Why are coasts considered natural systems?
They have inputs, outputs, flows and stores of sediment and energy.
What are the inputs of sediment into the coastal system?
- Eroded sediment from rivers and cliffs.
- Crushed shells of marine organisms.
- Offshore deposits transported by waves, tides and currents.
- Sediment from the formation of estuaries from sea levels rising.
What are the inputs into the coastal system?
Energy - wind, waves, tides and currents.
What are the outputs of coastal systems?
Sediment washing out to sea or being deposited further along the coast.
What are the flows/transfers within the coastal system?
What are the stores/components of the coastal system?
Landforms, eg beaches, dunes and spits.
Give an example of negative feedback in the coastal system:
- Beach is eroded.
- Cliffs are exposed to wave attack.
- Sediment eroded is deposited on beach.
- Beach grows in size.
Give an example of positive feedback in the coastal system:
- Beach forms.
- Waves slow down.
- More sediment is deposited.
- Beach size increases.
What do negative feedbacks do to the system?
Restore the balance of the system.
What do positive feedbacks do to the system?
Change the balance of the system.
Create a new equilibrium.
What are the sources of energy in the coastal system?
What are winds created by?
Air moving from areas of high pressure to areas of low pressure.
What can strong winds generate?
When the wind blows from the same direction.
What type of waves do prevailing winds cause?
Higher-energy waves than winds that change direction frequently.
What are waves created by?
Wind blowing over the surface of the sea, causing friction and giving the sea a circular motion.
The effect of a wave on the shore depends on what?
The height of the wave.
What is wave height affected by?
Fetch of the wave
The maximum distance of sea the wind has blown over in creating the waves.
High wind speed and long fetch create what sort of waves?
Higher and more powerful waves.
What causes a wave to break as it nears the shore?
- Friction with sea bed slows the bottom of the waves.
- Wave motion becomes more elliptical.
- Crest rises up and collapses.
What is the frequency of constructive waves?
6-8 waves per minute
What is the frequency of destructive waves?
10-14 waves a minute
Describe constructive waves:
- Low frequency
- Low & long
- Elliptical cross profile
- Powerful swash deposits material
Describe destructive waves:
- High and steep
- Circular cross profile
- Higher frequency
- Strong backwash removes material from the beach
Periodic rise and fall of the ocean surface caused by the gravitational pull of the Moon and the Sun.
What do the tides affect?
The position at which waves break on the beach.
The general flow of water in one direction which moves material along the coast.
Can be caused by wind or by variations in water temperature and salinity.
Give the characteristics of high-energy coasts:
- Inputs of energy from large, powerful waves.
- Sandy coves
- Rocky landforms
- Rate of erosion is higher than rate of deposition.
Give the characteristics of low-energy coasts: