coasts content flashcards
(148 cards)
1
Q
How can the coast be described as a system?
A
The coast is an open system that receives inputs (e.g. sediment, energy) and transfers outputs to other systems like terrestrial, atmospheric, and oceanic.
2
Q
In what circumstances might the coast be considered a closed system?
A
During scientific research and coastline management planning, the coast may be treated as a closed system for simplification.
3
Q
What are sediment cells?
A
- coasts can be split into sections ; sediment cells
= sections of coastline where sediment movement is largely self-contained, often treated as closed systems for sediment management. - 11 sediment cells in england and wales
4
Q
What is a sediment source
A
A source is where sediment originates, such as cliffs or offshore bars.
5
Q
What are through flows in a sediment cell
A
Through flows are the movement of sediment along the coast, primarily via LSD
6
Q
What is a sediment sink
A
A sink is a location where deposition dominates, such as spits or beaches.
7
Q
What is dynamic equilibrium in the context of sediment cells
A
Dynamic equilibrium is when the inputs and outputs of sediment are constantly changing but remain balanced overall.
- physical + human actions can change the balance of sediment w/in a cell
8
Q
Are sediment cells completely closed systems
A
No, they are not fully closed—changes in one cell may affect neighboring cells.
9
Q
What is a positive feedback mechanism in the coastal system?
A
A process that exaggerates change, making the system more unstable and moving it away from dynamic equilibrium.
10
Q
What is a negative feedback mechanism in the coastal system?
A
A process that balances change, helping return the system back to dynamic equilibrium.
11
Q
Give an example of negative feedback in the coastal system.
A
After a storm erodes a beach:
- Excess sediment is deposited as an offshore bar.
- The bar dissipates wave energy, protecting the beach.
- The bar is eroded instead of the beach.
- Once the bar is gone, normal conditions return, restoring equilibrium.
12
Q
How does the offshore bar help in negative feedback
A
It absorbs wave energy, preventing further erosion of the beach and helping stabilize the system.
13
Q
Give an example of positive feedback in the coastal system.
A
When people walk on sand dunes, they destroy vegetation = damages the roots,
- This weakens the structure of dunes, causing increased erosion.
- Eventually the dunes are lost, leaving the beach more exposed and further from equilibrium.
14
Q
Why does damaging vegetation on sand dunes lead to positive feedback?
A
The roots stabilize the dunes; damaging them makes dunes more vulnerable to erosion, accelerating the problem.
15
Q
littoral zone
A
the area of the coast where land is subject to wave action, making it a dynamic and constantly changing environment
16
Q
ST + LT factorss that affect the littoral zone
A
ST = tides and storm surges
LT = changes in sea level and climate change
17
Q
What is the backshore zone?
A
the area above the high tide line, only affected by waves during exceptionally high tides or storm events.
18
Q
What is the foreshore zone?
A
The foreshore is the area between the high and low tide lines—where most wave processes occur.
19
Q
What is the nearshore zone?
A
is the breaker zone, where waves start to break as they approach the coast.
20
Q
What is the offshore zone?
A
The offshore is the area beyond the influence of breaking waves, essentially the open sea.
21
Q
What is the breakpoint bar
A
A zone of breaking waves that forms a longshore bar—helping dissipate energy before waves reach the beach.
22
Q
valentines classification
A
describes the range of coastlines that can occur, focusing on whether they are advancing or retreating.
23
Q
what causes an advancing coastline?
A
Land emergence or deposition being the dominant process.
24
Q
What causes a retreating coastline?
A
Land submergence or erosion being the dominant process.
25
emergent coastlines
Coastlines where land is rising relative to the sea, often due to post-glacial adjustment.
26
submergent coastlines
Coastlines where land is sinking relative to the sea, often caused by rising sea levels or land subsidence.
27
post-glacial adjustment
A process where land 'wobbles' or rebounds after the melting of a glacier, affecting sea levels (isostatic change).
28
What are the two main processes that can dominate a coastline’s behavior?
erosion + deposition
29
isostatic change
local shifts caused by land rising or falling relative to sea level.
