Coastal systems and landscapes Flashcards
How is the coast a natural system?
Inputs of energy and sediment
Components of erosional landforms and landscapes
Components of depositional landforms and landscapes
Outputs of energy, sediment removal, sediment above tidal limit
What are the coastal zones?
- Offshore
- Nearshore
- Foreshore
- Backshore
Where is the offshore?
Beyond the point where waves have impact on the seabed
Where is the nearshore?
Between LWM and area where waves cease to have influence on seabed
Where is the foreshore?
Between HWM and LWM
Where is the Backshore?
Above HWM up to landward limit of marine activity
What are the zones in the foreshore?
- Swash zone
- Breaker zone
- Surf zone
What happens in the swash zone?
Turbulent water rushes up the beach as swash
What happens in the breaker zone?
Waves approaching begin to break
What happens in the surf zone?
Between waves breaking and moving up the beach as swash
What are the sources of energy?
- Waves
- Winds
- Tides
- Wave refraction
- Currents
How are waves sources of energy?
Frictional drag of wind
What are the two types of waves?
- Constructive
- Destructive
What are the features of a construction wave?
- Low height
- Low frequency (6-8/min)
- Swash more powerful than backwash
- Beaches built up, gentle beaches
What are the features of destructive waves?
- High heights
- High frequency (10-14/min)
- Backwash stronger than swash
- Sediment removed, steeper beaches
What is the energy of winds dependent on?
- Strength
- Duration
- Fetch
How are tides a source of energy?
Gravitational pull of the moon and to a lesser extent the sun
How is a spring tide created?
When the sun and moon are aligned (every 14 days)
How is a neap created?
When the sun and moon are at right angles
How often do High and Low tides occur?
Every 12h and 25min
What is wave refraction?
When energy of wave become concentrated on headlands and dissipated at bays, since waves in shallow water slow down due to friction with sea bed
What are the different types of currents?
- Longshore drift
- Rip currents
- Upwelling
What is a rip current?
Move away from the coastline at, for example, a headland
What is upwelling?
Cold water making its way to the surface
What is a sediment cell?
A stretch of coastline, usually bordered by two headlands, where the movement of sediment if largely contained
How many sediment cells are there in England and Wales?
11
What is there within sediment cells?
Inputs (sources)
Transfers and stores (sinks)
What is the sediment budget?
The amount of sediment that is available and tries to be in dynamic equilibrium
How can the sediment budget be upset?
By a storm or sudden increase in discharge or by human activity
eg groynes
What are geomorphological processes?
Processes involved in the change of landforms
What are examples of geomorphological processes?
- Erosion
- Transportation
- Deposition
- Weathering
What are the coastal processes of erosion?
- Wave quarrying
- Attrition
- Solution
- Hydraulic action
- Abrasion
What is wave quarrying?
Cavitation which traps aire causing huge pressure, which is released when wave withdraws
What is attrition?
Material being carried by the sea hit against each other becoming smaller, rounder and smoother
What is solution?
Rocks, normally limestone or other rocks containing carbon, are dissolved, through this is normally by rainfall
What is hydraulic action?
Sheer force of the water puts pressure on the rocks and forces them apart
What is abrasion?
Material is used by the waves
eg Shingle which is thrown at the cliff
What are the coastal processes of transportation?
- Saltation
- Traction
- Solution
- Suspension
- Longshore drift
What is saltation?
sediment bounces along the bed of the sea and dislodges other particles
What is traction?
bedload rolls along the sea bed
What is solution?
minerals are dissolved and are carried in the water
What is suspension?
particles are carried along in the water
What is longshore drift?
swash comes in at an angle due to prevailing wind direction, backwash straight back down due to gravity, moves material in a zig zag along the coastline
What are the coastal processes of deposition?
- Where marine energy is lost
- Aeolin - carried/deposited by the wind
When is marine energy lost?
- The wave slows down after breaking
- Where accumulation is quicker than removal
- Where the coastline changes direction
- Just before backwash
What is Aeolin?
Wind is often onshore during the day due to temperature differences
Sand is entrained (picked-up) and then moves through
Surface creep - rolls
Saltation - bounces
What are sub-aerial processes?
These are land-based and consist of weathering and mass movement
What are the different types of weathering?
- Mechanical
- Chemical
- Biological
What are the different types of mechanical weathering?
- Freeze-thaw
- Salt crystalisation
- Wetting and drying
- Exfoliation
What is freeze-thaw weathering?
water into cracks, expands 10%, puts pressure on rocks until they crack and break. The shattered, angular fragments are found at the base as scree (talus)
What is salt crystalisation?
salt crystals are deposited in cracks and accumulate under drier conditions, over time it applies pressure to the rocks and they crack.
What is wetting and drying?
