Sandbanks

• describe the location of Sandbanks


  • in Poole, Dorset on south coast of England

  • on a spit about 1km long that extends into the mouth of Poole Harbour
• What are the physical factors meaning management is needed?


  1. prevailing wind from SW means that waves have a large fetch from across Atlantic Ocean, so high energy

  2. climate change means sea levels will rise 0.6m in the next 100 years- will flood many properties and breach the spit and lowest point

  3. without management, £18 million of damage will occur to properties in 10 years

  4. very complex longshore drift patterns- longshore drift beyond spit could cause harbour entrance to become shallow
• What is the prevailing wind direction affecting Sandbanks?

  • from the SW

  • waves have a large fetch from across Atlantic Ocean
• Where is the spit likely to be breached if sea levels rise?


  at the junction of Shore Road and Banks Road as this is just 2m above sea level and 50m wide- will cut off from mainland
• What are the socio-economic factors meaning management is needed?

  1. many high value properties

  2. beach is major tourist attraction

  3. spit provides shelter to Poole Harbour, for water sports and used by commercial ships
• How high value are the properties on Sandbanks?


  • 4th most expensive properties in the world per m2

  • Sandbanks Hotel and Haven Hotel provide income through tourism and employment
• Why is the beach important socio-economically?


  major tourist attraction- has a Blue Flag Award due to water quality and safety for swimming
• How is the spit important to Poole Harbour?


  it provides shelter from waves- safe place for water sports and commercial ships use it to carry timber
• What is the shoreline management plan at Sandbanks?

  hold the line
• What does 'hold the line' mean?


  intervene against coastal erosion with hard or soft engineering techniques to prevent further retreat
• What is the concern about the defences for the future?


  risk that sea level rise will make management more difficult- making defences increasingly expensive
• Who is the defences at Sandbanks managed by?


  1. Poole Harbour Commissioners

  2. Poole Borough Council

  3. Environment Agency
• What plan are the defences part of?


  the Two Bays Shoreline Management Plan in the sediment cell covering Poole Bay and Christchurch Bay
• What defences have been put in at Sandbanks?

  groynes and beach renourishment
• How many groynes were constructed? Cost?

  1. 10 wooden groynes and 5 rock groynes constructed

  2. each groyne cost £100,000
• What is the aim of the groynes?


  limit sediment movement by longshore drift and loss of beach sediment
• What has been the influence of the groynes on physical processes?


  1. maintain a wide, deep beach

  2. minimise sediment movement by LSD- restricts sediment entering harbour

  3. more sand absorbs wave energy and reduces erosion rates
• What would erosion rates by without the groynes?

  1.6m/year
• What is beach renourishment?


  sand from other sources is used to replace sediment lost from beaches through LSD or erosion
• How is beach renourishment done at Sandbanks?


  sand is dredged from offshore and sprayed onto beach, this is called 'rainbowing
• How much does beach renourishment cost?

  £20 per m3
• What is the issue with this?


  recent trial showed that dumping sediment from the harbour just offshore is much cheaper (£3) and natural currents will eventually transport this sediment onshore to build up beaches
• How much sand has been added to Poole Bay beaches by renourishment?

  over 35 million m3
• What has been the impacts of beach renourishment on coastal processes?


  1. wide beaches absorb more wave energy and water percolates after swash and reduces erosion rates
• What are the impacts of the groynes at Bournemouth on Sandbanks?


  1. groynes at Bournemouth hold back sediment, preventing longshore drift moving it east towards Sandbanks

  2. less sediment is available to be trapped at Sandbanks, and erosion may remove existing sediment, reversing positive impacts