30
eustatic changes
global shifts in sea level due to changes in ocean water volume
31
coastal erosion (CAASHQ)
- Corrasion
- Abrasion
- Attrition
- Solution (corrosion)
- Hydraulic actions
- wave Quarrying
32
corrasion
Sediment is picked up by waves and thrown against cliffs, eroding them. Erosive power depends on sediment size, shape, weight, amount, and wave speed.
- like chucking stones at watermelon 🍉
33
abrasion
Sediment is dragged along the shoreline, gradually wearing it down—like rubbing stones against a watermelon’s skin 🍉
34
attrition
Rocks and pebbles collide due to wave action, becoming rounder and smaller over time. It doesn’t directly erode the coastline.
35
hydraulic action
Waves force air into cracks in rocks; pressure causes cracks to widen and rock to fracture. Includes cavitation, where bubbles implode, forming jets that erode rock.
36
solution (corrosion)
Mildly acidic seawater dissolves alkaline rocks like limestone—similar to carbonation weathering and linked to the carbon cycle.
37
wave quarrying
Powerful breaking waves (up to 30 tonnes/m²) hammer cliffs, pulling away rocks and exposing them to further erosion.
- similar to hydraulic action just with greater force
38
When are coastal erosion rates at their highest, and why?
High, long-fetch waves: Carry more energy to erode the coast.
Waves hitting cliffs perpendicularly: Maximize force of impact.
High tide: Waves reach higher up the cliff, increasing erosion area.
Heavy rainfall: Weakens cliffs as water seeps through permeable rock.
Winter season: Destructive waves are more frequent and powerful.
39
How does the type of rock (clastic vs crystalline) affect erosion vulnerability
Clastic rocks (e.g., sandstone) are made of cemented particles and are more vulnerable. Crystalline rocks (e.g., igneous and metamorphic) have interlocking crystals, making them more resistant.
40
How do cracks, fractures, and fissures affect erosion?
More weaknesses in the rock make it more open to erosion, especially by hydraulic action.
41
erosion rate and structure of igneous rocks
- granite and basalt
- Very slow erosion (<0.1 cm/year)
- strong interlocking crystal structure = high resistance
42
erosion rate and structure of metamorphic rocks
- slate, schist, and marble
- Slow erosion (0.1–0.3 cm/year)
- Crystal all orientated in the same
direction = moderate resistance
43
erosion rate and structure of sedimentary rocks
- limestone
- Erode quickly (0.5–10 cm/year)
- lots of fractures and bedding planes make them weak and vulnerable.
44
How are Caves, Arches, Stacks, and Stumps formed?
Cave: Marine erosion widens faults in the headland.
Arch: Erosion continues through the headland.
Stack: Arch collapses under its own weight.
Stump: Marine erosion wears down the base of the stack until it collapses.
45
What is a wave-cut notch and how does it form? + wave-cut platform
- Marine erosion erodes the base of a cliff between high and low tide, forming a notch.
- After the notch causes the cliff above to collapse, a flat area of the former cliff base is left behind as a platform.
46
How do retreating cliffs form?
Through repeated wave-cut notch and platform formation, the cliff face collapses and retreats landward.
47
How is a blowhole formed?
A cave (marine erosion) and a pothole at top of cliff (chemical weathering) meet, creating a shaft where waves can force water upward and spray out of the top.
48
LSD
process where sediment is transported along the coast by waves approaching at an angle, moving sediment up in the swash and back down in the backwash.
- usualy from SW in england
49
coastal transportation processes
- LSD
- traction
- saltation
- suspension
- solution
50
tractions
Large, heavy sediment rolls along the seabed, pushed by currents.
51
saltation
Smaller sediment bounces along the seabed, lifted and dropped by currents.
52
suspension
Fine sediment is carried within the water column.
53
solution
Dissolved material is transported within the water itself.
54
what does the impact of trasnportation depend on?
- the severity of the angle that waves travel onto land
- can be swash-aligned or drift-aligned
55
swash-aligned coast
A coast where wave crests approach parallel to the shoreline, causing limited longshore drift and minimal sediment movement.
56
drift-aligned coast
A coast where waves approach at an angle, promoting strong longshore drift and significant sediment movement along the beach.
57
when does deposition occur
- when a wave loses energy meaning the sediment becomes too heavy to carry.
- gradual + continuous process (- a wave won’t drop all of its sediment all at once.)
