Costal Landscapes and Change Flashcards
What is the littoral zone?
It is a zone that stretches out into the sea and onto the shore. It is divided into 4 sections and is constantly changing.
What are the 4 Littoral zones?
Backshore
Foreshore
nearshore
offshore
What factors can effect the littoral zone?
Short term- waves, daily tides, seasonal storms
Long term- changes to sea level, climate change
What are the natural processes that will cause changes to the littoral zone?
Sediment input from sea and rivers
Destructive waves – erodes the beach
Constructive Waves – build up the beach
Longshore drift – moves material along the coast
Tidal Range – determines where wave action occurs
What are the human activity’s that will cause changes to the littoral zone?
Dredging of rivers (for navigation)
Dredging off offshore areas (material for construction)
Building of coastal defences
What are the inputs to the coast as a system?
Marine- waves, tides, storm surges
Atmospheric- weather/climate, climate change, solar energy
Land- rock type and structure, tectonic activity
People- human activity, costal management
What are the processes to the coast as a system?
Weathering Mass movement Erosion Transport Deposition
What are the Outputs to the coast as a system?
Erosional landforms
Depositional landforms
Different types of coasts
what Valentin’s classification of coasts?
Recognises that coasts can be erosional or depositional and emerging or submerging and that these effects can magnify or neutralise each other.
(circle split into 8 sections)
What are coasts classified depending on?
Their Geology
Level of energy
The balance between erosion and deposition
Changes in sea level
How can coats be classified in the long term?
Geology (discordant + concordant)
Sea level rise (eustatic +isostatic)
How can coasts be classified in the short term?
Wave energy (high energy coast + low energy coast) Wave type (constructive + destructive)
What are the three types of rock?
Igneous
Metamorphic
Sedimentary
How is igneous rock formed?
Created by volcanic activity when magma or lava cools, forming crystals that are usually hard
How is sedimentary rock Formed?
Formed of small particles that have been eroded, transported & deposited in layers or from remains of plants and animals
How is metamorphic rock formed?
Form from other rocks changing by extreme heat and pressure.
Usually form from layers / bands of crystals and very hard
What is costal morphology?
The shape and form of costal landscapes and their features
What is costal recession?
Another term for costal erosion
What is lithology?
The physical characteristics of particular rocks
Give an example of an igneous rock?
Granite
Give an example of an sedimentary rock?
Limestone and chalk
Give an example of an metamorphic rock?
Gneiss and marble
Give an example of an unconsolidated material?
Bolder clay (Holderness coast)
What is the resistance and erosion rates of igneous rock?
Very resistant, annual recession of 1mm per year on average
What is the resistance and erosion rates of Metamorphic rock?
Very resistant
What is the resistance and erosion rates of sedimentary rock?
Thinly bedded limestone – annual recession of 2.5cm per year
What is the resistance and erosion rates of unconsolidated material?
1m per year average at Holderness
What is the permeability of igneous rock?
Impermeable very few spaces of joints for water to pass through
What is the permeability of sedimentary rock?
Often porous – makes susceptible to weather
What is the permeability of metamorphic rock?
Impermeable very few spaces of joints for water to pass through
What is the permeability of unconsolidated material?
Loose materials and so permeable – lost of spaces for water to pass through
What is strata?
Layers of rock
What are bedding planes?
These are natural breaks in the strata, caused by gaps in time during periods of rock formation
What are joints?
These are fractures, caused either by contraction as sediments dry out, or by earth movements during uplift
What are folds?
Formed by pressure during tectonic activity, which makes rocks buckle and crumple (Lulworth cove)
What are faults?
Formed when the stress or pressure to which a rock is subjected, exceeds its eternal strength
The faults then slip or move along fault planes
What are dips?
This refers to the angle at which rock strata lie
What does lithology include?
Geological structure (number and angle of strata & bedding planes)
How porous the rock is (permeability)
Permeability is linked to grain size, rock structure (e.g. crystal) etc…
Composition (e.g - limestone is soluble in rain water because it is a diluted carbonic acid – chemical weathering)
Describe a high energy coastline?
In the UK they tend to be Atlantic facing coats, where the waves are powerful for much of the year (Cornwall)
Where rates of erosion exceeds the rate of deposition
What landforms are created at high energy coastlines?
