8.1. Coastal Processes Flashcards
Waves
Oscillation of the water surface which are generated by the frictional drag of wind as it blows across open water
- wave direction is a reflection of wind direction
What is the main agent that causes change in coastal environment
Waves
Factors influencing wave size
1) Wind speed
2) Length of time that the wind blows in a constant direction
3) Length of fetch
- coastlines facing a large ocean have a larger fetch than coastlines around an enclosed sea
What causes a big wave
- High wind speed
- long length of time that the wind blows in a constant direction
- long length of fetch
Fetch
The distance of sea over which the wind can blow
Wave crest
As the water in a wave falls, it forms the wave trough.
- This is the lowest point between two wave crests
Wave height
The difference in height between a wave crest and wave trough
Wave length
The distance between two wave crests
- waves are not usually evenly spaced
Wave period
The time taken for a wave to travel through one wave length
Wave velocity
The speed of movement of the wave crest
- can be calculated by dividing the average wave length by the average wave period
Wave frequency
The number of waves that break on the beach in a given period of time
Wave steepness
Calculated using the formula:
- wave height / wave length
- rato cannot exceed 1:7 (0.14) because at that point the wave will break
Wave energy
In deep water the energy of a wave is proportional to the wave length multiplied by the wave height squared
- this means that even a small increase in wave height can produce a large increase in wave energy
- wave energy is directly related to height
- energy of a wave is released when it breaks
Plunge line
The point at which the wave breaks
Swash
The body of foaming water that rushes up the beach when a wave breaks
- it obtains its energy from the energy released by the breaking wave