Lornshill Academy
Geography Department
National Revision
Physical Environments –oasts
Coasts (Case Study: Dorset)
Some coastlines can be worn away (eroded) by the force of the sea and some of these
features may result along the coastline.
Processes of Erosion
Hydraulic Action - the force of waves hitting a cliff (or sea wall) compresses water and air
into cracks and joints. This increase in pressure may lead to cracks widening and pieces of
rock breaking off.
Abrasion- Rock fragments may be picked up by waves and thrown against the rock face of
cliffs by subsequent waves. Sometimes the softer strata are abraded more than the harder
ones, giving a striped appearance. Abrasion is most effective at the base of cliffs.
Attrition- Rock fragments are worn down into smaller and more rounded pieces.
Currents and tidal movements cause the fragments to be swirled around and to grind against
each other. This type of erosion produces pebble beaches.
Corrosion (chemical solution)- Salts and acids in sea water can react with rocks , slowly
dissolving them away.
Erosional Features
Formation of a Stack
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Erosion by Abrasion is when material carried by the waves scrape against the headland
wearing it away.
Hydraulic action when waves force air under high pressure into cracks in the coastline.
Attrition is when beach material is knocked together reducing its size, this can
further add abrasion. • A discordant coastline is when there are altering layers of
hard and soft rock in contact with the sea; this allows the soft rock to be eroded
faster forming a headland.
Headlands cause waves to refract around them eroding the headlands from the side.
Lines of weakness or faults in the headland can be eroded to form small caves.
Blowholes can be formed when air trapped in the cave explodes upwards further
eroding a line of weakness.
Further erosion can take place to allow the cave to be eroded right through to the
other side of the headland forming an arch.
A stack is formed when the roof of the arch is no longer able to support itself and
collapses.
Formation of a wave cut platform
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In places where high land reaches the sea, cliffs form.
The cliffs are attacked by waves that are constantly crashing against them and
eroding them by hydraulic action, corrasion and solution.
The waves mostly attack the base of the cliff, to form a wave-cut notch.
As the waves continue to pound away at the foot
of the cliff, the wave-cut notch becomes wider
and deeper. This causes the rock above to crack
and weaken.
In time, pieces of rock fall off and then the
whole cliff above it collapses into the sea.
This causes the cliff to retreat further inland.
The whole process then starts again.
As the cliffs erode back a gently sloping rock
surface is left in front of them, called a wavecut platform
Formation of Headland and Bay
 Headlands and bays form along
coasts that are made of alternative
bands of hard (resistant) and soft
(less resistant) rocks.
 The waves erode the softer rocks
(clay) more quickly to form bays and
the harder rocks (chalk) are eroded
more slowly and left jutting into the
sea to form headlands.
 Overtime the bays will become
more sheltered and sandy beaches
will form.
Longshore drift
Direction of
movement
swash
Backwash is
always at right
angles to the
beach
Backwash
As can be seen in the diagram below, a pebble or sand particle moves from point A to B,
carried by the swash up the beach, the angle determined by the wave and wind direction.
It is then pulled down the beach from B to C, carried by gravity and the wave's backwash.
This process is repeated over and over again and the particle moves along the shoreline - this
is called longshore drift.
When large numbers of sand particles or pebbles are moved along a coastline in this way, a
depositional feature called a spit may form.
How do Sand Spits form?
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Longshore drift moves large amounts of material along the beach until there is a
change in the direction of the coastline. When the coastline veers inland, the sand
keeps on moving in the original direction, even though there is not a coastline to follow.
The sea has to be relatively shallow and sheltered, allowing the accumulation of sand
usually beyond a headland.
Sometimes a curve develops in the sand if the on- shore wind changes direction.
A salt marsh often develops in the curve, where it is especially sheltered.
Spits can become permanent if the prevailing wind picks up sand and blows it inland
forming sand dunes. They can be consolidated by vegetation. (Link to Biosphere Unit.)
How Do Bars, lagoons and tombolos form?
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A bar is where a spit grows right across a bay, cutting off the bay from the sea.
It usually does this due to the absence of any large river that might wash it away.
It can cut off a body of water called a lagoon to the landward side.
A lagoon is a body of brackish water- part salty, and part fresh. It often supports
specialised plants and animals, and is protected as a nature reserve.
If a bar links up with an off-shore island, it creates a tombolo.
Sandbar
These are deposits of sand, which block the entrance to a bay. They develop as a result of
long shore drift (L.D.). This is when a swash hits a beach at an angle; as it goes up the
beach it carries sediment with it. It returns down the beach with the sediment, as the
backwash due to gravity. This process repeats and so moves sediment along the beach. If
there is a bay, the sediment is pushed across by the L.D. to form a beach, which starts to
extend across the bay, eventually reaching the other side; forming a barrier across the bay
or a bar. The sediment on the bar gets smaller and rounder as it moved, Due to attrition
eroding the stones as they bang into each other. Behind the bar water is trapped giving a
lagoon, There is much deposition as no flow; giving mud flats. The bar may be broken during
stormy weather as waves wash their way through it.
Coastal Mapping
You have to be able to identify coastal features on maps including: sand spits, caves, arches,
stack, bays, headlands, cliffs & wave cut platforms.
Sand Spit: Sand extends out into the water and, if you look closely, you should see their
curved hook.
