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Coastal landscapes

 

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Key idea Specification content
The coast is shaped by a number of physical processes.

 

Wave types and characteristics.

Coastal processes: • weathering processes – mechanical, chemical • mass movement – sliding, slumping and rock falls • erosion – hydraulic power, abrasion and attrition • transportation – longshore drift • deposition – why sediment is deposited in coastal areas.

Distinctive coastal landforms are the result of rock type, structure and physical processes.

 

How geological structure and rock type influence coastal forms.

Characteristics and formation of landforms resulting from erosion – headlands and bays, cliffs and wave cut platforms, caves, arches and stacks.

Characteristics and formation of landforms resulting from deposition – beaches, sand dunes, spits and bars.

An example of a section of coastline in the UK to identify its major landforms of erosion and deposition.

Different management strategies can be used to protect coastlines from the effects of physical processes.

 

The costs and benefits of the following management strategies: • hard engineering – sea walls, rock armour, gabions and groynes • soft engineering – beach nourishment and reprofiling, dune regeneration • managed retreat – coastal realignment.

An example of a coastal management scheme in the UK to show: • the reasons for management • the management strategy • the resulting effects and conflicts.

 

Coastal landscapes 1 – waves, weathering & mass movement

Year 11 Coastal landscapes – Marine processes

Coasts – Erosive landforms

Coasts – depositional landscapes

Coasts – Management – managed retreat

What causes waves?

Waves are caused by the transfer of energy from the wind to the sea due to friction on the water’s surface.

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Why are some waves stronger than others? Explain is detail each of the causes: 1.Strength 2. Duration and 3. Fetch

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Constructive and destructive waves

Destructive waves:

Destructive waves have a fairly weak swash because the wave breaks almost vertically. However, it does have a much stronger backwash. Because the backwash is stronger than the swash, destructive waves erode and transport material away from beaches.

wave D

Constructive waves:

Constructive waves have a strong swash and a much weaker backwash. Because the swash is stronger than the backwash they tend to deposit material and build beaches up.

Wave c

 

Weathering and mass movement

weathering

Weathering – is the breaking down of rock. Caused by day to day changes in the atmosphere.

Chemical weathering is caused by a chemical reaction when rainwater hits rock and decomposes it (eaten away). Rainwater and seawater can be a weak acid.

  • Carbonation
  • Hydrolysis
  • Oxidation

weathering 1

Mechanical (physical) weathering

Rocks are being disintegrated rather than being decomposed – associated with extreme temperature.

Freeze thaw – Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable (allow water to pass through).

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Mass movement – is the downslope movement of rock, soil or mud under the influence of gravity. Heavy rainfall is usually the trigger.

1.Sliding, 2.Rock falls & 3.Slumping

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Marine processes

There are three marine processes namely; erosion, transportation and deposition.

Coasts being at the boundary of the land and the sea are extremely vulnerable to erosion.

They are attacked by the immense power of the sea and the weather. The main ways that the sea erodes the coast are:

Hydraulic Pressure: This is when sea water and air get trapped in cracks. The increasing pressure of the water and air cause the rocks to crack.

Corrasion (abrasion): Rocks been thrown into the cliffs by waves and breaking off bits of the cliff.

Corrosion (solution): The slight acidity of sea water causing bits of the cliff to dissolve.

Attrition: Rocks, sand and stones being thrown into each other by the sea current and waves.

Wave Pounding: This is the immense power of waves crashing into cliffs that causing them to weaken.

How is material transported? 

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Longshore Drift: This is the process of waves moving (transporting) material (load) along a coastline.

Swash: The waves breaking and traveling up the beach carrying load. Waves will break and the swash will travel in the direction of the wind.

Backwash: The waves returning to the sea with load. Waves will take the shortest possible route back to the sea (gravity).

Longshore drift only happens when the waves hit the beach at an angle. It is the process of the swash transporting material up the beach at an angle and the backwash returning directly under the force of gravity that causes material to be transported along the beach.

Prevailing (or dominant) Wind: This is the direction that the wind normally hits a coastline.

Groynes: are wooden or concrete fences (walls) placed out into the sea to stop longshore drift happening. (see the section on management)

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Deposition

When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves.

Deposition is likely to occur when:

  • waves enter an area of shallow water.
  • waves enter a sheltered area, e.g. a cove or bay.
  • there is little wind.
  • there is a good supply of material.

