Coasts Flashcards
What are coastal zones
Dynamic environment a with distributive landscapes formed by the interaction of a range of wind, marine and terrestrial processes
How much of the worlds population live on coastal plains
About 50%, with over 59% living within 150km of the sea
What kind of systems are coastal environments
Open systems
Example of feedback in a coastal system
Increased deposition on a beach but there is no corresponding change in the amount of sediment removed from the beach, then the beach features may change and the equilibrium is upset
What are inputs into an open coastal system
Energy from:
Waves
Tides
Sea currents
Sediment
Geology of the coastline
Sea level change
Transfers in an open coastal landscape
Erosions processes
Wind and water transport
Components in an open coastal system
Erosional landforms and landscapes.
Depositional landforms and landscapes.
Outputs in an open coastal system
Dissipation of wave energy.
Accumulation of sediment above the tidal limit.
Sediment removed beyond local sediment cells.
Example of a negative feedback mechanism in a coastal environment
A beach in dynamic equilibrium.
Sediment is erodes from the beach during a storm.
Sediment is deposited offshore forming an offshore bar.
Waves now forced to break before reaching the beach disposing their energy and reducing further erosion when they reach the beach.
When the storm calms, normal wave conditions rework sediments from the offshore bar back to the beach.
What do some negative feedback mechanism act to do
Stabilise coastal morphology and maintain a dynamic equilibrium
What kind of landscape is a coastal landscape
Geomorphological
What do coastal landscapes consist of
A constantly changing assemblage or erosion and depositional landforms; they are the result of continuous change in the elements of a coastal system
What do the processes operating in coastal systems that continually shape the coastal landforms create
Distinctive landscape features
What does the coastline itself consist of
A series of different zones where specific conditions prevail that depend on factors such as tides, wave action and the depth of the sea
What are the 5 different zones in a coastline
Backshore Foreshore Inshore Offshore Nearshore
Where is the backshore
The area between the high water mark (HWM) and the landward limit of marine activity.
When does changes to the backshore usually take place
Only during storm activity
Where is the foreshore
The area lying between the HWM and the low water mark (LWM).
What is the most important zone for marine processes in times that are not influenced by storm activity
Foreshore
Where is the inshore
The area between the LWM and the point where waves cease to have any influence on the land beneath them
Where is offshore
The area behind the point where waves cease to impact upon the seabed and in which activity is limited to deposition of sediments
Where is the nearshore
The area extending seaward from the HWM to the area where waves begin to break and no longer have an effect on the land beneath them
What 3 zones are included in the nearshore
Swash zone.
Surf zones.
Breaker zone.
What is the swash zone
The area where a turbulent layer of water washes up the beach following the breaking of a wave
What is the surf zone
The area between the point where waves break, forming a foamy, bubbly surface, and where the waves then move up the beach as swash in the swash zone
What is the breakerzone
The area where waves approaching the coastline begin to break, usually where the water depth is 5 to 10m
What does using a systems approach help to explain in a coastal landscape
Variations and changes that occur along a coastline. It also helps us to predict the possible consequences of natural processes or proposed human interventions. This can help us to foresee positive or negative impacts and plan for them
What is the coastline of England and Wales divided into
Eleven sediment cells where each cell can be seen as a system in which there are clear inputs (e.g from rivers), transfers of sediment (e.g longshore drifts), stores (beaches and spits) and transfers to the deep ocean
If changes occur in a a sediment cell what may it lead to
Feedback, either positive or negative
How can cliff erosion in a sediment cell lead to negative feedback
Cliff erosion leads to slumping, the mass of scree at the bottom of the cliff will, until it’s removed by wave action, protect the base of the cliff from further retreat. Here changes within the system reduces the causes of further disruption (dampening down the change)
What is scree
Collapsed cliff material at the base of the cliff
How can a spit create positive feedback
If a spit extends across a river estuary, reducing river velocity due to greater friction, this may lead to further spit growth and so yet further reduction in river velocity
Why are the sediment cells closed systems
Within each cell sediment is largely recycled, maintaining a state of relative balance and are, as such, closed sediment systems
What can coastal systems be seen operating at
Various scales
What will happen to a beach if inputs of sediment exceed outputs
The beach will extend in height, length and/or width
If we consider a single beach within its larger sediment cell, what can we observe
That if the beach experiences a positive sediment budget then somewhere else in the wider cell must be experiencing a sediment loss for the overall balance to be the same
By tracking the changes in the movement of sediment, what can we get a better understanding of
The connections within the system
While generally sediment cells are seen as closed systems, what is the reality
There is a slight loss of sediment to outputs beyond the system
Example of sediment being an output from a sediment cell
If wave enemy is very high or currents very strong, then sediment may be transferred to neighbouring cells, be ‘lost’ to deeper sea areas off-shore or be transferred to stores beyond the active coastal zone, such as upper beaches, coastal dunes and mudflats
What is a sediment sink
When sediment is permanently lost to the system, the destinations are known as sediment sinks
What do the conditions in each zone on a beach depend on
Factors such as tides, wave action and the depth of the sea
What are the 11 sediment cells
St Abb's head - Flamborough head Flamborough head - the wash The wash - river Thames River Thames - Selsey ball Selsey ball - Portland bill Portland bill - lands end Lands end - river Severn River Severn - st David's head St David's head - bardsey sound Bardsey sound - great orme Great orme - solway firth
What are many coastal features created by
The action of wind, waves, tides and sea currents
What is erosion
The wearing away of the earths surface by the action of ice, wind and water
What is weathering
The breakdown or decay of rock at or near the the earths surface in situ. Rock fragments will remain until they are removed by erosion processes. Weathering can be mechanical, biological or chemical
What is mass movement
The movement of material downhill by gravity and often assisted by rainfall
At the coast what is the main form of energy
Waves
What 3 things produce waves
Tectonic activity
Underwater landslides
Wind
What is wind
The movement of air from one place to another. Air moves from areas of high atmospheric pressure to areas of low atmospheric pressure. This movement is known as wind
What does the greater the pressure gradient between two places mean
The stronger the wind
What does prevailing wind mean
The most usual
In the UK, what is the prevailing wind direction
From the south-west
Before reaching our coasts, what have the prevailing winds blown over
The broad expanse of the Atlantic Ocean - this means it has blown over 3000 miles of open
What is the fetch
The distance which the wind blows over before reaching the coast
What are the 3 factors affecting wave energy
Fetch
Strength
And duration of wind
What leads to the formation of waves
As wind blows over the surface of the sea frictional drag leads to a transfer of energy and the formation of waves
How is wind an agent of erosion
As it can pick up and remove sediment (e.g sand) from the coast and then use it to erode other features
What is the most common type of wind erosion
Abrasion
Why is wind an important agent of moving sediment along the coast or further inland and beyond the shoreline
Becsuse it can pick up and move material
Once waves have been created by the wind, what do they become
The main agent that shapes the coastline
What can waves breaking at the coast do depending on their characteristics
Build up beaches or remove material
Why do waves break
Waves start out at sea and have a circular orbit.
As waves approach the shore friction slows the base of the wave.
This causes the orbit to become elliptical.
Until the top of the wave breaks over.
What are the characteristics of waves
Wave height - this is the height of the difference between a wave crest and the neighbouring trough
Wave length or amplitude - this is the distance between successive crests
Wave frequency or wave period - this is the time for one wave to travel the distance of one wave length, or the time between one fresh and the following fresh passing a fixed point
What is backwash
The action of water receding back down a beach towards the sea
What is swash
The rush of water up the beach after a wave breaks
What does the sea bed act as for waves
A source of friction as it is rough
What are constructive waves
Waves with a low wave height, but with a long wave length and low frequency of around 6-8/min. Their swash tends to be more powerful than their backwash and as a consequence beach material is built up.
What are destructive waves
Waves with a high wave height with a steep form and high frequency (10-14/min). Their swash is generally weaker than their backwash, so more sediment is removed than is added
How do constructive waves add to beach deposition
Their swash pushes more material from offshore up the beach than the backwash removed
Where is most of the energy in constructive waves used
In forward movement up the beach rather than flowing back down the beach and much water is lost percolation
As backwash is reduced in constructive waves, what happens to the following swash
It is less impeded in its movement up the beach
What are constructive waves associated with
A gentle beach profile, although over time they will build up the beach and make is steeper.
