threats to people at the coast

• What is dredging?

  • The removal of sediment from rivers or the sea
  • This impacts on the amount of sediment being deposited at the coast
• Why is dredging done?

  to deepen the area e.g for ports to facilitate the incoming and outgoing of ships
• What effect does the construction of dams have on the coast?

  • The construction of dams, traps river sediment behind the dam wall 
  • It is estimated 100 billion tonnes of sediment is stored behind the world's dams and this increases by a billion tonnes each year
  • Like dredging, this starves the coast of sediment
  • The reduction of sediment supplied to the coast due to dams and dredging leads to greater coastal erosion because:
  • Beaches decrease in size as they are not being supplied with sediment
  • Destructive waves have more impact by increasing the rate of coastal erosion
• How does coastal management affect coastal recession?

  • Coastal management can impact on the rate of recession because it affects the rate of erosion
  • In some areas coastal defences like sea walls and rip rap reduce the amount of erosion,this slows recession of the coast
  • In other areas coastal management affects the movement of sediment: Groynes at Hornsea on the Holderness coast reduce longshore drift this starves areas down the coast such as Mappleton of sediment also known as terminal groyne syndrome
• What is terminal groyne syndrome?

  • Groynes on the coast reduce longshore drift
  • This starves areas down the coast such as Mappleton of sediment, thus makes them more vulnerable to erosion
• What are rates of recession influenced by?

  different factors both short and longer term which include:

  • Wind direction/fetch
  • Tides
  • Seasons
  • Weather systems
  • Occurrence of storms
• How does wind direction fetch influence the rate of recession?

  • Wind direction at the coast varies and may change every day
  • The wind can be onshore or offshore
  • Rates of erosion (and so recession) are greater when winds are blowing onshore
  • In most areas, wind generally comes from one main direction - this is known as the prevailing wind direction
  • When prevailing wind direction is also the direction of the largest fetch this can lead to the build-up of large destructive waves causing rapid erosion
• How do tides influence the rate of recession?

  tides are the result of the gravitational pull of the moon and the sun

  the difference between high tide and low tide is called the tidal range

  high tide occurs twice a day

  rates of recession are greatest during high tide because this is the time when the water and waves reach the backshore

  the waves also have more energy when they reach the backshore leading to more erosion
• How do the different seasons affect the rate of coastal recession?

  • Rates of recession are likely to be greater in winter than in summer because, storm events that cause destructive waves are more common in winter months
• How do weather systems affect rates of coastal recession?

  • The UK is located between warm tropical air and cold polar air
  • It experiences periods of both high pressure (anticyclones) and low pressure (depressions)
  • During anticyclones there are gentle winds and low waves, so rates of recession are low
  • During depressions the winds are much stronger, leading to high waves and greater rates of recession
• How do storms affect coastal recession?

  storms lead to high energy destructive waves

  these waves increase the rates of erosion and thus, coastal recession

  • In Cornwall, over a two-week period, 1,350 cubic metres of cliff face was eroded along a 300-metre stretch of coastline, as a result of the 2013/14 storms
• How do storms affect coastal erosion?

  storm events are deep depressions (very low pressure)

  they produce large, high energy destructive waves and fast rates of recession

  global warming is predicted to increase intensity of atmospheric circulation, thus more frequent storm events as well as a higher intensity of storm events, thus increasing the rate of coastal recession
• How does wind direction and fetch affect coastal recession?


  winds change direction daily as different weather systems pass across or near the UK

  rates of recession will be higher when the wind is blowing onshore

  when wind blows from prevailing wind direction, strong winds produce large destructive waves and rapid recession

  where wind blows from a direction where there's a large fetch, builds up large destructive waves
• What is the difference between dominant wind and prevailing wind?

  dominant wind is the direction of the strongest wind

  prevailing wind is the direction of the most common wind
• businesses impact

  smaller businesses on receding coastlines may be abandoned, causing job losses for local people
• why is it difficult to sell coastal property?


  as homes on receding coastlines lose their value very quickly, people don't want to buy property that might end up in the sea in the next 20 years

  residents sometimes have to abandon their property
• what does coastal recession cause (social impact)?


  coastal recession forces people to relocate, which can break up communities and cause depopulation

  those who stay will feel isolated, particularly if loss of infrastructure leaves them disconnected from other places