58
gravity settling
As wave energy decreases, heavier sediment (e.g., rocks, boulders) is dropped first, followed by lighter particles.
59
flocculation
when Clay particles clump together due to chemical attraction and sink due to increased density.
60
depositional landforms
- spits
- bars
- tombolo
- cuspate forelands
- offshore bars
- sand dunes (5 stages)
61
spit (how is it formed + what determines the length of it)
- LSD deposits sediment in a sheltered area (e.g., behind a headland). A hook may form due to wind direction changes, and a salt marsh may develop behind it.
+ Nearby currents or rivers can limit growth, especially in estuaries where river flow interrupts deposition.
62
bar (how is it formed)
A spit grows across a bay, connecting two parts of coastline. Water behind it becomes a lagoon.
63
tombolo (what is it + how is it formed)
A bar or beach that connects the mainland to an offshore island,
+ formed by wave refraction slowing wave energy and causing deposition.
64
cuspate foreland (what is it)
A triangular feature (only occurs with triangular shaped headlands)
+ LSD along each side of the headland will create beaches, which where they meet, will form a cuspate foreland.
65
offshore bars (what are they + how do they form)
A region offshore where sand is deposited.
+ waves don’t have enough
energy to carry the sediment to shore. They can be formed as the wave breaks early, scouring the seabed and instantly depositing its sediment as a loose-sediment offshore bar.
66
sand dunes (when they occur + conditions needed + 5 stages of SD)
- occur when prevailing winds blow sediment to the back of
the beach
-> Large quantities of dry sand
-> Strong onshore winds
(allows the sand to dry, so that it is light enough to be picked up and carried by the wind to the back of the beach.)
-> Large tidal range
-> Obstacle to trap sand
5 stages ;
=> embryo dunes
=> yellow dunes
=> grey dunes
=> dune slack
=> heath and woodland
67
embryo dunes
stage 1 ; formed where sand accumulates around small obstacles like driftwood or pebbles.
+ upper beach area
68
yellow dunes
2nd stage ; taller dunes with vegetation developing on their surfaces, which helps stabilize them.
69
grey dunes
3rd stage ; Dunes where sand has turned to soil, supporting more diverse plant life due to moisture and nutrients.
70
dune slack
4th stage ; sandy soil develops (due to greater nutrients) = allows for less brackish plants to thrive + trees will grow with the coastal woodland becoming a natural windbreak to the mainland behind.
71
Why are depositional landforms vulnerable to change?
- consist of unconsolidated sediment
= making them easily affected by erosion or transport, especially during storms.
- A balance of sediment supply and erosion is needed to maintain stability.
72
weathering
The breakdown of rocks (mechanical, biological, or chemical) over time, leading to material being transferred into the littoral zone, contributing to sediment in the coastal environment.
73
mechanical (physical) weathering
The breakdown of rocks through physical forces without chemical changes, making the rocks weaker and more vulnerable to erosion.
1. freeze thaw
2. salt crystallisation
3. wetting + drying
74
1. freeze-thaw weathering
Water enters cracks in rocks, freezes and expands by 10%, increasing pressure and causing cracks to widen, weakening the rock over time.
75
2. salt crystallization
Salt left behind as seawater evaporates grows into crystals, which exert pressure on rocks, causing cracks to widen. It can also corrode ferrous rocks through chemical reactions.
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3. wetting and drying
Rocks, such as clay, expand when wet and contract when dry. Repeated cycles of wetting and drying cause the rock to weaken and break apart.
77
chemical weathering
The breakdown of rocks through chemical reactions, altering the rock's composition and weakening it.
1. carbonation
2. oxidation
3. solution
78
1. carbonation
Rainwater absorbs CO2, forming a weak carbonic acid that reacts with calcium carbonate in rocks (like limestone), forming calcium bicarbonate, which dissolves easily.
79
2. oxidation
When minerals (especially iron) are exposed to air, they oxidize, increasing their volume, contributing to mechanical weathering and causing rocks to crumble (rusty orange color).
80
3. solution
When rock minerals such as rock salt are dissolved.
81
biological weathering
the breakdown of rocks due to the actions of plants, bacteria and animals
1. plant roots
2. birds
3. rock boring
4. seaweed acids
5. decaying vegetation
82
1. plant roots
Roots growing into cracks in rocks exert pressure, eventually causing the rock to split and break apart.
