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Wave types - constructive and destructive

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

  • the - how far the wave has travelled
  • the strength of the wind
  • how long the wind has been blowing for
Long fetch (up to 8,000 km) - South-westerly wind will produce large powerful waves. Short fetch (less than 200 km) - South-easterly wind will produce small waves.

Wave types

There are two different types of waves - and . 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 . The water that flows back towards the sea is known as the . The energy of the swash and backwash determine the type of wave.

Destructive waves

Constructive waves are high in proportion to their length. They have a weak swash but a strong backwash. A tall breaker is a tall wave which breaks downwards with great force.

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

Destructive waves are low in proportion to their height. They have a strong swash and weak backwash.

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