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Coastal landforms

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Erosive landforms

Headlands and bays

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Headlands and bays form mainly along discordant coastlines where different types of rock face the oncoming waves at 90 degrees. Softer rocks are eroded much faster than harder rocks and so bays form. Hard rock outcrops form headlands. Over time headlands attract high energy destructive waves through wave refraction and the bays create sheltered low energy zones where constructive waves deposit material to form beaches.

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Wave refraction at a headland

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Wave refraction and the distribution of destructive and constructive waves around headlands – watch the following video and take notes:

Cliffs and wave cut platforms

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At high tide the power of the sea attacks and erodes the bottom of the cliff. Over time this erosion creates a wave cut notch (basically an eroded hole at the bottom of the cliff). As the wave cut notch gets bigger, the weight of rock above the notch gets greater. Eventually the cliff can not support its own weight and it collapses. The process then starts again, with the erosion of the sea making a new wave cut notch. As the process continues the cliff starts to move backwards (retreat). Because the cliff is moving backwards a wave cut platform (an expanse of bare rock) is created. Wave cut platforms are only visible at low tide.

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Caves, arches and stacks

Caves, arches, stacks and stumps are usually found on headlands. The waves always look for weaknesses in the headland (cracks and joints). If they find a crack or a joint they will start attacking it. Hydraulic pressure will be the main type of erosion. Overtime the crack may turn into a cave. Slowly the cave will get bigger and cut all the way through the headland, making an arch. As the arch gets bigger the weight of the arch roof gets too great and it collapses, leaving a stack. The stack is then eroded by the sea and weathered from the air leaving a stump. Blowhole: Sometimes the sea may erode through to the top of the headland (following a large crack). If this happens a blowhole is created.

Due to wave refraction and the energy of destructive waves being focused on the sides of headland many features of erosion form on the flanks of headlands. These include, cracks, wave-cut notches, caves, arches, blow holes, stacks and stumps

Wave refraction wraps waves and centres the energy around the headland. Due to a wave-cut platform of the headland, wave height builds quickly and destructive waves form and erode the sides of the headland.

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Coastal erosion on an OS map

Erosion features

Map erosion

On this extract, the term point (meaning headland) appears at Warren Point, 667421, ‘cliff’ at West Cliff, 692383 and cove, indicating where erosion has produced a small bay, at Redrot Cove at 668394.

Shape

The shape of the coast is also a good indicator.

In this extract the large headlands at Burgh Island, 646438 and Bolt Tail, 667396 stand out, suggesting a much more resistant rock type than in the area that lies in between these headlands.

Smaller headlands like Warren Point and Thurlestone Rock, 675414 enclose sandy bays like the ones depicted at 676416 on the map.

Off the headland there are small island Mew Stone 725359 and Little Mew Stone, 727358. These will be former parts of the headland now worn down to be stacks or stumps. Burgh Island was separated from the mainland by erosion.

Symbol evidence

Symbol evidence is also important and we see the symbols for cliffs at 688383 and steep slopes at 704368. Around here, contour lines appear to run into the sea, indicating the height of the cliffs at that point.

The flat rock symbol on the seaward side of the coastline indicates a wave-cut platform at 669421. (BBC Bitesize)

Depositional landforms

When water loses its energy, any sediment it is carrying is deposited. The build-up of deposited sediment can form different features along the coast namely: beaches, sand dunes, spits and bars.

Beaches

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The most important landform of deposition but ironically the one that students often forget is the beach. Beaches form at the foreshore through the transportation and deposition of material. Large beaches form at coastlines where there is a constant supply of sediment, generally under constructive waves. Constructive waves have dominant swash and transport material up the beach. Coastlines that have dominant destructive wave patterns tend to have narrower and steeper beaches because of the stronger backwash.

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Beaches are made up from eroded material that has been transported from elsewhere and then deposited by the sea. For this to occur, waves must have limited energy, so beaches often form in sheltered areas like bays. Constructive wave build up beaches as they have a strong swash and a weak backwash.