Bays and Headlands: Headland=look for the word point or head. Bay= look for the word
cove or bay.
Caves: Look for the word caves. Look for stacks nearby.
Cliffs: Look for the word cliff. The contour lines may appear to run into the sea, indicating
the height of the cliffs.
Wave Cut Platforms: Look for the flat rock structure of a wave cut platform stcikcing
out into the sea.
Stacks: These are found off the headland. They will look like small islands.
Arch: Look for the word arch. Eg Natural arch.
Coastal Maps in the exam may look like the examples below. How many features can you
spot?
(Dorset Case Study)
Land Uses
The Dorset Coast is a huge tourist trap but remember people live and work there. There are
many different ways that money is made:
Industry
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Offshore, sand and gravel is taken from the seabed providing employment. Wytch
Farm Oilfield is located at the South bank of Poole Harbour. It is the biggest
offshore oilfield in West Europe. It produces 65,000 barrels of crude oil a day, 10
million cubic feet of natural gas and 500 tonnes of liquefied petroleum gas. There are
three large ports with substantial international trade and five smaller harbours which
cater for local fishing and recreational craft.
Fishing
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Fishing provides employment for the local people. It also supports a wide range of
service industries which maintain vessels and equipment, providing further jobs. The
fishing grounds sustain 600 boats.
Tourism
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The scenery attracts many people who come for recreation or to sightsee.
The sightseers are attracted by the distinctive, white chalk cliffs, headlands with
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their caves/arches/stacks (Old Harry), wide sweeping bays (Lulworth Cove) and long,
sandy beaches (Shell Bay).
There are lots of opportunities for water sports such as swimming, waterskiing and
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yachting. Others enjoy long walks along the cliff tops and beaches.
Important wildlife refuges are found just behind the coast in the sand dunes
(Studland), lagoons and marshes (The Fleet) which encourages visitors. Rare
heathland plants and rare British Wildlife such as lizards and snakes can be found.
These encourage large numbers of visitors who spend their money in the local area
which creates jobs, opportunities for hotels, restaurants and shops.
Environmental Conflicts
Even though tourists bring many benefits they also cause a variety of conflicts. Conflicts
occur between the following groups:
Tourists Vs Residents
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The tourists cause a lot of congestion on the roads. The larger settlements of
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Bournemouth, Poole and Swanage all suffer from congestion.
The congestion is caused as 82% of tourists travel by car, they tend to visit at the
same time (Bank Holidays and weekends) and often drive slowly to admire views. In
addition, they take up most parking spaces, park where they should not and increase
local air pollution.
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The village of Corfe Castle also suffers badly. It is a major tourist attraction and is
on the only main road to Swanage. A lot of tourists and 500 heavy lorries pass
through every day. The congestion is also caused by narrow streets, street parking
and lack of proper car parks.
Tourists Vs Tourists
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Many tourists are attracted to Poole Harbour. Mid summer, there can be 4000 boats
in the harbour at any one time (yachts, fishing boats, jet-skiers, water-skiers etc).
Around the harbour are sunbathers, birdwatchers, sightseers and walkers. This is a
recipe for conflict. The noisy pursuits, eg. power boats upset the people wanting
peace and quiet, eg. the fishermen and birdwatchers. Increasingly powerboats are
being used in winter, which is when thousands of birds migrate here.
Tourists Vs Conservationists
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Tourist activities in Poole Harbour are polluting the water (oil and litter). Powerboats
are scaring migrating birds in winter.
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At Studland tourists are causing erosion of the sand dunes. Here, the dunes are
between the car parks and the beach. People walk through the dunes, trampling on
fragile plants (which bind the sand together) until they die. With less vegetation the
sand dunes themselves become eroded and wildlife disappears as the habitat changes.
Horses also add to the trampling as there is a riding centre nearby.
Measures taken to resolve conflict
Organisations such as public/official bodies (County Councils) and voluntary bodies (The
National Trust) take steps to sort out problems between the land users.
The County Councils (Public Body)
To ease traffic congestion in Bournemouth, Poole and Swanage the following solutions have
been tried:
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One way systems.
Encouraging other types of transport (by providing bus and cycle lanes).
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Phasing traffic lights.
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Restricting the hours of road works.
To ease traffic congestion in the Village of Corfe Castle, Dorset County Council have devised
several solutions:
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A railway line has been opened with steam trains running from Swanage to Norden,
just north of Corfe Castle. People can now visit these places without driving into or
through the Village.
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An extra car park has been developed in the village. This should reduce the street
parking, which should allow traffic to go faster.
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More cycle ways and summer bus routes have been developed, but a proposed by-pass
has been rejected.
To try and solve tourist conflicts in Poole Harbour, Poole Council have introduced:
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Zoning of Poole Harbour (different activities are zoned in different areas so they do
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not upset one another).
Maximum speed limits have been imposed in some parts, which prevents power boating
and waterskiing taking place.
The National Trust (Voluntary)
They have tried to ease conflicts with conservationists by;
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Lobbying to get certain areas a protected status. RSPB sites have been set up to
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protect wildlife and SSSI sites to protect vegetation.
Educating visitors by taking them on guided tours and providing information on boards
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and leaflets.
Restricting access to sensitive areas.
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Providing wardens to look after the area.