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
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.
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 .