Parts of a wave

A diagram showing the parts of a wave

crest – highest part of the wave

trough – lowest part of the wave

wave height – vertical distance between the crest and the trough

wave length – distance between two consecutive crests or troughs

Wave energy

Wave energy is dependent on two factors, speed of the wind and the fetch, which is the length of water surface over which the wind blows.

With a higher wind speed, the wave would have a higher energy. Similarly, a larger fetch would give higher wave energy.

Movement of waves

Waves change as they approach a coast. With increased friction between the waves and shallow seabed, waves slow down.

As the waves slow down, waves behind them push them, causing an increase in the wave height.

The crests of the waves are then thrown forward when the waves become too steep. Thus, they collapse and break, and develop into white foams after trapping air.
Swash rushing up a shore

The white foamy water rushes up the shore as swash, bringing materials up the coast.

Due to friction and gravity, the water then flows back into the sea as backwash, bringing back some of the materials back to the sea.
Backwash moving back into the sea

Types of waves

The work of waves on a coast is determined by the type of wave that break on the coast. They are two types of waves, constructive and destructive, differentiated by characteristics listed below.