WHAT IS COASTLINE?
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Coastline: the area of land where the sea meets the shore.
The sea breaks down moves around and builds up the coast.
This process is interaction between the atmosphere, hydrosphere and lithosphere.
COASTAL USES
Positives:
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Jobs from fishing, sea transport at ports and tourism.
Attractive place to live
❑Coastlines faces a constant battle against the sea from erosion and from weathering
Negatives:
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Risk of flooding, damage to property or cliffs collapsing
What is Geomorphology?
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It is the study our coastline changes over time through actions such as weathering, erosion,
transportation and deposition.
WHAT IS WEATHERING?
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Weathering is a process that changes the structure and appearance of materials like cliffs by
how they exposed to the atmosphere.
PHYSICAL WEATHERING
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Physical weathering is caused by the effects of changing temperature on rocks, causing the rock
to break apart.
CHEMICAL WEATHERING
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Rainwater and seawater can be a weak acid. If a coastline is made up of rocks such as limestone
or chalk, over time they can become dissolved by the acid in the water.
BIOLOGICAL WEATHERING
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Plants and animals can also have an effect on rocks.
Roots burrow down, weakening the structure of the rock until it breaks away.
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GEOLOGY
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Coasts change depends on geology (or rock type)of the area.
Flamborough head to the north headland is formed from chalk, a sedimentary rock which is
relatively hard.
So its means relatively stronger than surrounding rocks and can resist erosion loner.
GLACIAL TILL
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Glacial till is material left behind by the movement of a glacier.
This rock is made of clay with a mixture of boulders.
This material can be eroded and weathered more quicker than chalk.
WHAT FORMS OF EROSION TAKES PLACE ON THE COAST?
What is Erosion?
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Erosion is the wearing or breaking down of material like rocks.
Coastal erosion is the force of the sea changes the coastal landscape.
Waves get their energy from the wind. The stronger the wave, the more erosion it will cause.
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4 types of Erosion : Hydraulic Action, Abrasion, Corrosion(Solution) and Attrition.
Hydraulic Action: The power of the wave forces water and air into cracks in the rock.
This pressure forces fractures in rock to split apart.
Over time this creates faults and notches which get bigger.
Abrasion: The waves pick up rocks from the sea and throw them against other rocks or cliff faces.
Over times this rubs and smooths the rock, like using sandpaper.
Corrosion: Salts or chemicals in the water act to dissolve the rocks they touch.
(E g., limestone is dissolved by sea salt.)
Attrition: The Sea picks up angular rocks and knocks them into each other.
This chips away the corners to make them rounder.
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WHAT LANDFORMS ARE CREATED BY FORCES OF EROSION?
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As weathering and erosion process shape the coast, they create landforms.
Headlands and bays
Caves, arches, stacks and stumps
Wave-cut platforms
CAVES, ARCHES
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Caves are erosion from water will widen any cracks in the rock and widen them to become
caves.
Arches are erosion from water will continue to erode a cave in a headland until eventually it cuts
through the whole way through the rock.
STACKS
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Stack Erosion from water will continue to erode an arch and the weight of rock will become too
heavy and the roof of the arch will fall into the sea.
WAVE-CUT PLATFORM
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Wave-cut platform, also called Abrasion Platform, gently sloping rock ledge that extends from
the high-tide level at the steep-cliff base to below the low-tide level. It develops as a result of
wave abrasion; beaches protect the shore from abrasion and therefore prevent the formation of
platforms.
How does transportation change the coastline?
What is Transportation?
• Transportation is the movement of material in the sea and along the coast by waves.
Waves
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Waves are caused by the moment of wind. As the wind blows over the surface of the sea, it
creates friction on the surface, which pushes water along to build up a wave.
Water within the wave moves in circular patters, getting bigger as the wave gets taller and then,
when the wave meets the shore, it becomes unstable and is forced to break.
Constructive and destructive
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These waves shape beaches by either building them up or eroding them down.
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Swash and backwash
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Swash is when a wave breaks, water is washed up the beach.
Then the water runs back down the beach, which is called the backwash.
Constructive waves
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Strong swash and weak backwash.
The strong swash brings sediments to build up the beach.
The backwash is not strong enough to remove the sediment.
The waves are low and further apart.
Destructive waves
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Weak swash and strong backwash.
The strong backwash removes sediment from the beach.
The waves are steep and close together.
Summary
Longshore Drift
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The transport of sand and pebbles along the coast is called longshore drift.
Longshore drift
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Longshore drift transports beach material.
This means beaches change shape and the wave action can cause them to become smaller in
some places and bigger in others.
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The prevailing wind pushes a wave up the beach, picking up beach material in the swash
The backwash drags this material back down the beach
Another wave picks up beach material and moves it up the beach again
The backwash moves material back off the beach
The whole process keeps repeating,moving material back up and down the beach over and over,
eventually moving it along the beach until it meets a barrier. It can even move material around
headlands.
DEPOSITION LAND FORM
What is Deposition?
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When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying.
Deposition happens when the swash is stronger than the backwash and is associated with
constructive waves.
