Wave crest, trough, wavelength, wave height

1. COASTAL ENVIRONMENT
• Wave Terminology

2. WHAT IS A COAST?
• The area lying between the land and the sea.
It includes the shore and the cliffs
• a narrow zone where the land and the sea
overlap and directly interact.

3. WHAT IS A SHORE?
• The shore is the zone between the lowest water mark and
the highest water mark reached by storm waves.
• The shore can be divided into three sections:
1. Backshore:
• Stretches landwards from the high water level.
• Can be reached by high storm waves.
2. Foreshore:
• Lies between the low water level and the high water
level.
• Covered with water during high tide.
3. Offshore:
• Never exposed even during low tide

4. The shore

5. Wave Terminology
WAVES?
• The undulations of water in the
sea or oceans created by wind
blowing over their surfaces.
• The parts of a wave:
i. Crest - the highest part of a
wave
ii. Trough - the lowest part of a
wave
iii. Wave height- vertical distance
between the crest
and the trough
Parts of the wave
iv. Wave length- distance between
two consecutive crests or two
consecutive troughs

6. Wave Terminology
• Wavelength (L) - the distance between two
successive crests. It can be
determined by the formula:
L = 1.56T , 2
where L= wavelength, T=wave period
• Wave period (T) – is the time taken for a wave to
travel through one wavelength.

7. Wave Terminology
• Wave velocity (C) – is the speed of movement of a
crest in a given period of time.
• Wave steepness – the ratio of the wave height to
the wave length ( H / L ).
• Swell - is characterised by waves of low height,
gentle steepness, long wavelength and a
long period.
• Wave frequency - the number of waves per minute.

8. Wave Terminology
• Wave Fetch – is the amount of open water over
which a wave has passed.
• Plunge line – the point at which the wave breaks.
• Swash - the body of foaming water which then
rushes up the beach, while any returning
down to the sea is the backwash.
• Wave orbit - the shape of the wave. It varies
between circular and elliptical.

9. The Littoral Zones

10. The coast as an open system
• Landforms are the result of inputs of energy to surface
and near-surface materials
• At the coast, the main source of energy is waves
generated by the wind.
• The coast as a system is a highly complex system with
many factors influencing its characteristics.
• Along any one stretch of coastline, these factors
interrelate in a unique way, with each one assuming a
different degree of importance.

11. The ‘shaping’ influencing factors:

12. Questions
a. Using annotated diagram, explain the following
terms:
• Wave crest
• Wave trough
• Wavelength
• Wave height
b. Explain how coastal landscapes vary on account
of human activities and geological structures.