Sources of Energy in Coastal Systems


  • Created by air moving from areas of high pressure to low pressure.
  • Storms – pressure gradient is high and so strong winds.
  • Generate powerful waves.


  • Created by the wind blowing over the surface of the sea.
  • Friction gives its circular motion.
  • Height is affected by wind speed and fetch.
  • High wind speed and long fetch results in more powerful waves.
  • Friction on the sea bed slows the waves and makes their shape more elliptical; the crest collapses.
  • Swash- water washing up the beach.
  • Backwash- water washing back down the beach.
  • Constructive waves: low frequency (6-8 per minute); low and long; elliptical cross profile; powerful swash, weak backwash.
  • Destructive waves: high frequency (10-14 per minute); high and steep; circular cross profile; powerful backwash, weak swash.


  • Periodic rise and fall of the ocean surface.
  • Caused by the gravitational pull of the moon and the sun.
  • They affect the position at which waves break on the beach.
  • Between maximum high tide and minimum low tide is where most landforms are created and destroyed.



  • General low of water in one direction.
  • Caused by wind or by variations in water temperature and salinity.
  • Move material.