83
2. birds
Birds like puffins dig burrows into cliffs, weakening the rock and making it more prone to erosion.
84
3. rock boring
Many species of clams secrete chemicals that dissolve rocks and piddocks may burrow into the rock face
85
4. seaweed acids
Some seaweeds contain pockets of sulphuric acid, which if hit against a
rock or cliff face, the acid will dissolve some of the rock’s minerals. (e.g. Kelp)
86
5. decaying vegetation
Water that flows through decaying vegetation and then over coastal
areas, will be acidic, thus causing chemical weathering
87
What factors influence the type of mass movement that occurs?
- The angle of the slope
- rock’s lithology
- vegetation cover
- ground saturation (prev weather patterns)
88
What is the difference between a slide and a flow in mass movement? (2 diff categories of MM)
A slide involves sediment moving downhill while staying intact, whereas a flow involves the material mixing and flowing downhill.
89
types of flows
1. soil creep
2. solifluction
3. mudflows
90
1. soil creep
The slowest form of mass movement, where soil particles gradually move downhill.
91
2. solifluction
Occurs in tundra areas where the surface layers thaw in summer, but the lower layers stay frozen due to permafrost, causing the top layers to flow over the frozen ground.
92
3. mudflow
When an increase in water content reduces friction, causing earth and mud to flow over underlying bedrock.
93
types of slides
1. rock falls
2. rock slides
3. slumps
94
1. rock falls
Occurs on steep cliffs (over 40°), often due to mechanical weathering, causing rocks to fall down.
95
2. rock slides
Occurs when water between joints and bedding planes reduces friction, causing rocks to slide down the cliff.
96
3. slump
Occurs when soil is saturated with water, leading to a rotational movement of soft materials like clay and sand, forming rotational scars and terraced cliff profiles.
- saturated soil slips down a curved surface
97
How do temperature and climate affect sub-aerial processes?
In colder climates, mechanical weathering is more common, while in warmer climates, chemical weathering is more prevalent.
98
What are the two main characteristics that dominate cliff profiles?
- The resistance of the rock to erosion
- the dip in the rock strata in relation to the sea.
99
concordant coastlines
occurs when the rock strata run parallel to the coast, typically consisting of bands of more resistant and less resistant rock types.
100
landforms associated with concordant coastlines
- dalmatian coastlines (formed when sea-level rises, floods valleys that run parallel to the coast = creating long narrow islands seperated by narrow channels )
- haff coasts (where large bays are crossed by spits, creating a extensive lagoons. )
101
discordant coastline
occurs when the rock strata run perpendicular to the sea, leading to the formation of headlands and bays.
102
How does wave refraction affect discordant coastlines?
- causes waves to lose energy around headlands (erosion occurs here) and dissipate in bays, leading to the formation of features like beaches in the bays.
103
How does vegetation help stabilise coastal landforms?
Vegetation stabilizes coastal landforms by:
-> Binding soil together with plant roots, reducing erosion.
-> Providing a protective layer when submerged, preventing ground erosion.
-> Reducing wind speed at the surface, minimizing wind erosion.
104
difference between xerophytes and halophytes?
- Xerophytes are plants tolerant of dry conditions.
- Halophytes are plants tolerant of salty conditions (also called brackish plants).
105
What is plant succession on coasts?
- the long-term process where plant communities change over time.
- In coastal areas with sediment supply and deposition, pioneer plants grow in bare mud and sand.
> due to salty soil conditions, only brackish plants can grow there.
> As deposition continues, vegetation dies + releases nutrients = red saltiness of soil = allowing different plants to colonize.
106
example of a pioneer plant
Marram grass
-> It is tough, flexible, and can withstand sand blast.
-> Adapted to reduce water loss via transpiration.
-> Its roots can grow up to 3 meters deep and tolerate temperatures up to 60°C.
107
stages of salt marsh succession(aka halosere)?
1. Algal Stage – Gut weed and blue-green algae grow on bare mud. ; roots help to bind together.
2. Pioneer Stage – Cord grass and glasswort roots stabilize the mud. ; allowinf estuarine to grow.
3. Establishment Stage – Salt marsh grass and sea asters grow, increasing marsh height. ; as it creates a sea of vegetation.
