Coastal management Essay
This builds up the beach and protects the clefs from erosion. They are effective at building up the beach therefore protecting cliffs from wave attack. Can result in areas further down the coast being starved of beach material resulting in more erosion! Only last 25-30 years. Rip Rap (Rock armor): Large rocks placed at the bottom of the cliffs absorb the wave energy, they are effective at deleting the waves energy and cheap. Environmentally ugly and may put off tourists. Soft Engineering Soft Engineering is a less environmentally noticeable way of managing the coastline.
Beach Nourishment: Large amounts of sand are added to beaches to build them up and help absorb wave energy. This protects tourism as well as the coast and Is easy to carry out and fairly cheap. But it does not last very long as sand will continue to be transported along the coast by alongshore drift. Managed Retreat: This allows the natural erosion processes of the sea to occur, areas of low value land are allowed to flood hopefully protecting more Important areas further down the coast.
Cliff Stabilization: Cliffs are covered in matting and vegetation planted to help make them ore stable and resistant to erosion. Do
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Geographical processes waves Processes of Erosion Processes of Transportation Alongshore Drift Waves Waves are formed when the wind blows across the surface of the sea. The friction between the wind and the water pushes the water up creating waves. The height and power of a wave depends on two factors: 1 OFF speed The distance over which the wind has blown is called the fetch. The greater the fetch, the larger the wave as it has more time to gather energy. Example: Waves from Brazil travel 10,km before they hit the south west coast of England making them very powerful.
Constructive waves Constructive waves have three main features: They are low in proportion to their length normally less than one meter high They eave a strong swash which carries material up the beach and have a weak backwash which doesn’t take the material away They break gently, with only six and nine waves per minute. Constructive waves allow material to be deposited along the coastline as material is slowly but constantly moved up the beach. This leads to the formation of features such as spits, tomboys and bars.
Destructive waves Destructive waves have three main features: They are high in proportion to their length The backwash is much stronger than the swash so that rocks, pebbles and sand are aired back to the sea They are frequent waves, breaking at an average rate of between eleven and fifteen per minute Destructive waves erode the coastline and help to form features such as wave cut platforms, headlands, bays, arches, stacks, caves and stumps. Processes of Erosion Hydraulic Action When waves hit the coast they force water and air into cracks in the rocks.
As the water surges it compresses the pockets of air and when the wave retreats the air is released and quickly expands. This continued process weakens the Joints and cracks eventually causing the rock to shatter. Abrasion (also called corrosion ) Breaking waves throw sand, pebbles and sometimes boulders against the cliff face. These scrape away at the rock rather like sandpaper, eventually causing undercutting at the base of the cliff. Attrition Rocks and boulders eroded from the coast collide with each other and the rock face in the breaking waves.
They become smaller and more rounded. Corrosion Sea water dissolves soluble minerals and material from the rock. In particular limestone and chalk coasts are very susceptible to this type of erosion. Processes of Transportation Material is transported by the sea in four different ways. This is usually how material is moved and later dropped (deposited) to form features such as beaches and spits. Traction This is when rocks and heavy boulders are dragged along the sea bed.
This would usually occur when the waves do not have enough energy to carry the material in the water. Isolation This is when smaller boulders are bounced along the sea bed. Suspension Material such as sand grains, are light enough to be carried along in the water in suspension. Solution the naked eye but can be seen by the milky appearance of the sea. Remember the picture of the Sussex Coast? ) Alongshore Drift The transport of sand and pebbles along the coast is called alongshore drift.
The prevailing wind (the direction the wind usually blows from) causes waves to approach the coast at an angle. The swash carries the sand and pebbles up the beach at the same angle (usually 450). The backwash, however carries the material back down the beach at right angles (900) as this is the steepest gradient. If a pebble was placed in the water it would be carried along the coastline in a gig-gag motion ND would eventually be deposited when the waves lose energy.