C+-+Waves+shaping+our+coastlines

__**How waves form?**__

Waves are usually formed by the wind blowing across the sea. This causes ripples on the top of the surface and these develop into waves. The stretch of open water over which the wind blows is called the **fetch**. The longer the fetch the more powerful the wave.

Video showing wave formation - []



The above diagram shows you what happens when a wave moves closer towards the coast and crashes onto a beach.


 * Crest** - this is the top part of the wave and eventually topples onto the beach.
 * Swash** - this is the water that rushes up the beach
 * Backwash** - this is the water that flows back towards the sea

Types of waves

There are two types of waves; constructive and destructive waves. Constructive waves:


 * Constructive waves are waves that surge up the beach and have a powerful swash
 * They carry large amounts of sediment and 'contruct' the beach making it more extensive

Main characteristics: They have a strong swash and a weak backwash and are smaller in height compared to destructive waves. They are waves which contain a small amount of energy.

Destructive waves


 * Destructive waves are named because they 'destroy' the beach.
 * When the waves hit the beach they rear up and smash down onto the beach.
 * There is very little swash when the wave breaks but has a powerful backwash.
 * The backwash removes the sediment which leads to the 'destruction' of the beach

Main characteristics: They have a strong backwash, lots of energy and are waves which are high in height