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Coastal environments

 Coastal environments

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Coasts – videos from the BBC (click on the picture)

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Marine processes

IGCSE Edecxel Coastal environments intro

Waves do most of the work of marine processes. They erode, transport and deposit

material. Waves are created from wind. The size of the wave depends on: strength of the

wind, how long the wind blows for (duration) and the fetch.

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Wave Terminology

Crest: The top of the wave.

Trough: The low area in between two waves.

Wavelength: The distance between two crests or two troughs.

Wave height: The distance between the crest and the trough.

Wave Frequency: The number of waves per minute.

Velocity: The speed that a wave is traveling.

It is influenced by the wind, fetch and depth of water.

Swash: The movement of water and load up the beach.

Backwash: The movement of water and load back down the beach.

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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.

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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.

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Coastal Erosion (types of erosion)

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.

Sub aerial weathering: This is the top of cliffs being attacked by the weather, making the cliffs weaker and less stable. Wind, rain, the heat and the cold can all cause the cliffs to be eroded.

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Coastal landforms

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Bays and Headlands

Bays and headlands are formed when you get alternate layers of hard and soft rock. The sea is able to erode the soft rock a lot quicker than the hard rock making a bay. The harder rock forms a headland.

Bay: An indented area of land normally found between two headlands. Bays are usually more sheltered so there is less erosive power, meaning you often find beaches in bays.

Headland: A piece of land that sticks out into the sea. Waves refract around headlands so they experience a lot of erosion forming

features like arches and stacks.

Wave Cut Notch and Wave Cut Platform

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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, Stacks and Stumps

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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.

Transportation (longshore drift)

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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.

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Sea currents: Currents are the movement of water caused by differences in temperature, changes in wind or tides. Currents can be extremely strong and can transport large amount of material.

Saltation: The wind can also transport sand and even small stones across a beach. The process of the wind bouncing sand and small stones across a beach is known as saltation.

Depositional landforms

Beaches, spits, bars and tombolos are all made by a combination of longshore drift and deposition. They are collectively known as depositional landforms. Beach: these are the most common deposition all landforms. They result from an accumulation of material between storm and low tide marks. The sand, shingle and pebbles come from a number of sources.

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The beach

Click on the link above – write up about beaches – history and formation.

Spits: A spit is a long thin stretch of sand connected to the mainland but stretching out into the sea. Spits are formed in areas of calmer water where the sea has less energy. They are normally found near the mouths of rivers where the coastline changes direction creating some protection. Longshore drift happens in the direction of the prevailing (dominant) wind. When the direction of the coast changes, longshore drift does not stop, but continues out into the sea. If the sea has less energy (because it is protected), material is deposited instead of transported. If deposition is greater than erosion, then overtime a spit will build up. The end of the spit is usually hooked because of occasional winds and storms that blow in the opposite direction of the prevailing wind.

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Tombolo: A spit that joins the mainland with an island. The 30km long Chesil Beach on the south coast of England links the isle of Portland to the mainland.

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Bar: A spit that connects two headlands or runs across the face of a small cove (bay).

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A CASE STUDY OF COASTAL EROSION & MANAGEMENT

Click on the link below (PowerPoint – looking at Barton-on Sea)

IGCSE BARTON_ON_SEA

Coral reefs

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Coastal ecosystems and their distribution

Coral Reefs

IGCSE Edexcel-Coasts-Coral reefs

Coral reefs are a unique marine ecosystem. They are built up entirely of living organisms. A coral reef is a line of coral polyp found in warm shallow seas. Polyp are tiny carnivorous (meat eating) animals. Polyps live in groups called colonies. A polyp has a mouth at one end. The mouth is surrounded by a number of tentacles. These tentacles resemble feet, which is how they get their name (‘polyp’ is a Greek word meaning ‘many feet’). Polyps cannot move from their limestone homes. They mostly feed at night.

Their global distribution is shown below:

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Coral reefs – global position

The global distribution of coral reefs is determined by four factors:

• Temperature – (minimum temperature of 18 degrees C)

• Light – needed for growth

• Water depth – no less than 25 metres deep

• Salinity – need salt water for survival.

