Coasts Flashcards
What type of system is the coast?
Open system – interacts with other systems (e.g., atmosphere, tectonics, ecosystems).
What are the key components of a coastal system?
Inputs: Precipitation, wind, wave energy, sediment, sea level changes.
Outputs: Ocean currents, rip tides, sediment transfer, evaporation.
Stores: Beach, landforms, sediment.
Flows: Aeolian processes, erosion, longshore drift, transportation.
How does the Water Cycle affect coasts?
Sea level changes due to glacial/interglacial periods impact coastal processes and landform development.
How does the Carbon Cycle affect coasts?
Global warming increases sea levels, causing storm surges & flooding, impacting ecosystems.
What is a threshold?
A point where change exceeds equilibrium, leading to permanent system changes.
Examples of Positive Feedback:
Groynes trap sediment → increases erosion elsewhere.
Sand dune trampling → removes vegetation, leading to more erosion.
Rising sea levels → more flooding → more erosion & land loss.
Examples of Negative Feedback:
Strong storm waves erode sediment → bar forms offshore → waves break earlier → reduces erosion.
What are the main energy sources in coastal systems?
Wind
Waves
Currents
Tides
What is the role of wind?
Primary source of coastal energy – generates waves.
What is the pressure gradient?
Difference in air pressure determines wind strength.
Greater difference = steeper gradient = stronger wind & waves.
How are waves formed?
Wind blows over the surface of the sea, generating frictional drag which forms ripples. In the open sea, there is little horizontal movement of water, instead there is an orbital motion of the water particles. Closer to the coast, horizontal movement of water does occur as waves break onto the beach.
What factors affect wave energy?
Strength of wind
Duration of wind
Fetch (distance wind blows over open water)
Constructive waves characteristics?
6-8 per min
Low wave height, large amplitude
Strong swash, weak backwash
Builds up beaches
Destructive wave characteristics?
10-14 per min
Tall waves, short amplitude
Weak swash, strong backwash
Erodes beaches
What is wave refraction?
When waves bend around headlands and bays due to changes in water depth.
At Headlands, Waves converge → concentrated energy → more erosion.
At Bays, Waves diverge → low energy → more deposition.
What causes tides?
Gravitational pull of the moon & sun.
Two high tides & two low tides per day.
What’s the difference between spring and neap tides?
SPRING- sun and moon align, strongest pull, highest tides
NEAP- sun and moon at right angles, weakest pull, lowest tides
What is tidal range and the types?
The difference between high & low tide.
- macrotidal (4m+)
- mesotidal (2-4m)
- microtidal (>2m)
What are longshore currents?
occur as most waves do not hit the coastline head on, but approach at an angle. This makes a current parallel to the coastline, zigzagging in the same direction as longshore drift
What are Rip Currents?
Strong currents moving away from the shoreline, they develop when seawater is piled up along the coastline by incoming waves, due to sand bars. This ends up perpendicular to the coast. Bars of sediment funnels out backwash underneath the sea surface creating a current up to 5mph.
What is upwelling?
movement of cold water from deep in the ocean toward the surface. The more dense, cold water, replaces the warmer surface water and creates nutrient rico ocean currents. This forms part of global pattern of circulation.
What are storm surges?
- low pressure allows higher sea levels/ tide
- strong winds blow the water onto the white
- 1mb drop = 1cm increase in sea level
- the north seas shale creates a funnelling effect
Give the characteristics of a high energy coastline.
Large fetch, strong waves
Erosion > Deposition
Erosional landforms (cliffs, stacks, caves)
Give the characteristics of a low energy coastline.
Sheltered from strong waves
Deposition > Erosion
Depositional landforms (beaches, mudflats)
What are the main sources of sediment?
Rivers – major supplier, esp. in high rainfall areas.
Cliff erosion – rapid in soft rock
Longshore drift – moves sediment along coast.
Wind – transports sand for dune formation. Glaciers – deposit sediment as ice melts.
Offshore – waves/tides bring sediment onto beaches.
What are sediment cells?
Sections of coast, self-contained sediment systems.
11 sediment cells in England and Wales (e.g., Holderness Sediment Cell).
What is a sediment budget?
Positive budget: More sediment = coastline builds seaward.
