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theme b - Coggle Diagram

- - - - Relatively inexpensive.
      - Helps to trap the sand as it is carried along the shore by longshore drift
      - Easy to build into the coastline
    - - Wooden groynes need constant maintenance and replaced every 10 – 15 years.
      - Some people do not like the look of the groynes and people who like to walk along the beach don’t like having to climb up over these barriers.
      - As the groynes help to build up a beach in one place, there will be another place along the coastline that is now not getting any sand.
  - - - Gabions are just metal cages that are filled with rocks and are very inexpensive.
      - The rock cages are stacked together and as the waves hit the cages the wave energy is absorbed by the gaps in the rocks. This means that there is no energy left to cause any erosion.
      - Can be used very quickly to form a temporary or a more permanent solution.
    - - The cages are unattractive. Pollution and litter can build up which provides a breeding ground for rats.
      - The rock cages can often split due to the energy caused by winter storms. They need to be repaired and replaced frequently.
  - - - Protects the land and when built high enough will also prevent coastal flooding.
      - The curved sea wall will ensure that wave energy is reflected back out into the sea.
      - Sea walls can also help shape the landscape and provide walkways and urban architecture
    - - They need deep foundations – so will require a lot of building work. This can disrupt the natural habitats of animals.
      - As they reflect the wave energy back, this can cause coastal erosion either further along the coast or back in the sea where the waves eventually fall
      - The improvements in 2007 cost over £4 million for a relatively short section of wall.
      - Often require replacement every 25 years.
- - - - how long the wind is been blowing
      - how far the wave has travelled (fetch)
      - the strength of the wind
    - - constructive waves
        
        they break on the shore and depoisit material building up beaches
        
        they are created in calm weather and less powerful then destructive waves
        
        they have a long wavelength and are low in height
        
        they have a swash that is stronger than the backwash
        
        they are gentle -breaking at 6-9 waves per minute
    - - destructive waves
        
        erodes the coast line
        
        they have stronger backwash than swash
        
        occurs when wave energy is high an d the wave has a long fetch
        
        short wave length
        
        created in storm conditions-big strong waves are created when the wind is powerful- been blown for a long time- which creates energy
        
        high and steep
        
        more frequent-15 per min
  - - - waves can approach the coast at an angle because of wind. the swash of the wave carries material up the beach at an angle - the back wash flows back to the sea in a straight line 90 degrees - the movement of material is called transportation as the material is transports along the coast
      - continual swash and back wash transportation material sideways along the coast. this movement of materials is called long shore drift and occurs in a zigzag
    - - when the sea loses energy, it drops the sand, rock particles and pebbles that it has been carrying. this called depositions. depositions happens when the swash is stronger than the back wash and is associated with constructive waves
      - deposition is likely to occur when
        
        waves enter an area of shallow water
        
        waves entered a sheltered area e.g. a cave or bay
        
        there is little wind
        
        there is a good supply of material
    - - A
        
        attritin- waves smash rocks and pebbles on the shore into each other and they break and become smaller
      - S
        
        solution- acids contained in sea water dissolve some types of rock such as chalk or lime stonesol
      - C
        
        corrasion (abrasion)- when a wave hits the coast it throws pebble and sand against the cliff face. these break of small parts of the cliff and cause undercutting
      - H
        
        air may become trapped in joints and cracks on cliff face. when a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion
    - - bays are formed as the weaker soft rock sections of coastline are eroded. headlands stick out as they are harder, more resistant rock which aren't as easily eroded
        
        the formation and headlands may take thousands of years, but gradually the bay will become sheltered and sand will be depoisited. the sea will concentrated on eroding away the headland
    - - process of cliff erosion
        
        the sea attacks the base of the cliff forming a wave cut notch
        
        the notch increases in size causing the cliff to collapse
        
        weather weakens the top of the cliiff
        
        the backwash carries the rubble towards the sea forming a wave cut playform
        
        the process repeats and the cliff continues to retreat
      - a wave cut platform is the narrow flat area often seen at the base of a cliff
      - a cliff is a vertical rock face along the coast
    - - cave widens and deepens and becomes an arch e.g. dundle door, doorset
      - the waves erode the arch roof until it collapses, forming a stack
      - weak areas are pounded by waves and open to make a cave
      - headlands retreats. the stack is eroded until it becomes a stump
    - - the breaking down or dissolving of rocks and minerals on earths surface. water, ice, acids, salt, plants , animals and changes i temperature are all agents of weathring
      - once the rock has been broken down, process called erosion transports the bits of rocks and minerals away
      - process
        
        water freezes and expands forcing crack widens
        
        ice thaws contracts and water get deeper into cracks again
        
        water collects in rock crack
        
        repeated expansion and contraption causes further cracks till rocks splts
  - - - Longshore drift moves material along the coastline (erosion is taking place further back along the coastline). The prevailing winds help to transport material along the coast.
      - Deposited material starts to build up where the coastline changes direction.
      - A spit start to form 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 or salt marshes form.
    - - up of eroded material that has been transported from elsewhere and deposited by the sea.
      - Constructive waves help to build up beaches. The material found on a beach (i.e. sand or shingle) depends on the geology of the area and wave energy.
      - A cross-section of a beach is called a beach profile.
      - The material found on a beach varies in size and type as you move further away from the shoreline. The smallest material is deposited near the water and larger material is found nearer to the cliffs at the back of the beach.
      - Large material is deposited at the back of the beach in times of high energy, for example during a storm. Most waves break near the shoreline, so sediment near the water is more effectively broken down by attrition.
    - - This is a beach where strong swash waves will be assisted by windy and stormy conditions to throw larger pieces of shingle further up the beach. Shingle beaches will usually contain many different ridges across their profile.
        The smallest material will be found on the beach face and larger pieces of shingle/ pebble will be thrown to the back of the beach. Shingle beaches usually have much steeper profiles.
- - - - advantages
        
        Absorb the energy of waves. Allows the build-up of a beach.
      - disadvantages
        
        They can be expensive to obtain and transport the boulders. Can also look unattractive.
    - - advantages
        
        Prevents longshore drift moving beach material along the coast. Allows the build-up of a beach. Beaches are a natural defence against erosion and an attraction for tourists.
      - disadvantages
        
        They can be unattractive. Costly to build and maintain.
    - - advantages
        Protects the base of cliffs, land and buildings against erosion. They can prevent coastal flooding in some areas.
      - disadvantages
        Expensive to build and maintain. Curved sea walls reflect the energy of the waves back to the sea. This means that the waves remain powerful. Can also be unattractive.
  - - - Replaces beach or cliff material that has been removed by erosion or longshore drift.
      - The main advantage is that beaches are a natural defence against erosion and coastal flooding. Beaches also attract tourists.
      - Relatively inexpensive option but requires constant maintenance to replace the beach material as it is washed away.
    - - Areas of the coast are allowed to erode and flood naturally. Usually this will be areas considered to be of low value - e.g. places not being used for housing or farmland.
      - The advantages are that it encourages the development of beaches (a natural defence) and salt marshes (important for the environment) and cost is low.
      - Managed retreat is a cheap option, but people will need to be compensated for loss of buildings and farmland.