Headlands
Cliffs
Shoreline platforms
Describe a low energy coastline?
Sandy and estuarine coasts are generally found here
Stretches of the coast where the waves are less powerful, or where the coast is sheltered from large waves
Where the rate of deposition exceeds the rate of erosion
What landforms are created at low energy coastlines?
Beaches
Spits
Costal plains
What is a discordant coastline?
Where the geology alternates between bonds of more resistant and less resistant rock, which run at right angles to the coast
What is a concordant coastline?
This is where bands of more resistant and less resistant rock run parallel to the coast
What are Dalmatian coasts?
They are another type of concordant coastline
They have formed as a result of a rise in sea level
What is a Haff coastline?
It consists of concordant features of long spits and sandy lagoons aligned parallel to the coast
What is a wave length?
The distance between one peak of a wave to the next corresponding peak
What is a wave crest?
The top of a wave (opposite of a trough)
What is a wave trough?
bottom of a wave (opposite of crest)
What is swash?
When a wave reaches the shore, the water that rushes up the beach
What is backwash?
The water that flows back towards the sea
What is wave height?
The wave height of a surface wave is the difference between the height of a crest and the trough
What is fetch?
How far the wind has travelled
What are constructive waves?
Linked to low energy coastlines Low surging waves long wavelength Strong wash Weak backwash Beach gain 6-9 per minute
What are destructive waves?
Linked to high energy and storm weather, leads to erosion Long fetch High plummeting waves Short wavelengths Weak swash Strong backwash Beach loss 11-16 per minute
What is beach morphology?
It means the shape of a beach, including its width and slope (the beach profile) and features such as berms, ridges and runnels. It also includes the type of sediment (shingle, mud, sand) found at different location on the beach
What is a beach profile?
A cross section of a beach
What are the temporal factors effecting beach morphology?
Over a day, as a storm passes and destructive waves change to constructive ones as the wind drops
Between summer and winter (see next slide)
When there are changes to the climate (e.g. if global warming resulted in the UK climate becoming on average stormier, then destructive waves and ‘winter’ beach profiles would become common
Describe summer beaches?
Shallower profiles as constructive waves are more common.
As constructive waves are less frequent, waves energy dissipates and deposits over a wide area
The swash of a constructive wave deposits larger material at the top of the beach – creating a berm
Describe winter beaches?
Steeper profiles as destructive waves are more common.
As destructive waves are more frequent, berms are eroded by plunging waves
Strong backwash transports sediment offshore creating offshore bars
What are berms?
The shingle ridges often found towards the back of a beach
What are offshore bars?
Elongate ridges and mounds of sand or gravel deposited beyond a shoreline by currents and waves
What is abrasion?
This is when pebbles grind along a rock platform, much like sandpaper
Over time the rock becomes smooth
What is hydraulic action?
This is the sheer power of the waves as they smash against the cliff
Air becomes trapped in the cracks in the rock and causes the rock to break apart
What is corrosion?
This is when sea water dissolves certain types of rocks
In the UK, chalk and limestone cliffs are prone to this type of erosion
What is attrition?
This is when rocks that the sea is carrying knock against each other
They break apart to become smaller and more rounded
What are the erosional landforms?
Headlands and bays Wave cut notch Structure platform Cliff Cave, Arch, Stack and Stump
How is a cave formed?
Caves occur when waves force their way into cracks in the cliff face
The water contains sand and other materials that grind away at the rock until the cracks become a cave
Hydraulic action is the predominant process
How is an arch formed?
If the cave is formed in a headland, it may eventually break through to the other side forming an arch
How is a stack formed?
The arch will gradually become bigger until it can no longer support the top of the arch
When the arch collapses, it leaves the headland on one side and a stack (a tall column of rock) on the other
How is a stump formed?
The stack will be attacked at the base in the same way that a wave-cut notch is formed
This weakens the structure and it will eventually collapse to form a stump
How is a cliff formed?
Cliffs are shaped through erosion and weathering
Soft rock erodes quickly and forms gentle sloping cliffs, whereas hard rock is more resistant and forms steep cliffs
How are wave cut notches and shoreline platforms formed?
