Coastal ecosystems Flashcards
What is abrasion
Where loose material in the waves hits and breaks down the walls, floors of the river, cliff or glacier
What is backshore
The upper beach closest to the land, including any cliffs or sand dunes
What is beach morphology
the surface shape of the beach
What is coastal recession
The retreat of a coastline due to the erosion, seallevel rise or submergence
What is a concordant coastline
A coastlne where bands of alternate gelogu run parallel to the coast (same type of rock however alternation as erodes)
What is a dalmation coast
A concordant coastline with several river valleys running perpendiculer to the coast. They becme flooded to produce parallel long islands
DEFRA’s 1:1 Cost-benefit Analysis
The evaluation of a coastal town’s economic value compared to the cost of the management required
What is a discordant coastline
a coastline whee bands of alternate geology run perpendiculer to the shore
What is dynamic equlibrium
Where a natural system tries to archive a balance by making coastal change in response to a constantly changing system
What is an emergent coastline
A coastline that is advancing relative to the sea level at the time
What is Eustatic sea level change
Global changes to sea levels
What is foreshore
The lower part of the beach overed twice a day at high tide (the part of the beach that receives the most reguler wave action)
What is freezethraw weathing
A form of physical sub-ariel weathering where water freezes in the cracks of a rock, expands and enlarges the crack, therefore weakens the rock
What is geology
The structural arrangement of the rock
What is glacial erosion
The removal of loose material by glacier ce, involving plucking, abrasion, crushing and bsal meltware (necessary in the formation of fjords)
What is grading
The layering of sediments based on their size
What is a high energy environment
A coast where wave action is predominantly large destructive waves, causing much erosion. The rate of erosion exceeds the rate of deposition
What does impermeable rock mean
A rock that does not allow rainwater to pass through
What is Isostatic sealevel change
A change in local coastline or land height relative to the sea level
Littoral Cell
A section of the coast, whin which involves much sediment movement. A littoral cell is not a closed system
What does permeable rock mean
A rock that allows rainwater to pass through it
What is plant succession
Change to a plant community due to growling conditions adapting (e.g. sand dunes and salt marshes)
What are subariel process
A combination of mass movement and weathering that affects the coastal land above sea level
What is a submergent coastline
A coast that is sinking relative to the sea level at the time
What is a till
Deposits of aguler rock gragments in a fine medium
What causes a submergent coastline
Ethier Eustatic change from rising sea levels or isostatic change possibly from glacial ice
What is a sediment cell
The concept of a sediment cell is that coasts are split up to sections and bordered by prominent headlands.
Within each cell there are smaller sub cells.
This means the movement of sediment is almost contained so the sediment has dynamic equilibrium.
The sediment cell has inputs such as wind, waves, pollution and outputs such as rip tides and ocean currents.
Sediment cells also have stores such as beaches, spits, cliffs. These stores are transferred throughout
The sediment cell through processes such as longshore drift
What is the littoral zone
The littoral zone is the area of land between the cliff’s or dunes on the coast and the offshore
area that is beyond the influence of the waves .
Describe the process of the formation of a wave - start to finish
Winds move across the surface of the water, causing frictional drag (resistance to the
wind by the water) which creates small ripples and waves . This leads to a circular orbital
motion of water particles in the ocean
● As the seabed becomes shallower towards the coastline, the orbit of the water particles
becomes more elliptical, leading to more horizontal movement of the waves
● The wave height increases, but the wavelength (distance between two waves) and
wave velocity both decrease
● This causes water to back up from behind the wave until the wave breaks (collapses)
and surges up the beach
What factors affect wave energy
Strength of the wind
Duration of the wind (how active the wind is)
Size of the fetch (the distance over which the wind blows)
What are the features of a constructive wave: (formation, wavelength, frequency, wave and swash characteristics and effects on beach)
Formation: Formed by weather systems that operate in the open ocean
Wavelength: Long wavelength
Frequency: 6-9 per minute
Wave characteristics: Low waves, which surge up the beach
Swash characteristics: Strong swash, weak backwash
Effects on beach: Occurs on gently slopped beaches
What are the features of a Destructive wave: (formation, wavelength, frequency, wave and swash characteristics and effects on beach)
Formation: Localised storm events with strong winds operating close to the coast
Wavelength: Short wavelength
Frequency: 11-16 per minute
Wave characteristics: High waves, which plunge onto the beach
Swash characteristics: Weak swash, Strong backwash
Effects on beach: Occurs on steeply slopped beaches
The types of waves in a coastal environment vary depending on the time of year. Explain how
In the summer constructive waves dominate but in the winter destructive waves dominate.