4. Stabilization – Sea thrift, scurvy grass, and sea lavender grow, preventing salt submersion.
5. Climax Vegetation – Rush, sedge, and red fescue grass grow, since the marsh submerged only 1-2 times per year.
108
characteristics of high-energy coastlines?
Strong, destructive waves
Large fetch
Rocky headlands and landforms
Erosion > Deposition
Common in areas with strong winds and deep water
109
characteristics of low-energy coastlines
Weak, constructive waves
Sheltered areas
Sandy beaches and depositional features
Deposition > Erosion
110
factors that affect wave size
Wind strength
Wind duration
Water depth
Fetch distance
111
Constructive waves
▪ Strong swash, weak backwash
▪ Low wave height, long wavelength
▪ Low frequency
▪ Depositional
112
Destructive waves
▪ Strong backwash, weak swash
▪ High wave height, short wavelength
▪ High frequency
▪ Erosional
113
How do seasonal changes affect wave types?
- summer = constructive, winter = destructive
- as a storm begins, constructive turns into destructive
- Climate change may cause more frequent destructive waves as UK becomes stormier
- Dams prevent sediment being transported from rivers and entering into the coastal area
which means erosion could increase.
114
short-term sea level changes causes :
- Tides (Moon's gravity)
- Wind strength/direction
- Atmospheric pressure (low pressure = higher sea level)
115
how does the moons gravity affect Tides
-> moons gravitational attraction distorts the earth towards it = water moves creating a 'bulge' (more water means higher tide)
-> on the side opposite the moons pull, inertia tries to counteract => so water tires to move away = creates another bulge
-> on remaining parallel sides, gravity + inertia are balances = tides lower as less water.
116
What is isostatic sea level change?
Local sea level change caused by:
- Post-glacial rebound or subsidence
- Tectonic activity (earthquakes, volcanoes)
117
What is eustatic sea level change?
Global sea level rise due to:
- Thermal expansion of water as it warms
- Melting of polar ice caps -> Driven by climate change
118
storm surge
A short-term rise in sea level caused by low atmospheric pressure during a depression or tropical cyclone.
119
What factors can aggravate a storm surge?
Land subsidence (tectonics or post-glacial adjustment)
Loss of natural vegetation (e.g., destruction of mangrove forests)
Global warming – warmer oceans = stronger/more frequent storms
120
Why are mangroves important for storm protection?
Provide natural barrier to waves and storm surges
Help stabilize sediment
Protect against cyclones and flooding
Their removal for tourism, housing, or industry increases coastal vulnerability
121
economic consequences of storm surges?
Lower property values in high-risk areas = as area becomes known to be a sig risk.
Loss of insurance options for residents as many insurers dont prov home insurance to ppl living along coastlines that are at extreme risk of erosion / storm surges.
Economic decline in local economies
122
environmental consequences of storm surges
Destroy plant succession stages
Damage depositional landforms (e.g. beaches, dunes) = more likely to be destroyed due to their unconsolidated nature
Accelerate cliff erosion, increasing collapse risk
123
What is an environmental refugee?
A person displaced due to environmental changes, such as coastal flooding or rising sea levels.
124
Why is the number of environmental refugees expected to rise?
1 billion+ people live in at-risk coastal areas
Rising eustatic sea levels and more storm surges increase displacement
Loss of homes, livelihoods, and cultures forces migration
125
What are the two main types of coastal engineering strategies?
Hard engineering – man-made structures (e.g., sea walls, groynes)
Soft engineering – works with natural processes (e.g., beach nourishment)
126
4 key coastal management approaches?
1. Hold the line – Keep the coast where it is
2. Advance the line – Build defences to move the coast outward
3. Managed realignment – Let the coast move inland in a controlled way
4. Do nothing – Allow natural erosion and retreat
127
What factors are considered when deciding on a coastal policy?
Economic value of assets
technical Feasibility of solutions
Ecological/cultural importance
Impact on communities & stakeholders
128
What is a Cost-Benefit Analysis (CBA) in coastal management?
A process that compares the costs (e.g. construction, maintenance) to the benefits (e.g. land, homes protected). Projects must show benefits ≥ costs.