The sea attacks the base of the cliff between the high and low water mark
A wave-cut notch is formed by erosional processes such as abrasion and hydraulic action - this is a dent in the cliff usually at the level of high tide
As the notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face
The backwash carries away the eroded material, leaving a wave-cut platform
The process repeats. The cliff continues to retreat
How are headlands and bays formed?
Bands of soft rock such as clay and sand are weaker therefore they can be eroded quickly This process forms bays
A bay is an inlet of the sea where the land curves inwards, usually with a beach
Hard rock such as chalk is more resistant to the processes of erosion
When the softer rock is eroded inwards, the hard rock sticks out into the sea, forming a headland
Give some examples of sediment transportation?
Angle of wave attack
Currents
Tides
Process of long shore drift
Give some examples of depositional landforms?
Beach
Tombolo
Spit
Offshore bar
What is traction?
Relatively large and heavy rocks are rolled along the seabed
What is saltation?
Smaller and lighter rock bounce along the seabed
What is suspension?
How lighter sediment is carried
What is solution?
How dissolved sediment is carried
What are tides?
They are changes in the water level of sea and oceans
Caused by the gravitational pull of the moon and to a lesser extent, the sun
The UK coastline experiences two high and two low tides a day
What is the tidal range?
The relative difference between high and low tides
What is long shore drift?
The movement of material along a coast by waves which approach at an angle to the shore but recede directly away from it
What are the depositional landforms?
Spits Beaches Bars Tombolo's Cuspate forelands
What are spits?
A spit is an extended stretch of sand or shingle jutting out into the sea from the land
Spits occur when there is a change in the shape of the landscape or there is a river mouth
How is a spit formed?
Sediment is carried by longshore drift
When there is a change in the shape of the coastline, deposition occurs
A long thin ridge of material is deposited
This is the spit
A hooked end can form if there is a change in wind direction
Waves cannot get past a spit, therefore the water behind a spit is very sheltered
Silts are deposited here to form salt marshes or mud flats
What is a bar?
Sometimes a spit can grow across a bay, and joins two headlands together
This landform is known as a bar
They can trap shallow lakes behind the bar, these are known as lagoons
Lagoons do not last forever and may be filled up with sediment
what is a beach?
Beaches are made up from eroded material that has been transported from elsewhere and then deposited by the sea
For this to occur, waves must have limited energy, so beaches often form in sheltered areas like bays
How are beaches formed?
Constructive waves build up beaches as they have a strong swash and a weak backwash
How are tombolo’s formed?
A tombolo is formed when a spit connects the mainland coast to an island
A spit is a feature that is formed through deposition of material at coastlines. The process of longshore drift occurs and this moves material along the coastline
What is a cuspate foreland?
A large, triangular area of coastal deposition, which is dominated by many shingle ridges and is often terminated on the landward side by poorly drained terrain
It is the result of a long episode of local marine aggradation under wave advance from two dominant directions
What are erosional processes effected by?
Wave type
Wave size
Lithology
What is the sediment cell concept?
Sediment cells are areas along the coastline and in the nearshore area where the movement of material is largely self-contained
What are the sources of the sediment cell?
Erosion of cliffs Onshore currents supplying sediments to the shore Land sediments eroded by rivers Wind blown sediments from land Subaerial processes
What are the transfers of the sediment cell?
Longshore drift Wave Transport through swash and backwash Tides moving sediments in and out Currents- localised or large scale Wind along shore or on- and off shore
What are the sinks in the sediment cell?
Backshore depositional landforms
Foreshore depositional landforms
Nearshore depositional landforms
Offshore sediment deposition to deep offshore waters
What is the sediment budget?
The amount of sediment available within a cell is called a sediment budget
What is negative feedback in a sediment cell?
Wave erosion causes rock falls, which then protect the base of a cliff from further erosion
What is positive feedback in a sediment cell?
Damage to sand dunes during storms conditions, which may create a ‘blow out’ allowing the wind to move more sand away, preventing grasses from re-growing
Allowing further erosion to occur
What is weathering?
The gradual breakdown of rock, in situ, at or close to the ground surface
What is mass movement?
The movement of weathered material down slope, as a result of gravity
What are the three types of weathering?
Chemical
Biological
Mechanical
What is chemical weathering?
The erosion or disintegration of rocks, building materials, etc., caused by chemical reactions (chiefly with water and substances dissolved in it) rather than by mechanical processes
What is mechanical weathering?
