Coasts Flashcards
What does the size and energy of the wave depend on?
-the fetch- how far the wave has travelled
-the strength of the wind
-how long the wind has been blowing for
What is the swash and backwash?
A swash is the wave to comes up a beach
A backwash is the water that flows back towards the sea
What are the characteristics of destructive waves?
-weak swash and strong backwash
-occurs in stormy conditions, with strong winds
-the strong backwash removes sediment from the beach
-the waves are steep and close together
-tall waves with short wavelength
-they arrive quickly and have a high frequency – a lot of them come in a short period of time
What are the characteristics of a constructive wave?
-small waves, with low wave height and long wavelength
-occurs in calm conditions, without much wind
-strong swash and weak backwash
-the strong swash brings sediments to build up the beach
-the backwash is not strong enough to remove the sediment
-the waves are low and further apart
What is freeze-thaw weathering?
Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable
-Water enters cracks in the rock.
-When temperatures drop, the water freezes and expands causing the crack to widen.
-The ice melts and water makes its way deeper into the cracks.
-The process repeats itself until the rock splits entirely.
Explain the process of biological weathering
Plant roots can get into small cracks in the rock.
As the roots grow, the cracks become larger.
This causes small pieces of rock to break away.
Explain chemical weathering
Rainwater and seawater can be a weak acid. If a coastline is made up of rocks such as limestone or chalk, over time they can become dissolved by the acid in the water.
What is mass movement?
the downhill movement of sediment that moves because of gravity
What is rock fall?
Bits of rock fall off the cliff face, usually due to freeze-thaw weathering.
What is mudflow?
Saturated soil (soil filled with water) flows down a slope.
What is a landslide?
Large blocks of rock slide downhill.
What is a rotational slip?
Saturated soil slump down a curved surface.
What is longshore drift?
Longshore (littoral) drift is the movement of material along the shore by wave action. It happens when waves approach the beach at an angle. The swash (waves moving up the beach) which moves in the prevailing wind direction angle, carries material up and along the beach. The backwash (waves moving back down the beach) carries material back down the beach at right angles due to gravity.
What are discordant and concordant coastlines?
Discordant coastline occurs where bands of differing rock type run perpendicular to the coast.
The differing resistance to erosion leads to the formation of headlands and bays.A hard rock type is resistant to erosion and creates a promontory whilst a softer rock type is easily eroded creating a bay.
A concordant coastline occurs where the bands of differing rock types run parallel to the coast.
The outer hard provides a protective barrier to erosion of the softer rocks further inland.
How is the wave-cut platform formed?
The sea attacks the base of the cliff between the high and low tide marks.
Erosion processes of hydraulic action and abrasion, create a wave-cut notch.
Over time the notch increases in size and the upper cliff is unsupported, while weathering weakens the upper cliff.
These processes cause the
cliff to collapse.
A wave-cut platform is the bedrock that is left behind as the cliff moves backwards.
The backwash carries the rubble towards the sea smoothing the wave-cut platform through abrasion.
The process repeats and the cliff continues to retreat.
How do rocks affect erosion?
Soft rock, e.g. sand and clay, erodes easily to create gently sloping cliffs. Hard rock, e.g. chalk, is more resistant and erodes slowly to create steep cliffs.
What are headlands?
A headland is a cliff that sticks out into the sea and is surrounded by water on three sides. Headlands are formed from hard rock, that is more resistant to erosion, such as limestone, chalk and granite. Headlands form along discordant coastlines where bands of soft and hard rock outcrop at a right angle to the coastline (see image below). Due to the different nature of rock erosion occurs at different rates. Less resistant rock (e.g. boulder clay) erodes more rapidly than more resistant rock (e.g. chalk).
What are bays?
The areas where the soft rock has eroded away, next to the headland, are called bays.
How are sea caves formed?
Cracks in the rock erode through abrasion.
Caves occur when waves force their way into cracks in the cliff face. The water contains sand and other materials that grind away at the rock until the cracks become a cave. Hydraulic action and abrasion are the predominant erosion processes.
How are arches formed?
If the cave is formed in a headland, it may eventually break with erosion like abrasion through to the other side forming an arch.
How are stacks and stumps formed?
The arch will continue to be eroded (attrition) and will gradually become bigger until it can no longer support the top of the arch. When the arch collapses, it leaves the headland on one side and a stack (a tall column of rock) on the other.
The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapse to form a stump.
What is a beach?
Beaches
are a common feature of a coastline. Beaches are made up of eroded material that has been transported from elsewhere and deposited by the sea.Constructive
waves help to build up beaches. The material found on a beach depends on the geology of the area and wave energy.
The material found on a beach varies in size and type as you move further away from the shoreline. The smallest material is deposited near the water and larger material is found nearer to the cliffs at the back of the beach.
Large material is deposited at the back of the beach in times of high energy, for example during a storm. Most waves break near the shoreline, so sediment near the water is more effectively broken down by attrition.
What is a shingle beach?
This is a beach where strong swash waves will be assisted by windy and stormy conditions to throw larger pieces of shingle further up the beach. Shingle beaches will usually contain many different ridges across their profile.
The smallest material will be found on the beach face and larger pieces of shingle/ pebble will be thrown to the back of the beach. Shingle beaches usually have much steeper profiles. This is because the wave will percolate through the shingle, making the backwash too weak to remove the material.
How is a spit formed?
When longshore drift transports material along the coast, it sometimes comes across an estuary or a change in the direction of the coastline.
In either case, the transport process tends to carry on moving the material in the same direction.
Over time, a ridge of material will build up into the deeper water.
This will form a spit.
Eventually the spit may form a substantial feature, many miles long with sand dunes and plants, possibly even buildings on it.
