The Coastal System Flashcards
What are the inputs in a coastal system?
Sediment can be brought into the system in various ways. Energy inputs come from wind, waves, tides and currents.
What are the outputs in a coastal system?
Sediment can be washed out to sea, or deposited further along the coast.
What are the flows in a coastal system?
Processes such as erosion, weathering, transportation and deposition can move sediment within the system.
What are the stores in a coastal system?
Landforms such as beaches, dunes and spits are stores of sediment.
Define a negative feedback loop?
Its 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 in size.
Define a positive feedback loop?
A positive feedback is when a change in the system causes other changes that have a similar effect. 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 long term growth of the beach stops.
How are waves created and what gives the water a circular motion?
Waves are created by the wind blowing over the surface of the sea. The friction between the wind and the surface of the sea gives the water a circular motion.
What is the wave fetch?
The fetch is the maximum distance of sea the wind has blown over in creating the waves.
How do waves break?
As they approach land they break, the bottom of the wave touches the sand and slows down due to increased friction. The top of the wave becomes higher and steeper until it topples over.
Name 4 characteristics of a constructive wave?
Low frequency (6-8 waves per minute), they’re low and long and have a more powerful swash than backwash which carries material up the beach.
Name 4 characteristics of a destructive wave?
High frequency (10-14 waves a minute), high and steep. They have a more powerful backwash than swash which removes material from the beach.
What are tides?
Tides are the periodic rise and fall of the ocean surface, caused by the gravitational pull of the Moon and the Sun.
What is a current?
A current is the general flow of water in one direction - it can be caused by wind or by variations in water temperature and salinity.
What is the sediment budget?
The difference between the amount of sediment that enters the system and the amount that leaves the system.
What is a positive sediment budget?
If more sediment enters than leaves, its a positive sediment budget and overall the coastline builds outwards.
What is a negative sediment budget?
If more sediment leaves than enters, its a negative sediment budget and overall the coastline retreats.
What are sediment cells?
These are lengths of coastline (often between headlands) that are entirely self contained for the movement of sediment (sediment does not move between the cells). This means that processes going on in one cell does not affect the movement of sediment in another cell -each cell is a closed coastal system.
Name three factors that affect the size of the wave?
Wind speed and duration.
Fetch- the distance over which the wind is has blown. Large fetch = destructive whereas a short fetch = constructive.
Shape of the ocean floor and coast.
Describe wave refraction?
As the wave approach’s a coast they are refracted so that their energy is concentrated around headlands but reduced around bays. Waves then tend to approach coastline parallel to it, and their energy decreases as water depth decreases.
Describe a spring tide?
When the moon is between the Earth and the sun, the combined gravitational pull creates the biggest bulge of water and the highest tide. At this time the high tides are at their highest at the low tides are at their lowest, so the tidal range is at its greatest.
Describe a neap tide?
When the Earth, moon and the sun form a right angle, their gravitational pulls interfere with one another and this is when neap tides occur, giving the lowest high tides and the highest low tides (smallest tidal range). Small tidal range concentrates wave attack zone and is associated with smaller beaches and smaller wave cut platforms (e.g. Mediterranean Sea).