Beach Huts on the Beach at Saunton Sands Near Braunton on the North Devon Coast

Sandy beach – gentle gradient

Sandy beaches are usually found in bays where the water is shallow and the waves have less energy. Pebble beaches often form where cliffs are being eroded, and where there are higher energy waves.

pebble

Pebble beach – steep gradient

Characteristics Sandy beach Pebble beach
Gradient Almost flat Steep
Waves Constructive Destructive
Distance inland Long way Not far
Back of beach Sand dunes Storm beach with large pebbles
Other Water filled depressions called runnels Pebbles increase towards the back

A cross-profile of a beach is called the beach profile. The beach profile has lots of ridges called berms. They show the lines of the high tide and the storm tides.

beach_profile

 

Sand dunes

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Dunes form where the beach is wide enough to allow for the accumulation of wind-blown sand, and where prevailing onshore winds tend to blow sand inland. Obstacles—for example, vegetation, pebbles and so on—tend to slow down the wind and lead to the deposition of sand grains.

For a sand dune to form it needs:

  • a large flat beach
  • a large supply of sand
  • a large tidal range
  • an onshore wind
  • an obstacle for the dune to form against (drift wood)

Wind move the sand in three ways:

  1. Suspension 2 Saltation and 3 Creep

transportation

How do dunes change inland?

sand dunes

Spits

A spit is an extended stretch of sand or shingle jutting out into the sea from the land. Spits occur when there is a change in the shape of the landscape or there is a river mouth.

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Spits are long narrow ridges of sand and shingle which project from the coastline into the sea. The formation of a spit begins due to a change in the direction of the coastline, where a low energy zone is found. This can also be at the mouth of the estuary. The main source of material building up a spit is from long shore drift and current, which brings material from further down the coast.
Where there is a break in the coastline and a slight drop in energy, long shore drift will deposit material at a faster rate than it can be removed and gradually a ridge is built up, projecting outwards into the sea – this continues to grow by the process of long shore drift and the deposition of material.

Water becomes trapped behind the spit, creating a low energy zone, as the water begins to stagnate, mud and marshland often begins to colonise behind the spit.

spit

Bars

A spit can grow across a bay and joins two headlands together. This landform is known as a bar. They can trap shallow lakes behind the bar, these are known as lagoons. Lagoons do not last forever and may be filled up with sediment.

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bar

Deposition features on an OS map

map deposition

A good start is to look for name evidence. On this extract, the term ‘sands’ appears at 833443, Slapton Sands. Start ‘Bay’ itself lies between the headlands of Start Point, 8337 and Combe Point (to the north-east, off the map extract area). In Scotland, the term ‘links’ often indicates a sandy area along a coastline.

Shape

The shape of the coast is also a good indicator. In this extract the smoothness of the coastline shown indicates a depositional coastline. This contrasts with the roughness of the erosional coastline area around Start Point.

Longshore drift

When sand spits appear on an OS map the direction of the longshore drift can be determined as it will be moving towards the point where the end of the spit is being formed. Here, however, the direction cannot be determined from the map as the spits have formed sand bar right across the river mouths.

Sand spits

Sand spits are fairly easy to identify on an OS map. The fact that they extend out into the water is a good way of spotting them and if you look closely you can see the curved hook at the end.

Coastal management

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It’s becoming increasingly important for councils and governments to start managing coastlines in order to protect them from increasing coastal erosion and flooding due to altering sea levels. The reason for coastal management is obvious, to protect homes and businesses from being damaged and even destroyed by coastal erosion or flooding. Failure to do so can have severe economic and social effects, especially along coastlines which are used for tourism and industry.

Management of coastlines is also important to help protect natural habitats, however governments generally don’t engage in coastal management where there isn’t an economic risk as effective coastal management is very expensive.

Ways in which the coast can be managed

When engaging in coastal management, there’s four key approaches that can betaken:

Hold the line – Where existing coastal defences are maintained but no new defences are set up.

Advance the line – New defences are built further out in the sea in an attempt to reduce the stress on current defences and possibly extend the coastline slightly.

Retreat the line (surrender) – Move people out of danger zones and let mother nature unleash take control.

Do nothing – The easy option, deal with the effects of flooding and erosion as they come or just ignore them. This is generally what happens in areas where there’s no people, and so nothing of “value” (to the government) to protect.

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Coastal management – hard and soft engineering

The two ways in which we manage the coastline against the sea are by either using hard engineering or soft engineering techniques – or a combination of both.