- Costs and benefits include
both tangible and intangible things.
129
What does ICZM (Integrated Coastal Zone Management) involve?
Managing the whole coastal zone (sediment cell) = often involves management between
different political boundaries (diff councils work tgther)
Involves all stakeholders
Sustainable development is key
Works with natural processes
130
Shoreline Management Plans (SMPs)
Long-term plans for each sediment cell in England & Wales
Identify natural and human activities
Consider 4 options (Hold the line, Advance the line, Managed realignment, Do nothing)
131
hard engineering defences
- offshore breakwater
- groynes
- sea walls
- rip-rap
- revetments
132
offshore breakwater
- Rock barrier which forces waves
to break before reaching the shore
👍 Effective at reducing waves’ energy
👎 Visually unappealling
👎 Navigation hazard for boats
👎 Can interfere with LSD
133
Groynes
- Timber or rock protrusions that
trap sediment from LSD
👍 Builds up beach, protecting cliff and
increasing tourist potential
👍 Cost effective
👎 Visually unappealling
👎 Deprives areas downwind of sediment
increasing erosion elsewhere
134
Sea Walls
Concrete structures that absorb
and reflect wave energy, with curved surface
👍 Effective erosion prevention
👍 Promenade has tourism benefits
👎 Visually unappealling
👎 Expensive to construct and maintain
👎 Wave energy reflected elsewhere,
with impacts on erosion rates
135
Rip Rap (Rock Armour)
- Large rocks that reduce wave
energy, but allow water to flow through
👍 Cost effective
👎 Rocks are sourced from elsewhere,
so do not fit with local geology
👎 Pose a hazard if climbed upon
136
Revetments
Wooden or concrete ramps that
help absorb wave energy
👍 Cost effective
👎 Visually unappealling
👎 Can need constant maintenance, which creates an additional cost
137
soft engineering defences
- beach nourishment
- cliff regrading + drainage
- dune stabilisation
- marsh creation
-
138
Beach Nourishment
Sediment is taken from offshore
sources to build up the existing beach
👍 Builds up beach, protecting cliff and
increasing tourist potential
👍 Cost effective and looks natural
👎 Needs constant maintenance
👎 Dredging may have consequences on local coastal habitats
139
Cliff Regrading and Drainage
Reduces the angle of the cliff to
help stabilise it. A steeper cliff would be
more likely to collapse
👍 Cost effective
👎 Cliff may collapse suddenly as the cliff is drier leading to rock falls which pose a hazard
👎 May look unnatural
140
Dune Stabilisation
Marram grass planted. The roots
help bind the dunes, protecting land behind
👍 Cost effective and creates an
important wildlife habitat
👎 Planting is time consuming
141
Marsh Creation
Type of managed retreat allowing low-lying areas to flood
👍 Creates an important wildlife habitat
👎 Farmers lose land and may need
compensation as a result
142
key goals of sustainable coastal management
Manage natural resources (fish, farmland, water) to ensure long-term productivity
Provide alternative livelihoods before ppl lose existing jobs
Educate communities about adaptation
Monitor coastal change + then adapting or mitigating
Manage flood risk or consider relocation
143
Who are the winners in coastal management decisions?
ppl who benefit :
- Economically (property/businesses protected)
- Socially (community remains intact)
- Environmentally (habitats protected)
144
Who are the losers in coastal management decisions
People who suffer losses:
- Lose homes or property
- Forced to relocate (lose social ties)
- Lose businesses or jobs
- May feel angry or ignored
145
Why has coastal management funding become more limited since 2010?
Because DEFRA's central government funding was reduced, meaning only high-priority areas get support.
146
Why might ‘do nothing’ be chosen as a management strategy
SMPs consider whole sediment cells, not just one area
Limited budgets – not all areas can be defended
Some areas are low value or technically unsuitable for protection
147
How does a sea wall impact sediment cells?
Reflects wave energy → increased erosion downdrift
Reduces erosion → less sediment transported
Smaller beaches → more cliff exposure to erosion
148
How do groynes affect sediment transport?
Trap sediment → build up beach on one side
Starve downdrift areas of sediment
Leads to erosion in those areas due to lack of beach protection
