Coastal systems and landscapes advanced information Flashcards
what is an input
Sediment can be brought into the system through wind, waves, tides, and currents.
what is an output
Sediment can be washed out to sea or deposited further along the coast.
What is a flow/transfer
Processes such as erosion, weathering, transportation, and deposition move sediment within a system.
What is a store/component
Landforms such as beaches, dunes and spits are stores of sediment.
What is dynamic equilibrium
Coasts are often in dynamic equilibrium where inputs and outputs are balanced. A change in one input or output causes negative feedback that restores balance.
What is a negative feedback
When a change in a system causes other changes that have the opposite effect.
E.g beach eroded, exposes cliffs to wave attacks, sediment eroded from cliffs restores beach.
What is positive feedback
When a change in a system causes other changes that have a similar effect.
E.g As a beach forms it slows down waves, causes more sediment to be deposited, increasing the size of the beach.
How is wind a source of energy in coastal environments
Wind is created by air moving from areas of high pressure to areas of low pressure.
Strong winds can generate powerful waves. Prevailing winds where wind blows in the same direction for a long time can cause high energy waves.
How are waves a source of energy in the coastal system
Created by wind blowing over the sea, the friction between them gives a circular motion to waves.
High wind speed and long fetch create higher waves. Friction with sea bed slows wave and makes it oval shaped then the crest of the wave rises up and collapses.
What is a constructive wave
Low frequency.
Low and long.
Powerful swash to deposit material up the beach.
What is a destructive wave
Higher frequency.
High and steep.
Strong backwash removes material from the beach.
How are tides a source of energy
Tides are the periodic fall and rise of the ocean surface caused by the moons gravity.
Tides affect position waves break on the beach. Area of land between maximum high tide and minimum low tide is where landforms are destroyed and created.
How are currents a source of energy
A current is the general flow of water in one direction caused by wind or by variations in temperature and salinity.
Currents move material along the coast.
What is a low energy coast
Low input of energy meaning small gentle waves. Caused by gentle offshore winds. Often have saltmarshes or tidal mudflats. Rate of deposition is often higher than rate of erosion.
What are the sediment sources in coastal systems
Rivers carry sediment from inland.
Sediment eroded from cliffs by waves and weathering.
Sediment from crushed shells of marine organisms.
Waves, tides and currents transport sediment into the coastal zone from off-shore deposits.
What is a sediment budget
The difference between the amount of sediment that enters and leaves the system.
Positive sediment budget - coastline advances.
Negative sediment budget - coastline retreats.
What is a sediment cell
Coast is divided into sediment cells. They are enclosed systems so sediment is not transported between them. Each cell is a closed coastal system.
What is abrasion (type of erosion)
Bits of sediment carried by the waves are smashed against cliffs and rocks causing bits to fall off.
What is hydraulic action (type of erosion)
Air in cracks in the cliff are compressed by water from waves. Causing high build up of pressure which causes rock to break off.
What is cavitation (type of erosion)
As waves recede compressed air expands violently exerting pressure on the rock and causing bits to break off.
What is wave quarrying (type of erosion)
Energy of a wave when it crashes against a rock is enough to break bits off.
What is solution/corrosion (type of erosion)
Soluble rocks like chalk are gradually dissolved by the seawater.
What is attrition (type of erosion)
Bits of rock in the water smash against each other and break.
What is solution (type of transportation)
As sediment is dissolved in the water it is carried by the water like chalk when it’s dissolved in the water.
What is saltation (type of transportation)
Larger bits of sediment like pebbles are too heavy to be carried in suspension so are bounced along the sea bed by the force of the water.
What is suspension (type of transportation)
Very fine sediment such as clay is whipped up by turbulence and carried along by the water.
What is traction (type of transportation)
Very large particles like boulders are pushed along the seabed by the force of the water.
What is longshore drift (type of transportation)
When swash carries sediment up a beach parallel to the prevailing wind and backwash carries sediment down the beach at right angles to the shoreline.
What is marine deposition
When sediment carried by seawater is deposited.
What is aeolian deposition
When sediment carried by the wind is deposited.
Why does deposition occur
When sediment load is exceeded by landslide for example.
Friction increases like waves in shallow water and wind over land the water or wind is slowed down.
Flow becomes turbulent such as a rock in the water.
If wind slows waves will also lose energy.
What is salt weathering
Saline water enters cracks in rocks. As the tide goes out and water evaporates salt crystals form. As they form they expand and exert pressure on rock causing bits to break off.
What is freeze-thaw weathering
Occurring areas where temperatures go above and below 0 degrees when water enters cracks in rocks and then temperature drops below 0 degrees the water will freeze and expand. This puts pressure on the rock causing bits to fall of.
What is Chemical weathering
Breakdown of rock by changing its chemical composition. For example carbonic acid reacting with carboniferous limestone causing it to dissolve.
What is wetting and drying (type of weathering)
Some rock contains clay. When it gets wet it expands. The pressure it exerts causes parts of the rock to break off.
How does a saltmarsh/mudflat form
Form in sheltered, low energy environments like an estuary.
Silt and other sediment is deposited where the tide and river meet. Flocculation(particles hit into each other).
Mudflat forms.
Colonised by salt resistant halophytes. Vegetation then traps more silt and mud building saltmarsh upwards.
Less salt resistant vegetation can grow as the saltmarsh is submerged for a smaller period of time.
What are coastlines of emergence
When sea level falls a new coastline emerges from the sea.
What are fjords)
Fjords form from glacial cut valleys. They are narrow with very steep sides. They have a shallow mouth with a raised bit of ground called a threshold formed through deposition from the glacier. Can be up to 1000m deep in some places.
What are the predicted impacts of climate change on coasts
Increases in temperature will cause a rise in sea level due to the melting of ice sheets and the thermal expansion of water.
Sea level currently rises by 2mm a year if greenhouse gas emissions remain high it is predicted to go up to 8-16mm a year by 2100.
What is hard engineering
Building defensive structures.
What is a sea wall
Absorbs wave energy and reflects it back out to sea.
Expensive to build and maintain and is ugly.
What is a groyne
Fences built at right angles to the shoreline. Prevent longshore drift taking sediment away from the beach creating wider beaches.
Cheap to build but starves beaches down the coast.
What is soft engineering
Involves coaxing natural processes along.
What is beach nourishment
Sand is added to beaches from elsewhere making them wider and more resistant to erosion.
What is beach stabilisation
Plants and vegetation is planted on beaches to stabilise them and make them wider which makes cliffs more resistant to erosion.
Is hard or soft engineering more sustainable
Hard engineering interferes with natural processes and is expensive to maintain. Soft engineering is cheaper and only encourages natural processes. Therefore soft engineering is more sustainable.
What is shoreline management
The coastline is split into sediment cells. All local authorities in the sediment cell come up with a plan called an SMP. The plan is devised to protect important sites without causing issues in other areas of the coastline. They can decide to hold the line, advance the line or do nothing.
What is integrated coastal zone management
The water and land are seen as interdependent. The plan considers all aspects such as economic, social, land and sea when devising a strategy. Aims to protect the coastline in a relatively natural way. Considers different uses of the coastline like fishing or tourism. Local, regional and national authorities all have input into the plan.