Hard Engineering: This building a physical structure, usually out of wood or concrete to protect the coast. Hard engineering is usually more effective, but it can be very expensive and ugly to look at.

Soft Engineering: Rather than building physical structures made out of wood and concrete, soft engineering is working with nature. The results of soft engineering look much more natural and may not even be noticed. The advantage with sot engineering is that it does not ruin the look of the coastline and it can be cheaper. However, the main problem is that most forms of soft engineering cannot withstand strong storms. In fact, a hurricane can strip a recently replenished beach of all of its sand.

Sea wall: are made out of concrete are aimed to absorb the waves energy. Sometimes they are recurved to direct the waves energy back out to sea. They can be very effective, but again are expensive, ugly and reduce access.

Groynes: are designed to stop longshore drift transporting away beach material. They can be effective in maintaining a beach, but need replacing regularly, look ugly and can cause problems down the coast, because they are not receiving beach material.

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Revetments: They are similar to sea walls, but often built out of wood. Often found at the foot of cliffs they are designed at absorb the waves energy.Again they need replacing regularly and do not protect against big storms.

Rip-rap: Rip-rap is basically giant boulders placed at the foot (bottom) of cliffs. Rip-rap is designed to absorb the waves energy and protect the cliffs behind. Rip-rap can be effective, but does look ugly, may reduce access to the beach and can be expensive.

Gabion: also uses large boulders, but this time the boulders are placed in cages. This means that gabion can be installed quickly and again is fairly effective.

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Breakwater: Breakwaters are built out into the sea. They are a coats first line of defence. Instead of breaking on the coast, waves, break on the breakwater. They are often found around the mouths of rivers and ports. They are expensive and can disrupt shipping and animals.

Soft engineering techniques:

Beach Nourishment: This is simply adding more sand to the beach. Beaches are natural defences, so by making them bigger, you are creating a natural defence. Sand is sometimes taken from the sea bed or dunes inland.

Cliff Regrading: This means make cliffs less steep. Cliffs often become unstable because of undercutting. By reducing the angle you should reduce the undercutting and the risk of the cliff collapsing.

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Beach Drainage: Cliffs often collapse because they become saturated and the increased stress causes them to collapse. By removing some of the excess water you should reduce stress on the cliff.

Dune Stabilisation: Dune stabilisation is planting vegetation on the berm of the beach or on the dunes. By planting vegetation you should be making them more stable (roots) and reducing the moisture content (root uptake).

Managed Retreat: This is not always a popular solution, because it is basically allowing the sea to take back land. Low value land is often chosen to be flooded by the sea. By allowing this you are changing some inland ecosystems by adding salt water.

Coastal management case study: Holderness coastline

Coast Holderness%20Map

The Holderness coastline is located on the east coast of England. It is the fastest eroding coastline in Europe.

Reasons for management

The coastline is rapidly eroding at an average of 1.8 metres a year. There are several reasons why the coast at Holderness is eroding so quickly:

  • Rock type– the cliffs are made from less-resistant boulder clay (made from sands and clays) which slumps when wet.
  • Naturally narrow beaches– these beaches give less protection to the coast as it doesn’t reduce the power of the waves.
  • Man-made structures– groynes  have been installed to stop long-shore drift. This narrows unprotected beaches elsewhere even more.
  • Powerful waves– waves at Holderness travel long distances over the North Sea (so have a long fetch) which means they will increase in energy.

Management strategies

  • Bridlington is protected by a 4.7 km long sea wall.
  • Hornsea is protected by a sea wall, groynes and rock armour.
  • Coastal management at Withersea has tried to make the beach wider by using groynes, and also uses a seawall to protect the coast.
  • Mappleton is protected by rock groynes.
  • Spurn Head is protected with groynes and rock armour.

Conflicts

  • There has been an increase in erosion at Great Cowden because of the groynes used in Mappleton. This has led to farms being destroyed by the erosion and the loss of 100 chalets at the Golden Sands Holiday Park.
  • Some people disagree with where the sea defences are located, especially if it means the land in their community is not protected.
  • Some sea defences negatively impact tourism and reduce the amount of money coming in to the area.

