Flashcards in Coastal Landscapes Deck (130):
What is weathering?
Weathering is the breakdown of rocks at or near to the surface of the ground.
How many types of weathering is the and what are they?
3 and chemical, biological and mechanical
What is chemical weathering?
Rainwater is slightly acidic. When rainfalls on rocks such as limestone and chalk a weak chemical reaction takes place cause ing the rock to weaken and break down
What is biological weathering?
The roots of growing plants can widen cracks in rocks. Burrowing animals and nesting birds in cliff faces can also cause the rock to weaken and decay
What is mechanical weathering?
This is caused by the repeated freezing and thawing of water in a crack or hole in the rock. When water freezes, it expands by about 10%, causing stresses within the rock. When the ice melts, water seeps deeper into the rock along the deepened crack. After repeated cycles of freezing and thawing, fragments of rock may break off
What is mass movement on the coast?
Mass movement is the downslope movement of rocks and soil from the cliff top under the influence of gravity
What do types of mass movement are there?
When rocks fall, slumping and sliding
What are the 4 different ways waves can erode the coast?
Abrasion, hydraulic action, attrition, solution
What is abrasion?
It's when fragments of rock, pebbles and sand are picked up by the waves and thrown against the cliff face, causing pieces of rock to break off
What is hydraulic action?
When waves crash against the cliff, the impact, force and weight of the water against the rocks wears away the rocks. It also compresses air in joints and faults in the rock, causing pressure to build and loose rocks to be dislodged. As the waves retreat, the compressed air is released, often explosively, causing the rock to weaken further
What is attrition?
Rocks fragments and pebbles carried by the waves are reduced in size as they collide against each other and the cliff face. They are eventually broken down into sand-sized particles, which are more easily transported by waves
What is solution?
This is the chemical action on rocks by seawater. It is most effective on limestone rocks, in which calcium is dissolved and carried away in solution
What do loose wet rocks do?
Slump under the gravity along the curved slip planes
When does slumping happen?
It happens when the rock is saturated. Loose wet rocks slump down under the pull of gravity along curved slip planes
When does slumping often occur?
On clay coasts
The eroded material will be transported along the coastline by different processes depending on the size of the material and the amount of energy in the waves: the four methods are traction, saltation, suspension and solution. The transport of sand and pebbles along the coast by waves is called longshore drift
How does longshore drift occur?
Waves approaching the coast carry sand and pebbles. Longshore drift is the process of transportation which moves sand and pebbles along the coast. Waves often approach the coast at an angle. The swash carries the sand and pebbles up the beach at the same angle as the wave. The backwash then draws the sediment back down the beach at right angles to the coastline, as this is the steepest gradient. The process is repeated resulting in a zigzag movement of sediment around the goats of the UK is controlled by the direction of the prevailing wind
What is longshore drift?
The transportation of sand and pebbles
What are the 4 different ways waves transport material?
Traction, saltation, suspension and solution
What does traction do?
(Wave transport) large boulders are rolled along the sea bed by waves
What is saltation
(Wave transport) smaller stones are bounced along the seabed
What is suspension?
(Wave transport) sand and small particles are carried along the flow
What is solution?
(Wave transport) some minerals are dissolved in seawater and carried along the flow
How is the coastal landscape shaped?
By the interaction of the different physical processes of weathering, mass movement and erosion
Name 3 types of soft rock
How are destructive waves formed?
Destructive waves are formed by strong winds that have blown over large fetch areas. The waves are powerful and lead to coastal erosion. Destructive waves are tall and steep, they are closely spaced and break frequently - typically between 11-15 waves break per minute, the back wash is much stronger than the swash, so rocks, pebbles and sand are carried back out to sea. If beaches form, they tend to be narrow and steep and offer cliffs little in the way of protection as they cannot absorb much of the wave energy
What are constructive waves?
Constructive waves are associated with light winds. The waves have less energy and encourage deposition. They are low in height and widely spaced, breaking gently - typically 6 - 9 waves break per minute. The swash is stronger than the backwash, so more material is carried up the beach than is removed. The resulting beaches tend to be wide and shallow, and they help protect the cliffs from erosion as the wave energy is absorbed by the beach
What does the unpredictability of the uk's weather and climate affect?
