Download Coasts 1

Section 1 - The Coastal System
In the coastal system the inputs consist of
INPUTS
1) Energy from waves, wind, tides and currents.
2) Sediment from rivers and erosion of coastline
3) Changes in sea level
4) Human activity
Processes
The processes form from erosive and constructive
wave action, longshore drift and the wind.
OUTPUTS
The outputs of the system are Landforms, sediment
accumulation, changes to wave energy
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
1) Velocity – Wind speed
2) Duration – Time over which the wind blew
3) 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
What is happening in the diagram?
Wave movement from Waugh : An integrated approach
Constructive waves
These tend to be low waves with long wavelength
http://www.youtu
be.com/watch?v=
XWZAz9Qbzos
Frequency 6-8 per minute, gentle spill onto beach
Weak backwash which doesn’t remove sediment
Material is moved up the beach and build up is gentle
http://www.curriculumbits.com/prodimages/details/geography/geo0003.html
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
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/WaveMotion.swf
http://www.sln.org.uk/geography/Do
cuments/animations/Wave%20refra
ction%20and%20orthogonals.ppt#2
78,6,Slide 6
http://www.wiley.com/college/strahler/0
471480533/animations/ch19_animation
s/animation2.html
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.
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
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
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.