 

 

The Holderness Coast is a great case study to use when examining coastal processes and the features associated with them. The area contains ‘text book’ examples of coastal erosion and deposition. The exposed chalk of Flamborough provides examples of erosion, features such as caves, arches and stacks.The soft boulder clay underlying Hornsea provides clear evidence of the erosional power of the sea. Mappleton is an excellent case study of an attempt at coastal management.

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Spurn Point provides evidence of longshore drift on the Holderness Coast. It is an excellent example of a spit. Around 3% of the material eroded from the Holderness Coast is deposited here each year.

Flamborough

Flamborough is the headland that forms the most northerly point of the Holderness Coast.

Geology

The most striking aspect of Flamborough Head are the white chalk cliffs that surround it. The chalk lies in distinct horizontal layers, formed from the remains of tiny sea creatures millions of years ago. Above the chalk at the top of the cliffs is a layer of till (glacial deposits) left behind by glaciers 18,000 years ago, during the last ice age. As the cliffs below are worn away by the action of the waves, the clay soil often falls into the sea in huge landslips.

Coastal features

The aerial photograph below shows Selwicks Bay, the most easterly bay at Flamborough and the location of the lighthouse. To the north of the bay is an arch and to the south you can see a stack.

Coast stack annotatedflampic

The sea attacks the coast around the headland in two ways. Waves beat against the vertical cliffs and, at the high water line, weak points in the chalk are worn away into caves. The weakest points are where vertical cracks or fault lines have appeared in the horizontal beds of chalk. At places on the cliffs where the chalk juts out, these caves are worn away into rock arches. If the top of an arch collapses, the result is a pillar of chalk cut off from the rest of the headland – this is called a stack. Flamborough Head has many caves and arches, as well as a few stacks. The process of erosion that has created them can take hundreds of years to do its work.

Hornsea

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Hornsea is the main settlement on the Holderness coasts. It has a population of around 8,500 and is an important holiday destination. Because it generates a large income through tourism, it was decided to protect Hornsea. On the sea front a 3 metre high recurved sea wall was built to absorb and reflect wave energy. Groynes were also placed along the beach to try and prevent longshore drift and keep Hornsea’s beach intact. On top of the sea wall, the cliff was also strengthened by building a concrete promenade. The promenade has a road on it, small cafes and shops and seating areas.

(Hornsea is a small coastal town located between Bridlington and Withernsea along the Holderness Coast. A 2.9km stretch of shoreline fronts the town of Hornsea. A high density urban development containing residential and various tourist related properties, Hornsea’s local economy is dependent on tourism and recreation as well as incorporating a small fishing industry.)

Geology
Hornsea lies upon unconsolidated till. This material was deposited by glaciers during the last ice age 18,000 years ago.

Coastal features
The groynes on Hornsea beach ensure wide and relatively steep beaches. The beach material is made up of sand and shingle.

Coastal management
The position of the coastline at Hornsea has been artificially fixed since existing coastal defences were erected in the early 1900s. Hard defences in the form of a concrete seawall and timber groynes afford protection and an on going refurbishment programme ensure this has continued.

Mappleton

Mappleton is a small settlement south of Hornsea. It only has a small number of houses, a church, a farm and a small caravan park. Because Mappleton was so small it was decided not to protect it. With no coastal defences, Mappleton was quickly disappearing into the sea. The residents of Mappleton were not happy and protested to the local government, blaming Hornsea’s defences on Mappleton’s accelerating erosion. The main blame was placed on Hornsea’s groynes. Because groynes stop longshore drift, Mappleton was receiving no sediment from up the coast, so its beach was disappearing. The prevailing wind on the Holderness coast, is from the NE so longshore drift goes from north to south. The local government was forced to agree with the finding, so Mappleton was protected with a rock groyne, some rip-rap and the cliff was regraded.

(Situated approximately 3km south of Hornsea lies the village of Mappleton. Supporting approximately 50 properties, the village has been subject to intense erosion at a rate of 2.0m per year, resulting in the access road being only 50m from the cliff edge at its closest point.)

Geology
Mappleton lies upon unconsolidated till. This material was deposited by glaciers during the last ice age 18,000 years ago.

Coastal features
The two rock groynes at Mappleton have helped develop wide and steep sandy beaches.

