Thursday, 10 January 2019
COASTAL ENVIRONMENTS - WAVES
• Waves contain a lot of energy & are one of the key agents of change at a coastline
• Waves are formed by the frictional drag of the wind as it blows across open water
• Therefore, wave direction is a reflection of wind direction
HOW IS A WAVE FORMED?
1. Wind causes friction at the surface of the sea
2. This causes a swell - a wave is created
3. Energy from the wind causes the water to move in circular motions - forming a wave
orbit
4. The water doesn’t actually move, the energy waves pass through the water
FACTORS INFLUENCING SIZE & POWER OF THE WAVE:
- Strength/speed of the wind - stronger wind means greater friction & more powerful
waves
- Length of fetch - this is the distance has travelled uninterrupted. A large fetch generates
a larger wave
- Length of time wind blows in the same direction - wind stability generates larger waves
WAVE TERMINOLOGY:
- Wave Crest = as the water in a wave rises, it forms the wave crest. The top of the wave
- Wave Trough = as the water in a wave falls, it forms the wave trough. This is the low point
between 2 wave crests
- Wave Height = the difference in height between the wave crest and wave trough
- Wave Length = the distance between 2 wave crests. Waves 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. Calculated by dividing the
average wave height by average wave period
- Wave Frequency = the number of waves that break on the beach in a given time
- Wave Steepness = calculated by: wave height/wave length. This ration cannot exceed
1:7 (0.14) as at this point the wave will break
1
COASTAL ENVIRONMENTS - WAVES
• Waves contain a lot of energy & are one of the key agents of change at a coastline
• Waves are formed by the frictional drag of the wind as it blows across open water
• Therefore, wave direction is a reflection of wind direction
HOW IS A WAVE FORMED?
1. Wind causes friction at the surface of the sea
2. This causes a swell - a wave is created
3. Energy from the wind causes the water to move in circular motions - forming a wave
orbit
4. The water doesn’t actually move, the energy waves pass through the water
FACTORS INFLUENCING SIZE & POWER OF THE WAVE:
- Strength/speed of the wind - stronger wind means greater friction & more powerful
waves
- Length of fetch - this is the distance has travelled uninterrupted. A large fetch generates
a larger wave
- Length of time wind blows in the same direction - wind stability generates larger waves
WAVE TERMINOLOGY:
- Wave Crest = as the water in a wave rises, it forms the wave crest. The top of the wave
- Wave Trough = as the water in a wave falls, it forms the wave trough. This is the low point
between 2 wave crests
- Wave Height = the difference in height between the wave crest and wave trough
- Wave Length = the distance between 2 wave crests. Waves 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. Calculated by dividing the
average wave height by average wave period
- Wave Frequency = the number of waves that break on the beach in a given time
- Wave Steepness = calculated by: wave height/wave length. This ration cannot exceed
1:7 (0.14) as at this point the wave will break
1