Why do constructive waves rarely reach the foot of the cliff
Because the wave energy is absorbed by the beach
Why do destructive waves mean beach material is easier to remove
As they crash down they loosen beach material
Why is the swash of destructive waves short lived
As energy has gone into a more vertical impact
What is the net effect of destructive waves
The removal of beach material along the shoreline
What does the strength of the backwash of destructive waves do
Takes material down the beach and impedes the next swash
What are most beaches subject to an alternating cycle of
Constructive and destructive waves e.g constructive waves build up a beech resulting in a steeper beach profile which encourages destructive waves
What landform is associated with constructive waves
Berms
What landform is associated with destructive waves
Storm berms
Example of negative feedback because of waves
Constructive waves operate to build up a beach, eventually the beach profile steepens which can encourage destructive waves (plunging rather than surging) which then remove material from the beach and deposit it offshore. This, in turn, can result in the beach profile becoming less steep again, encouraging constructive rather than destructive waves to form. All things being equal, this will continue until a state of dynamic equilibrium is reached
What happens when waves approach a coastline that is indented
They are refracted and become increasingly parallel to the coastline.
Around headlands, why do waves have greater energy to erode
Waves tend to break and have higher frequency, wave height and steepness, which gives them greater energy
How does wave refraction occur on a headland
waves approaching the headland meet shallower water first, while the part of the wave approaching the bay is still in deeper water. Friction with the sea floor slows the headland approaching waves and causes their frequency to increase.
In bays what leads to a constructive impact of waves
The waves spread out and become less frequent which leads to a reduction in wave energy
What is the overall effect of wave refraction
Wave energy becomes concentrated on the headland. It accounts for the presence of erosive features of headlands and deposition features in bays
In theory, how would continued erosion of the headland and deposition in the bay’s result in a state of equilibrium
The shape of the coastline would remain static due to a balance between the potential erodibility of the rocks and the effects of wave refraction (in reality though conditions rarely remain stable enough for long enough for this to happen)
What is a current
Refers to the permanent or seasonal movement of surface water in the seas and oceans.
What are the three types of currents
Longshore currents (sometimes known as littoral currents)
Rip currents
Upwelling
Why do longshore currents occur
Because most waves approach the coastline at an angle. The result is a flow of water (current) running parallel to the shoreline. This moves water and transports sediment parallel to the shoreline
What are rip currents
Strong localised underwater currents that occur on some beaches and move water away from the shoreline.
How do rip currents form
They develop when a series of plunging waves cause a temporary build up of water at the top of the beach. Met with resistance from the breaking waves, water returning down the beach (the backwash) is forced just below the surface following troughs in the beach profile. The fast-flowing offshore surge of water can be hazardous to swimmers
What is upwelling
The movement of cold water from deep in the ocean towards the surface
How does upwelling occur
The dense cold water replaces warmer surface water and creates nutrient rich cold ocean currents. These currents form part of the pattern of global ocean circulation currents
What is wave refraction
When waves approach a coastline that is not regular shape, they are refracted and become increasingly parallel to the coastline. The overall effect is that wave energy becomes concentrated on the headlands, causing greater erosion. The low-energy waves spill into the bay, resulting in beach deposition
What is longshore or littoral drift
When waves approach the short at an angle and swash and backwash then transport material along the coast in the direction of the prevailing wind and waves
What are tides
What’s in the water levels of seas and oceans caused by the gravitational pill (another source of energy) of the moon and, to a less extent, the sun
What creates a high tide
The moon pulls water towards it, creating a high tide, and there is a compensatory bulge on the other side of the earth. In areas of the world between these two bulge the tide is at its lowest
What are the 3 classifications of tidal range
Macrotidal - more than 4m
Mesotidal - 2-4m
Microtidal - less than 2m
What tides does the UK coastline experience each day
2 high tides and 2 low tides
What is the tidal range
The relative difference in height between low and high tides
What do tidal ranges determine
The upper and lower limits of erosion and deposition and the amount of time each day that the littoral zone is exposed to weathering
What is the tidal range affected by
The relative position of the sun and the moon
How are Spring tides formed
Twice in a lunar moon when the moon, sun and earth are in a straight line so the tide raising force is strongest
How are neap tides formed
Twice a month, the moon and sun are positioned at 90* to each other in relation to the earth. This alignment gives the lowest monthly tidal range
What do tidal ranges generate
Relatively prideful tidal currents which are an important source of energy
What are tidal currents important in
As they are particularly strong in estuaries and narrow channels, the currents are important in the transfer of sediment within the costal system or beyond (as an output)
When do tidal or storm surges occur
When meteorological conditions give rise to strong winds combine with high tides to produce much higher water levels than normal.
Example of a place tidal or storm surges occur and why
in the North Sea when intense low pressure weather systems (depressions) have the effect of rising sea levels. The sea level can rise by about 1 centimetre for every 1 millibar drop in pressure. Strong winds drive waves ahead of the storm, pushing the sea water towards the coastline. This has the effect of piling water up against the coast. The shape of the North Sea means that as sore S move south water is funnelled into a narrowing channel.
What intensifies the effect of storm surges
Spring tides
What is a high energy coast
A coastline where strong, steady prevailing winds create high energy waves and the rate of erosion is greater than the rate of deposition
What is a low energy coast
A coastline where wave energy is low and the rate of deposition often exceeds runs rate of erosion of sediment
What is a sediment cell
A distinct area of coastline seperated from other areas by well-defined boundaries, such as headlands and stretches of deep water
Characteristics of high energy coastlines
Consistently strong waves.
Strong, steady prevailing winds with long fetch to create high energy waves.
Rate of erosion is greater than rate of deposition.
Net transfer of material from coastline to sea.
Erosion landforms like headlands and bays found here.
In the UK where are high-energy coastlines found
Along stretches of the Atlantic-facing coat, such as Cornwall or North-west Scotland
Characteristics of low energy coastline
Waves are less powerful.
Rate of deposition is greater than the rate of erosion.
Wave energy is low.
Typical landforms include beaches and spits.
More likely to be in a state of equilibrium.
In the UK where are low-energy coastlines found
Lincolnshire
Why are low energy coastlines likely to be in a state of stable equilibrium
Because they have key inputs, transfers and outputs in balance
Globally, where does most sediment come from
Rivers, streams and coastal erosion, although there are local variations
What are 6sources of sediment
Rivers Cliff erosion Longshore drift Wind Offshore Storm surges
How are rivers a source of sediment
Sediment is transported in rivers and is deposited in river mouths and estuaries where it is then reworked by waves, tides and currents. Most coastal sediment originates from rivers
When is cliff erosion particularly an important source of sediment
This can be particularly important along stretches of coastline where rocks are soft.
Example of cliff erosion being an important source of sediment
One example in the Holderness Coast where glacial fill forms unstable cliffs of Boulder clay.
How is longshore drift a source of sediment
Sediment is transported from one stretch of coastline (as an output) to another stretch of coastline (an an input)
How is wind a source of sediment
In glacial or arid regions, wind blow sand can be deposited in coastal regions. Sand dunes can act as both a sink and source of sediment (sand)
How is offshore a source of sediment
Sediment from offshore csn be transferred into the coastal (littoral) zone by waves, tides and currents.
How did the Chesil Beach in Dorset form
Sea levels rose at the end of the last glacial period, resulting in a considerable amount of coarse sediment being bulldozed onto the south coast of England.
What can sediment cells be divided into
Smaller sub-cells such as the cell 2 on the east coast of England, which stretches from Flamborough Head to the Wash has a sub-cell within it that stretches from Flamborough Head to the mouth of the Humber Estuary
What is a sediment budget
The balance between sediment being added to and removed from a sediment cell costal system
What leads to a positive budget or a surplus of sediment and causes the shoreline to build towards the sea
If more material is added to the sediment cell than is removed then there is a net accretion of material
What results in a negstive budget or deficit of sediment and causes the shoreline to retreat land wards
If more material is removed from the cell than is added
In principle, what does the sediment budget seek to achieve
A state of dynamic equilibrium where erosion and deposition are balanced
What can upset the balance of a sediment budget in dynamic equilibrium
Events such as an increase in river sediment as a result of a food. This, in turn, leads to deposition in the river estuary. A severe storm might also upset the balance by eroding a beach and transferring sediment outside the system
What does calculating the sediment budget for a cell require
The identification of all sediment sources and sinks and an estimation of the amount of sediment added and removed each year. Calculating the budget is extremely difficult and relies on the use of complex models and estimations
What are processes
The ‘how’ and ‘why’ of change in a system. They are the mechanisms that operate on the inputs and results in particular outputs.
