Coastal systems and landscapes
Coastal systems
Coast- the interface between land and sea, it is an open system
Positive feedback- a process in which an initial change will bring about an additional change in the
same direction. E.g. a groyne
Negative feedback- a process in which an initial change will bring about an additional change in the
opposite direction. E.g. a sea wall
Dynamic equilibrium- a state of balance between continuing processes where outputs equal inputs
if unequal system regains equilibrium via feedback
4 factors that effect dynamic equilibrium of a beach
Supply of sand- the sand gets eroded then deposition puts the sand back
The energy of the waves- destructive waves are higher energy so erode and constructive
waves are low in energy
Changes in sea level- ice melt and rainfall increase sea level then evaporation decreases it
The location of the shoreline- when sea levels rises the location of the shore lines moves
back
Beachy head- short term change
Chalk coastline
Cliff retreated so more sediment
Beach at a more gentle angle
Factors that affect the nature, shape and form of a coastline:
Human Marine Atmospheric Terrestrial
Coastal defences Waves and tsunamis Solar energy Geology
Conservation Tide Gravity Relief
Buildings Biotic features (coral) Climate Tectonics
Pollution Salt spray Gravity Weathering
Coastal zones
Nearshore- area extending seaward from the high water mark to the area where waves begin to
break
Breaker zone- area where waves approaching coastline begin to break usually where the water
depth is 5 to 10m
Swash zone- area of beach between surf zone and foreshore zone that is exposed by processes of
wave swash and backwash
, Sediment sources, cells and budgets
Sediment cells- a cell is a length of coastline within which the movement of sediment is largely self-
contained so there is a balance between erosion and deposition
Sediment cells:
11 in England and Wales
Separated from each other by well-defined boundaries e.g. headlines
In the cell longshore drift takes from area of erosion to area of deposition
Represent a closed system
Sediment cell is a system:
Inputs-
o River system
o Subaerial system- run-off, weathering, and mass movement
o Longshore drift- from other sections of coast
o Man generated debris
Outputs-
o Dune erosion
o Wind erosion
o Dredging
Stores-
o Beach
o Spit
o Bar
Transfers-
o Longshore drift
Sediment cell budgets
Positive budget more material added to cell than removed surplus of sediment shoreline
builds towards the sea
Negative budget more material removed from cell than added deficit of sediment shoreline
retreats landwards
Tides and ocean currents
Tides- the periodic rise and fall of the level of the sea in response to gravitational pull of the sun and
moon
3 influences on the tide:
Gravitational pull (sun and moon)
Earth rotation 24h
Moon circles the earth 27 days- 6h 13m difference between high and low tide
Spring tides
The bulge of water creates a high tide
, When the moon, sun and earth are aligned
Creates extreme high and low tides so high tidal range
Neap tides
The moon and sun are perpendicular to each other
The sun diminishes the gravitational pull
Small bulges- lower than normal high tides so low tidal range
Bay of Fundy- Canada
Tidal range is greatest where the sea is funnelled into a constricted
channel and the volume of water is forced to rise as it is contained
High tide is over 15m high
Tidal surges (storm surge):
Storm surge- the pushing of water against a coastline to abnormally high levels
Depressions (low pressure weather system) can affect sea level
Severn Bore- Bristol channel
When tide is high these are confined in the narrow Severn river
Tidal range of 13m
A sudden influx of water sends a 1m high tidal wall of water upriver
Ocean currents- are large scale movements of water in the oceans
They are caused by:
The tides
The wind
Thermohaline circulation
Coastal processes
Erosion- the wearing away of materials by natural processes
Types of erosion:
Corrasion (abrasion)- When rocks are thrown against a cliff face
Hydraulic action- Erosion of the water hitting against a rock surface
Solution- Minerals dissolved in the water
Attrition- When rocks hit against each other breaking them down
Cavitation- when the wave recedes the air that was compressed is released
Wave quarrying- energy of wave forcing itself into crack/ line of weakness in a cliff
4 ways in which sediment is transported:
Traction- large, heavy pebbles are rolled along the riverbed
Saltation- pebbles are bounced along the riverbed
