AQA A-level Coasts Knowledge Booklet
Coastal Systems
1. Coastal Systems
● Simple system approach of a coast (inputs, outputs, stores, transfers and processes)
● Sediment Budget refers to the gains and losses of sediment within a sediment cell
○ Positive sediment budget:more inputs than outputsof sediment leading to a
sedimentsurpluswhich creates awider beach
■ Human management strategies eg. groynes can help accumulation
of sediment (surplus)
○ Negative sediment budget:more outputs than inputscause a sediment
deficitwhich creates anarrower beach
■ Sediment is lost via LSD, wind and sea removal or human
interference
○ Neutral sediment budget: inputs = outputs so the beach is in equilibrium
● Sediment cells AKA littoral cells are the area within sediment moves (11 in UK)
○ They are normallyclosed systemssince they containthe sediment within an
area
■ This area is often kept isolated between headlands
○ These cells can become open systems during extreme natural variation eg.
storms which can carry sediment around a headland
■ When sediment is permanently removed from an area the area
becomes asediment sink
● Feedbacks in the Coastal System
○ Positive feedbacks - when the change is amplified
■ Sea levels rise → vegetation on sand dunes is removed → more
erosion of sand dunes → wind is able to erode more → sand dunes
become fully eroded
○ Negative feedbacks - when the change is restored
■ Erosion of sand dune → sand transported by the waves to form
off-shore bar → incoming waves are slowed by obstacles →
deposition occurs → sand dunes build back up
● Types of equilibrium in a coastal system
○ Steady-state - energy entering = energy leaving so the coast stays the same
all year round
○ Dynamic equilibrium - change is gradual, the system is constantly adapting to
find an equilibrium
, ○ M
etastable equilibrium (only for coasts) - dramatic events change the
equilibrium of the coast eg. a storm
2. Energy in the Coastal System
● Wind energy
○ Solar energy creates areas of high and low pressure. When air moves from
high to low pressure wind is formed. Wind blows over the water to form
waves. (Air always moves to the area of lowest pressure)
● Wave energy
○ Waves are bodies of water that move in circular motions between the crest
and trough. Energy is transferred between the crest and trough to create
oscillatory waves
○ In shallow water, friction slows the circular motion but the upper motion
continues to create a transition (breaker wave)
○ Many factors affect the energy of a wave:
■ atmospheric pressure → areas of low pressure eg. north atlantic =
higher energy waves
■ wind direction → prevailing winds = higher energy waves
■ fetch → the longer the fetch = higher energy waves
■ storm surges → intense areas of low pressure = higher energy waves
Coastal Systems
1. Coastal Systems
● Simple system approach of a coast (inputs, outputs, stores, transfers and processes)
● Sediment Budget refers to the gains and losses of sediment within a sediment cell
○ Positive sediment budget:more inputs than outputsof sediment leading to a
sedimentsurpluswhich creates awider beach
■ Human management strategies eg. groynes can help accumulation
of sediment (surplus)
○ Negative sediment budget:more outputs than inputscause a sediment
deficitwhich creates anarrower beach
■ Sediment is lost via LSD, wind and sea removal or human
interference
○ Neutral sediment budget: inputs = outputs so the beach is in equilibrium
● Sediment cells AKA littoral cells are the area within sediment moves (11 in UK)
○ They are normallyclosed systemssince they containthe sediment within an
area
■ This area is often kept isolated between headlands
○ These cells can become open systems during extreme natural variation eg.
storms which can carry sediment around a headland
■ When sediment is permanently removed from an area the area
becomes asediment sink
● Feedbacks in the Coastal System
○ Positive feedbacks - when the change is amplified
■ Sea levels rise → vegetation on sand dunes is removed → more
erosion of sand dunes → wind is able to erode more → sand dunes
become fully eroded
○ Negative feedbacks - when the change is restored
■ Erosion of sand dune → sand transported by the waves to form
off-shore bar → incoming waves are slowed by obstacles →
deposition occurs → sand dunes build back up
● Types of equilibrium in a coastal system
○ Steady-state - energy entering = energy leaving so the coast stays the same
all year round
○ Dynamic equilibrium - change is gradual, the system is constantly adapting to
find an equilibrium
, ○ M
etastable equilibrium (only for coasts) - dramatic events change the
equilibrium of the coast eg. a storm
2. Energy in the Coastal System
● Wind energy
○ Solar energy creates areas of high and low pressure. When air moves from
high to low pressure wind is formed. Wind blows over the water to form
waves. (Air always moves to the area of lowest pressure)
● Wave energy
○ Waves are bodies of water that move in circular motions between the crest
and trough. Energy is transferred between the crest and trough to create
oscillatory waves
○ In shallow water, friction slows the circular motion but the upper motion
continues to create a transition (breaker wave)
○ Many factors affect the energy of a wave:
■ atmospheric pressure → areas of low pressure eg. north atlantic =
higher energy waves
■ wind direction → prevailing winds = higher energy waves
■ fetch → the longer the fetch = higher energy waves
■ storm surges → intense areas of low pressure = higher energy waves