What two sets of geomorphological processes are coastlines affected by
Marine processes
Sub-aerial processes
What are marine processes
These operate upon the coastlines that are connected with the sea, such as waves, tides and ,offshore drift
What are sub-aerial processes
These include processes that slowly break down the coastline, weaken the underlying rocks and allow sudden movement or erosion to happen more easily. Material is broken down in situ, remaining in or near its original position. These processes may affect the shape of the coastline, and include weathering, mass movement and run-off
What do all processes do to create a wide range of uniquely coastal landscapes
Interact
How much energy can waves generate as they break against the foot of a cliff
25-30 tonnes m^-2
In 2014, what happened in Dawlish
A particularly powerful storm hit Dawlish and destroyed part of the sea wall and a section of rail track cutting the rail connection between Devon and Cornwall for months. This storm altered the Devon coastline as large a,punts of sediment were swept away from beaches and sand dunes at Dawlish Warren (spit) were severely eroded.
How does coastal erosion play a key role in the coastal system
By removing debris from the foot of cliffs and provides an important input into coastal sediment cells
In reality, what do the processes of marine erosion do
Work together to erode a stretch of coastline
What are the 5 types of marine erosion
Hydraulic action Wave quarrying Abrasion Attrition Solution
What is wave quarrying
When waves break against a rock face with joints facing the wave, air inside the joints is highly compressed, creating enormous pressure within the fissure. As the water pulls back, there is an explosive effect of the air under pressure being released. The overall effect of this over time is to weaken the cliff face and storms may then remove large chunks of it.
What is wave quarrying sometimes known as
Cavitation
What is hydraulic action
The impact on rocks of the sheer force of water itself (without debris). This can exert enormous pressure upon a rock surface, weakening it and dislodging pieces.
What is abrasion
The material that the sea picks up also wears away rock rocks. As waves advance, they pick up sand and pebbles from the seabed. When they break at the foot of the cliff, the transported material is hurled at the base of the cliff - chipping away at the rock.
What is solution
Some calcium-based rocks such as chalk and limestone, is readily soluble and dissolved minerals can then be removed in solution. This process is very similar to a type of weathering called carbonation.
What is attrition
Whilst attrition doesnt directly alter the shape of the coastline it does result in a wearing away of rock participles. Angular rock fragments are smoothed and reduced in size forming pebbles, shingle and sand. This occurs due to friction as particles are rolled over each other by the action of waves and currents.
What are the 7 factors that affect the rate of coastal erosion along any stretch of coastline
Waves Fetch Sea depth Shape of the coastline Beach presence Human activity Geology
How do waves affect the rate of coastal erosion
Steeper high-energy waves have a greater erosive power than low energy waves. The point at which the wave breaks is important too. Waves that break at the foot of a cliff release more energy than those that break off-shore.
How does fetch affect the rate of coastal erosion
A wave that has built up over s greater distance will have generated more energy
How does sea depth affect the rate of coastal erosion
A steeply-shelving sea bed will create higher and steeper waves
How does the shape of the coastline affect the rate of coastal erosion
Headlands attract wave energy through refraction
How does the beach profile affect the rate of coastal erosion
Beaches absorb wave energy and provide some protection against erosion. Steep, narrow beaches are effective at dissipating energy from flatter waves. Flatter, wider beaches spread out incoming wave energy and are better at dissipating high waves. Shingle beaches absorb the impact of steel waves as well due to energy being dissipated through friction
How does human activity affect the rate of coastal erosion
Beach material (sand and shingle) is removed from some coastlines leading to an increase in erosion. In other areas coastal protection may reduce the rate of erosion C
How does geology affect the rate of coastal erosion
Perhaps the most important factor in determining the nature of the erosion all processes. It includes lithology, structure and dip
What is lithology
The physical strength and chemistry of rocks
What is structure of a coastline
The variation and arrangement of rocks along a coastline
How does lithology affect the rate of coastal erosion
Some rocks, like granite are very resistant to erosion whist others, such as clay are very vulnerable. Some rocks, like limestone, are well-jointed and cracked, which means that the sea can penetrate along lines or weakness, making them more vulnerable to erosion
Example of lithology determining erosion
Granite at lands end has been eroded by 10cm while Boulder clay at the Holderness Coast has been eroded by 120cm in the last century
How does structure affect the rate of coastal erosion
Along some coastlines rocks lie parallel to the coast (concordant coastline) whereas in some areas rocks lie perpendicular (discordant)
What is dip
Where cliffs have horizontal strata/bedding planes they may dip or slope
How does dip affect the rate of coastal erosion
When rocks dip inland steeper cliffs may form. Where rocks dip towards the coasts, cliffs tend to produce more gently sloping features
What are concordant coastlines sometimes called
Pacific e.g Dorset
What are discordant coastlines sometimes called
Atlantic
How do coves form
Along a concordant coastline, a resistant rock like limestone can protect the coastline from erosion, only allowing the sea to break through in a few places. Where the sea does break through it can more readily excavate the clay behind to form a cove e.g Lulworth Cove
Which coastline has examples of both concordant and discordant coastlines
The southern coast
What can wave and tidal energy that is not used for erosion of lost through friction be used for
Transportation
What does transportation represent
A significant transfer/flow of material is controlled and determined by the power of the waves
What does transportation of material by seawater depend on
The size and weight of the material and the energy of the transporting flow
What are the 4 types of transportation
Traction
Saltation
Suspension
Solution
What is traction
Large stones and boulders are rolled along the sea bed and beach by moving sea water. They are too heavy to be picked up and carried and will only move if energy level are high enough
What is saltation
Small stones bounce along the seabed and beach. This process is also associated with high energy conditions. As the particles land they may dislodge others.
What is suspension
Very small particles of sand and silt are carried along by the moving water, within the flow. Suspension is most likely when flow is turbulent. Large amounts of suspended load, especially near estuaries, can cause a murky appearance of the sea
What is solution
Dissolved materials are transported within the mass of moving water. This form of transportation plays an important role in the carbon cycle, transferring and depositing carbon in the oceans.
Describe the process of longshore drift
Swash transports material up the beach whilst backwash removes it back down the beach.
When the wind direction is oblique to the shore, swash rushes up the beach in the same direction as the wind, and so carries material up the beach at an angle.
The backwash then pulls material down the beach at right angles to the shore (due to the force of gravity).
The net effect of this is a zigzag movement of sediment up and down the beach.
What is longshore drift response for
Transferring vast amounts of sediment along the coastline and eventually out to sea.
What happens if the process of longshore drift is interrupted by coastal managment
It can lead to distortions of natural patterns
How do offshore currents, including rip currents, move material out to sea
At right angles to the shore. The material they transport is usually deposited some distance from the shore to form sand banks
When does deposition take place
When the velocity of the water or wind falls below a critical value for a particular size of particle and can no longer be transported. It occurs once the energy flow that is moving material declines
What are the four reasons deposition occurs
Currents may weaken or prevailing winds may lighten in strength altering the energy source.
Where opposing currents meet, turbulence may occur, resulting in deposition below the surface. Can happen at end of spit.
As waves move over the seabed or shore land features, friction occurs which results in deposition of heavy particles.
Where rivers or land slips add additional sediment to the sea deposition may occur, as energy is insufficient to transport the additional load.
What are areas of deposition like beaches, spits, mudflats, sand dunes and offshore bars classed as
Sediment stores or ‘sinks’
What do aeolian processes relate to
Wind
What does wind play an important role in shaping
The coastline
How does aeolian deposition occur
During the day, wind fends to be on-shore, as the sea is usually colder than land. When there is a large tidal range, large amounts of sand may be exposed at low tide. This provides a supply of sediment that can be picked up and transported by the wind. Sand is most likely to be carried by the wind and is usually transported close to the ground and over relatively short distances.
What are sub-aerial processes
Land-based and include weathering and mass movement
What are the links to the carbon cycle and water cycle during the process of weathering
Freeze-thaw weathering and carbonation
Why are weathering processes common at the coast
Due to the presence of air and water, cycles of wetting and drying and exposed rock surfaces.
What are the three main categories of weathering
Mechanical/physical
Biological
Chemical
What does mechanical/physical weathering involve
The break up of rocks without any chemical changes taking place
What are two examples of mechanical weathering
Freeze-thaw (frost shattering)
Wetting and drying
Where is freeze-thaw weathering common
In latitudes where temperatures fluctuate above and below freezing and there is a ready supply of water
How does freeze-thaw weathering occur
Water enters cracks in the rocks and freezes when the temperature drops below 0*C.