Coastal management
In 1991 almost £2 million was spent on two rock groynes and a rock revetment to protect Mappleton and the B1242 coastal road. Blocks of granite were imported from Norway for the sea defences. The purpose of the two rock groynes was to trap beach material. As the result of the coastal management a substantial beach accumulated between the groynes halting erosion.

coasts mappleton path

Spurn Point

Location

The area known as Spurn forms the southern extremity of the Holderness coast and includes the unique feature of Spurn Point, a sand and shingle spit 5.5km long, reaching across the mouth of the Humber.

Geology

Spurn is made up of the material which has been transported along the Holderness Coast. This includes sand, sediment and shingle.

Coastal features

Spurn Point is an example of a feature geographers call a spit.
Coast spurn point

The spit forms a sweeping curve which continues the line of the coast. The sand which forms the spit has been transported along the Holderness Coast by longshore drift. The energy in the waves transporting the material reduces where the North Sea meets the Humber Estuary. As a result the material is deposited. This process is known as deposition.

Coasts spurn point lighthouse 278_7cj5b0v5vi

Fieldwork – Coasts

Introduction a range of techniques that you can use for fieldwork in coastal environments. These techniques can be used in the traditional way to study and analyse coastal processes and landforms. Alternatively, why not update your fieldwork slightly to investigate one of the topical and relevant issues in the list below, using the same set of techniques.

Coastal investigations – Why not try…?

  • Investigating the value which people place on a local beach
  • Investigating a litter problem or another issue: why does it happen there, who is most responsible and what is their perception of the beach environment, how might the issue be resolved or minimised
  • Investigating coastal management strategies, for example groynes as habitats. What lives on or around them? How might their removal affect the ecosystem
  • Investigating water quality at the local beach – does it deserve its blue flag? Should it have one
  • Undertaking a cost-benefit analysis of coastal protection measures at a particular location
  • A ‘what would happen if…?’ study. For example, what would happen if all coastal protection measures were removed
  • Considering the possible implications of climate change and sea level rise. What impact will projected forecasts of more extreme weather events and rising sea level have on existing coastal management schemes

Technique one: Beach profiles

Aims

  • To survey the shape (morphology) of a beach
  • To compare beaches or coastlines in different locations
  • To examine the effects of management on beach processes and morphology
  • To investigate seasonal changes in the beach profile
  • To examine relationships between the beach profile and other factors, for example rock type, cliff profile, sediment size or shape

Equipment

  • Tape measure
  • Ranging poles
  • Clinometer or pantometer
  • Compass
  • Recording sheet

Methodology

  1. Select sampling points for beach profiles across the width of the beach
  2. At each sample point in turn, place a ranging pole at the start and finish (at A and H on the diagram). Point A should ideally be the low tide mark, or as close to this as is safe
  3. Note the main changes in slope angle up the beach, and use them to inform the ‘sections’ for the profile. (A through to H on the diagram)
  4. For each change in slope, use the clinometer to take a bearing to record the slope angle (ii). For example, from point A to point B in the diagram below. It is important to ensure that the bearing is taken from a point on the ranging pole that coincides with the eye level of the person using the clinometer. Many ranging poles have stripes which can be used for this purpose. Alternatively, bearings can be taken from the eye level of a person of a similar height holding the ranging pole
  5. Measure the distance along the ground of the section (i), and record this information alongside the slope angle
  6. Repeat processes four and five for each break in slope that you have identified

Fieldwork

Figure one: Surveying the morphology of the beach using a clinometer and ranging poles. Data collected using this technique can be used to create beach profiles.

Pantometers can be used by one person, and the slope can be surveyed systematically at regular, short intervals.

Clinometer

Figure two: Using a clinometer to measure the angle of a beach profile.

Considerations and possible limitations

  • Varying tidal conditions can affect access and safety. Make sure you check tide times before you embark on your fieldwork
  • Low tide is the best time to measure beach profiles, but places a time constraint on the activity. This can be overcome if groups of students complete profiles at different locations simultaneously and share their results
  • It is important to ensure that the ranging poles are held straight and prevented from sinking into sand, both of which may affect angle readings
  • Sampling technique is an important consideration. A balance needs to be struck between time available and the need for a number of profiles across the width of the beach to ensure the validity of results
  • There may be some user error when taking readings with a clinometer, and the sophistication of models of clinometer can vary enormously
  • If using a pantometer, this piece of equipment must be kept vertical when taking readings

