Sources of Energy at the Coast

• Sources of energy at the coast

  • The sun
  • Wind.
• The primary source of energy for all natural systems is the Sun. Heat and light from the Sun is converted by natural processes, such as photosynthesis and plants to form energy.
• Wind is quite simply the movement of air from one place to another
• In the UK, the prevailing (dominant) winds come from the south-west the result from air moving from the subtropical high pressure belt at about 30 °N to the subpolar low pressure belt at about 60 N.
• A number of factors effect wave energy

  1. The strength of the wind - determined by the pressure gradient.
  2. The duration of the wind - the longer the wind blows, the more powerful waves will become.
  3. The fetch - the distance of open water from which the wind blows, the longer the fetch, the more powerful the waves.
• Different type of waves

  • Constructive
  • Destructive.
• Constructive waves

  • Low wave height
  • Long wavelength
  • Swash loses energy rapidly
  • Very weak backwash, which has insufficient energy to take material away from the beach
  • Material is slowly but constantly moved up the beach to form ridges.
• Destructive waves

  • High wave height
  • Hi frequency
  • Steep form which plunges down when breaking
  • Create a powerful backwash as there is little forward movement
  • Create a powerful backwash as there is little forward movement
  • Very little materials moved up the beach, leaving back. Wash to pull material back down the beach
• Wave refraction

  • Waves refract (bend) towards shallow water. The quicker the change in water depth, the greater the refraction. The more curvy the coastline, the more refraction occurs. Waves lose energy as they refract due to frictional drag.
  • At a curvy coastline Waves refract onto the headland. The waves become higher, steeper with a shorter wavelength. High energy waves concentrate on the headland. Increased erosion. Waves refract out onto abay Waves in the deep water are still moving forward so the wave bends. Low energy waves concentrated in the bays. Increased deposition
• Longshore currents occur as most waves do not hit the coastline head on' but approach at an angle to the shoreline. This generates a flow of water (current) running parallel to the shoreline. This not only moves water along the surf zone but also transports sediment parallel to the shoreline,
• Rip currents are strong currents moving away from the shoreline. They develop when seawater is piled up along the coastline by incoming waves.Initially the current may run paralel to he coast before flowing out through the breaker zone, possibly at a headland or where the coast changes direction. These can be extremely hazardous to swimmers and small boats
• Tides are the periodic rise and fall of the level of the sea
• Neap = a tide just after the first or third quarters of the moon when there is least difference between high and low water.
• Spring = a tide just after a new or full moon, when there is the greatest difference between high and low water.