Other factors are necessary at the local level, namely:

• Wave action – need well oxygenated water

• Exposure to air – cant be exposed to the air for too long or else they will die

• Sediment – corals need clear clean water (blocks light).

Types of reefs:

Fringing Reef: Fringing reefs circle or fringe the coastline or islands. They are often protected by barrier reefs further out to sea, so the plants and animals that live in fringing reefs are suited to low wave energy environments.

Barrier Reef: These occur further from the sea and are commonly separated from the mainland or island by a deep lagoon. Barrier reefs are normally older and wider than fringing reefs. The Great Barrier reef in Eastern Australia is a barrier reef and stretches for 1600km.

Atoll: They rise from submerged volcanoes. They are similar to barrier reefs in terms of biodiversity and form. However, they are confined to submerged oceanic islands, unlike barrier islands which can follow continental coastlines e.g. Great Barrier Reef.

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Benefits of coral reefs:

They support 25% of marine species (about 1 million species of plants and animals)

They protect coastlines from erosion

They form as a natural barrier against tropical storms and even tsunamis (they can absorb energy). Act as natural recycling agent for carbon dioxide from sea and atmosphere

They contribute material to the formation of beaches (eroded coral reef)

They are source of raw material (coral for jewellery and ornaments) Many species are being found to contain compounds useful in medicine.

They benefit the tourism industry because many people like to dive and snorkel over coral reefs

They provide important fishing grounds The global value of coral reefs in terms of coastal protection, fishing and tourism has been estimated at $375 billion.

Damage to coral reefs

Rising sea levels mean that the depth of water above coral reefs is increasing. This means that in the future many coral reefs will not receive enough sunlight to survive. Increases in the global climate means that many corals are being bleached. Coral reefs are extremely sensitive to changes in temperature and can bleach (die and turn white) even with only small increases.

Hurricanes. Although coral reefs act as a natural defence against tropical storms, they can be severely damaged during tropical storms.

Fishing techniques like dynamite, cyanide and trawling can damage corals. Corals are sensitive and take hundreds and thousands of years to grow. Damaging fishing techniques therefore can cause long term damage.

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Deforestation. As areas of land are deforested, especially in the tropics (Indonesia, Thailand, Philippines) there is greater surface run-off and more sediment enters the rivers and is ultimately discharged into the sea. The increased sediment reduces visibility and means less sunlight reaches the coral.

Overfishing. Not only do damaging fishing techniques damage the coral but also overfishing. Coral reefs have very delicate food webs and if you remove elements of the food web, it can upset the balance of the reefs.

Pollution. The growth of urban settlements and tourist developments, as well as increased coastal traffic can also cause pollution to reefs.

Tourism. Tourism can damage reefs in many ways. Anchors from tourist boats can damage reefs. Motor boat engines can kill animals. Divers can touch and damage coral and tourist developments can release pollution.

Marine trade. There are many products, like coral, turtle shells, star fish and sea shells that get removed from corals and sold. This removal of coral and animals damage the reefs.

Coral reef management:

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Damaging fishing practices like dynamiting can be banned. It is important that this is enforced or the practices will carry on. Conservation zones where tourists aren’t allowed or there numbers are restricted can be created. Areas where coral reef cannot be farmed can be created

Fish stocks can be enhanced and quotas imposed on amount being caught

Sewage outlets can be moved downstream of coral reefs

Banning the dropping of anchors on coral reef.

Reduce the use of fertilisers near coral reefs

Finally one of the most important is educating people about why coral reefs are important and how we can protect them.

 http://www.youtube.com/watch?v=eIul2ObvKV8

Mangroves

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Mangroves literally live on the coastline – they have one foot on land and the other in the sea. They live in a constantly changing environment because they grow in the intertidal zone. The water in this environment is ‘brackish’ meaning it is made up of salt and fresh water. Mangroves are not only able to survive these changing water conditions, they can cope with great heat and chocking mud.

The global distribution of mangroves is mainly between latitudes 25° N and 25° S. The remaining mangrove forest areas of the world in 2000 was 53,190 square miles (137,760 km²) spanning 118 countries and territories.