The rates of coastal erosion retreat, impacting on landforms and landscapes
What is the different impacts do coastal erosion have due to?
The four seasons, for example, cd temperatures in winter lead to freeze-thaw weathering
What are the effects of stormy weather
Storm frequency is high in many parts of the UK
Coasts are often subject to strong winds, increasing the eroding power of the waves, and heavy rainfall contributes to the mass movements
Frequent storms can damage coastal landforms like spits. Spurn head along the Holderness coast is at risk of being cut off from the mainland
Beach sediment can be removed from a reaction of coastline
Sand dunes can be removed by storms
where do prevailing winds come from in the uk?
What does prevailing wind from the south-west bring?
It brings warm moist air from the Atlantic and frequent rainfall,Munich contributes to weathering and mass movement on the coast
What is the definition of coastal erosion?
Coastal erosion is the removal of material from the coast by wave action, causing the coastline to retreat inland called coastal recession. This results in loss of land and damage to buildings, roads and railways and can increase the risk of coastal flooding
What is the definition of coastal retreat?
When coastal erosion causes the coastline to move further inland
Explain how the uk's climate contributes to coastal erosion
The uk's climate is temperate maritime,Monica means winters are mild and and and summers are warm and wet. The prevailing wind from the south-west often brings rainfall to the country. The large amount of rainfall causes coastlines to be eroded through weathering, and can lead to mass movement and cliff collapse,Mohicans lead to coastal retreat. Storm frequency is high, which brings heavy rainfall and strong winds that increase the erosional power of waves. The seasonal nature of the climate means that rocks in the coast are subject to freeze-thaw weathering in winter, which adds to erosion
What distinctive landforms are there that have been caused by coastal erosion?
Headlands, bays, headland features and wave-cut platforms
Where do headlands and bays develop?
On coastlines with a mix of hard and soft rock
How are headlands and bays formed?
Hydraulic action and abrasion erode sea cliff. On a discordant coast they erode at varying rates as rocks of different hardness and resistance meet the sea. The stronger or harder rocks, such as chalk and of stone are able to resist wave attacks and erosion for longer. These sections of cliff stand out as prominent rocky headlands.
The softer or weaker rocks, such as the mudstones and siltstones are eroded back more quickly to form bays
Hard rocks like chalk are often left jutting out in sea, forming what?
Soft rocks such a sands are eroded more quickly forming what?
Cliffs are common coastal features. Cliffs are shaped through weathering and erosion. Soft rock erodes easily to creat gently sloping cliffs. Hard rock erodes more slowly to create steep cliffs
When are stacks formed?
Continued erosion by the sea widens the arch. As the sea undercuts the base of the arch, more pressure is placed on top of the arch. Eventually the weakened roof of the arch collapses, leaving a stack, a pinnacle of rock, separated from the mainland.
Further erosion and weathering over time may cause the stack to collapse to leave a small, flat stump, which is often covered by high tide
When is a cave formed?
As destructive waves break against the headland, any lines of weakness in the rock such as joints or faults are attacked. Through hydraulic action and abrasion, the waves erode the rock along the joint or fault which will increase in size and may eventually form a cave
When is an arch formed?
Waves continue to erode caves, in particular through hydraulic action. When a wave breaks, it blocks off the entrance to the cave and traps air within it. The trapped air is compressed, increasing the pressure on the sides, roof and back wall of the cave. If the cave forms part of a narrow headland, the pressure from the waves may result in the back of the cave becoming pushed through the other side. The cave then becomes a natural arch as it is open on both sides
What can the erosion of cliffs create?
What are wave-cut platforms?
A gently sloping rocky area is left at the bottom of the retreating cliff. The platform is covered at high tide but exposed at low tide. It's surface is not smooth because differences in rock structure are picked out by abrasion to create many grooves, rock pools and ridges within the bare rock
What causes the formation of distinctive landforms including beaches, spits and bars
The process of deposition
What are beaches accumulations of?
Sand and shingle formed by deposition and shaped by erosion,transportation and deposition
What are can beaches be?
Straight or curved
Have are curved beaches formed?
By waves refracting, or bending, as they enter a bay
What can beaches have on them?