Constructive waves may become destructive waves if a storm begins
Climate change may increase the storm frequency within the UK
Coastal management may affect the type of waves that occur
What is a form of negative feed back in beaches and waves
The presence of contructive waves cause deposition on the beach which lead to the beach becoming steaper and favouring formation of destructive waves. The destructive waves erode the beach and reducing the beach profile which favours and leads to the formation of constructive waves
What is spring tide
The highest high tide and the lowest low tides occur when the mood and the sun are in alignment as their gravitational force effectively pul the oceans towards them
What is neap tide
The lowest high tide and the highest low tide, this occurs when the sun and the moon are perpendicular to each other. Both of their gravitational forces act against each other, so the overall pull is minimised at high tide, but therefore creates a higher low tide. The neap tide creates the smallest tidal range possible
What is a low-energy environment
Waves are predominelty constructive and tends to occur in sheltered areas. They tend to be fairly sandy areas. The rates of deposition exceed the rate of erosion
What is wave refraction
The process by which waves turn and lose energy around a headland on uneven coastlines. The wave energy is focused on the headland, creating erosional features. The energy is dissipated in bays
What are the marine erosion processes
Corrasion, Abrasion, Attrition, Hydraulic Action, Corrosion
What is abrasion
The process by which rocks and other material carried by the sea are picked up by strong waves and thrown against the coastline
What is attrition
Wave action causes rocks and pebbles to hit against each other, wearing each other down which causes them to become rounded over time and eventually smaller.
What is hydraulic action
As waves crashes onto rocks or cliff faces, they force air in cracks, joints an faults within the rock. The high pressure causes cracks to force apart and widen. This causes the rock to fracture. Can lead to cavitation where bubbles in the water explode.
What is corrosion
The midly acidic sea water can cause alkaline rock such as limestone to be eroded.
Factors affecting erosion
Wave (rate of waves and type)
Beaches
Sub-ariel process (landslides - weakens cliff)
Rock type (Sedimentary - weak, Indigenous/metamorphic - strong)
Rock faults (Increased surface area)
Rock lithology
What is longshore drift
Waves hit beach at angle due to prevailing wind. Waves push sediment in wind direction up the beach as swash.
Due to gravity the wave then carries the sediment down the beach as back wash
What is flocculation
Clay particles clump together due to chemical attraction and then dink due to high density.
What is weathering
Weathering is the breakdown of rocks over time, leading to the transfer of material into the littoral zone, where it becomes input into the sediment cells
What is mechanical weathering
the breakdown of rocks due to exertion of physical forces without chemical changes taking place
What is is freeze-thaw
Water entering the cracks of rocks and then the water freezes and expands by 9% which increases the pressure acting on the rock, causing cracks
What is salt crystallisation
Salt water enters the cracks of the rock, and as seawater evaporates, salt is left behind. The salt crystals grow over time, exerting pressure on the rock, and causing cracks
What is chemical weathering
The breakdown of rocks through chemical reactions
What is carbonation
Rainwater absorbs carbon dioxide from the air which creates a weak carbonic acid which reacts with calcium carbonate in rocks to calcium bicarbonate which can be easily dissolved. This happens with limestone
What is oxidation
When minerals gets exposed to oxygen and become oxdisd which increases volume .
What is biological weathering
The breakdown of rocks by organic activity
How do plant roots cause erosion
Roots by growing into the cracks of rocks, which cause pressure and split the rocks apart
How do animals cause erosion
Animals such as rabbits burrowing
What is mass movement
The movement of material down a slope under the influence of gravity. Act as input to littoral zone
What are the mass movements
Rotational slide, Rock falls, Landslide, Mudflows
Salt marshes
Notes
Sand dunes
Notes
What are emergent coastlines
Where the land has been raised in relation to the coastline
What are submerged coastlines
Where sea level rises or the coastline sinks in relation to the sea
What are rias
Rias are formed when rising sea levels flood narrow winding inlets and river valleys. They are deeper at the mouth of the inlet, with the water depth decreasing further inland
Example: Camel trail, Padstow
What are Fjords
Fjords are formed when rising sea levels flood deep glacial valleys to create natural inlets and harbours.
What are Dalmatian coasts
This type of coastline occurs when valleys running parallel to the coast become flooded as a result of sea level change. This leaves a narrow long series of rugged islands
Example: Croatia’s Adriatic coast
What is the dune structure (backwards)
Embryo dune, yellow dune, grey dune, dune slack, heath and woodland (climatic cliamax)
Where do mudflats and saltmarshes tend to form
where flow of water from the river meets with incoming tides and waves from the sea, causing water flow to virtually cease. This can also occur in low-energy areas such as behind a spit. then floculation and pioneer species etc
What are the risks to coastal environments
Storm surges, human activity
What are storm surges
they are the result of low pressure created by significant weather events (such as tropical storms) causing the sea level to rise dramatically and overwhelm sea defensives.
What are the impacts of storm surges
- Removing natural vegetation (mangroves can limit this though) as it destroys plant sucessions and destroys coastal landforms. Increasing risks of rock falls and other mass movements
- they are more likely to happen due to climate change and to be more intense
What are the consequences to communities on the coastline
reduced house prices as the areas is prone to natural disasters
Leading to economic loss for homeowners and local economies
What are the impacts of coastal flooding
Environmental refugees, over 1 billion people live on the coast that are at risk of coastal flooding. 75% of all the world’s large cities are coastal.