As it freezes, water expands by almost 10%, meaning ice occupies more space and so exerts pressure on the surrounding rock.
With repeated freezing and thawing, fragments of rock break away and collect at the base of the cliff as scree.
What is scree used by the sea to do
Aid erosion processes such as abrasion
Where are wetting and drying cycles common
On the coast, where there are rocks that are rich is clay
What is the process of wetting and drying
The clay expands when wet and contracts and cracks when dry. Over time this can cause the rocks to break up. In addition the cracks can allow water to seep into the cliff and make them susceptible to other processes, like mass movement
What is involved in biological weathering
The break down of rocks by organic activity, including vegetation and coastal organisms.
Where is biological weathering common
Along coastlines
How can the roots of surface plants on cliff tops be biological weathering
They can create and expand tiny fissures. These cracks widen as roots grow which can break up the rock
How can sun-surface seaweed be biological weathering
It attaches itself to rocks and can weaken and detach them as it sways in the currents of stormy conditions
How can some organisms be biological weathering
Algae for example can secrete chemicals that aid solution (chemical weathering)
How can marine organisms be biological weathering
Such as the paddock (shellfish), have specially adapted shells that enable it to drill into solid rock. They are particularly active in areas of chalk
How can cliff nesting birds like puffins and martinis and animals like rabbits be biological weathering
They can burrow into the cliffs
Where is chemical weathering common
On the coast where rocks are exposed to the air and moisture so chemical processes can break down the rocks
What is chemical weathering
As mineral compounds undergo chemical reactions, they can alter the rock structure. Examples include oxidation, carbonation, solution and hydrolysis
When does oxidation occur
When rock minerals reach with oxygen. Rocks containing iron compounds experience oxidation to form a rusty red powder, leaving the rocks more vulnerable to weathering
When does carbonation occur
When carbon dioxide dissolved in rain water makes a weak carbonic acid (H2CO3). This reacts with calcium carbonate (CaCO3) in rocks like limestone and chalk to create calcium biocarbonate which then dissolves easily in water.
Where is carbonation more effective
In locations with cooler temperatures as this increases the amount of carbon dioxide that is dissolved in water
What is solution in terms of weathering
The dissolving of rock minerals, such as halite (rock salt)
What is hydrolysis
Where mildly acidic water reacts or combines with minerals in the rock to create clays and dissolvable salts, this itself degrades the rock, which makes it more susceptible to further degradation
What is mass movement
The downhill movement of material under the influence of gravity. It can be rapid or slow.m
Where are mass movement processes a common feature
On coastlines with higher relief
What are the processes of mass movement important in doing
Transferring energy (in response of gravity) and sediment - the sediment forms an important input to shoreline processes, forming the ‘tools’ for erosion and providing material to be transported and deposited elsewhere along the coastline
What are 6 types of mass movement
Rockfall Landslides Mudflow Rotational slip or slumping Soil creep Runoff
What is rockfall
Each roofs, stacks and cliff faces collapse as a weakness becomes unsupportable. Rockfalls are sudden and are often associated with steep or vertical cliffs in well-jointed and often quite resistant rock. Scree forms at the base of the cliff until material is removed by waves
What kind of weathering causes rockfall
Mechanical
What are landslides
Occur on cliffs made from softer rocks, which slip as a result of slope failure. Landslides can be triggered by heavy rain as water can lubricate less consolidated materials such as Boulder clay or weathered shales and sandstone
What are mudflows
Fine particles of mud flows down the face of cliffs, often heavily saturated by persistent rainfall which adds to its bulk and makes it behave more like a liquid. Mudflows are often sudden and fast flowing so can represent a natural hazard
What is rotational slip or slumping
Where softer material overlies much more resistant materials, cliffs are subject to slumping. With lots of lubrication, whole sections of the cliff may move downwards along a concave slide plane, producing a rotational movement
Where are rotational slips or slumping more common
In glacial deposits along the East Yorkshire coast
What is soil creep
The gradual movement downhill of individual soil particles. The presence of soil increases the likelihood of soil creep. It results in terracettes on slopes
What is runoff
Where overland flow occurs down a slope or cliff face, small particles may be moved downslope and onto the beach or into the sea
What are the different landforms of erosion
Headlands and bays
Cliffs and wave-cut platforms
Cliff profile features including caves, arches and stacks
What are landforms
Individual components of a landscape
What is a landscape
Made up of a number of landforms which give them their key characteristics
What does the nature of the coastal landscape depend on
The coastal geology, climate, nature of the tides and saves and a range of other factors
What can coasts be
Erosional or depositional
Emergent or submergent
Inputs of landform formation
Coastal geology
Climate
Nature of waves
Processes of the formation of landscapes
Erosion Weathering Deposition Wave refraction Sea level change
Outputs of landform processes
Sediment
Landforms
How do headlands and bays form
On a discordant coastline with areas of alternating more and less resistant rock erosion occurs initially faster in the areas of less resistant rock. Over time this will form bays between protruding headlands of more resistant rock
Why is erosional energy concentrated on headlands
Due to wave refraction
Why are bays the subject to deposition
Due to lower energy waves
What forms in bays and what do they do
Beaches and they protect the coastline from further erosion
On a concordant coastline how do headlands and bays form
Weaknesses in more resistant rock are exploited by the waves and erosion occurs in the less resistant rock behind
How do wave-cut notches form
Where destructive waves break between high and low tide lines at the foot of a cliff their energy is concentrated over a fairly small area which means that the cliff becomes undercut forming a notch
How do wave-cut platforms develop
When cliffs become undercut to form a wave-cut notch, the cliff above is weathered and under stress due to the lack of support from below, over time this results in the cliff collapsing. Over a series of collapses a wave-cut platform develops.
What does the rate of cliff collapse during wave-cut platform formation depend on
The characteristics of both the cliffs and the waves
Characteristics of a wave-cut platform
Fairly smooth and flat (sloping at least than 5*) and may be smoothed by further abrasion.
Unlikely to grow to wider than 500m.
Why is a wave-cut platform unlikely to grow wider than 500m
Over time the waves break further and further out to sea as the waves have to travel over more and more platforms before the cliffs. This means the wave energy is dissipated before it reaches the bottom of the cliff so the rate of cliff erosion decreases and the platform ceases to grow. Good example of a negative feedback loop
What does the steepness of the resulting cliff after a wave-cut platform forms depend on
The rock type of and rate of erosion and weathering, harder cliffs which have more recent experienced cliff collapse are likely to be steeper, softer rocks with a wider wave cut platform are likely to have a slower rate of erosion and a more gentle profile
Where do wave-cut platforms forms between
The high and low water mark
What does the formation of wave-cut platforms cause the coastline to do
Retreat
Example of cliff profile features
Caves, arches and stacks and their associated features
Why do cliff profile features tend to form on headlands
Because, due to wave refraction, wave energy is focused
What does whether or not cliff profile festered form depend on
The nature of the rocks and the waves
What forms a geo and a cave
Where there is a weakness in the rock due to a crack, fault, joint or impurity in the rock, it is exploited by hydraulic action at is enlarged and either forms a narrow, steep sided inlet called a geo or where the cliff becomes undercut a cave forms
What forms a blow hole
Where the cave faces the oncoming waves the full force of the waves is applied to the rear of the cave, this can enlarge joints in the cave roof and if the overlying rocks are sufficiently weakened they may collapse forming a blow hole
What forms an arch
Often canes form in headlands as erosion is strongest here. Where canes are eroded on either side of a headland they may erode right through the headland and form an arch
How does a stack form
The roof of the arch is weathered through sub-aerial processes and chemical weathering from the sea-spraying splashing below, and it’s unsupported roof eventually collapses leaving a stack
How does a stump form
The stacks base is in the intertidal zone so it is subject to erosion. The upper part of the stack also becomes weathered and over time the whole stack collapses, usually in stages. This leaves behind a stump which will eventually be eroded to the level of wave-cut platform
What can the speed of erosion for forming cliff profile features range from
Between hundreds to tens of thousands of years for the entire process
Famous examples of cliff profile features in the UK and abroad
UK - Old Harry’s Rocks in Dorset
Victoria, Australia - Twelve Apostles are a series of stacks that have associated caves and arches
What is the form and characteristics of depositional features controlled by
The inputs and outputs
When a depositional feature forms somewhere in a sediment cell, what does that mean for elsewhere in the cell
It is being eroded
Where does deposition usually take place
In areas where the waves are very low energy or where there is a large supply of sediment
What are beaches
Accumulation of sediment and represent important temporary stocks within a sediment cell
Where do beaches form
Between the highest point reached by storm waves and lowest Spring tides
What are beaches formed of
Either sand or shingle and are formed of material from offshore sandbars, longshore drift, wind blown sand from up the coast and mass movement from the cliffs behind the beach
Relief of a sand beach
Gentle in slope (<5*)
Why do sand beaches tend to be gentle in slope
Becsuse the sand grains are small and easily compactible which means little water percolates through the sand therefore the majority of water moving up the beach also returns through backwash which smooths and flattens the beach.