Negative budget: More sediment loss = coastline retreats inland.
what is weathering?
the breakdown or disintegration of rock in its original place leading to the transfer of material
what are the three types of weathering??
mechanical, biological and chemical
describe what freeze thaw weathering is.
water enters a crack, freezes, expands and forces the crack to widen causing a rock to break off
what is salt crystallisation?
when salt evaporates, it leaves crystals that grow and exert stress on the rock causing it to break down.
how does wetting and drying contribute to weathering?
frequent cycles of wetting and drying cause clay to expand and contract leading to cracks and rocks to break down
what is biological weathering?
occurs when plants, animals or decaying vegetation cause rock breakdown
how does carbonation contribute to chemical weathering?
rain absorbs CO2 forming carbonic acid which dissolves calcium carbonate in rocks
what is oxidation in the context of weathering?
the reaction of rock minerals with oxygen like iron causes rocks to weaken and become more susceptible to further weathering
what is solution in chemical weathering
the dissolving of rock materials due to weak acids reacting with minerals
what is mass movement?
mass movement is the downslope movement of material under the influence of gravity often assisted by rainfall
what are the factors affecting mass movement
cohesion, slope height, grain size, temperature, freeze thaw action, saturation
what is soil creep?
the slowest form of mass movement where soil particles rise and fall creating a zig zag motion and terracettes
describe mudflows
saturated soil flows over weak bedrock reducing friction and causing rapid downslope movements
what is rockfall?
a sudden collapse of individual rock fragments often triggered by mechanical weathering leading to scree
how do landslides occur?
blocks of rock move rapidly downhill along a planar surface often caused by rainfall or earthquakes
what is a landslip/ slump?
a curved mass movement of weak clays and sands underlain by impermeable rock often caused by pure water pressure
what is runoff?
the movement of sediment downhill due to water flowing over the surface entering the littoral zone
how does temperature and climate affect weathering?
warming climates favor chemical weathering while colder promote mechanical
what are the key types of erosion in coastal processes?
abrasion, hydraulic action, wave pounding, weathering and solution
what is hydraulic action?
air trapped in cracks by waves is forced out under high pressure breaking up rock
describe corrasion
when sand and pebbles are flung at a cliff by waves eroding it through abrasion
what is abrasion?
the sandpapering effect where sediment dragged across the shore erodes the cliff face
what is attrition
when rocks and pebbles collide with each other breaking down into smaller rounder pieces
what is wave pounding?
the powerful crashing of waves against the cliff that weakens and breaks apart the rock
what is wave quarrying?
waves cause trapped air in cracks to expand explosively eroding the rock
what is solution/ corrosion?
weak acids in seawater dissolve alkaline rocks causing them to erode
what factors affect erosion?
geology, wave type, fetch, configuration, beach presence, human activity and sub aerial processes
what is traction?
larger objects roll along the seabed staying in contact with the floor
what is saltation?
sediment bounces along the seabed occasionally being suspended
what is suspension?
sediment remains suspended in the water never touching the seabed
what is solution in coastal transportation
dissolved sediment moves along with the water
what is longshore drift
sediment is moved along the coastline by waves approaching at an angle and backwash moving perpendicular
what happens to sediment during LSD
sediment becomes smoother, smaller, spherical and sorted
what is surface creep?
wind slides sediment along the surface causing small particles to move
what is saltation in wind transformation?
wind lifts sand and carries it for distances up to 30m
what is deposition
when sediment is too heavy to be carried by water or the wave looses energy causing sediment to accumulate
what are two types of deposition
marine deposition and aeolian deposition
what factors lead to marine deposition
abundant eroded material, reduced wave velocity, sediment accumulating faster than being removed, waves slowing down
what is flocculation?
the process where clay particles clump together in saltwater and sink due to ionic bonding aiding in estuarine deposition
What is the difference between a landscape and landform?
Landscape- The whole section of land including the sea, coastline, beach and surrounding area
Landform- Individual features that make up the landscape.
What factors influence landforms?
Coastal geology and lithology, nature of tides and waves, climate.
What factors determine coastal landscapes?
High/low energy coastlines, dominant processes (erosion/deposition), human management.
How can coastlines be classified?
Concordant/discordant,
cliffed/flat/graded shoreline, emergent/submergent.
How do headland and bays form?
- A discordant coastline of alternating bands of hard and soft rock
- Initially erosional processes predominate in areas of soft rock forming waves.
- The hard rock erodes slower than the soft rock so there is differential erosion, it also forms headlands.
- Due to wave rarefaction, the headlands receive the highest energy waves and more venerable to erosion.
- The bays receive low energy waves that allow sediment to accumulate forming beaches.
Why do headlands experience more erosion?
Wave refraction concentrates energy on headlands, making them more vulnerable.
What happens in bays?
Low-energy waves deposit sediment, forming beaches.
What is a wave-cut platform?
A gently sloping rock surface left behind as a cliff retreats.
How do wave-cut platforms form?
- When waves break against the foot of the cliff, erosion creates a wave-cut notch
- As the notch gets bigger, the cliff is undercut, collapsing the above rock
- As erosion continues, the cliff retreats leaving behind a gently sloping wave cut platform that appears at low tide
What is the angle and maximum length of a wave-cut platform?
