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Key Question 1: What is a coastal system and what are the
dynamics of coastal environments?
The Coastal System
The coast is the interface between land and sea. One way to study the coast is to view
it as a system. The coast is an open system. Energy inputs from waves drive the system.
They interact with the geology, sediments, plants and human activities along the
coastline. From time to time the energy input is boosted by storm surges and tidal
waves.…read more

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This produces a zig-zag
movement of sediment along the beach
known as longshore drift. The action of
waves constantly moves and sorts different
sized material beach material..The action of
longshore drift sorts beach material, due to
the amount of energy required to move
sediments. Larger particles will need more
energy and therefore move at a slower pace.
Largest beach sediment is found updrift,
and the smallest material, which is more
easily moved, downdrift.…read more

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High and low energy coasts in the UK.
High energy coasts are ones in which wave power is strong for a significant proportion
of the year. The distribution of these coasts is largely controlled by the climate and
direction they face. Strong winds capable of generating the largest waves are more
frequent in areas of the world with a Cool Temperate Western Maritime climate
(CTWM).…read more

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Maximum wave heights decrease from west to east and from north to
south across the British Isles away from exposure to the open ocean and onshore
westerly winds. Fetch is the limiting factor for the height of waves generated by
easterly winds in the North Sea. No matter how long an easterly gale blows, the waves
breaking against the eats coast can never reach the height of those from westerly
gales along the west coast.…read more

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Dynamic equilibrium in the coastal system
Why do some coastlines erode away? Why do some grow?
All beaches exist in a dynamic equilibrium involving four factors:
1. The supply of sand
2. The energy of the waves
3. Changes in sea-level
4. The location of the shoreline
It is the balance of these four factors and how they interact with each other that
determines whether a beach erodes or grows.
The concept of dynamic equilibrium is central to our understanding of natural systems.…read more

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As mentioned earlier, sand effectively armors the shore
against wave attack and erosion.
It is only because most people see coasts as broadly stable over the human life span
that they do not recognise that coastal change is constant and that; over the long-
term, commonly inevitable. Rates of change differ substantially over space and time.…read more

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Dynamic equilibrium
Like meta stable equilibrium, this too involves a change in equilibrium conditions but
in a much more gradual manner. A good example is the response of coasts to the
gradual rise in sea levels that were experienced through the twentieth century as a
result of climate change.…read more

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Wave types
Waves are undulations of the
water surface caused by winds
blowing across the sea. They
consist of orbital movements of
water molecules which diminish
with depth. In the open ocean wind
rippling water can lead to growth
into recognisable waves. The
circular motion of waves at the
surface is copied below in a series
of circles which become smaller
with increasing depth. All of this
changes as the waves are driven by the winds and currents into shallow coastal
waters.…read more

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Fetch, wind direction and wind strength are the main factors determining the
height and energy of breaking waves. Fetch is the distance of uninterrupted
water surface over which the wind has blown to form the waves. The loner the
length of open water over which the winds travel, the longer the fetch and the
greater the amount of energy released when waves break in the coastal zone.…read more


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