Any of the various weathering processes that cause physical disintegration of exposed rock without any change in the chemical composition of the rock: Collision between rock surfaces can cause mechanical weathering
What is biological weathering?
is the weakening and subsequent disintegration of rock by plants, animals and microbes
Growing plant roots can exert stress or pressure on rock. Although the process is physical, the pressure is exerted by a biological process (i.e., growing roots)
What does resultant of mass movement depend on?
The angle of the slope or cliff
The rock type and its structure
The vegetation cover
How the wet ground is
What are the types of mass movement?
Soil creep Mudflow Slump Rock fall Landslide
Why are sea levels rising?
Ice caps and glaciers are melting
Thermal expansion
What causes the sea level to change?
Terrestrial water storage, extraction of ground water, building of reservoirs, changes n run off, and seepage into aquafers
Subsidence in river delta region, land movements, and tectonic displacements
surface and deep ocean circulation changes storm surges
As the ocean warms the water expands
Exchange of the water stored on land by glaciers and ice sheets with ocean water
What case study would I use for sea level change?
Kiribati
What is eustatic change?
When the sea level itself rises or falls
What is isostatic change?
When the land rises or falls, relative to the sea-level
What causes natural climate change?
Eccentricity
Tilt
Precession
What is eccentricity?
When the earth encounters more variation in the energy that it receives from the sun when earths orbit is elongated than it does when earths orbit is elongated than it does when the earths orbit is more circular
What is tilt?
The tilt of the earths axis varied between 22.2 and 24.5degreese
The greater the tilt angle is, the more solar energy the poles receive
What is precession?
A gradual change, or “wobble” in the orientation of earths axis affects the relationship between earths tilt and eccentricity
What are some emergent coastlines?
Raised beaches
Fossil/ relic cliffs
What are some submergent coastlines?
A ria
A fjord
A fjard
Dalmation coasts
What are raised beaches?
Raised beaches- as the land rose as a result of isostatic recovery, former shoreline platforms and their beaches were raised above the present sea level
Example- Isle of Arran
What are Fossil/Relic cliffs?
as the land rose as a result of isostatic recovery, former shoreline platforms and their beaches were raised above the present sea level
Example- Isle of Arran
What is a Ria?
They are one of the most distinctive features associated with rising sea levels
They form when valley in a dissected upland area are flooded
Example- devon
What is a fjord?
They are long and steep sided with a U shaped cross-section and hanging valleys
Formed when deep glacial troughs are flooded by a rise in sea level
Example- New Zealand
What is a Dalmatian coast?
They are similar to rias
In this case, the rivers flow almost parallel to the coast- rather than right angles to it
Example- Croatia
What is a fjard?
It is a flooded inlet with a low rocky banks on either side formed by post-glacial drowning of glaciated lowland rocky terrain
Example- the Gulf of Finland.
What case study would I use for a rapid costal retreat?
Holderness (Yorkshire)
What are factors effecting costal erosion?
Geology Coastal defences Marine Processes Weakly consolidated rocks Subaerial processes Offshore dredging Large destructive waves Large scale mas movement Constant weathering Small constructive waves Resistant rock
What case study would I use for dredging?
Australia
What case study would I use for sea level rise?
The Nile Delta
What are factors effecting rates if recession?
Wind direction
Tides
Weather systems
What case study’s would I use for local and global influences on costal flooding?
Bangladesh
North sea storm serge’s
Typhoon Haiyan, Philippines
What are some of the costal risks from global warming?
Sea level rise Delta flooding Tropical cyclones Storm surges Wind and waves Costal erosion
What case study’s would you use when comparing the consequences of costal flooding?
Australia
Philippines
What case study would I use when talking about a country trying to mitigate sea level rise?
Maldives
What are some hard engineering strategies?
Groynes Rip rap Sea wall Revetment Offshore breakwaters Gabions
What are some soft engineering strategies?
Beach nourishment
Cliff drainage
Dune stabilisation
Cliff regrading
What case study would I use when talking about coastal engineering management?
Colwyn bay
What case study would I use when talking about decision making?
Tal-y-bont, Mid wales
What is the appropriate location for a groyne?
High value frontages influenced by strong long-shore processes where nourishment or recycling are undertaken
Best on shingle beaches or within estuaries
What is the cost of groynes?