5-degree angle, up to 500m long.
How does a wave-cut platform create negative feedback?
It reduces wave energy by causing waves to break earlier, slowing erosion.
Talk about formation of stumps
- Waves erode joints and cracks to form caves
- Caves made larger to form arches
- The arch collapses to leave a stack.
- Stack erodes to leave a stump (underwater at high tide)
When joints are eroded vertically, the overlying rock collapses developing a blowhole
Geo- erosion burrows through, however the roof isn’t able to carry the weight so falls through
What happens when a cave grows larger?
It forms an arch.
How do stacks and stumps form?
An arch collapses, leaving a stack, which erodes into a stump.
What is a blowhole?
When vertical erosion creates a hole that water sprays through.
What is a Geo?
When erosion burrows through but the roof isn’t able to carry the weight so falls through
What influences beach characteristics?
Wave energy, sediment type, seasonal changes.
Difference between swash-aligned and drift-aligned beaches?
Swash-aligned: Waves approach perpendicularly, limited longshore drift.
Drift-aligned: Waves approach at an angle, sediment moves via longshore drift.
Examples of mini beach formations?
Berms (high tide ridges), cusps (curved dips), runnels (small ridges from tides).
How does a spit form?
- Sand or shingle moved along via longshore drift due to the prevailing winf direction being at an angle to the coastline.
- A change in coastline shape means the sediment builds up accross the estury mouth forming a spit.
- The river flow prevents the spit from fully extending and joining to the mainland.
What stops a spit from extending indefinitely?
River flow prevents full extension.
Difference between a simple and compound spit?
Simple spit: One recurved end.
Compound spit: Multiple recurved ends due to changing wind directions.
What is a tombolo?
A sand ridge connecting an island to the mainland
What are barrier beaches and islands?
Beaches- offshore bars which rise above sea level
Islands- colonized by vegetation
What conditions are needed for sand dunes to form?
Large sand supply, strong onshore winds, macro tidal range, vegetation.
What are the stages of dune succession?
Embryo Dunes – Initial accumulation, prone to erosion (80% exposed).
Fore Dunes – Pioneer plants stabilize sand.
Yellow Dunes – Marram grass holds dunes together (20% exposed).
Grey Dunes – Soil formation supports vegetation growth (<10% exposed).
Wasting Dunes – Water-loving plants grow in depressions.
Mature Dunes – Coastal woodland develops.
Talk about sea level in the quaternary period
During the quaternary period, there was several alternating periods of cooling and warming (glacial and inter-glacial) that influenced the sea levels in response to the nature of precipitation.
What the difference between eustatic and isostatic change?
Eustatic Change- When sea level itself rises or falls globally
Climate Change
Isostatic Change- Local changes in sea level resulting from the land rising or falling.
Talk about the stages of eustatic and isostatic change through glacial and interglacial periods
- Climate gets colder (glacial period) therefore more precipitation falls as snow. Eventually forming glacial ice as it gets compacted. The precipitation doesn’t go back into the sea so levels fall (Eustatic change)
- The weight of the ice causes land surface to sink (isostatic), this only effects some coastlines and sea levels increase.
- The climate begins to get warmer so ice melts and replenishes the main store and sea level rises (eustatic)
- As ice is removed, land area begin to move up to their previous levels (isostatic reajustment)
What is tectonic sea level change
Tectonic Sea Level Change- Caused by movement of the Earths crust such as by earthquakes and volcanic activity.
Talk about riasd?
Created by rising sea levels drowning a river estuary or valley and floodplain. They are wider at te mouth and narrower inland. Rias are common in South West England where sea levels rose after the last ice age like Kingsbridge estuary in Devon
Talk about Fjords
FJORDS- Drowned glacial valleys typically found in places like Norway and Western Scotland. They have steep valley sides and are fairly straight with a typical u shaped cross section and are depths of 1000km. They deepen further inland normally with a shallow threshold at the mouth
Talk about dalmation coastlines
DALMATION COASTLINE- ridges with a hilly topograthy, high relif and valleys running parallel to the coast flood forming a series of offshore islands in croatia. They are formed by differential flooding of valleys due to rising sea levels submerhing lower land.
Talk about emergent landforms
RAISED BEACHES- areas of former wavecut platforms and their beaches are raised above present sea level common in western scotland. The remains of old cliff landforms are found behind called relic cliffs. Isle of Arran
MARINE PLATFORM- Where gently sloping formerly submerged land has been exposed.
Talk about contempary sea level change
Since records began 20,000 years ago, sea levels have always been rising however, since 1880 and the industrial revolution, sea levels have increased by around 235mm which is enough to overwhelm some sea defences especially combined with high storm surges.