What is coastal management
There are 2 types: Hard enginerring and soft engineering . It follows ‘erosion is occurring in this area so lets build a beach or a sea wall to reduce erosion’
What is hard engineering
It involves man-made structures with the aim of preventing erosion. They are very effective at preventing erosion however they are high cost and have a significant environmental impact due to concentrate and other man-made materials.
What are the hard engineering methods to stop erosion
Offshore Breakwater, Groynes, Sea Wall, Rip Rap (rock armour), revetments
What is soft engineering
soft engineering aims to work with and complement the physical environment by using natural methods of coastal defence
What are the soft engineering methods to stop erosion
Beach Norishments, CLiff regading and drainage, Dune stabilisation, Marsh creation
What is Offshore breach water, pros and cons
Rock barrier which forces waves to breack before reaching shore.
Pro: Effective at reducing waves’ energy
Con: Visually unappealing
Navigation hazard for boats
Can interfere with Longshore-drift
What are groynes, pros and cons
Wooden or rock protrusions that trap sediment from LSD
Pro:Builds up beach, protecting cliff and increasing tourist potential
Cost effective
Con: Visually unappealing
Terminal groyne syndrome (deprives other areas of sediment)
What are sea walls, pros and cons
Contrete structures that absorb and reflect wave energy, with curved surfaces
Pro:Effective erosion prevention
Promanade has tourism benefits
Con: visually unapealing
Expensive to construct/maintain
Wave energy erode elsewhere as reflected
What are Rip Rap (rock armour) pros and cons
Large rocks that reduce wave energy, but allow water to pass through
Pro: Cost effective
Con: Rocks are sourced from elsewhere, so do not fit with local geology
Pose a hazard if climbed upon
What are Revetments, pros and cons
Wooden or concrete ramps that help absorb wave energy
Pro: Cost effective
Con: Visually unappealing
Can need constant maintenance which creates extra cost
What is beach nourishment, pros and cons
Sediment is taken from offshore sources (stores) to build up existing beach
Pro: Builds up beach protecting cliff and increases tourist potential
Cost effective and looks natural
Cons: not a long-lasting solution and dredging may have consequences on local coastal habitats
What is cliff regrading and Drainage, pros and cons
Reduces the angle of the cliff to help stabilise it.
Pro: cost-effective
Con: cliff may collapse suddenly as the iff is drier,
may look unnatural
What is dune stabalistion, pros and cons
Marram grass planted, the roots help bind the bunes, protecting the land behind
Pro: cost-effective and creates an important wildlife habitat
Con: planting is time consuming
What is marsh creation, pros and cons
Type of managed retreat allowing low-lying areas to flood
Pro: creates and important wildlife habitat
Con: Farmers lose land and may need compensation as a result
What is cost-benefit analysis
A process carried out beofre any form of coastal management takes place. It takes into account the expended cost of construction, demolition and maintenance etc and compres it to expected benefits of a scheme which may included value of land, business. Benfits have to out way costs (DEFRA’s 1:1)
What are hostile stratergies
it is recognised that all of the different coastline are interlinked and function together as a whole.
What are ways to manage coasts sustainably
Managing natural resoruces
Education communities
Monitoring coastal changes
What is the Integrated Coastal Zone Management (ICZM)
It is a method of sustainable coastline management, it represents the idea that large sections of coastline are managed with one integrated strategy.
What does the ICZM recognise about coastal management
sediment eroded in one lackted may form a protective beach elsewhere and therefore a decision to protect one coastal community may not outwight the disadvantages of explosion another community to increased erosion
What are shoreline management plans (SMPs)
They have been created for each sediment cell in the UK to help with coastline management. And consider them to be closed systems (though they not in reality)
What are examples of SMPs
Hold the line: defences to maintain current position of shore line
Managed retreat: allowing the coastline to advance inwards to create its own natural defences using enginerring/defensives
Advance the line: defences are build to to more the shoreline outwards
No active intervention: let nature take its course
What factors are consider when choosing a SMP
The economic value of assets
Technical feasibility of engineering solutions
Ecological and cultural value
What are negative impacts of coastal management
Sea wall just refelcts wave energy down drift to increase erosion elsewhere also causes less sediment where needed
How are wave-cut platforms formed
The erosion process (hydraulic action and abrasion etc) takes place on the foot of the cliff. This erodes inwards. This causes the cliff to become more and more undercut as erosion continues. it will then eventually collapse. This process repeats and the cliff slowly retreats inland. Leaving a gently sloping wave-cut platform. Only a small distance as waves no longer break on a cliff due to the platform
Example: Southerndown, Wales.
How are raised beaches formed
due to the isostatic sea level change. caused by glacial rebound. Post-glacial elasticity as the crust rebounds to lift the beach which exposes wave-cut platforms and degraded cliffs.
Example: Isle or portland