Relief of shingle beaches
Steeper (10-20*)
Why are shingle beaches steep
Because the larger sediment size means that it is less easily compacted and therefore the waves, having broken, percolate back through the shingle meaning that the backwash doesn’t really transport material back down the beach. This creates a beach which is unlikely to be eroded
What are many beaches
A combination of sand and shingle
Why does larger sediment tend to be at the top of a beach
Because it takes high energy storm waves to deposit the material
What is a storm berm
At the top of a beach a wide flatter area is deposited by a strong swash during spring high tide. Won’t be affected by normal swash.
What are berms
Below the storm berm. These are a series of ridges that mark a series of high tide lines and are built by constructive waves
When do cusps on a beach form
Where the waves break directly onto the beach. Both swash and backwash are strong and generally equal to each other. They generally form at the junction where the sand on the lower part of the beaches meets the shingle on the upper part of the beach. The cusps curved sides channel incoming swash into the centre of the cusp which creates a stronger backwash flowing out of the centre of the cusp which further deepens the cusps
What are ripples
Further down the beach than cusps, ripples may form in the sand due to the action of the tides moving back and frothed across the sand
Where do ridges on a beach form
At the low water mark where backwash deposits sediment. They run parallel to the coast and are broken by runnels where water runs through to return to the sea.
What are the two types of beaches
Swash-aligned and drift-aligned
What is a swash-aligned beach
Waves are parallel to the coast so backwash is at the same angle so beach can build up
What is a drift-aligned beach
Waves approach at an angle so long shore drift occurs. Sediment may be graded with fined and rounder sediment down-drift as it is easier to transport. These beaches result in spits, tombolos and barrier beaches
Where are swash aligned beaches usually found
On irregular coastlines where longshore drift is impeded, and waves hit sections of the coast head-on
What are spits
Long, narrow ridges of deposited sediment which are joined to the mainland at one end and stick out into the sea or across an estuary or bay
What are the two types of spits
Simple or compound
What are simple spits
Either straight or recurved but do not have minor spits or recurved ridges along their landward edge
What are compound spits
Have a series of minor spits or recurved ridges along their landward side which may show their former position
Example of a simple spit
Spurn Head, Humberside
Sandy Hook Spit, New Jersey, USA
Example or a compound spit
Hearst Castle Spit, Hampshire
How do spits form
Where material is moved along the coast through longshore drift but where the coastline changes direction (often due to an estuary or river mouth) sediment starts to build up in the sheltered lee of the headland which begins to form a spit.
What makes a spit more permanent
During a storm larger material is deposited above the high water mark
What extends a spit further
Finer material continues to be moved along the spit through longshore drift and into the deeper water of the estuary/bay where enemy is lost and the sediment is deposited which extends the spit further. In some cases if the spit is growing across a river mouth turbulence where the river current and the coastal currents meet may cause further deposition
When may the end of the spit become recurved
As wave refraction and secondary winds and waves carry and deposit sediment round the end of the spit
What forms a compound spit
If the end of the spit recurves enough this is another change is coast line direction so the spit may continue to grow in the original direction. This may happen a number of times creating a compound spit.
What forms a salt marsh
A river flowing out to sea is likely to prevent the spit from growing right across an estuary but very fine sediment may be deposited by the river in the ‘slack’ low energy zone behind the spit. This forms a salt marsh which is an important coastal habitat
What may salt marshes be stabilised by
The growth of salt-tolerant plants
How does a tombolo form
Where a spit connects an island to the mainland
Example of a tombolo
St Ninian’s in Shetland
Why may the formation of a tombolo lead to salt marsh formation
The formation of the tombolo creates more sheltered conditions on the lee-side of it which may lead to deposition thus also salt marsh formation
When do barrier beaches form
Where a spit extends across a bay or joins two headlands together. They can only form where there is no current flowing off the land.
Example of barrier beach
The south coast of the UK including Slapton Ley, Devon
When are most barrier beaches thought to have been first formed
When gravel deposited in the English Channel when glaciers melted after the last Ice Age was deposited on the coast by constructive waves, forming the barrier beach. Longshore drift has since added more material to these.
What does the formation of barrier beaches and the subsequent deposition of sediment from longshore drift show
That landforms can be the product of a number of processes over a range of timescales
What forms behind a barrier beach
A lagoon which is usually shallow and marshy and in tropical locations mangroves can form
Overtime what happens to lagoons
They become full of silt and eventually dry up
When do barrier islands form
Where barrier beaches become separated from the mainland
Characteristics of barrier islands
Made of sand or shingle
Long (up to 100 miles long)
Narrow
Becoming vegetated as they get older and vegetation succession occurs
While the formation isn’t entirely understood, what is thought to be the formation of barrier islands
Though they are formed of sediment deposited when glaciers melted 18,000 years ago at the end of the last ice age. It’s probable that currents deposited this material in barrier beaches and that the melting ice also mean that sea levels rose leaving these beaches separated from the mainland.
Where are barrier beaches usually found
In areas with low tidal ranges and gently sloping offshore coastlines
In some cases, why do very long barrier islands get split into a series of shorter islands
Inlets develop between them to allow tides to rise and fall around the island
Example of barrier island
The West Frisian Islands in the Netherlands - they have marsh between the islands and the mainland and tidal inlets between them
How are offshore bars formed
Sediment deposited by costal currents including longshore drift but they remained submerged or semi-submerged offshore beyond the breaker zone. They are formed where currents deposit sand off-shore.
Along the Uk, what results in winds blowing onshore
Local differences in air pressure as the wind blows from the high pressure over the sea (the sea is cooler than the land) to the lower pressure area of the land (the land is warmer than the sea)
What does onshore wind mean
They sand is transported up the each through saltation
What do areas which have a high tidal range have
Large expanses of sand which are exposed and can dry out at low tide and therefore more likely to have sand dunes forming
What provides sources of sand for sand dune formation
Onshore wind
Offshore sand bars
Areas which have a high tidal range and large expansion of sand
What are the stages of sand dune formation
- Sand is trapped by an obstacle. Often on a storm berm where driftwood is deposited.
- More sand is trapped so obstacle grows, slowing the wind and contributing to further deposition.
- First dunes are called embryo dunes which can be colonised by pioneer species. Plant root stabilises the dune and decaying plant matter adds organic content to the sand.
- As dunes grow they become out of the reach of high tide and are known as yellow dunes.
- More sand accumulates and plants continue to grow and add organic matter to dunes, they become fixed and ‘grey’ as the humus (organic content) increases.
- Dune slacks may form between the dunes where the water table is at the surface.
- Inland from grey dunes, you find mature dunes or dune health/woodland. This is the final stage in succession called the climax vegetation.
- Within the system it is possible to find blowouts where the wind has been funnelled through the areas and has removed the sand. Wildlife of human activity can often be a catalyst for the formation of blowouts.
Example of pioneer species
Marram grass and sea couch
What are the characteristics of embryo dunes
1 m high and 80% exposed sand, low water table
Characteristics of yellow dunes
5m high and 20% exposed sand, rising water table
Characteristics of grey dunes
8-10m high and less than 10% exposed sand, rapidly rising water table
What are grey dunes able to support
Larger plants which require more water and organic matter such as gorse bushes
What forms in dunk slacks
Aquatic ecosystems
What is found in mature dunes
Hardy trees such as birch and shrubs like fodder broom and heather grow which further increase humus levels, moisture retention and decreases the pH. this is called the climax vegetation
What is the process of succession started on sand known as
A psammosere succession
What is the pH of embryo dunes
8.5 (alkaline)
Foredune/yellow dune
7.5 (alkaline but almost neutral)
What is the Ph of mature dune
6 (acid)
Which are the mobile dunes and the fixed dunes
Embryo + foredune and yellow dune are mobile whereas grey dunes are fixed
Where are the largest sand dune in the Uk
West coast
Example of a sand dune
Studland Bay near Southhampton
Examples of estuarine landforms
Mudflats and salt marshes
Where do estuarine landforms form
On low energy coastlines and in areas of lower energy such as river estuaries where tidal currents are slowed down or behind spits where slack (low energy) water is found
How do mudflats form
In estuaries or behind spits slow flowing water from the river carrying lots of suspended sediment meets saline sea water which causes flocculation to happen as clay particles aggregate (join together). These larger, heavier, clay particles sink to the bed of the estuary. At low tide in the inter-tidal area this mud is exposed with water left flowing in channels between the mud flats.
