Systems and Processes - Waves and Tides

  • Created by: Lisa Paul
  • Created on: 03-04-18 15:29


The coastline is under the direct influence of waves.

Waves are a ridge of water formed by:

  • 1.   Frictional Drag between wind blowing over the water surface of the sea. Friction causes a disturbance forming ripples which then develop into waves. 
  • 2.   Sub-marine earth movements/under water earthquakes -> Tsunamis.
  • 3. Major land slides (land fails)  into the sea or water sea areas.

Once created and driven by the wind, waves are the primary agent in shaping the coast.

Wave Terminology

  • Crest: Top of a wave
  • Trough: Base of a wave
  • Wave Height: The vertical distance between a wave crest and its neighbouring trough.
  • Wave Length: The horizontal distance between two succesive crests.
  • Wave frequency: The number of crests passing a fixed (wave period) pointi n a given time e.g. the number of waves breaking on  a beach per minute. 

Fetch: The distance of open water over which the wind blows to create waves. The longer the fetch the greater the potential for larger waves. the more energy the waves will posess.

Wave energy is controlled by...

  • The force/strength of the wind and its dircetion 
  • The duration of the wind (how long it blows for)
  • The Fetch

Waves can be described or classified as constructive or destructive. 

Characteristics of Constructive Waves

  • Builds up beaches by depositing sediment
  • Spilling/ Surging
  • Low in height
  • Low Energy
  • Strong swash
  • Very weak back wash
  • Long wave length
  • More common in summer than in winter
  • Gently sloping wave front
  • Low Frequency 6-8 per min
  • Formed bys storms ofter hundreds of meters way. Distant weather system

Characterisitics of Destructive Waves

  • Plunging
  • High energy
  • Restricted swash
  • More common in winter than in summer
  • Steep wave front
  • Tall wave (Over one metre)
  • HIgh frequency (10-14 per minute)
  • Formed by local storms close to the coast
  • Net beach sediment loss
  • Very strong backwash
  • Short wave length
  • Destroy beaches by removing sediment from them. 

Wave Refraction

Topography determines the effects of wave action on the coastline.

When waves approach a coastline that is not regular in shape (e.g. an indented one of headlands and bays), they are refracted (bent) until their orientation is one that is parallel to the shore.

The diagram shows 2 headlands seperated by bays. As each wave nears the coast, in the shallower water in front of the headland, the wave decelerates due to friction between it and the sea below. This causes the wave to slow down, become taller in height with a shorter wave length, greater wave steepness and…


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