Section 1 The Coastal System

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Coastal Environments
Section 1 - The Coastal System
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• In the coastal system the inputs consist of
• Energy from waves, wind, tides and currents.
• Sediment from rivers and erosion of coastline
• Changes in sea level
• Human activity

INPUTS
Processes
The processes form from erosive and constructive
wave action, longshore drift and the wind.
The outputs of the system are Landforms, sediment
accumulation, changes to wave energy
OUTPUTS
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• Waves
• Waves are created by the action of the wind
  blowing over the sea.
• There are three main factors that will determine
  the energy it holds
• Velocity Wind speed
• Duration Time over which the wind blew
• Fetch Distance over which it blew
• Waves will increase in height as they near the
  shore until they break.
• Swash the movement of water up the beach
• Backswash - the movement of waves running down
  the beach

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What is happening in the diagram?
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Wave movement from Waugh An integrated approach
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Constructive waves These tend to be low waves
with long wavelength Frequency 6-8 per minute,
gentle spill onto beach Weak backwash which
doesnt remove sediment Material is moved up the
beach and build up is gentle
http//www.youtube.com/watch?vXWZAz9Qbzos
http//www.curriculumbits.com/prodimages/details/g
eography/geo0003.html
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Destructive waves High, steep waves High
frequency 10-14 per minute Powerful backwash as
wave breaks downwards leaving little movement
forward This also inhibits next swash Beach
profile is steeper
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Wave refraction When waves hit the approach the
coastline they are affected by the differences in
depth in the sea bed. As the waves move closer
they will the shallower parts will cause friction
and slow them down. The deeper area will be less
impeded. Gradually the waves become more parallel
to the shape of the coastline.
http//daphne.palomar.edu/lyon/Animations/WaveMoti
on.swf
http//www.sln.org.uk/geography/Documents/animatio
ns/Wave20refraction20and20orthogonals.ppt278,6
,Slide 6
http//www.wiley.com/college/strahler/0471480533/a
nimations/ch19_animations/animation2.html
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There is a concentration of energy on the
headland as the waves here will be higher and
possible higher local sea level. A current from
the headland may move material along the bays.
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Tides Caused by the gravitational pull of the
moon and sun Moon has greatest influence due to
its distance (pull is lower) Oceans closest to
the moon have an outward bulge This causes high
tide and low tide is the draining of water from
areas. Moon orbits earth every 29 days and high
tides follow its path. Approx two high / two low
per day. Spring Tide Highest tide where earth
is between the moon and sun Neap Tide When moon
and sun are at right angles and interfere with
each other
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Tides patterns are also influenced by ocean bed,
land masses and coriolis force. Tidal range
The difference between high and low tide. This
is often very large in narrow necks of water such
as the English channel. Tidal range will
determine the rates of erosion
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Sediment Cells and sources Sediment cells vary
in size. They are complete units that are self
contained in terms of the movement of sand or
shingle. They move sediment around the cell
through a variety of processes where inputs and
outputs are balanced.