Talk about the effects of contempary sea level change
More powerful and frequent storms- an increase in sea level leads to more intense storms which increases the risk of flooding and storm surges which destroys havitats, leads to erosion and more deposition.
More extreme weather- cold snap, increase freeze thaw action leads to more mass movement like rockfall. \drought- less rain, less acid rain and carbonation so less erosion and mass movement. More cracks so more freeze thaw action later on or erosion via hydrolic action.
Ice Sheet and Glacial Retreat- formation of fjords, sea levels rise so submergent landscapes→ eustatic. More flooding on coastline and isostatic rebound leading to emergent lamdscapes
Animal and Biodiversity Loss- More extreme weather causes both vegetation to die and more animals migrate or species beocme extinct as cant live in conditions leading to more habitat loss and greater erosiom or less erosion due to less burrowing animals and nesting birds
- Conflict- direct impact ie bombing, defence managment and human intervention
- Migration- more coastal managment, so more likely to protect (cost,benefit,analysis) cauing harm to other coastlines or reducing processes in their ome. More migration may lead to more path erosion and litter.
Talk about medium term changes
- Wave cut platforms expand as cliffs erode over decades.
- Salt marshes and mudflats develop in sheltered estuaries as sediment accumulates over time.
- Managed retreat and coastal realignment projects create new landforms (e.g., salt marshes in Medmerry, UK).
Talk about long-term changes
- Isostatic Rebound in Scotland:
- Submergent landforms (e.g., fjords, rias) formed after the last Ice Age when glaciers melted and flooded valleys.
- Continental drift and plate tectonics slowly alter the shape of coastlines over millions of years.
- Changes in global sea level due to climate change over thousands of years can reshape entire coastal systems.
Talk about groynes
Groynes are wooden or steel structures built nearly at a right angles to waves built in order to control longshore drift by trapping moving sediment.
- builds up the beach which can protect cliff and increase tourism
- Cost Effective
- Visually unappealng
- Deprives areas downwind of sediment increasing erosion elsewhere
Talk about sea walls
concrete structures that absorb and reflect wave energy with a recurved end which throws waves back out into the sea and reduce wave impact. They also provide a physical barrier to flooding.
- Effective erosion prevention
- Promenade provides tourism benifits and pathways
- Visually unappealing
- Expensive to construct and maintain
Talk about rock armour
arge boulders dumped in front of a cliff or sea wall used to reduce wave energy while providing gaps for water to filter through.
- cost effective
- rocks are sourced from elsewhere so dont fit with the natural geology and take a lot of money to transport
Talk about gabions
Operate on the same princple as rip rap howeer using smaller boulders in small wire cages that can be joined together creating walls.
Talk about revetements
Concrete or wooden structures placed accross a coastline to take the full force of the wave energy and prevent further erosion
Talk about cliff fixing
driving iron bars into the cliff face to absorb wave power and stabalise the cliffs.
Talk about offshore reefs
These force the waves to break offshore reducing the impact on the base of the cliffs and act as a substructure for the formation of ecosystems.
Talk about barrages
Large structures built to prevent flooding on major estuaries and other sea inlets. They act as a dam accross an estuary.
Talk about dune regeneration
dunes are a key factor in absorbing wave energy however, they are fragile environments which are easily destroyed. We can manage them in numerous ways including:
- Planting marram grass
- afforestation
- aelective grazing
- restricting access
Talk about managed retreat
This involves abandoning the current line of sea defences then developing the land in some way, for example, with salt marshes to reduce wave power.
Talk about land use management
Even if its inevitable that a coastal area will be eroded or flood in the future, a local authority may be able to mitigate the impact. It involves addressing people’s behaviour and educating the local community. Officials can help people plan for the future anf encourage land-owners to think about how to use their st-risk-land for example for grazing.
talk about doing nothing
People question weather its easier to just let nature takes its course and pay compensation then to pay millions of pounds to manage coastal managment systems. However, this can cause conflict as certain people dont want proterties to be damaged.
Talk about shoreline management plans
Shoreline Management Plans (SMPs) are an important sustainable approach to coastal management. They divide the coastline into sediment cells, ensuring a coordinated strategy for managing coastal erosion and flooding.
- Hold the Line – Maintaining existing coastal defences.
- Advance the Line – Building new defences further out to sea.
- Managed Retreat – Allowing controlled flooding in some areas.
- Do Nothing – Letting nature take its course without intervention.
Talk about intergrated coastal zone management
ICZM is a holistic and long-term approach that considers economic, social, and environmental factors. It aims for sustainable coastal management by involving multiple stakeholders
- Involves multiple countries or regions for transboundary cooperation.
- Uses a mix of hard and soft engineering strategies.
- Aims to reduce conflict between stakeholders (e.g., tourism vs. conservation).
