Longshore Drift is the transport of sand and pebbles along the coastline. The prevailing wind (the direction the wind usually blows from) causes the waves to approach the coast at an angle. The swash carries the sand and pebbles up the beach at the same angle (usually 45 degrees). The backwash, however carries the material back down the beach at right angles as this is the steepest gradient. If a pebble was placed in the water it would be carried along the coastline in a Zig-zag motion and would eventually be deposited when the waves lose energy. The genearl direction of the longshore drift is decided by the prevailing wind. In the diagram below the prevailing wind is approaching from the south-west. Therefore the longshore drift is moving material west to east.
Each coastal council spends a significant amount of money on sea defences each year and the Eastbourne coastline has a vigorous line of defence. The introduction of the harbour at the crumbles which was first proposed in the 1960's, The Water Agency petitioned against the proposal because of the detrimental effects they considered the harbour would have on coastal processes and the exsiting sea defences. However in 1980 a bill was enacted as the Eastbourne harbour act which enabled developers to proceed. In 1988 an agreement was entered into with Southern Water for the purpose of safeguarding the sea defences in front of the proposed 3000 houses. In the winter of 1999/2000 there was a near failure of the defences and resulted in 450 meter long revetment and shingle replenishment costing £2.5 million.
Questions to qualify
1. At stage one discribe the sea defence to prevent the effects of longshore drift.
2. Discribe what you can see at this stage that shows that Longshore drift occurs?
3. From what you can see, which direction does the longshore drift move?
4. At stage two there is a semi buried stairway, how many upright post support the Stainless rail on the East side?
5. At stage three discribe the man made sea defence.
6. From what you have read and can see what if any are the effects of the sea defences at stage three on the Pevensey bay coastline which is a few miles past the harbour?
7. Please post a picture if you wish but do not show the stage clues
Finally please emai/ message your answers to me before posting a found log.