Using the data within an investigation

  • Data can be used to draw profiles onto graph paper using distance from sea as the horizontal axis and using an angle measurer to complete the profiles. The graphs can then be analysed and comparisons made across the width of the beach
  • Profiles can be measured at different locations on the same stretch of coastline or in different seasons and compared
  • Different stretches of coastline which may have different natural characteristics, for example sand and shingle, or human characteristic, for example managed and unmanaged can also be compared
  • Beach profiles can be used in conjunction with other data collected to examine relationships between different variables

Technique two: Sediment analysis

Aims

  • To examine the sorting of beach material, either across the beach profile (following the sample lines used for profiling) or across the width of the beach (linking to the process of longshore drift)
  • To investigate the effect of management structures, for example groynes, on the sorting of beach material
  • To investigate the origin of beach material through the study of sediment cells
  • To compare sediment analysis at beaches in a range of locations and attempt to explain similarities and differences
  • To examine the relationship between beach sediment and other factors, for example the size and slope of the beach

Equipment

  • Clear ruler, pebble meter or stone-board
  • Roundness or angularity charts/indexes
  • Recording sheet
  • Quadrats (optional)
  • Random number table (optional)

Methodology

Techniques for measuring are the same as for sediment analysis in river studies. Please refer to this section for more information.

However, thought should be given to the sampling technique used to ensure that a representative sample is obtained.

Quadrats can be used to select sediment for sampling. Alternatively, ten surface pebbles touching your foot can be selected at each location. There are many different methods of sampling sediment. The different methods should be analysed by the researcher and an informed decision made as to which is the most appropriate for the aims of the investigation.

Considerations and possible limitations

  • Deciding on the sampling strategy is very important in reducing subjectivity and increasing the validity of results. A sampling method should always be adopted to avoid the temptation to select the pebbles
  • Sample size should be large enough to provide a representative sample of the ‘parent population’, yet not too large to be unmanageable
  • The sharpest point of a stone must be measured when using the Cailleux scale and judgement of this may vary from person to person creating subjectivity
  • In reality, using Power’s scale will reveal mostly class five/six
  • Anything which may affect the results should be noted, for example recent storms or management structures which may alter the composition of beach material

Technique three: Measuring longshore drift

Aims

  • To examine the transport of material along a stretch of coastline
  • To compare processes of sediment transport in different locations along the coastline
  • To investigate the effect of management techniques on the movement of beach material along the coastline
  • To examine the causes and effects of changes to the dominant direction of longshore drift
  1. Observing swash and backwash, and transport of material

Equipment

  • Float, for example an orange or cork
  • Stopwatch
  • Tape measure

Methodology

  1. Decide on an appropriate distance to measure longshore drift over, for example 10 metres
  2. Lay out tape measure close to water and mark start and finish points
  3. Place your float into water in the breakwater zone at the start point
  4. Observe and time the object’s movement across the pre-set distance

Similar results can be obtained if the distance travelled by the object is recorded over a specified time, for example five minutes.

Considerations and possible limitations

  • Tidal and wind conditions, the size and weight of float used and the slope angle of the beach may all affect measurements
  • Take note of the wind speed and direction on the day the fieldwork is undertaken as this may affect the speed at which the float is transported. This is particularly important if further sampling for the investigation is undertaken on another day
  • Obstructions to the movement of float, for example rocky outcrops, may affect results.
  • Floats may be lost during the investigation. Repeated experiments or the use of more than one marker can reduce this problem
  • Floats should be placed in the water ahead of the start line to allow them to settle prior to recording, and avoid giving the floats extra momentum
  • The float should lie low in the water to ensure that it is not influenced by the wind
  • The measuring should be undertaken in an area where there are no swimmers or paddlers for safety reasons and to ensure the reliability of results
  • Any anomalies should be recorded, for example obstructions which may affect the movement of the float
  • Weather and sea conditions can have a dramatic affect on observations

Using data within an investigation

  • Data would not be used in isolation, but in conjunction with other data collected as supporting evidence
  • Most commonly used when comparing managed and unmanaged stretches of coastline, particularly the impact of management techniques on transport processes within the sediment cell
  1. Investigating the impact of groynes on the movement of sediment

