Sea/Storm wave – Simply, a wave created by a storm
Swell wave – Created by a storm in a different location
Prevailing Wind – The most common wind direction
Velocity – Stronger the wind, the stronger the waves
Fetch – the stretch of open water wind has travelled over
What is a wave?
An undulation on the surface of the water
---> A movement in the water
Waves are usually formed by the wind blowing over the sea. Friction between
the air and the surface of the water causes ripples to form and these develop
into waves. During a storm, the wind creates sea waves, which continue under
their own momentum to form swell waves. The prevailing winds are the type
which blow most often. The size and energy of waves is affected by many
factors. Wind velocity refer to the speed of the wind. The faster the wind is
blowing, the more energy the wave will have. How long the wind has been
blowing for (wind duration) will also influence wave energy. A longer duration
will lead to more powerful waves. The fetch is the distance on open water
which the wind blew. A longer fetch means the wind and therefore waves can
pick up more energy. Finally, water depth is another important factor. Areas of
deeper water have less friction and therefore wave energy is higher.
Wave Frequency – the number of waves per minute
Wave crest – highest point of a wave
Wavelength – distance between wave crests
Wave trough – lowest point of a wave
Wave period – The time taken for a wave to travel between one wavelength
2
, Wave steepness – The ratio of the wave height to the wavelength (cannot be
steeper than 1:7 as the wave will break)
Swash – Forward movement of waves up the beach
Backward – The backward movement of the waves down the beach. This
occurs at right angles to the beach because of gravity
Wave Orbit – The circular movement of the water within a wave.
In open water, waves appear to move
In open water out at sea, waves are simply energy moving through water. It is
the energy that moves only.
The water itself only moves up and down, not horizontally.
Why waves break
1. Waves start out at sea and have a circular orbit
2. As waves approach the shore, friction slows the base of the wave
a. The seabed is rough and acts as a source of friction
3. This causes the orbit to become elliptical
4. Until the top of the wave breaks over
Backshore Nearshore Offshore
- Back of the beach - Waves become shallow - Goes quiet
- Lots of large sediment enough to form bars - Beyond the influence of
- Area between high - Waves break waves
water mark and - The most interesting - No obstacles
landward limit zone
Inputs Stores Outputs Flows
- Sun’s energy - Coastal landforms - Evaporation - Mass movement
- Water and - Sea - Water and - Longshore Drift
sediment from sediment carried
offshore out to deep sea
- Water and
sediment from
land
3
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