The Coast

Define the coast.

The coast is a narrow zone where the land meets the sea. It is constantly changing due to the effect of land, marine and air processes.

The Coastal SystemInputs Processes Outputs

Marine:

Waves

Tides

Salt Spray

Atmosphere:

Sun

Precipitation

Air Pressure

Wind Speed & Direction

Humans:

Pollution

Recreation

Settlement

Defences

Erosion

Transportation

Depostion

Beaches

Sand Dunes

Spits

Bars & Tombolos

Headlands & Bays

Cliffs

Wavecut notches

Wavecut platforms

Caves

Arches

Stacks

Stumps

Waves

• BBC - Learning Zone Class Clips - Understanding wave formation - Geography Video

Waves

• Waves are created by wind blowing over the surface of the water.

• Friction is created which drags the water in the same direction that the wind is blowing.

• The distance that the wave travels is called the fetch.

Waves

• The size and energy of a wave is determined by:

• The length of time that the wind has been blowing

• The strength of the wind

• How far the wave has travelled = fetch

• BBC - GCSE Bitesize: The action of waves

Key Terms

Key Terms

The wave height (H) is the distance between the crest and the trough

Wave period (T) is the time taken for a wave to travel through one wave length. This can be timed either by counting the number of crests per minute or by timing 11 waves and dividing by 10, i.e. the number of intervals

Wave length (L) is the distance between two successive crests

Key Terms

Wave velocity (C) is the speed of movement of a crest in a given time period.

Wave steepness (H ÷ L) is the ratio of wave height to wave length. Most waves have a steepness of between 0.005 and 0.05. The ratio cannot exceed 1:7 (0.14) because at that point the wave will break.

Waves formed by distant storms and traveling large distances are known as swell. These waves are characterised as having a low height (in relation to wave length), gentle steepness, long wave length and long period.

Waves that result from local winds and travel only short distances are known as sea. They are high (in relation to wavelength) and steep and have a short wavelength and short period.

Destructive Waves

• destructive waves are created in storm conditions. • are created from big, strong waves when the wind is powerful

and has been blowing for a long time. • occur when wave energy is high and the wave has travelled

over a long fetch. • tend to erode the coast. • have a stronger backwash than swash. • have a short wave length and are high and steep.

Constructive Waves

• constructive waves are created in calm weather and are less powerful that destructive waves.

• break on the shore and deposit material, building up beaches.

• have a swash that is stronger than the backwash. • have a long wavelength, a low height.

Why does a wave break?

A wave breaks because it slows down in shallower water and becomes steeper. This process is called shoaling. When a wave becomes too steep it breaks. The point at which it breaks is called the plunge line. Water rushing up the beach is called the swash. Water running down the beach is called the backwash.

Tides

Remember

• Spring Tides are high

• Neap tides are lower

• Oceanography

• BBC - Learning Zone Class Clips - Surfing the Severn bore - Science Video

Why are tides important?

Sediment