Moderate, but must include for recycling or npurishment
What is the effectiveness of groynes?
Good on exposed shorelines with a natural shingle upper beach
Can also be useful in estuary stop deflect flows
Unlimited structure life for rock groynes
What are the benefits of groynes?
Encourages upper beach stability and reduces maintenance commitment for recycling or nourishment
What are the problems of groynes?
Disrupts natural processes and public access along upper beach
What are the appropriate locations for beach nourishment/ replenishment?
All locations, including those with limited blown sand for natural recovery
What is the cost of beach nourishment/ replenishment?
Low to moderate
But requires ongoing maintenance
What is the effectiveness of beach nourishment/ replenishment?
Short term defence against erosion, and enhancement of natural recovery, moderate resistance to single storms
Enhanced by fencing and vegetation transplanting, and can be successfully used to burry hard defences
What is the benefits of beach nourishment/ replenishment?
Accelerates natural recovery of foredunes and provides short term defence against single severe storms
What are the problems with beach nourishment/ replenishment?
Removes material from other sites
Possibly transferring erosion or environmental damage to a different frontage
May introduce beach debris, non indigenous sediment and/or vegetation, potentially damaging local economy
What the appropriate locations for offshore breakwaters?
Exposed dunes of high ecological and landscape value
What is the cost of offshore breakwaters?
Moderate to high, and may need some shoreline maintenance
What is the effectiveness of offshore breakwaters?
Causes lee side accretion, but least effective during storm surge conditions, unlimited structure life
What are the benefits of offshore breakwaters?
Natural processes are only partly disrupted, allowing dunes to stabilise
Rocks create new intertidal habitat
What are the problems with offshore breakwaters?
May cause a navigation hazard
Visually intrusive at low tide
Disrupt amenity use of beach
What are the appropriate locations for seawalls?
Exposed frontages with extensive and high value backshore assets
What are the costs of sea walls?
High but low maintenance
What is the effectiveness of sea walls?
Provides good medium long term protection, but continued erosion will cause long term failure
What are the problems with sea walls?
Continued erosion may cause undermining and structural failure
Complete disruption of natural beach-dune processes
What are the appropriate location for riprap?
Sites suffering severe and ongoing erosion where important and extensive backshore assets are at risk
What is the cost of rip rap?
High but with relatively low maintenance
What is the effectiveness of riprap?
Low risk option for important backshore assets
Permeable face absorbs wave energy and encourages upper beach stability
What are the problems of riprap?
Strong landscape impact
Can alter dune system permanently as sand tends not to build up over the rocks if beach erosion continues
What is the appropriate locations for revetments?
Sandy beach sites suffering periodic moderate to severe erosion where backshore assets are at risk
Useful for estuary
What is the cost of revetments?
Moderate but require maintenance
What is the effectiveness of revetments?
Provides reasonable fixed defences, but have a limited life of 5-10years due to deterioration of the baskets
What are the benefits of revetments?
Useful solution where Armor rock is considered too costly
Various forms available
Can be buried by sand and vegetation
Permeable face absorbs wave energy and encourages upper beach stability
What are the problems of revetments?
Limited life, leading to unsightly and hazardous wire baskets along beach and the release of non-indigenous cobbles to the beach system
Wire affected by saltwater, vandalism and abrasion
What does sustainable costal management mean?
Managing current and predicted future risks to the wider coastal zone in terms of people’s economic livelihood, social well-being and local culture and environmental impacts
What is the ICZM?
Integrated Coastal Zone Management
) is a process for the management of the coast using an integrated approach, regarding all aspects of the coastal zone, including geographical and political boundaries, in an attempt to achieve sustainability
What are the four main approaches of costal management?
Advance the line- Building of new defences on the seaward side of the coast.
Land reclamation
Hold the line- Creation/maintenance of defences along existing coastline
Managed/strategic retreat/realignment- Management and monitoring of the coastline to allow coastal processes to take-over gradually
No active intervention- no active management or monitoring of the coastline
What processes does a plan to build costal defences go through?
Stakeholder interests
Engineering feasibility
Environmental impact assessment
Budget/cost
What is the EIA?
Environmental Impact Assessment
What are the stages of the EIA?
Screening Scoping Assessment Consultation Decision making
What case study would I use for costal management in the developing world?
Namibia
