decreased sediment flow due to dam construction?

  • Impacts on longshore drift (LSD)
  • Increased coastal erosion in Ghana and neighboring countries