A Level Geography - Coastal Systems

• Coastal erosion threatens coastal communities, property and infrastructure.
• What are the four key components that a system has?

  - Inputs

  - Outputs

  - Flows

  - Stores of energy and sediment
• Give an example of an input in a coastal system?

  Sediment can be brought into the system in various ways. Energy inputs come from waves, wind, tides and currents.
• Give an example of an output in a coastal system?

  Sediment can be washed out to sea, or deposited further along the coast.
• Give an example of a flow in coastal system?

  processes such as erosion, weathering, transportation and deposition can move sediment within the system.
• Give an example of a store in a coastal system?

  Landforms such as beaches, dunes and spits are stores of sediment.
• What is an isolated system?

  Isolated systems do not interact with anything outside the system boundary, as a result there are no inputs of energy or matter. These types of systems are very rare in nature and most controlled lab experiments are this type of system.
• What is a closed system?

  Closed systems have inputs and outputs of energy but not matter.
• What is an open system?

  Open Systems are ones where there are inputs and outputs of both matter and energy across the boundary. Most ecosystems are examples of open systems.
• Define dynamic equilibrium

  If the inputs and outputs of a system are the same then the system is at equilibrium. If something happens to break this equilibrium the system will change to restore the equilibrium. This is known as dynamic equilibrium when the system responds to disturbance.
• What is feedback?

  If one of the elements of the system changes, for example there is increased deposition on a beach but there is no corresponding change in the amoount of sediment removed from the beach, then the beach features may change and the equilibrium upset. This is called feedback.
• What is positive feedback?

  Positive feedback tends to magnify a process and increase its output.

  
  

  For example, as a beach starts to form it slows down waves, which can cause more sediment to be deposited, increasing the size of the beach. the new equilibrium is reached when the long term growth of the beach stops.
• What is negative feedback?

  Negative feedback is when a change in the system causes other changes that have the opposite effect. For example, as a beach is eroded, the cliffs behind it are exposed to wave attack. Sediment eroded from the cliffs is deposited on the beach, causing it to grow again.
• Where is the littoral zone?

  The area of land between the cliffs or dunes on the coast and the offshore area that is beyond the influence of the waves.
• where is the backshore?

  The area between the high water mark (HWM) and the landward limit of marine activity. Changes normally take place here only during storm activity.
• Where is the foreshore?

  The area lying between the HWM and the low water mark (LWM). It is the most important zone for marine processes in times that are not influenced by storm activity.
• Where is the inshore area?

  The area between the LWM and the point where waves cease to have any influence on the land beneath them.
• Where is the offshore area?

  The area beyond the point where waves cease to impact upon the seabed and in which activity is limited to deposition of sediments.
• Where is the nearshore area?

  The area extending seaward from the HWM to the area where waves begin to break.
• Where is the swash zone?

  The area where a turbulent layer of water washes up the beach following the breaking of a wave
• Where is the surf zone?

  The area between the point where the waves break, forming a foamy, bubbly surface and where the waves move up the beach as swash in the swash zone.
• What is swash?

  Turbulent layer of water that washes up the beach after a wave has broken
• Where is the breaker zone?

  The area where waves approaching the coastline begin to break, usually where the water depth is 5 to 10m.
• What creates waves?

  Waves are mostly formed by wind blowing over the surface of the sea.

  Some tsunami waves are formed by underwater tectonic activity or landslides.
• How does the wind form waves?

  The friction between the wind and the surface of the sea gives the water a circular motion.

  
• What factors determine the height of waves?

  Wave height is affected by the wind speed and the fetch of a wave. The fetch is the maximum distance of sea the wind has blown over in creating the waves. A high wind speed and long fetch will create higher and more powerful waves.
• Why do waves break?

  As the waves approach the shore they break. Friction with the sea bed slows the bottom of the waves and makes their motion more elliptical. The crest of the wave rises up and then collapes.

  
• What is backwash?

  The movement of water back down the beach due to gravity.
• Define wave height?

  This is the distance from the calm sea level to the maximum height of the wave (crest).
• Define wavelength?

  The distance between two corresponding parts of a wave.
• Define wave period?

  The time it takes one wavelength to pass a fixed point.
• What is wave velocity?

  Wave velocity (measured in metres per second) is equal to the product of the wavelength and frequency of the wave.
• What is wave frequency?

  The number of wave crests that pass a fixed point each second.
• Describe the wave height of constructive and destructive waves?

  -Constructive waves have a low wave height.

  -Destructive waves have a high wave height. Usually over a metre.
• Describe the steepness of constructive and destructive waves?

  -Constructive waves tend to be quite flat.

  -Destructive waves are very steep
• Describe the wave length of destructive and constructive waves?

  -Destructive waves have a small wave length only 20 metres between crests.

  -Constructive waves have a long wave length, usually 100 metres between crests.
• Describe the wave period of constructive and destructive waves?

  -Constructive waves have a long wave period. Usually 7.5 to 10 secs.

  -Destructive Waves have a short period (4 to 6 secs)
• Describe the frequency of constructive and destructive waves?

  -Constructive waves have a low frequency (6 to 8 breaks per min)

  -Destructive waves have a high frequency

  (10 to 14 breaks per minute)
• Describe the energy of constructive and destructive waves.

  -Constructive waves are very low energy

  -Destructive waves are very high energy.
• Describe the swash of constructive and destructive waves?


  Constructive waves have a strong swash and weak backwash. Whereas destructive waves have a weak swash, but a strong backwash.