The Coastal System Flashcards
What are the features of a system?
They have inputs, outputs, flows and stores of sediment and energy.
What are the inputs of the coastal system?
- Sediment enters the system in many ways e.g. fluvial sediment
- Energy inputs: wind, waves, tides and currents
What are the outputs of the coastal system?
- Evaporation
- Sediment: deposited further along coast
What are the flows/transfers of the coastal system?
Processes:
- Erosion
- Weathering
- Transportation
- Deposition
What are the stores/components of the coastal system?
Landforms:
- Beaches
- Spits
- Bars
- Dunes
Coastal systems are generally in D____________ E________________.
DYNAMIC EQUILIBRIUM - (Inputs and outputs are balanced)
What is meant by negative feedback?
A change in the system causes other changes that have the opposite effect.
Negative feedback - restores the balance of the system.
Give an example of negative feedback in the coastal system
Beach eroded Cliffs behind it exposed to wave attack Sediment eroded from cliffs Deposition Beach grows in size
What is meant by positive feedback?
A change in the system causes other changes with a similar effect.
Give an example of positive feedback in the coastal feedback
Beach starts to form
It slows down waves
Causes more sediment to be deposited
Increases size of beach
NEW EQUILIBRIUM IS REACHED WHEN LONG TERM GROWTH OF THE BEACH STOPS
What is a landform?
Individual features which are created by coastal processes
What is a landscape?
The entire area of sea, coastline and immediate land behind the sea front. Within the landscape are characteristic landforms.
What are the 4 sources of energy in coastal systems?
- Wind
- Waves
- Tides
- Currents
Winds are created by a__ moving between areas of h____ p_______ to areas of l__ p_______.
The steeper the gradient…
Air
High pressure
Low pressure
… the faster the winds move.
Strong winds can generate powerful w_______.
What are prevailing winds?
Waves
Are winds that consistently blow from the same direction, causing higher-energy waves that change direction frequently.
Waves are created by the _____ blowing over the surface of the sea.
The friction between the 2 causes gives the water a ________ ________
Wind
Circular motion
The effect of a wave on the shore depends on its _____
This is affected by wind _____ and the f____ of the wave.
A higher wind speed and a longer fetch create ________ and more __________ waves
Height Speed Fetch Higher Powerful
What is the swash?
Water washing up beach
What is the backwash?
Water washing back towards the sea
What are the characteristics of constructive waves?
Low frequency
6-8 per minute
Low and long
Powerful swash = deposition
What are the characteristics of destructive waves?
Higher frequency
10-14 per minute
Higher and steeper (a more circular cross profile)
Stronger backwash = erosion
What is meant by wave frequency?
How many waves pass a point in a particular time
What is a tides?
The periodic rise and fall in the level of the sea caused by the gravitational pull of the sun and the moon.
Tides affect the position at which waves b____ on the beach.
High tide - they break _______ up the shore
Break
Higher
Where are most landforms created and destroyed?
Between the high and low water mark?
What are spring tides?
Help
What are neap tides?
Help
What is a tidal range?
The difference in height between the low and high tide marks
A small tidal range leads to erosion being…
concentrated at base of cliff
What are currents?
The general flow of water in one direction
Currents are caused by…
Currents move material along the coast.
Wind or by variations in water temperature and salinity
HIGH-ENERGY COASTS
- Recieve high inputs of energy in the form of large, powerful w_______
- These are caused by…
- strong winds
- long fetches
• Landforms include:
- Cliffs, caves, stacks and arches
The rate of erosion is…
Waves
Higher than the rate of deposition
LOW-ENERGY COASTS
- Low input of energy (small and gentle waves, due to sheltered nature of area, short fetches)
- Reef or Island offshore can protect a coast from powerful waves
- Landforms
- Saltmarshes
- Tidal mudflats
• The rate of deposition…
Is often higher than the rate of erosion
What are the sources of sediment in the coastal system? (5)
- Rivers (carry material from inland)
- Sea level rise floods river valley forming estuary, estuary sediment becomes part of the coastal system
- Sediment is eroded from cliffs (mass movements too)
- Waves, tides and currents can transport sediment into the coastal zone from offshore deposits (eg sandbanks)
- Wind - aeolian processes
What is the sediment budget?
The difference between the amount of sediment that enters the system and the amount that leaves
What is meant by a positive sediment budget?
More sediment enters than leaves
Coastline builds outwards
What is meant by a negative sediment budget?
More sediment leaves than enters
Coastline retreats
What are sediment cells (or littoral cells)?
A stretch of coastline within which sediment movement is more or less contained.
Processes of one cell do not affect the movement of sediment in another cell, (cells are closed systems)
