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Summary AQA A-Level Geography Coasts Revision Notes $6.53   Add to cart

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Summary AQA A-Level Geography Coasts Revision Notes

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Comprehensive revision notes for the AQA A-Level Geography Coasts topic. Includes coastal processes, landforms and formation, alongside case study information.

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  • August 30, 2022
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Coasts as natural systems




Fetch: The distance of open water which a wind blows over uninterrupted by major land
obstacles – the length of fetch can determine the size and energy of waves reaching the
coast

Backshore: The area between the high-water mark(HWM) and the limit of marine activity

Foreshore: the area between the HWM and the LWM

Inshore: Area between the LWM and the point where waves have no influence on the land
beneath them

Offshore: The area beyond the point where waves cease to impact the sea bed and activity
is only deposition of sediments

Nearshore: The area from HWM to where waves begin to break – also includes:
1. Swash Zone: the layer of water that washes up the beach after a wave breaks
2. Surf Zone: The area between where waves break and where waves move as swash
3. Breaker Zone: The area where waves begin to break approaching the coastline

INPUTS: Energy from waves, winds, tides and currents, sediments, geology of coastline, sea
level changes

COMPONENTS: Erosional and depositional coastal landforms

OUTPUTS: Dissipation of wave energy, accumulation of sediment, sediment removed from
sediment cells

,Sources of Energy

Wind

- Where wind speeds are persistently high and uninterrupted wave energy is higher,
local weather patterns can have a short term impact on wind speed – but most
coasts have a prevailing wind direction
- Fetch
- Wave Formation: waves are created by the transfer of energy from the wind over
the sea surface – called frictional drag – the energy acquired by waves depends on
the strength, fetch and time frame of the wind
- Wind also can act in erosion – pick and remove sediment – abrasion the most
common form as wind carries sediment and that sediment wears away landscape
features – therefore also important in moving sediment along the coast, inland and
beyond the tidal zone

Waves

Waves are the primary agent of shaping the coast

Wave Height: Height between the
crest A and trough B

Amplitude/Wave Length: Distance
between successive crests

Wave Frequency: The time for one
wave to travel the distance of a wave
length




As waves approach, shallow water friction with the sea bed slows the wave down – this
increase the height of the wave until the water breaks onto the shore
- Water going up the beach = swash – going down the beach = backwash
- Waves are either constructive or destructive

, Constructive Waves




- As they approach the wave front steepens slowly and spills gently onto surface
- Swash loses volume and energy as water percolates through beach material – weak
backwash and therefore insufficient force to pull sediment out

Destructive Waves




- Steep and high wave height + high frequency
- As they approach the wave front steepens rapidly and plunges down when breaking
- Creates a powerful backwash – weak swash so more sediment is removed than built
on the beach

Dynamic Equilibrium

- Over time destructive waves move material back towards the sea reducing the beach
angle and therefore encouraging constructive waves – constructive waves increase
the beach angle and therefore encourage destructive waves – NEGATIVE FEEDBACK
- Therefore dynamic equilibrium should be maintained but it is almost impossible
because wind strength and direction are not constant

Wave Refraction

- The topography of the coast effects waves
- When waves approach a coastline that is not regular in shape they are refracted as
they become parallel to the coastline

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