Coasts Notes:
Waves: Created by the transfer of energy from wind to the surface of the sea. As the strength of the
wind increases, the wave size and frictional drag also increase.
Wave energy depends on 3 factors:
Wind velocity
Period of time over which wind has blown
Fetch- the maximum distance open water over which wind has blown (large fetch = higher
energy waves
Swell Waves: Travelled by distant storms
Low height, gentle steepness, long wavelength, long period
Sea Waves: Local waves caused by wind
Tall heigh, steep, short wavelength, short period (higher energy)
Wave Height: vertical distance between the wave crest and trough
Wave Period: time taken for a wave to travel 1 wavelength
Wave Velocity: the speed of movement of a wave
Wave Steepness: ration of the height to the wavelength (H/L)
Wave Energy: the energy possessed by a wave in deep water
Waves in Deep Water:
When depth is > than ¼ length of wave
Wind drag on the sea surface cases the water to move in an orbital motion
Waves are surface features- the size of the orbit decreases with depth
Waves in Shallow Water:
When the water depth is <1/4 of the wavelength
Friction with seabed increase
As the base of the wave slows down, the circular oscillations become elliptical
, Wave Refraction:
As waves approach an irregular coastline they are refracted
e.g. they become increasingly parallel to the coastline
The waves nearer to the shore slow down due to friction drag
on the seabed, whereas those in the deeper water continue to
move quickly
The causes the wave to bend
This process also created longshore currents which carries
sediment inshore from the headland
Constructive Wave: A low wave that is created in a calm weather and are less powerful than
destructive waves. They break on the shoer and deposit material, building up beaches. Their swash is
stronger than their backwash.
Destructive Waves: Created in storm conditions, from big, strong waves when the wind is powerful
and has been blown for a long time. They occur when wave energy is high, and the wave has
travelled over a long fetch. They break down the coast as they have a stronger backwash than swash
Sediment Cell:
Also known as the littoral cell system
Model of study of process and patterns of a section of coast
Each cell is a self-contained unit where inputs and outputs are balanced,
and sediment is transferred within the cell
E.g. from the River Tyne to St Abbs Head in the UK
Beaches and Bays:
Beaches are depositional landforms which are found in low
energy intertidal zones at coasts.
Made up of many different materials e.g. sand, silt, gravel,
shingle, and rocks
Formed by many different processes such as:
o Long Shore Drift- sediment moves in a diagonal movement in the direction of the
prevailing wind
o Cliff Erosion- hydraulic action knocking off particles
o Material from nearby rivers and offshore sources such as constructive waves
Berms are also formed on beaches- a terrace of a beach that has formed in the backshore,
above the water level at high tide
Shape of the beach is constantly changing from weather, movement of water, type of wave
(constructive = build up of beach and deconstructive = beach broken down)
Constructive waves are common in the summer whereas destructive in the winter month
Regularly located within bays due to the shelter they provide from strong winds, reducing
destructive waves occurring
Waves: Created by the transfer of energy from wind to the surface of the sea. As the strength of the
wind increases, the wave size and frictional drag also increase.
Wave energy depends on 3 factors:
Wind velocity
Period of time over which wind has blown
Fetch- the maximum distance open water over which wind has blown (large fetch = higher
energy waves
Swell Waves: Travelled by distant storms
Low height, gentle steepness, long wavelength, long period
Sea Waves: Local waves caused by wind
Tall heigh, steep, short wavelength, short period (higher energy)
Wave Height: vertical distance between the wave crest and trough
Wave Period: time taken for a wave to travel 1 wavelength
Wave Velocity: the speed of movement of a wave
Wave Steepness: ration of the height to the wavelength (H/L)
Wave Energy: the energy possessed by a wave in deep water
Waves in Deep Water:
When depth is > than ¼ length of wave
Wind drag on the sea surface cases the water to move in an orbital motion
Waves are surface features- the size of the orbit decreases with depth
Waves in Shallow Water:
When the water depth is <1/4 of the wavelength
Friction with seabed increase
As the base of the wave slows down, the circular oscillations become elliptical
, Wave Refraction:
As waves approach an irregular coastline they are refracted
e.g. they become increasingly parallel to the coastline
The waves nearer to the shore slow down due to friction drag
on the seabed, whereas those in the deeper water continue to
move quickly
The causes the wave to bend
This process also created longshore currents which carries
sediment inshore from the headland
Constructive Wave: A low wave that is created in a calm weather and are less powerful than
destructive waves. They break on the shoer and deposit material, building up beaches. Their swash is
stronger than their backwash.
Destructive Waves: Created in storm conditions, from big, strong waves when the wind is powerful
and has been blown for a long time. They occur when wave energy is high, and the wave has
travelled over a long fetch. They break down the coast as they have a stronger backwash than swash
Sediment Cell:
Also known as the littoral cell system
Model of study of process and patterns of a section of coast
Each cell is a self-contained unit where inputs and outputs are balanced,
and sediment is transferred within the cell
E.g. from the River Tyne to St Abbs Head in the UK
Beaches and Bays:
Beaches are depositional landforms which are found in low
energy intertidal zones at coasts.
Made up of many different materials e.g. sand, silt, gravel,
shingle, and rocks
Formed by many different processes such as:
o Long Shore Drift- sediment moves in a diagonal movement in the direction of the
prevailing wind
o Cliff Erosion- hydraulic action knocking off particles
o Material from nearby rivers and offshore sources such as constructive waves
Berms are also formed on beaches- a terrace of a beach that has formed in the backshore,
above the water level at high tide
Shape of the beach is constantly changing from weather, movement of water, type of wave
(constructive = build up of beach and deconstructive = beach broken down)
Constructive waves are common in the summer whereas destructive in the winter month
Regularly located within bays due to the shelter they provide from strong winds, reducing
destructive waves occurring