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The importance of mangroves

Mangroves, the only type of tree which spends its entire life submerged in saltwater, offer a bounty of benefits. During storms, they act as natural buffers against the sea, protecting homes and lives by absorbing wave surges (an even more important feature given the threat of climate change). By trapping sediments, mangroves help slow down land erosion, a serious problem for agricultural and property development. And the livelihoods of local fishermen are often staked to the health of mangroves, as they provide habitats for aquaculture catches such as crabs and shrimps, nursery grounds for 70% of commercially caught fish, and act as a critical force in balancing the flow of nutrients out to sea that enable nearby coral reefs to thrive.

Threats to mangrove forests and their habitats include:

Clearing: Mangrove forests have often been seen as unproductive and smelly, and so cleared to make room for agricultural land, human settlements and infrastructure (such as harbours), and industrial areas. More recently, clearing for tourist developments, shrimp aquaculture, and salt farms has also taken place. This clearing is a major factor behind mangrove loss around the word.

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Overharvesting: Mangrove trees are used for firewood, construction wood, wood chip and pulp production, charcoal production, and animal fodder. While harvesting has taken place for centuries, in some parts of the world it is no longer sustainable, threatening the future of the forests.

River changes: Dams and irrigation reduce the amount of water reaching mangrove forests, changing the salinity level of water in the forest. If salinity becomes too high, the mangroves cannot survive. Freshwater diversions can also lead to mangroves drying out. In addition, increased erosion due to land deforestation can massively increase the amount of sediment in rivers. This can overcome the mangrove forest’s filtering ability, leading to the forest being smothered.

Overfishing: The global overfishing crisis facing the world’s oceans has effects far beyond the directly overfished population. The ecological balance of food chains and mangrove fish communities can also be altered.

Destruction of coral reefs: Coral reefs provide the first barrier against currents and strong waves. When they are destroyed, the stronger-than-normal waves and currents reaching the coast can undermine the fine sediment in which the mangroves grow. This can prevent seedlings from taking root and wash away nutrients essential for mangrove ecosystems.

Pollution: Fertilizers, pesticides, and other toxic man-made chemicals carried by river systems from sources upstream can kill animals living in mangrove forests, while oil pollution can smother mangrove roots and suffocate the trees.

Climate change: Mangrove forests require stable sea levels for long-term survival. They are therefore extremely sensitive to current rising sea levels caused by global warming and climate change.

Sand dune formation

Coasts frippdunes

Sand Dunes are very dynamic, which means they are constantly changing. Sand dunes are found behind berms and are basically an extension of the beach. They are formed by dry sand being blown up the beach. Coastal sand dunes are accumulation of sand shaped into mounds and ridges by the wind.

They develop best where:

• There is a wide beach and large quantities of sand

• The prevailing wind is onshore

• There are suitable locations for the sand to accumulate

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Embryo Dune: Embryo dunes are the starting dunes of sand dunes. They form in the sheltered area behind the berm and strand line.

Foredunes: Small embryo dunes can join to make foredunes. Foredunes tend to be very yellow because they only have limited vegetation so no real humus layer develops.

Yellow Dunes: Sea couch and marram grass begin to grow on the foredunes so they become more stable and grow. As the dune grows and the vegetation develops a humus layer develops.

Grey Dunes: A developing humus layers starts changing the colour of the dune from yellow to grey.

Mature dunes: As the humus layers grows more, the dunes can sustain more plants, flowers and even trees.

Dune slack: As the size of the dunes develop water can collect between the dunes. Marsh plants can grow in these wet areas.

Blowout: A blowout is a depression or hole in the dune caused by the wind.

Humus: Is the layer of decaying plant and animal matter that adds nutrients to the ground.

Succession: The changing types of plants from basic sea couch to trees is known as succession.

Water table: The line between saturated and unsaturated ground.

Task: To find out how and where sand dunes are formed

Using the video, the embedded presentation and the diagram below, create a PowerPoint fact sheet on the formation and structure of sand dunes.  

Coasts 962966225

You should include the following:
How sand dunes are formed
Information on each of the six sections of a sand dune system
A photo of each section
An example of human uses of a sand dune ecosystem e.g.