Coastal systems
Coast- the interface between land and sea, it is an open system
Positive feedback- a process in which an initial change will bring about an additional change in the
same direction. E.g. a groyne
Negative feedback- a process in which an initial change will bring about an additional change in the
opposite direction. E.g. a sea wall
Dynamic equilibrium- a state of balance between continuing processes where outputs equal inputs
if unequal system regains equilibrium via feedback
4 factors that effect dynamic equilibrium of a beach
Supply of sand- the sand gets eroded then deposition puts the sand back
The energy of the waves- destructive waves are higher energy so erode and constructive
waves are low in energy
Changes in sea level- ice melt and rainfall increase sea level then evaporation decreases it
The location of the shoreline- when sea levels rises the location of the shore lines moves
back
Beachy head- short term change
Chalk coastline
Cliff retreated so more sediment
Beach at a more gentle angle
Factors that affect the nature, shape and form of a coastline:
Human Marine Atmospheric Terrestrial
Coastal defences Waves and tsunamis Solar energy Geology
Conservation Tide Gravity Relief
Buildings Biotic features (coral) Climate Tectonics
Pollution Salt spray Gravity Weathering
Coastal zones
Nearshore- area extending seaward from the high water mark to the area where waves begin to
break
Breaker zone- area where waves approaching coastline begin to break usually where the water
depth is 5 to 10m
Swash zone- area of beach between surf zone and foreshore zone that is exposed by processes of
wave swash and backwash
, Sediment sources, cells and budgets
Sediment cells- a cell is a length of coastline within which the movement of sediment is largely self-
contained so there is a balance between erosion and deposition
Sediment cells:
11 in England and Wales
Separated from each other by well-defined boundaries e.g. headlines
In the cell longshore drift takes from area of erosion to area of deposition
Represent a closed system
Sediment cell is a system:
Inputs-
o River system
o Subaerial system- run-off, weathering, and mass movement
o Longshore drift- from other sections of coast
o Man generated debris
Outputs-
o Dune erosion
o Wind erosion
o Dredging
Stores-
o Beach
o Spit
o Bar
Transfers-
o Longshore drift
Sediment cell budgets
Positive budget more material added to cell than removed surplus of sediment shoreline
builds towards the sea
Negative budget more material removed from cell than added deficit of sediment shoreline
retreats landwards
Tides and ocean currents
Tides- the periodic rise and fall of the level of the sea in response to gravitational pull of the sun and
moon
3 influences on the tide:
Gravitational pull (sun and moon)
Earth rotation 24h
Moon circles the earth 27 days- 6h 13m difference between high and low tide
Spring tides
The bulge of water creates a high tide
, When the moon, sun and earth are aligned
Creates extreme high and low tides so high tidal range
Neap tides
The moon and sun are perpendicular to each other
The sun diminishes the gravitational pull
Small bulges- lower than normal high tides so low tidal range
Bay of Fundy- Canada
Tidal range is greatest where the sea is funnelled into a constricted
channel and the volume of water is forced to rise as it is contained
High tide is over 15m high
Tidal surges (storm surge):
Storm surge- the pushing of water against a coastline to abnormally high levels
Depressions (low pressure weather system) can affect sea level
Severn Bore- Bristol channel
When tide is high these are confined in the narrow Severn river
Tidal range of 13m
A sudden influx of water sends a 1m high tidal wall of water upriver
Ocean currents- are large scale movements of water in the oceans
They are caused by:
The tides
The wind
Thermohaline circulation
Coastal processes
Erosion- the wearing away of materials by natural processes
Types of erosion:
Corrasion (abrasion)- When rocks are thrown against a cliff face
Hydraulic action- Erosion of the water hitting against a rock surface
Solution- Minerals dissolved in the water
Attrition- When rocks hit against each other breaking them down
Cavitation- when the wave recedes the air that was compressed is released
Wave quarrying- energy of wave forcing itself into crack/ line of weakness in a cliff
4 ways in which sediment is transported:
Traction- large, heavy pebbles are rolled along the riverbed
Saltation- pebbles are bounced along the riverbed
