Where do sources of energy in coastal systems come from?
WIND: Created by air moving from high to low pressure, Strong wind can generate powerful waves and in some areas wind consistently blows in the same direction, called a PREVAILING WIND, creating higher energy waves.
Waves are caused by the wind blowing over the surface of the sea, giving the sea a circular motion.
The effect of a wave depends on its height. Wave height depends upon wind speed and the FETCH of the wave, the maximum distance that wind is blown the sea. As waves approach the shore friction with the seabed causes them to take on a more elliptical (oval) shape, the wave CREST rises up and then collapses, the wave trough is the opposite. There are two types of wave:
Have a low frequency of around 6-8 per minute, they’re low and long, more elliptical, the powerful awash deposits lots of sediment.
Have a high frequency of 10-14 per minute and are high and steep, their strong backwash removes more sediment than is deposited.
Tides are the periodic rise and fall of the ocean surface, caused by the gravitational pull of the Moon and sun, they affect where waves break and the area between low and high tide is where landforms are found.
CURRENTS: The general flow of water in one direction, it can be caused by wind or variations in water temperatures and salinity, moves material along the coast.
What are the Sediment sources?
Rivers erode sediments into the coastal system.
Sea level rise can flood river estuaries collecting their sediments.
Sediments is eroded from cliffs and the coastline by waves, weathering and landslides.
Sediments can be formed by crushed shells of marine organisms.
Waves, tides and currents can transport sediment into the coastal zone from offshore deposits like sandbanks.
THE DIFFERENCE BETWEEN THE AMOUNT THE ENTERS AND LEAVES THE SYSTEM IS THE SEDIMENT BUDGET, if it’s positive the coastline builds out and if negative the coastline retreats.
The coast in the U.K. is divided into sediment of littoral cells, they are closed systems of self contained sediment.