Coasts are shaped by the sea and the action of waves. The processes that take place are erosion, transportation and deposition.
The size and energy of a wave is influenced by:
- how long the wind has been blowing
- the strength of the wind
- how far the wave has travelled
Waves can be destructive or constructive
With a contructive wave-The swash is stronger than the backwash
With a destrictive wave- Backwash is stronger than the swash.
Dissolving rocks such as limestone and chalk because of the acids contained in the sea water.
Crushes pebbles into each other. They break and become smoother.
Waves with rock and sand grind against the cliffs, a bit like sandpaper!
Waves push air into the cracks in the cliffs, and erodes away.
Cliffs are one of the most common features in coastlines.
Cliffs are shaped through erosion and weathering. (Breakdown on rocks due to weather conditions!)
soft rock, like sand and clay erodes easily
Hard rock like chalk erodes slowly.
Process of cliff erosion
- Weather weakens the top of the cliff.
- The sea attacks the base of the cliff forming a wave-cut notch.
- The notch increases in size causing the cliff to collapse.
- The backwash carries the rubble towards the sea forming a wave-cut platform.
- The process repeats and the cliff continues to retreat.
A Destructive wave causes erosion!
Soft coastlines erode more easily, because the sand and clay are not a strong structure, there fore erode more easily.
when a wave erodes a headland it sometimes creates a cave!
A wave cut notch can be caused by hydraulic action but being started by a crack in the rock.
holbeck hall hotel
It eroded because of soft rock which is easily weathered such as heavy rainfall causing it to fall down into a slipping plane.
The development of Spurn Head
- Longshore drift moves material along the coastline.
- A spit forms when the material is deposited.
- Over time, the spit grows and develops a hook if wind direction changes further out.
- Waves cannot get past a spit, which creates a sheltered area where silt is deposited and mud flats orsalt marshes form.
Is like a spit! But connects an island to a mainland. (Think of minecraft)
What they put in the sea to help erosion and cliffs.
Hard engineering methods!
Sea wall: Moves energy of the wave away from the coast.
Rock armour (rip-rap) : Cheaper than the sea wall. Sloping feature that breaks up or absorbs the energy of the wave, but may still let water and sediment through.
gabions: Metal cage stacked with rocks to form a wall. used to protect the the cliffs but they are short term as they damage easily.
A breakwater: Often used to protect a harbour but can be used for a coastline.
Groynes: designed to slow down long shore drift and build up the beach.
Swash and backwash
Swash: The foam that comes onto the sand from the wave.
Back wash: The water that comes away from the swash.
Caused by prevailing winds, Sediments of the beach being brought along by the swash and backwash.
What is a bar?
A bar is similar to a spit but it carries along and creates its own land and oins to another piece of land.
Instead of trying to stop nature, soft engineering is ways of working with nature!
Soft engineering techniques.
Letting the coast flood, and using ways to work with it.
Eg, letting farmland flood from the sea, using the water to grow trees.
Beach replenishment: Instead of using groynes, they put more sand down to soak up the water. (Using a way to control flooding but making the beach look nice at thee same time.)
Beach recyling: As pieces of beach sediments (rocks, sand etc) Move from west to east, some parts of the beach loose some sediments and gain some sediments. To try and even this out material is moved back into there original position to eeven out the beach!