Over time what can mudflats become
Salt marshes
Where are the largest mudflats and salt marshes in the UK
Morecambe Bay in Lancashire
Like sand dunes, what can the formation of mudflats and salt marsh ecosystems be described as
A step-by-step sequence of succession. This is called a halosere
What is a halosere
Salt-tolerant succession/ecosystem
What is the halosere of mudflats and salt marshes
- Vegetation like eelgrass begins to grow.
- This slows currents down which leads to more deposition although it’s uneven depending on where the eelgrass is.
- Pioneer species begin to colonise the area (these are halophytes).
- Deposition continues and the plants continue to grow and die which raises the surface of the marsh. As this happens the mudflats are submerged for shorter periods of time and the mudflats become a salt marsh.
- more complex flowering species like sea lavenders become established as they are less tolerant to salt than the pioneers.
- More deposition occurs and vegetation becomes more dense which further raises the surface level and soil conditions improve.
- Where the marsh rises above the level of Spring high tide trees and scrub starts to grow as the climax vegetation.
- As the land rises above sea level, rushes and reeds become established, eventually leading to the growth of trees such as alder, ash then oak to complete the succession.
Why do eelgrass not count as a pioneer species
It is a sea plant
What does a halophytes vegetation mean
Salt-tolerant
Example of a pioneer species that grows on a mudflat
Spartina (e.g cordgrass) which is the dominant vegetation of the Uk
Why is spartina the dominant vegetation on Mudflats in the UK
As it has a fine mat of roots, which binds the mud together and thus traps more sediment
What does climax vegetation mean
The natural end-point of succession
In reality, why is the climax vegetation not always reached in estuarine landforms
As farmers graze sheep on the salt marsh (in some puns you can order salt-marsh lamb for Sunday lunch)
What are the characteristics of coastal landscapes that we see today the result of
The factors that shaped them during the Holocene (roughly the time since the end of the last glacial period some 12,000 years ago)
What are the range of factors important in producing the present coastal landscape features
Local tectonic activity.
Sea level change - global and local.
Climatic change - natural and that enhanced by human activity.
Changing ocean currents and wave regimes.
Natural disaster or events like tsunami.
Changing sources, types and amounts of sediment.
The changing nature of humans activity.
All of the above have continually changed over the millennia but will have left their mark as features in the coastal landscape of the present day, where contemporary costal processes will inevitably continue to alter and modify them further,
Characteristics of mature dunes
6-8 metres and high water table
Example of mudflats in the USA
Cape Cod and Plymouth Bays off Massachusetts
What are the functions of Spartinas two root systems
A fine mat of surface roofs to bind the mud and long, thick, deep roots that can secure up to 2 metres of deposited material. This enables the plant to trap more mud than other pioneers, and thus it has become the dominant vegetation on tidal flats in the British Isles
Where may hollows form on a salt marsh
Where seawater becomes trapped and evaporates, leaving salt-pans in which the salinity is too great for plants to survive.
What are the two ideas relating to sea level change
Eustatic change
Isostatic change
What do changes in sea levels create
Distinct landforms of emergence (falling sea level relative to the land) and submergence (rising sea level relative to the land)
What is isostatic sea level change
A change in the level of the land relative to the sea as a result of the changing level of the land.
Examples of isostatic sea level change
Contentment’s collide and fold mountains form the land is forced to rise up out of the sea
What are the changes of isostatic sea level change
Local/regional
What ads the scales of isostatic sea level change
A rise or fall in the sea level as a result of a change in the actual level of the water in the oceans.
Example of eustatic sea level change
Temperatures increase water expands meaning that sea levels rise when sea temperatures are warmer
What are the scales of eustatic change
Global changes
18,000 years ago, what were sea levels like
Last glacial maximum: sea levels were on average 110m below their current level which meant the the UK was joined to mainland Europe and Scandinavia by a large land bridge where the North Sea now is called Doggerland.
10,000 years ago, what were sea levels like
The northern North Sea was flooded and the coastline and Europe was beginning to look as it does today but Doggerland still linked what is now the UK to what is now the Netherlands and Denmark
9,500 years ago, what were sea levels like
They rose rapidly in 500 years
Prior to the industrial revolution, what were sea levels like
Fairly stable for about 3000 years
Recently, how much have sea levels risen
6cm on average from the mid-19th century and 19cm during the 20th century. Current sea levels are rising at 3.2mm per year
Why are current sea levels rising at 3.22mm per year
Due to thermal expansion
What is the predicted increase in sea levels for 2100
4-6m rise although this could be greater depending on how Greenland and Antarctic ice sheets respond to warming temperatures
What is stage 1 of a typical sequence of sea level rise that reflects the advance and retreat of the ice
As climate gets colder, marking the onset of a new glacial period, an increasing amount of precipitation falls as snow. Eventually, this snow turns to glacier ice. Snow and ice act as a store for water, so the hydrological cycle slows down - water cycled from the sea to the land (evaporation, condensation, then precipitation) does not return to the sea. As a consequence, sea levels falls and this affects the whole planet. Such a worldwide phenomenon is known as a eustatic fall.
What is stage 2 of a typical sequence of sea level rise that reflects the advance and retreat of the ice
The weight of ice causes the land surface to sink. This affects only some coastlines and then to a varying degree. Such a movement is said to be isostatic and it moderates the eustatic sea level fall in some areas.
What is stage 3 of a typical sequence of sea level rise that reflects the advance and retreat of the ice
The climate begins to get warmer. Eventually the ice masses on the land begin to melt. This starts to replenish the main store and sea level rises worldwide (eustatic). In many areas this floods the lower parts of the land to produce submergent features such as flooded river valleys (rias) and flooded glacial valleys (Fjords)
What is stage 4 of a typical sequence of sea level rise that reflects the advance and retreat of the ice
As the ice is removed from some land areas they begin to move back up to their previous levels (isostatic readjustment). If the isostatic November is faster than the eustatic, then emergent features are produced such as raised beaches. Isostatic recovery is complicated as it affects different places in different ways. In some parts of the world it is still taking place as the land continues to adjust to having masses of ice removed. Today, the southeast of the British Isles is sinking while the northwest is rising. This reflects the fact that the ice sheets were thickest in northern Scotland and that this was the last area in which the ice melted.
What are the 3 cause of isostatic change
Tectonic activity.
Glaciation.
Post-glacial readjustment.
How is tectonic activity a cause of isostatic activity
Land can move up or down as a result of tectonic activity. This could be a few meters as a result of one event
Example of small scale tectonic activity causing isostatic activity
The Tohoku earthquake in Japan in 2011 some sections of the coastline dropped 0.84 meters.
Example of large scale tectonic activity causing isostatic activity
Fossils in the Andes, Alps and Himalayas all show that the rocks found in these fold mountains were once in the ocean floor, but have been forced up thousands of meters as part of the formation of the mountains
What is glaciation
During an ice age glaciers and eventually ice sheets form over the land in areas cold enough. This causes the land surface to become pressed into the upper layer of the mantle (the asthenosphere) and therefore relative sea levels rises.
What is post-glacial readjustment
Following the melting of ice sheets and glaciers on land the land is able to rise back up as the asthenosphere rebounds. This is called isostatic recovery
Why is isostatic recovery responsible for falling sea levels in Scotland
During the last ice age Scotland was the part of the UK covered with the thickest ice and melted last
How does isoline maps show isostatic sea level change across the UK
Positive numbers show land rising, negative numbers show falling land relative to sea level
What are the three causes of eustatic change
Thermal expansion of water
Changes in ice sheet extent.
Tectonic activity.
