WHY ARE COASTS UNDER THREAT? | * Sea level rises caused by global warming. * Pollution from sewage discharge. * Litter. * Overfishing. Many fish stocks around the world are being over fished to dangerous levels. * Erosion. Many coastlines are being eroded by stronger storms and also rising sea levels. * Tropical storms. Because of rising sea levels, the frequency of storms and magnitude (strength) are increasing causing flooding, storm surges and wind damage. * Privatisation. More and more stretches of the beach are privately owned (houses, hotels, etc.). This is making it increasingly hard for locals to access previously open areas. The privatisation of areas is also increasing the cost of land, making it less affordable for many residents. |
Waves- Waves are formed because of friction between the wind and the sea. The shape and the energy of the wave that is moving. Water particles tend to move up and down in a circular motion. When waves near the coast, the bottom of the wave is slowed by friction with the sea bed. Because the top of the wave is experiencing less friction, it moves faster and eventually topples over the bottom of the wave and breaks. The size of the wave is effected by three factors: * Duration of wind * Strength of wind * Fetch (the distance that a wave travels)
Crest: The top of the wave.
Wavelength: The distance between two crests or two troughs.
Wave height: The distance between the crest and the trough.
Wave Frequency: The number of waves per minute.
Velocity: The speed that a wave is traveling. It is influenced by the wind, fetch and depth of water.
Swash: The movement of water and load up the beach.
Backwash: The movement of water and load back down the beach.
Coastlines are very rarely perfectly straight. Coastlines normally have a series of bays and headlands. As waves reach shallower water, the bottom of the waves experience greater friction with sea bed. This greater friction causes the waves to slow down. If you have a series of bays and headland, waves will start to slow down around the headland where the water is shallower, but continue to travel more quickly into the bay area where the water is deeper. Because the section of the wave centred on the headland is travelling slowly and the sections either side are travelling more quickly the wave begins to refract (bend) around the headland. This concentrates the wave energy on the headland and disperses the energy across the bay.
Destructive waves: Destructive waves have a fairly weak swash because the wave breaks almost vertically. However, it does have a much stronger backwash. Because the backwash