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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.