How is thermal expansion of water a cause of eustatic change
As water is heated it expands so even if the mass of the ocean (the total amount of water) stays the same. Warmer water has a larger volume so takes up more space and sea level therefore rises
How are changes in ice sheet extent a cause of eustatic change
Where ice forms on land during a glacial period it removes water from other stores including the the ocean so sea lev is fall. When ice on land melts there is less water locked up in ice on the land so more available to other stores including the ocean and therefore sea levels or rise
How is tectonic activity a cause of eustatic change
Where new land is being formed under the ocean, usually at mid-ocean ridges, this new rock/crust takes up space in the ocean basins, which would have been occupied by water so the water is displaced and sea levels rise. Times of higher amounts of volcanic activity at mid ocean ridges have higher eustatic sea levels and times of lower amounts of volcanic activity have lower eustatic sea levels.
What is total sea level change
The balance between isostatic and eustatic change
What is the total sea level change in Scotland today
Isostatic recovery is changing the level of the land to rise faster than thermal expansion and melting ice sheets are causing sea level to rise so the overall effect is that sea level is falling in Scotland and landforms of emergence are forming
What have coastlines of emergence been subject to
A fall in sea level whether this is as a result of eustatic or isostatic change or, more likely, as a combination of the two
All along the West Coast of Scotland what has isostatic recovery resulted in
The formation of distinct landforms of emergence
How do raised beaches form
Where the sea level drops relative to the land so what was a beach becomes stranded above the high water mark
Where are raised beaches common
On the West Coast of Scotland, for example on Arran
What are relict feature
Marine features such as courts and cliff profile features like caves that are left above the high tide level in which case they are called relief features e.g relict cliffs
Example of a relict features
Kings Cave on Arran
Why may raised beaches appear as flat, grassy terraces
They are subject to vegetation succession once above the high tide level
Why do wave cut (marine) platforms look like once left exposed above the level of the current wave cut platform
Less visible as they may well be covered in beach sediment from the current beach
What have coastline of submergence been subject to
A rise in sea level whether this is as a result of eustatic or isostatic change or, more likely, as a combination of the two
Why can a number of distinct features of submergence be seen along the south coast of England
As the isostatic tilt of the UK results in rising sea levels relative to the land as the land sinks
What are rias
Flooded river mouths/valleys
How do rias form
Where the sea level rises relative to the land, river valleys flood and appear as coastal inlets with relatively steep coastlines where the old valley sides are and the floodplain has been flooded by the sea
Example of a ria
The mouth of the river exe at Exmouth. Poole Harbour (near studland Bay). They make excellent harbours
What is a fjord
They are flooded valleys however they are flooded glacial valleys. They can often be very long
Why do Fjords have very steep, often near vertical, sides
When glaciers erode they creep steep sided, U-shaped valleys
Why is the mouth of the fjord often shallower than further inland
Glaciers can overdeepen their valley so this is often the case
Example of a Fjord
The Songnefjord in Norway in Norway is over 200km long from the sea to the head of the fjord
When do Dalmatian coasts occur
Where river systems which once ran parallel to the coast (generally due to concordant geology) are flooded resulting in a series of long islands which would once have been the hills along the valley sides parallel to the coastline
What are the landforms on the coastline of submergence
Rias
Fjords
Dalmatian coasts
What is the key difference between rias and Fjords and Dalmatian coasts
Rias and Fjords run perpendicular to the coastline, Dalmatian coast islands and peninsulas run parallel to it
Example of a Dalmatian coast
Croatia
Globally, how is sea level increasing
Eustatically as climate change causes thermal expansion and the melting of ice sheets
While sea levels are increasing globally, what may some coastlines experience
Localised sea level fall due to isostatic factors
What does how much sea levels increase by vary according to
Predictions of how much warming is likely to occur and how the Antarctic and Greenland ice sheets are likely to respond
What do average predictions of sea level increase vary between
18 and 59 cm compared to 1990 by 2090
What are changes in sea level the result of
Two processes: increases in the volume of the ocean, subsidence of the ocean
What are the 9 impacts of sea level change
Major centres of UK population including London, Hull and Middlesbrough are at risk from inundation.
Lots of UK agricultural land could be lost through both flooding and increased coastal erosion.
Major road and rail links such as the east coast Mainline are at risk.
Numerous power stations and gas and oil terminals which are often built along the coast risk flooding.
Ground water may become contaminated with sea water resulting in it becoming unstable.
River flooding may increase in frequency as rising sea level reduces the gradient of the long profile of the river.
Loss of coastal habitats such as mangroves.
Submergence of low-lying islands like the Maldives.
Migration away from coastal areas, in Bangladesh alone 11% of land is likely to be permanently flooded.
Where is there valuable arable land in the UK
Along the east coast
What are coastal systems a product of
A series of processes acting at a range of scales over a range of timescales from hourly changes in tide levels to geological-time scale changes in continental movement
What does any coastline have
A range of features formed by past processes but present processes are also acting upon these
Example of landforms created by past processes but present processes are acting upon it
Raised marine terraces in Scotland are still being affected by present-day erosion at high tide
What is really important to understand about a coastal landscape
It is made up of a combination of short-duration, medium-term and long-term ones
What landforms are current systems in coasts likely to be responsible for
The current systems are responsible for more recent features but they are likely to be modifying relict (previous) ones
What are the aims of coastal management
To provide defence against, and mitigate the impacts of flooding.
To provide protection against, and mitigate the impacts of coastal erosion.
Stabilise beaches affected by longshore drift.
Stabilise sand dune areas.
Protecting fragile estuarine landscapes.
What are the four defence options
Hold the line
Do nothing but monitor
Retreat the line
Advance the line
What is hold the line
Retain the existing coastlines by maintaining current defences or building new ones where existing structures no longer provide sufficient protection
What is do nothing but monitor
On some stretches of coastline it is not technically, economically or environmentally viable to undertake defence works. The value of the built environment here does not exceed the cost of installing coastal defences.
What is retreat the line
Actively manage the rate and process by which the coast retreats
What is advance the line
Build new defences seaward of the existing line
What is hard engineering
Involved building of entirely artificial structures using various materials such as rock, concrete and steel to rescue or stop the impact of coastal processes
Example of a sea wall
Minehead, Somerset
Norfolk
What is a sea wall
Concrete barrier along the coast that absorbs the energy of the waves. Sometimes they are curved in order to deflect the wave back out
Advantages of sea wall
Effective and will stop erosion.
Protects the coastline.
What are the disadvantages of sea walls
Have to be maintained and repaired.
Expensive to repair.
Looks ugly and not natural.
Last 100 years, deflecting the waves can make the base of the wall weak and therefore they require the constant maintenance throughout this period
Cost of sea wall
£6,000 per metre + maintenance
Example of groyne
Minehead, Somerset.
Norfolk
What is a groyne
Traditionally these are wooden but recently they are rock. They rescue the route at which longshore drift carries material along the beach by trapping it on one side
Advantages of groynes
Creates a bigger beach to help protect the coast from the sea.
Relatively cheap.
What are the disadvantages of groynes
More erosion on cliffs.
Preventing the sand from moving can cause erosion rates to increase further down the coast.
Only last around 30-40 years.
Cost of groynes
£1000 per metre if wooden and £1000 per cubic metre if rock
Example of rock armour
Minehead, Somerset.
Norfolk.
What is rock armour
Made from granite or other hard rocks. Placed at the base of a cliff to absorb the energy of the waves but let water drain through them.
Advantages of rock armour
Relatively cheap.
Last around 120 years.
Use natural resources e.g rock.
Disadvantages of rock armour
Still let some water through so some erosion still takes place.
Looks environmentally ugly.
Sustainable sourcing as it can be taken from a quarry.
Price of rock armour
£1000 per metre
Example of revetments
Norfolk
What are revetments
Slipping concrete or wooden defence facing the sea. Wooden structures also trap the beach material.
Advantages of revetments
Absorb the wave energy.
Better looking than a sea wall.
Disadvantages of revetments
Wooden structure lasts around 10 years.
Concrete ones last 30 years.
Less durable than a sea wall and need replacing quicker.
Don’t give total protection to the base of the cliff.
Price of revetments
Up to £4500 per metre
Example of offshore break water
Elmer Beach, West Sussex
What are offshore break water
Built parallel to the coast, it is off the coast and made of rock. Waves are faced to break before they reach the shore and reduces wave energy
Advantages of offshore break waters
Increase in wildlife.
Very effective at reducing the energy or the waves.
Out to sea so don’t spoil the beach.
Disadvantages of offshore break waters
Implications for fishermen.
Very expensive.
Being out at sea means they can be tricky to maintain.
Cost of offshore break water
£1.3 million for one
What is soft engineering
Trying to work with the physical and natural processes within an area rather than building large man made structures to protect the land form a wave attack
Example of beach replenishment/ beach nourishment
Miami Beach
What is beach replenishment
Sand is replaced along the beach. Done by taking material from sea bed and dumping it on to shore.