Sand or pebbles (shingle)
Where are shingle beaches usually found?
Found where cliffs are being eroded and where waves are powerful
What are Ridges in a beach parallel to the sea called? What does it show
They are called berms and the one highest up the beach shows where the highest tide reaches
What is a spit?
A spit is a long and narrow ridge of sand of sand or shingle, one end of which is attached to the land while the other end projects out to sea. If the spit is formed of sand, sand dunes are usually found at the back of it. The area behind the spit is sheltered, leading to the deposition of slit and mud and the creation of a salt marsh
How are spits formed?
The formation of a spit begins in the same way as that of a beach. Material is transported along the coast by longshore drift and is deposited where there is a bend in the coastline or a river mouth occurs. Gradually, more and more sediment is deposited, forming a ridge that extends into the sea. Fresh water and seawater are trapped behind this ridge as it forms. As the ridge extends into deeper and more open water, the tip is affected by the wind and waves approaching from different directions. These cause the end of the spit to curve
Explain how a bar is formed
The formation of a bar begins in the same way as a spit. Material is transported along the coast by longshore drift and deposited where there is a bend in the coastline. Deposition continues in a line across the entrance to the bay or river mouth trapping fresh water behind
What is sand and minerals carried by waves deposited by?
What different factors influence depositions?
Sheltered spots (e.g bays)
Gentle gradient offshore causing friction
They all reduce wave energy
Explain how longshore drift transports material along the coastline
The direction of material movement is determined by the prevailing wind direction. Waves approach the coastline at an acute angle, bringing sediment onto the beach in the swash. Sediment is then dragged back to the sea in the backwash, under the force of gravity at a right angle. The process continues in a zigzag pattern, moving along the beach.
What do the geological structure of coasts, rock type, and wave action all influence?
They all influence coastal landforms
What affects how fast coastal erosion occurs?
What are created when soft rock and hard rocks occur together?
What are the characteristics of soft rock such as clay?
Soft rock is easily eroded by the sea
Cliffs will be less rugged and less steep than hard rock coasts
Soft rock landscapes include bays
What are the characteristics of hard rock, such as granite?
Hard rock is resistant to all types of erosion
Cliffs will be high, steep and rugged
Hard rock landscapes include wave-cut platforms and headlands where caves, arches and stacks are formed
What are concordat coasts?
Concordat coasts are where bands of resistant and less resistant rocks ru parallel to the coastline
What are discordant coasts?
A coast where bands of hard and soft rock lie at right angles to the coastline forming headlands and bays
Describe rocks with joints and faults
Joints are smaller cracks; faults are larger.
Both make rock more prone to erosion.
Rocks with more joints and faults are eroded more quickly
Name 3 hard rocks
The ways in which humans use coastal environments can landscapes what does this affect?
People and the environment
What does urbanisation have an impact on in coastal landscapes?
Weight of buildings makes cliffs more vulnerable
Changes to drainage increase soil saturation
Raises interest in protecting coastal landscapes
How does agriculture affect coastal landscapes?
Increases soil erosion
Creates wildlife habitats
How does the industry have impact on coastal landscapes?
Increases air, noise and visual pollution
Can destroy habitats for birds, animals and sealife
Brings wealth and jobs to an area
What are the effects of coastal recession and flooding?
Wildlife habitats destroyed
Cliffs become dangerous for walkers
Disruption to communication networks - roads and railway lines - creating difficulties for commuters
Decreasing value of properties and difficulties in obtaining home insurance
Loss of businesses (caravan parks, cafes, golf courses) from disappearing cliffs
Increased deposition further along the coast
Loss of people's homes
Explain how coastal recession and flooding can affect people
One of the ways coastal recession can affect people is through the loss of homes. Many of the villages on the edge of the U.K. Coastline are disappearing, losing homes to the power of the sea. Transport systems can be disrupted and damaged, especially important railways that run along the coastlines. This prevents people from making journeys or means long detours are needed, which cost time and money. Farmers lose valuable farmland due to coastal recession, which means they lose income. In areas where homes have been flooded, people may have to pay more for home insurance, making it more expensive to live there
There are advantages and disadvantages to different coastal management techniques why do they need to be given careful consideration?