Many spits show a series of hook or recurved spit end which relate to material moved by winds creating waves from a different direction.
What happens behind the spit?
In the low-energy environment behind the spit, deposition of fine silt and mud will occur and salt marsh forms.
How are bars and tombolos formed?
Over time, spits may move inland and many are regularly broken by storms and reform in subsequent years.
If longshore drift carries material across a bay, it may form a bay barrier or bar.
Such bars rarely form across estuaries as the power of the river erodes material from the ends of the spit if the gap becomes very narrow. If longshore drift transports material across to a nearby island, then it forms a tombolo linking the island to the mainland.
How do estuaries influence spits?
The river current will prevent the spit from reaching across the bay and forming a bar.
What are the advantages and disadvantages of soft engineering method beach nourishment?
Beaches are made higher and wider by importing sand and shingle to an area affected by longshore drift to increase its height and width to provide protection from erosion or flooding by absorbing wave energy.
Advantages:
The approach is cheap and retains the natural appearance of the beach. Beaches are a natural defence against erosion. Additionally, the beach is a valuable amenity for tourism, bringing economic benefits to the area.
Disadvantages:
Offshore dredging of sand and shingle increases erosion in other areas and affects the marine ecosystem. Large storms will require further beach replenishment, increasing costs.
What are the advantages and disadvantages of soft engineering method managed retreat?
This is when areas of the coast are allowed to erode. This is usually in areas where the land is of low value.
Advantages:
Managed retreat retains the natural balance of the coastal system. Eroded material encourages the development of beaches and salt marshes. Creates new habitats and it is cheap.
Disadvantages:
People lose their livelihood, e.g. farmers. These people will need to be compensated. It is difficult to predict the sea’s movements
What are the advantages and disadvantages of soft engineering method Dune regeneration?
Dune regeneration involves taking action to build up dunes and increase vegetation. This helps to strengthen the dunes and prevent coastal retreat. New sand dunes can be created to protect from coastal flooding. Often, marram grass is planted to hold the dunes together.
Advantages:
Dune regeneration provides a barrier between land and sea, absorbs wave energy, and provides cheap stabilisation. It also maintains a natural-looking coastline.
Dune regeneration can increase biodiversity by providing a greater range of natural habitats for plants, animals and birds.
Disadvantages:
During dune regeneration, the land must be carefully managed so that any new vegetation planted is appropriately protected from trampling by humans. This could involve temporarily fencing off the dunes or providing wooden walkways. Storm waves can also damage dunes.
What are the advantages and disadvantages of hard engineering method
of groynes?
Groynes are wooden barriers constructed at right angles to the beach to retain the material. The beach material, including sand and pebbles, are trapped between groynes and cannot be transported away by longshore drift. Groynes encourage a wide beach which helps absorb energy from waves, reducing the rate of cliff erosion.
Advantages:
-keeps the beach in place for tourist industry
-effective for a long time
Disadvantages:
-disrupt natural processes continues erosion below where the groynes are place
-unattractive and makes it difficult to walk on the beach.
What are the advantages and disadvantages of hard engineering method of rip rap (large boulders piled)?
Rock armour(rip rap) is a barrier of large boulders placed in front of a cliff or sea wall to absorb wave energy and reduce backwash by encouraging percolation.
Advantages:
-dissipates wave energy and is effective for many years
-can be cheap depending on rock type
Disadvantages:
-makes beach inaccessible
-unattractive
-doesn’t work in storm conditions.
What are the advantages and disadvantages of hard engineering method
of Sea Walls?
Seawalls are usually built along the front of cliffs to protect settlements or another land of high economic importance. They are often recurved which means waves are reflected back on themselves. This can cause the erosion of material at the base of the seawall
Advantages:
-visible making residents feel safe
- very effective for many years
Disadvantages:
-ugly and very expensive
-wave scouring
What are the advantages and disadvantages of hard engineering method
offshore reef?
A man made structure of rocks or concrete built from the coastline
Advantages:
-allow build up of sand
-break the waves further removes their erosive power
Disadvantages:
-difficult to install
-may be removed by heavy storms
Impacts of coastal flooding:
Coastal flooding does not only impact people directly, as in injured or dead, but it can also damage or destroy houses, businesses, infrastructure, and agriculture (including the death of livestock).
Effects of coastal erosion:
Coastal erosion is the process by which rising sea levels, storms, and other phenomena wear down or carry away the rocks, land, and sand making up a coastline. This process causes the loss of tens of thousands of acres of land in the UK. each year, as well as millions of pounds in property damage.
Coastal erosion also has an impact on industries dependent upon coastlines.
Explain reasons why rates of coastal erosion may change over time.
In the winter storms are more powerful which means that waves have
more energy
The prevailing wind direction may change leading to more waves
approaching the coastline from the direction of the fetch .
Climate change/ changing weather patterns lead to waves having more
energy
Explain one way that constructive waves can affect beaches.
Constructive waves deposit material onto the beach because they
have a strong swash
Explain one reason why some cliffs erode faster than others.
Cliffs made from harder rocks will erode less rapidly because they are
more resistant to erosion .
Where cliffs have lots of faults they will erode more rapidly because
they have more lines of weakness
Does a sandy beach or a pebble beach have a steeper slope?
Shingle or pebble beaches are typically steep because as the waves flow through the porous surface of the beach, the effect of backwash erosion is reduced. Porous means the sea water passes through easily.
The UK’s coastline is home to a number of __________. If they are flooded the UK may lose money from international trade. What one word completes the sentence?
Ports
Which type of coastal management works in conjunction with natural processes: hard engineering or soft engineering?
Soft engineering does not involve building artificial structures, but takes a more sustainable and natural approach to managing the coast.