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Sand dune management: Ainsdale, Merseyside

Salt marshes

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Salt marshes, like the mangrove, is an ecosystem of the intertidal zone. They occupy the midway location between mudflats that are permanently submerged by water and terrestrial (land) vegetation lying above the high tide mark. Salt marshes are usually found behind spits, in estuaries or on low energy coastlines. Because there areas tend to have low levels of energy, deposition exceeds erosion. The continued deposition means mudbanks are formed and they are exposed at low tide. Salt and water resistant grass is able to grow on these mudbanks, forming salt marshes.

The salt resistant vegetation (halophytic) means more sediment (load) is trapped and water is restricted to channels, rather than the whole salt marsh. As the height of the salt marsh increases more types of vegetation are able to colonise (move in) and grow.

The area of land that is inundated (covered) by sea water only at high tides and sometimes only spring tides is called the sward zone. Plants in the sward zone can only survive being under sea water for a maximum of four hours a day.

Threats to salt marshes:

Salt marshes are among the most used and therefore threatened ecosystem in today’ s world. The threats include:

• Reclamation to create farmland, sites for industry and port development

• Industrial pollution

• Agricultural pollution

• Pressure for developers

They are also being threatened by changes associated with global warming – more storms and higher water levels.

IGCSE Salt marshes

Factors affecting coasts

Geology – the difference between hard and soft rocks is a strong influence on the shape of the coastline. A coastline made up of weak rocks, such as clays and sands, will be easily eroded back by destructive waves. Bays will be created. Coastlines of more resistant, harder rock will not be eroded so quickly. They often jut out into the sea, as headlands. The difference between hard and soft rocks will also have an impact on the shape and characteristics of cliffs.

Vegetation – the longer a coastal landform, such as a sand dune, has existed, the greater the chances that it will be colonised by vegetation. In order to survive, the vegetation has to be able to cope with the particular conditions, such as high levels of salt in both the air and the soil. The major impact of vegetation is to help protect and preserve coastal landforms.

Sea-level changes – one of the obvious effects of global warming and climate change is that low-lying coasts will be drowned by rising sea levels. This problem will be made worse by the fact that many of the world’s most densely populated areas are located on coastal lowlands. In fact, rising sea levels are nothing new. During the Ice Age, sea levels also changed, but to a much greater extent. They fell as more and more of the world’s water was locked up in ice sheets and glaciers. The sea levels then rose again as the ice sheets and glaciers melted.

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A rising sea-level gives rise to what is called a submergent coastline. The main features are rias (drowned river valleys) and fjords (drowned glacial valleys). An emergent coastline is associated with a falling sea level. The most common landforms are raised beaches. These are areas of wave-cut platform and their beaches now found at a level higher than the present sea level. In some places, relict cliffs with caves, arches and stacks are found where there are raised beaches.

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Raised beach

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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.

Coastal management – work

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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.

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.

Hard engineering techniques:

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.

Case Study – Holderness Coast

Coast Holderness%20Map

The Holderness coast is a 61km stretch of coast running from Flamborough Head in the north to Spurn Head (a spit) in the south. The Holderness coast is located in the NE of England. The Holderness coast is one of the fastest eroding coastlines in the world and the fastest eroding in Europe. On average the coast erodes at about 2 metres a year. The reason the Holderness coast is eroding so quickly because of the local geology. 18,000 years ago the north of England was covered in ice (last ice age). As the ice melted it deposited huge amounts of glacial deposits. These glacial deposits actually extended the Holderness coast out into the sea. However, the glacial deposits (known as boulder clay) that make up the coast are extremely weak and vulnerable to erosion. Since Roman times, the coast has eroded by about 4km and around 30 villages have been washed into the sea, along with hundreds of square kilometres of farmland.

The Holderness Coast is one of Europe’s fastest eroding coastlines. The average annual rate of erosion is around 2 metres per year. This is around 2 million tonnes of material every year. Under lying the Holderness Coast is bedrock made up of Cretaceous Chalk. However, in most place this is covered by glacial till deposited over 18,000 years ago. It is this soft boulder clay that is being rapidly eroded.

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

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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