Coasts Revision Guide Q7

This is a revision guide based on OUP Press textbook and case studies

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Question 7 Coasts Paper 1
Waves- how are they formed and how do they affect the coast?
Waves are caused by friction between the wind and water causing the water to swell.
The size and energy of a wave is influenced by:
how long the wind has been blowing
the strength of the wind
how far the wave has travelled (the fetch)
Swash: The wave breaking on the beach
Backwash: The wave going back out to sea under the force of gravity.
Prevailing wind: The most common wind direction.
Constructive Waves Destructive Waves
They are created in calm weather and Destructive waves are created in
are less powerful than destructive storm conditions.
waves. They are created from big, strong
They break on the shore and deposit waves when the wind is powerful and
material, building up beaches. has been blowing for a long time.
They have a swash that is stronger They occur when wave energy is high
than the backwash. and the wave has travelled over a
They have a long wavelength, and are long fetch.
low in height. They tend to erode the coast.
They have a stronger backwash than
They have a short wave length and
are high and steep.

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Coastal processes- weathering
When rocks and surface materials are broken down through the actions of the atmosphere
we call it weathering. Weathering weakens rocks at the coast and makes them more likely
to be affected by mass movement and erosion
It is a sub aerial process
Chemical: when weak acids for example rain dissolves the rocks.
Physical : Freeze thaw weathering- due to temperature, frost, water etc.…read more

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When the sea loses energy, it drops the beach material / sediment, 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, eg a cove or bay.
there is little wind.…read more

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Cliff erosion and wave cut platforms
Cliffs and wave-cut platforms
The process of cliff erosion.
1. Weather weakens the top of the cliff.
2. The sea attacks the base of the cliff forming a wave-cut notch through abrasion and
hydraulic action.
3. As erosion continues the notch increases in size undermining the cliff. This causes the
cliff to collapse.
4. The backwash carries the rubble towards the sea forming a wave-cut platform.
5. The process repeats and the cliff continues to retreat.
Wave cut platforms.…read more

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Longshore drift moves material along the coastline.
2) There is a sharpe change in direction of the coast e.g. river
or bay.
3) A spit forms when the material is deposited.
4) Over time, the spit grows and develops a hook if the
prevailing wind changes direction.
Waves cannot get past a spit, which creates a sheltered area
where silt is deposited and mud flats or salt marshes form.
Bars (lagoon): A spit that extends from headland to headland.…read more

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The extra weight/pressure acting on the cliff causes it to move.
The clay flows down towards the sea as part of a mud or debris flow
As it moves it rotates
CASE STUDY: The impact of rising sea levels: The Maldives
Located in the Indian Ocean
Small country made up of over 1000 islands
Lowest Country in the world
Highest point is 2.…read more

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Difficult to protect it all.
Tourism is big business and provider of jobs.
Densely populated with resorts such as Barton-on-sea.
Why is it eroding rapidly?
1- Marine processes weaken base of cliff. Hydraulic action and abrasion.
2- Sub aerial processes attack cliff top ­ weathering, slumping, sliding.
3- Geology- permeable sand lies on top of impermeable clay and is saturated during heavy
rains. This can make cliff top heavier and unstable.…read more

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A wall built on the edge of the coastline. Protects the base of cliffs, land and buildings
against erosion. Can prevent coastal flooding
in some areas. Strong and durable. Made of
reinforced concrete.
Expensive to build. £10k per metre. Curved
sea walls reflect the energy of the waves
back to the sea. This means that the waves
remain powerful. Over time the wall may
begin to erode. The cost of maintenance is
high with the wall having to be replaced
every 30-40 years.…read more

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The main advantage is that beaches are a natural defence against erosion and coastal
flooding. Beaches also attract tourists.
It is a relatively inexpensive option but requires constant maintenance to replace the
beach material as it is washed away.
Managed retreat
Areas of the coast are allowed to erode and flood naturally. Usually this will be areas
considered to be of low value - eg places not being used for housing or farmland.…read more

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The Environment Agency took charge to protect the area.
Opened in September 2006 and is one of the largest flood storage schemes in
Europe .
It allows flood water from the Humber estuary to spill out of the river during the
highest tides to fill the low lying land.
By flooding the Alkborough flats they protect places such as Hull.
The site's capacity is so great that it could reduce high tide levels in the upper
estuary by as much as 150mm -15cm.…read more


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