Equipment

  • Metre ruler
  • Compass
  • Record sheet
  • Camera

Methodology

  1. Using the compass, identify and record the aspect of each side of the groyne, for example the western and eastern side of each groyne
  2. Use the meter ruler to measure from the top of the groyne to the surface of the sediment on each side
  3. Take digital pictures to illustrate differences in sediment levels
  4. Repeat for each groyne, or identify and use a suitable sampling strategy if there are too many groynes to sample them all

Considerations and possible limitations

  • Measurements should be taken at the same point along the length of each groyne, and tidal conditions and safety are therefore a consideration when undertaking this fieldwork
  • Care should be taken to ensure that the metre ruler doesn’t sink into the sand, and that it is held straight

Using the data within an investigation

  • The findings of the investigation can be used to study the impact of physical and environmental processes on a stretch of coastline, including seasonal variations or variations in response to weather conditions, for example changes in the prevailing wind direction or storm events
  • Graphical representation of data can be used to compare sites
  • The data could be used within an investigation into the impact or success of coastal management strategies
  • A comparison of different sites could be made, comparing managed with unmanaged sites, or sites managed in different ways. The impact of coastal management strategies on other beaches further along the coastline can also be studied using this method.
  • Findings can be used to label and annotate images, see examples below from Swanage Beach in Dorset

Figure three: Annotated images of the beach at Swanage, Dorset showing evidence of longshore drift.

Fieldwork groynes

Figure four: Measuring the height of sediment to the west of a groyne

Keith Barlett from the Royal Manor Arts College in Dorset has written an article introducing an investigation which uses this methodology.

Technique four: Cliff surveys

Aims

  • To examine physical characteristics and features along a stretch of coastline
  • To identify different rock types and investigate the links between geology and physical features
  • To compare coastlines with different geologies
  • To study evidence of coastal erosion, including sub-aerial weathering, mass movement, basal erosion by the sea, human activity
  • To investigate and analyse strategies for protecting against coastal erosion

Equipment

  • Plain paper, pencil and rubber for sketch
  • Camera
  • Geological guides
  • Secondary evidence, for example photographs, maps, newspaper cuttings
  • Tape measure
  • Clinometer

Methodology

Cliff height

  • Standing a safe distance from the cliff, measure distance (A) using a tape measure. A distance of around 10 meters may be appropriate, but this depends on the size of the beach
  • Use a clinometer towards the top of the cliff to measure angle (B)
  • The height of the cliff is calculated as follows:
    • Distance (A) x tan of angle (B) + height of observer

Fieldwork cliff height

Figure 5: The method for measuring the height of a cliff using a clinometer.

Cliff sketch

A detailed sketch of the physical and human features of the cliffs at predetermined sampling points. Once cliff height has been established, the sketch can be drawn reasonably accurately to scale. Observations and annotations should be made of:

  • Obvious features, for example high tide level, caves, wave-cut notch, wave-cut platform, gullying
  • Basic geology (can be added later)
  • Structure, for example bedding planes and joints, folding and faulting
  • Conservation considerations, for example nesting birds, other animals
  • Type of vegetation and any evidence of effect on erosion
  • Evidence of erosion or mass movement, for example slumping, rock falls
  • Human activity, for example built structures, management/protection measures, recreational activities

Photographic evidence can also be used to support and reinforce sketches.

Considerations and possible limitations

  • Be aware of the safety implications of working close to cliffs, it can be dangerous
  • It is important to consider the sampling strategy, where to carry out cliff surveys and how many to do – before the investigation is started
  • There may be some user error when taking readings with a clinometer, and the sophistication of models of clinometer can vary enormously

Using the data within an investigation

  • Cliff profiles can be used in conjunction with other data collected to examine relationships between different variables, for example beach profiles or sediment analysis
  • An investigation could examine the links between the beach morphology, sediment and cliff features
  • An investigation could examine the links between the geology of the cliffs and beach material or movement
  • It is possible to compare different stretches of coastline with different geologies to see how they vary in terms of geology, sediment and beach morphology
  • Secondary data, for example historical maps, photographs or articles from local newspapers or websites can be used to examine recession rates. Predictions could be made for future rates of cliff recession, alongside suggestions for future management

A study of the range of different techniques used to manage the cliffs could highlight costs and benefits as well as potential impacts on physical processes and human activity. Each technique could be assessed in terms of its effectiveness at reducing rates of recession.

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