It is likely to occur when:
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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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SPITS
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A spit forms when longshore drift pushes material out from the headland. If the wind changes
direction then the spit will curve and create a salt marsh behind.
 Spits form where the coastline changes direction and longshore drift continues to move material
along the beach.
 Longshore drift will deposit material in the sea after the coastline has changed direction.
 Over time the level of the sand deposited will buildup until it is above sea level.
 The spit cannot develop right across the bay as the moving water from a river prevents the buildup of sand.
 Sand spits often have a curved or hooked end.
 This is created when secondary wind and wave direction causes a wave to strike from a different
direction.
 The beach appears to extend out into the sea and is known as a spit or sandspit.
BARS
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A bar forms when longshore drift pushes material along, creating a spit that joins up two
headlands.
SAND BAR
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A sand bar is formed when there is a bay. Where there is no river flowing into the sea, sand can
be deposited faster than it is removed.
Longshore drift moves sand across the bay. Shallow water allows deposited sand to build up.
The deposited sand eventually joins up with the other side of the bay and blocks off the water.
This feature is called a sand bar and the area behind is known as a lagoon.
TOMBOLO
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A tombolo is where a spit joins onto an island.
 A tombolo is formed when a spit connects the mainland coast to an island. A spit is a feature that
is formed through deposition of material at coastlines. The process of longshore drift occurs and
this moves material along the coastline.
 Material is pushed up onto beaches at an angle when the swash brings it onto the coastline at a
45 degree angle. The backwash takes it back out towards the sea at a right angle to the coast.
 Through this process material is constantly moved along the coastline. When the coastline
changes direction or there is a river estuary the process of longshore drift continues. This causes
material to be deposited in a long thin strip that is not attached to the coast and is known as a
spit. If this feature moves in the direction of island and connects it to the mainland then it
becomes a tombolo.
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COASTAL CHANGES
Holderness
Erosion
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The Holderness Coast is one of Europe’s fastest eroding coastlines. The average annual rate of
erosion is around 2 metres per year. The main reason for this is because the bedrock is made up
of till (soft clay). This material was deposited by glaciers around 12,000 years ago.
The coastline stretches along the coast of the East Riding of Yorkshire, known as Holderness, from
Flamborough Head in the North, to Spurn Head in the south. Since Roman times, the Holderness
Coast has retreated 4 km – at least 29 villages have been lost to the sea.
COASTAL CHANGES
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Erosion of the cliffs and sea bed here results in 3 million cubic meters of sediment being
transported south by longshore drift each year.
GEOLOGY
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The Holderness Coastline is made up of soft boulder clays (tills) left after the retreat of the
Devensian ice sheets about 12 000 years ago. They can be seen on the coast, being rapidly eroded
by the sea. To look at, they are a mass of brown clay containing pieces of rock (erratics) brought
here by the glaciers from Scandinavia, Scotland, the Lake District and Northeast England. These
soft, recent deposits sit on a platform of chalk which slopes away gently to the east.
 Boulder clay is structurally weak, and has little resistance to erosion. It produces sloping cliffs
between 5 and 20metre high. Chalk surrounds the boulder clay. This is a much stronger rock
but has eroded along fault lines and bedding planes forming structures like cliffs, caves, arches
and stump.
LONGSHORE DRIFT AND BEACH MATERIAL
 The beaches here are the main problem. Boulder clay erodes very easily and produces very small,
fine clay particles, these are easily transported by longshore drift out to sea and along the coast,
rather than accumulating in front of the cliffs, forming a layer of protection from the waves. The
beaches are narrow and fail to absorb the wave energy, during high tide there is not enough beach
and waves hit the base of the cliffs.
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Tides flow to the south, transporting material along the coast. There is an imbalance as the harder
chalk up the coast does not provide enough material for places like Hornsea so backwash removes
more than what is deposited by swash.
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LOST VILLAGES WHO IS NEXT?
Skipsea on the Holderness coast
▪Since Roman times about 5.6 km has been washed into the sea
▪In next five years a population of 600, many homes are set to disappear completely in next 5 years.
▪Environmental Agency informed 7000 homes would disappear due to coastal erosion in England and
Wales over next 100 years.
MAPPLETON
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Mappleton an average of 2 m of land is lost each year.
1984 43m from the cliff edge yet by 2017 10m!
The council has enforced a hold the line policy.
WHAT DEFENSES CAN BE USED TO PROTECT THE COAST?
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Decisions need to be made whether to protect (hold line) or Leave the coastlines.
Hold the line: Hard and soft engineering is used to keep the coastline Do Nothing.
Allow coastal process and erosion to occur despite lose.
TWO CATEGORIES OF COASTAL MANAGEMENT TO HOLD THE LINE
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Hard engineering: usually more expensive and involves more dramatic physical structures and
changes.
Soft engineering which usually involves trying to work more closely with nature and us usually
cheaper.
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COASTAL MANAGEMENT STRATEGY
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Costal engineers, councils, residents and the Environment Agency work together to analyze a
coastal line to determine the risk and the cost.
Often the best solution is a combination of hard and soft engineering.
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