coastal terminology lesson 1
DESCRIPTION
Wave crest, trough, wavelength, wave heightTRANSCRIPT
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COASTAL ENVIRONMENT
•Wave Terminology
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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.
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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
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The shore
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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
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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.
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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.
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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.
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The Littoral Zones
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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.
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The ‘shaping’ influencing factors:
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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.