Because of the changes that can happen to the landscape
What can alter wave patterns, resulting in increased erosion further along the coast?
Soft or hard techniques
What can many hard engineering techniques spoil?
The visual landscape
What is a sea wall?
They are concrete walls, built at the foot of cliffs or the top of a beach; sometimes curved to reflect the waves back out to sea
Protects cliffs and buildings
But it's Very expensive - £5000-£10 000/m and can be unnatural to look at and can restrict access to the beach and can increase erosion to the beach
It's a type of hard engineering
What are groynes? Names some advantages and disadvantages
They are wooden or rock structures built along the beach at right angles, they trap sediment and broaden the beach. The beach then absorbs the wave energy
Prevent sea removing sand and cheaper - £2000/m of timber and quick to construct
Interrupting the movement of sediment can have an impact further along the coast
This is hard engineering
What is rip rap? Name some advantages and disadvantages
They are large boulders piled at the foot of the cliff or the top of the beach
Rocks force the waves to break dissipating their energy and protecting the cliffs and absorbs wave energy and are cheaper - £1000-3000/m and they can be put in place quickly
However transport costs can be high, they do not fit in with local geology and they can impede access to the beach
This is hard engineering
What does soft engineering aim to do?
To work with nature to help maintain the coastline
Name 3 types of hard engineering
Rip rap defences
Name two types of soft engineering
What is beach replenishment? And what are the advantages and disadvantages
Sand or shingle is added to a beach to make it higher or wider
The beach can absorb more wave energy and protect the coastline, sediment is obtained locally so it blends in, easy and cheap to maintain (£2000/m) and it encourages tourism
However it needs constant maintenance, which can become expensive and the work is often undertaken in the summer which can disrupt beach users
This is soft engineering
What are the pros and cons of an offshore reef?
Waves break on reef and lose power
May interfere with fishing
More expensive - £5000/m
This is soft engineering
Where is Holderness coast?
East Yorkshire coastline
What is the significance of Holderness?
Soft Boulder clay is easily eroded, susceptible to slumping after heavy rainfall; chalk is more resistant (flambourough Head)
Exposed to strong waves (fetch) from the North Sea
On the Holderness coast what is happening with coastal erosion?
A combination of strong waves (especially during storms) and rock type ensure the coast is eroded rapidly
On the Holderness coast what is happening with mass movement?
Clay frequently slumps from the cliffs after rainfall
On the Holderness coast what is happening with transport and where does deposition happen?
Strong waves move the eroded material away from the coastline, deposition happens further south
What human processes are at work on the Holderness coast?
Hard engineering on parts of the coast have protected areas from erosion and cliff collapse
Hard engineering in some places has prevented transport, making erosion worse in other places
What changes are caused to the coastal landscape of the Holderness coast?
Some parts are undergoing coastal retreat at a rate of nearly 2 m/year
And farmland, property and settlements have been lost to th sea, changing the landscape permanently
What is sand dune regeneration? Name advantages and disadvantages
Grasses, bushes and trees are planted to stabilise dunes.
It helps dunes to develop and maintains a natural coastal environment. Popular with people and wildlife. Relatively cheap.
However areas of the beach have to be fenced off, prohibiting access, and it takes time for the dune vegetation to become established.
This is soft engineering
When rocks fall how is it mass movement
These happen suddenly when pieces of rock from a weathered cliff fall. This often occurs as the rock as the base of the cliff has been undercut by the action of the waves, leaving the rock above unsupported and causing it to collapse
What is slumping?
It's a type of mass movement, this often occurs after long periods of rainfall. The rain seeps through permeable rocks such as sandstone. At the junction where the permeable rock meets an impermeable rock such as clay, the saturated soil and weaker rock slumps and slides in a rotational manner along a curved surface
What is sliding?
It's a type of mass movement, it is similar to slumping but the movement of material occurs along a flat surface, usually a bedding plane. Large amounts of soil and rock move down slope rapidly and can cause a lot of damage
What is coastal erosion?
Costal erosion involves the action of waves wearing away the rocks along the coastline and roving the coastal sediments
When does deposition occur?
When there is not enough energy to carry the eroded material any further. This material is deposited or laid down, for example as sand in a bay to form a beach
How are waves generated?