Advantages of beach replenishment
Makes the beach more effective at dispersing the energy of the waves.
Replaced material lost by longshore drift.
It’s attractive as beach looks untouched.
Disadvantages of beach replenishment
Does not prevent long shore drift so it has to be done repeatedly, making it expensive.
Involves using a dredger which is noisy upsetting tourism.
Kills marine life from sea bed.
Cost of beach replenishment
£3000 per meter but has to be done once or twice a year
What is managed retreat
Involved allowing the coast to take back the land, by removing existing sea defences and allowing the land behind them to flood. Overtime land becomes marshland allowing habitats to form
Advantages of managed retreat
New habitats.
Marsh acts as a natural sea defence protecting the land behind it from erosion.
A fairly cheap sea defence.
Disadvantages of managed retreat
Some people may not agree over which land should be flooded causing conflict.
Cost of managed retreat
Cost is variable
What is cliff regrading and drainage
Reducing the angle of a cliff to stabilise it. Drainage removes excess water to prevent landslides and slumping.
Advantages cliff regrading and drainage
Cheap.
Very effective on clay or loose rock cliffs but not rock like chalk.
Disadvantage of cliff regrading and drainage
Causes soul to dry out.
Some homes may need to be demolished as it effectively causes retreat.
If cliff drys out too much it may cause it to crumble and collapse.
Cost of cliff regrading and drainage
£200-2000 per 100m
£2-20per meter
What is dune stabilisation
Methods such as planting of marram grass and fencing off areas are employed to protect the dunes from erosion
Advantages of dune stabilisation
Maintains a natural coastal environment.
Provides wild life habitats.
Cheap and sustainable.
Disadvantages of dune stabilisation
Time consuming.
May still be eroded if people ignore signs to stay off certain areas.
Cost of dune stabilisation
Variable
Since the 1990s what have UK governments focused on with management and mitigation of coastal floods and erosion
Sustainability
What are examples of sustainable approaches to coastal management
Shoreline management plans and
Integrated coastal zone management
When was the integrated system of Shoreline Management Plans (SMPs) introduced
In 1995 to avoid a piecemeal approach to management
How many SMPs are around the coast of England and Wales and what do they corespond with
22 and they correspond with the sediment cells and sub-sediment cells
What are SMPs designed to identity
The most sustainable approach to managing the flood and coastal erosion risks to coastlines
What do SMPs aim to plan for
Short term (0-20years) Medium term (20-50) Long term (50-100)
What are the key features of the SMPs
Provide an assessment of the risks associated with the evolution of the coast.
Provide a framework to address the risks to people and to the developed, historical and natural environment.
Address risks in a sustainable way.
Provide the policy agenda for coastal defence management planning.
Promote long term management policies for the twenty-second century.
Aim to be technically sustainable, environmentally acceptable and sustainable economically viable.
Ensure management plans comply with international and national nature conservation and biodiversity legislation.
Incorporate a ‘route map’ to allow decision makers to make changes to the short term and medium term plans to ensure long term sustainability is maintained.
Provide a foundation for future research and the development of new coastal management strategies in the future.
Are ‘live’ working documents to be continually reviewed and updated, setting new targets for future management objectives.
What does each SMP describe
How each management unit, or stretch of coastline covered by the plan, is to be managed e.g hold the line, do nothing, managed retreat or advance the line
Where did the term ‘integrated coastal zone management’ originate from
The UN Earth Summit of Rio de Janiero in 1992
Where were the guidelines about how ICZM should operate set out
In the Agenda 21 documents released following the summit
What does the European Commission describe ICZM as
Integrated coastal management aims for the coordinated application of the different policies affecting the coastal zone and related to activists such as nature protection, aquaculture, fisheries, agriculture, industry, offshore wind energy, shipping, tourism, development or infrastructure and mitigation and adaption to climate change. It will contribute to sustainable development of coastal zones by the application of an approach that respects the limits of natural resources and ecosystems, the so-called ‘ecosystems-based approach’.
Integrated coastal management covers the full cycle of information collection, planning, decision making, management and monitoring of implementation. It is important to involve all stakeholders across the different sectors to ensure broad support for the implementation of management strategies
Why did the European Commission, Following Rio develop its framework for ICZM
To promote integrated coastal management.
What was the background to the ICZM initiatives
Coastal zones are some of the most economically productive areas in the world.
The natural assets of coasts have for millennia made them popular for:
-settlements
-tourist destinations
-business centres
-port.
Around 200 million people live near Europe’s coastline.
The Commission feels this concentration of people and economic activity is putting great pressure on our coastal environment and creates excessive exploration of natural resources, all of which leading to: biodiversity loss, habitat destruction, pollution, conflicts between stakeholders, overcrowding in some locations.
Why does the European Commission suggest that the revised ICM initiative is required
They are some of the areas most vulnerable to climate change and natural hazards.
Coasts are especially at risk of: flooding, erosion, sea level rise, extreme weather events.
The life’s of people in many coastal communities are already changing due to the impacts of these issues.
In the past, what was coastal management often viewed as having
A sectoral approach, where the local authorities made decisions for their stretch of coastline and other agencies and interest groups tries to manage their particular environment, cause or social group
Why was a sectoral approach to coastal management not good
In the view of the European Commission, this led to decision that undermined each other, an inefficient use of resources and failure to meet sustainability objectives
What is ICZM designed to do
Integrate the interests of all stakeholders to avoid conflict. It aims to co-ordinary policies that affect the coastal zone and the activities that take place there
What coastal activities does the ICZM aim to co-ordinate policies for
Nature conservation/protection Aquaculture (farming marine organisms like lobsters) Fishing Agriculture Industry Offshore wind energy Shipping Tourism Infrastructure development Development to adapt to and mitigate climate change
What approach does the ICZM employ
An ‘ecosystem-based approach’ that operates within the limits of natural resources and ecosystems
If operated properly, how should ICZM operate
In a cycle with each stage generating feedback to be addressed by the following stage
Information collection -> planning -> decision making -> managing and monitoring of implementation and then back to the beginning
In March 2013, what did the European Commission launch
A directive to establish a framework for maritime spatial planning (MSP)
What was MSP launched to do
Build on and work alongside ICZM by adopting some of the techniques already employed by land-use planners.
What is often involved in MSP
Mapping the activities of all stakeholders in a particular coastal zone, so that all those involved can visually assess the cumulative impact of their actions on a particular ecosystem. This can then inform future plans.
What techniques does MSP utilise
Powerful GIS and geo-spatial mapping because various scenarios can be visually played-out to help agree upon the most sustainable way forward
What is MSP hopes to play an integral role in
Improving the interaction between sea and land based activities including:
Connecting offshore wind turbines to the electricity distribution network on land.
Assessing the impacts of strategies to protect coastlines against erosion and flooding on activities like aquaculture and fisheries, and their impacts on marine ecosystems.
Examples of observational and measurement techniques to collect quantitative data in a coastal system
Annotated field-sketches.
Measuring: characteristics of waves e.g if they are constructive, the movement of material by longshore drift, the size and shape of beach sediment, the gradient of beaches and sand dunes - beach and dune profiles, wind direction and speed and the dimensions and characteristics of coastal landforms.
Other techniques can be used to identify, measure and map the types of sea defences used along a coastline.
What does coastal fieldwork produce
Quantitative data that is easily mapped using a range of geo-spatial mapping techniques to give a clear visual representation of the findings of the research
What kind of assessment is required when looking at many aspects of a situation
A holistic assessment
What are the different situations needing to be looked at on a coast
The challenge of mitigating the worst impacts of any sea level rise.
Improving resilience of communities.
Helping them adapt to their changing circumstances.
What are some examples of qualitative techniques in coastal landscapes
Participant observation and in-depth interviews.
On a local level, questionnaires and interviews
How are participant observation and in-depth interviews good techniques to collect data in the coastal landscape
They would be one way of engaging with the views of the populations knocked to inform the development of bottom-up solutions to further issues. This would be good with marginal coastal communities of Southern Bangladesh
How can questionnaires and interviews be used with coastal communities in the British Isles
To assess the views of various stakeholders about any proposed sea defences for a particular stretch of coast. The qualitative results of such surveys could then be analysed alongside more empirical data about factors such as financials cost and impacts on natural coastal processes to produce thorough cost-benefit or SWAT analyses of any proposed coastal management schemes, that include the view of all stakeholders.
