COASTAL ENVIRONMENT

•Wave Terminology

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.

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

The shore

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

iv. Wave length - distance between two consecutive crests or two consecutive troughs

Parts of the wave

Wave Terminology

Wave Terminology

• Wavelength (L) - the distance between two successive crests. It can be determined by the formula:

L = 1.56T2,

where L= wavelength, T=wave period

• Wave period (T) – is the time taken for a wave to travel through one wavelength.

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.

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.

The Littoral Zones

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.

The ‘shaping’ influencing factors:

Questionsa. 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.