Waves are generated by wind blowing over the sea. Friction with the surface of the water causes ripples to form, which grow in pro waves. The amount of energy in waves, and therefore their ability to erode, transport or deposit material along the coast, depends on their height
What are the height and weight of waves determined by?
Wind strength/speed - the stronger the wind, the greater the friction on the surface of the sea, and the bigger the wave
Wind duration - the length of time the wind has been blowing
Fetch - this is the distance of open water over which the wind has been blowing: the longer the fetch the more powerful the wave
What happens as a wave approaches the shore?
The base of the wave is slowed by friction with the seabed, but the upper part continues to travel forward. Eventually the top of the wave topples over and breaks against the cliff face or onto the beach. The water that surges up the beach until it runs out of energy is called the swash. The water that then runs back down the beach under Gravity is called the backwash
Where are fewer bay and headlands formed?
Along concordant coastlines where the rock type is the same along its length, and so the rate of erosion is similar. If the outer rock is a more resistant rock such as limestone, the cliffs are likely to be high and steep. The harder Rick acts as a barrier, but if breached, the sea is able to erode the softer rock behind. This creates a cove - a circular area of water with a narrow entrance from the sea
When are cliffs formed?
Cliffs begin to form when destructive waves attack the bottom of the rock face, between the high and low water marks. Through hydraulic action and abrasion, the waves u deduct the cliff, forming a wave cut notch. As the notch gets deeper, the overhanging cliff above becomes increasingly unsupported and eventually collapses. Once the waves have removed the rock debris, they begin to erode and undercut the new cliff face. Through a continual sequence of wave erosion and cliff collapse, the cliff face and coastline gradually retreat inland
When are beaches formed?
Beaches are formed when eroded material is transported by longshore drift and deposited by constructive waves along the coastline. Sandy beaches are often found in sheltered bays (known as bay head beaches). They are usually wider than pebble beaches and slope gently down to the sea. Pebble beaches are often found in high areas where cliffs are being eroded and where there are high-energy waves. They have steep gradients
Describe beach profile
The profile (cross section) of beaches is rarely smooth. At the top end, they may include a storm beach made up odd could ears and shingle deposited by the largest waves during storm conditions. Below this, a ridge of shingle and sand, called a berm makes the normal tide. A series of berms can be left by a retreating tide. The smallest material (sand) is deposited near the sea.
What is a bar?
A bar is a ridge of sand or shingle across the entrance to a bay or river mouth. Fresh water is trapped behind it to form a lagoon
On an OS map what is eastings?
The vertical lines with numbers that run eastwards across the top or the bottom of a map
On an OS map what are northings?
The horizontal lines with numbers that run northwards up the side of the map
What is a grid reference for?
Grid references are used to locate places on maps. Four-figure grid references are used to give a general location by referring to the square in which a feature is located. Six-figure grid references are used to give a precise location. Always go along the corridor and up the stairs
Maps come in different scales
If a map had a scale of 1:50 000, this means that the map represents things 50 000 times smaller than they really are.
On OS maps of coastal areas, the same symbol can be used for different landforms. What are the steps to identify a costal landform on an OS map?
Find the height water mark:this is shown by a black line on 1:500000 maps and a blue line (labelled mean high water springs I places) on 1:25000 maps.
On which side of the high water mark is the symbol? Cliffs and sand dunes will be on the landward side; wave cut platforms and beaches will be on the seaward side
How fast is the coast changing?
Some parts of the UK coast are eroding at a faster rate than others. Across England and Wales, about 28% of the coastline is eroding by more than 10cm each year
Rising sea level
Sea level along the English Channel has risen by about 12cm in the past 100 years. Levels are expected to rise by another 11-16cm by 2030 due to global warming. A warmer climate causes seawater to expand and also causes ice sheets and glaciers to melt, leading to increased sea levels as a result, the likely effects are as follows: cliffs that are currently being undercut and collapsing will continue to retreat; the position of the wave cut notch and the level of the wave cut platform.
Areas of soft coastline may experience more erosion and retreat due to more frequent and stronger storms
What is a storm surge?
