Summary AQA Alevel geography coastal systems and landscapes notes

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