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When the wind blows over the sea, it creates waves. The size and energy of the wave depends on certain factors:

• the fetch - how far the wave has travelled
• the strength of the wind
• how long the wind has been blowing for

Wave types

There are two different types of waves - constructive and destructive. They can affect the coastline in different ways. When a wave reaches the shore, the water that rushes up the beach is known as the swash. The water that flows back towards the sea is known as the backwash. The energy of the swash and backwash determine the type of wave.

Destructive waves

The characteristics of a destructive wave are:

• a weak swash and strong backwash
• occurs in stormy conditions, with strong winds
• the strong backwash removes sediment from the beach
• waves that are steep and close together
• tall waves with short wave length
• they arrive quickly and have a high frequency - a lot of them come in a short period of time

Constructive waves

The characteristics of a constructive wave are:

• small waves, with low wave height and long wave length
• occurs in calm conditions, without much wind
• a strong swash and weak backwash
• the strong swash brings sediments to build up the beach
• the backwash is not strong enough to remove the sediment
• waves that are low and further apart