A storm surge is a large-scale increase in sea level (up to 3 metres around the UK) as gale-force winds drive water towards the coastline. Surges can last from hours to days, span hundreds of kilometres and cause significant damage and loss of life
Describe the North Sea storm surge of 1953
The storm lasted two days, flood defences were breached and coastal towns is Lincolnshire, east anglia and Kent were devastated as seawater rushed into the streets. In England 370 people were killed and 24000 properties and 65090 hectares were damaged
What are the human causes of coastal erosion?
Structures like Groynes are built to trap sand, however removing sediment from this system results in increased erosion further along the coast
Erosion from sea cliffs is a important source of sediment for nearby beaches. If cliffs are protected from erosion, the supply of sediment into the coastal system stops, resulting in beach erosion somewhere else
How does erosion affect settlements?
Over 20 million people in the UK live on the coast. At Holderness for example, over 29 villages have been lost due to erosion in the past 1000 years
How does erosion affect infrastructure?
Roads, railways, oil refineries and ferry and shipping ports are located along the coast.
How does erosion affect tourism?
Tourism plays a major part in local economies:for examp,e about 13% of jobs at dawlish are in tourism
How does erosion affect agriculture?
Sea level rise and increased coastal erosion is already leading to the loss of farmland
What is the department for environment, food and rural areas affairs (Defra) responsible for?
For the protection of the coastline from flooding and erosion in England and Wales. It does this by deciding which parts of the coastline should be protected and how
To make the decision of which parts of the coastline should be protected and how more manageable, the coastline has been divided into short sections. The environment agency and local authorities are then responsible for deciding how coastal erosion and flood risk should be managed in each one. Together they develop a shoreline management plan in order to do what?
Reduce the threat of flooding and erosion to people and the environment
Benefit the environment, society and economy, in line with the governments sustainable development principles
What are the possible plan policies for shoreline management plans?
No intervention - no planned investment in defending against flooding or erosion
Hold the line - maintain the existing shoreline by building defences
Managed realignment - allow the shoreline to change naturally, but manage and direct the process
Advance the line - build new defences on the seaward side
In most cases, a decision is made to hold the line. By taking this approach, authorities have the option of using hard or soft engineering
What does soft engineering do?
Takes a more natural approach, allowing the processes to work and the land to change in a more environmentally friendly way
What does hard engineering involve?
Involves building artificial defences, usually out of concrete, to interrupt natural processes or to dissipate the energy of the waves to lower their impact on the coastline
Describe the sand spit, a seaside resort on the south coast of Devon
It was designated a local natural reserve in 1978 and a national nature reserve in 2000 it's a unique habitat
Fishing industries is a historically and culturally important aspect
This spit is a popular tourist destination, 480000 visitors each year
The area is served by a wide range of public transport, including trains, buses and ferries
The spit is home to a few residential properties and a number of small businesses
The exe estuary is popular for water based activities eg sailing, windsurfing, kitesurfing, water-skiing, kayaking etc
What physical factors changed the spit at dawlish warren?
When dawlish warren formed 7000 years ago, it was two sand spits - the outer warren and the inner warren - separated by greenlake. By the 1930s erosion had caused the two warrens to join enclosing the lake and a single spit. The spit has continued to change due to erosion and deposition. High Spring tides accompanied by strong winds (storm surges) have driven waves across the ridge that forms the spits southern and eastern extents. Erosion of the beach and dunes has caused the spit to retreat. 5m were lost on the southern face due to storms at the same time sands transported from the south and south west have helped to rebuild some areas and extend the spit to the east
How is the dawlish warren beach being protected?
Recharging the beach by adding extra sand.
Maintaining the sea wall and rock armour at the western end of the spit, near the tourist facilities and village.
Repairing, replacing and possibly extending the wooden groynes along the beach.
Building a new flood defence near the visitor centre to reduce the risk of tidal flooding to the village.
Removing the rock-filled wire baskets (gabions) to allow the sand dunes to follow a more natural alignment
What is the environmental impact of coastal defences?
There is a sea wall and groynes around dawlish, so sand is no longer being transported by longshore drift to the spit. This can cause coastal squeeze where coastal habitats such as saltmarches are prevented from moving inland in response to storms or rising sea level and so become smaller over time. Is any habitats were lost to this new ones called compensatory habitats would have to be provided