Common on the coastline, in the inter-tidal zone, with clay and shale which expands when wet and contracts when dry. This produces cracks which are then vulnerable.
What is exfoliation?
Rock under considerable heat will expand and then cooled by the sea causing rapid contraction. This repeated process causes the outer layer to crack and peel off - onion-skin weathering
What are the different types of chemical weathering?
- Carbonation
- Oxidation
What is carbonation?
Sea and rain absorb carbon dioxide forming carbonic acid which then dissolves the calcium carbonate in rocks such as limestone or chalk into calcium bicarbonate, especially in cracks and joints.
What is oxidation?
Rocks containing iron (ferrous) compounds experience this when turned into a ferric state (rusting) when oxygen and water are available, leading to disintegration.
What are the different types of biological weathering?
Growing plant roots widen cracks, in windy conditions these can widen. On the coastline the Piddock drills holes in rocks, puffins excavate nests and seaweed can move in storm conditions weakening rock
What is mass movement?
A sub-aerial process, involving the downhill movement of material under the influence of gravity
What are the different types of mass movement?
- Soil creep
- Rotational slumping
- Rock falls
- Landslides
- Mudflows
- Runoff
What is soil creep?
very slow movement (1cm/yr), dislodged by raindrops or wave splash and freeze/thaw or wetting/drying
What is rotational slumping?
Heavy rain infiltrates unconsolidated soil e.g. glacial till (East coast), impermeable soil traps water adding weight, undercutting causes collapse on slip plane
What is rock falls?
physical weathering, weaknesses exposed and can’t support
What is landslides?
significant section, unconsolidated shales & sandstones, usually been lubricated
What is mudflows?
excessive amounts of rainfall, infiltration can’t take place, fine particles of mud
What is runoff?
intense rainfall, impermeable surface, transports fine material
What are the landforms of erosion?
- Caves, arches and stacks
- Cliffs and wave cut platforms
- Headlands and Bays
What is an example of caves, arches and stacks?
Old Harry, Swanage
What is an example of cliffs and wave cut platforms?
Watchet, West Somerset, KImmeridge BAy
What is an example of headlands and bays?
Swanage bay
What are the landforms of coastal deposition?
- Beaches
- Simple and compounds spits
- Tombolos
- Offshore bars
- Barrier islands
- Bar/barrier beach
- Sand dunes
- Saltmarch/mudflats
What is an example of simple and compound spits?
Sandbanks, Hurst Castle, Spurn Point
What is an example of a Tombolos?
Chesil Beach joining Isle of Portland
What is an example of an offshore bar?
Hordle Cliff
What is an example of barrier island?
Long Island - New York
What is an example of a Bar/barrier beach?
Slapton Sands
What is an example of sand dunes?
Ainsdale, Braunton Burrows, Oxwich
What is an example of saltmarch/mudflats?
Keyhaven Marshes (Hurst Castle)
What are the factors and processes in the origin and development of cliffs and wave cut platforms?
Waves attack base of cliff, via abrasion and hydraulic action
Creates a wave-cut notch which is undercut, becomes unstable and collapses
Notch migrates inland and cliff retreats leaving a gently sloping wave-cut platform, exposed at low tide.
Wave cut platform smoothed via abrasion and solution
Most less than 0.5km
What is a discordant coastline?
geology at right angles e.g. Purbeck, Dorset
What is a concordant coastline?
geology runs parallel to coast e.g. South Dorset, and Dalmation Coast
What are the factors and processes in the origin and development of cliff profile features to include caves, arches and stacks?
- Lithology
- Structure
- Geomorphology
How is lithology a factor in the origin and development of cliff profile?
The physical properties of a rock such as its resistance to erosion - the rock type.
How is structure a factor in the origin and development of cliff profile?
whether the rocks run parallel or perpendicular, joints and bedding planes
- Horizontal - produce steep cliffs
- Dip towards the sea - less stable, joints exposed
- Dip towards the land - more stable
How is geomorphology a factor in the origin and development of cliff profile?
the shape of the coastline e.g. refraction
What are the factors and processes in the origin and development of beaches?
- Shingle produces steeper beaches due to less powerful backwash
- Material more angular, larger, more varied towards top of beach - due to cliff falls, less attrition, storms move material up the beach
- Swash-aligned - no drift, bays, waves parallel
- Drift-aliged - drift, waves oblique, regular coastline
- Berm - ridges runing parallel marking high tide marks
- Cusp - embayments caused by save dividing around horns
- Ridges & Runnels - spreading of the waves energy across the beach creates these
What are the factors and processes in the origin and development of spits?
LSD, coastline changes direction, deposition occurs and conginues in direction of LSD, change in wind direction causes recurved end, also via wave refraction, mudflats and slat marshes behind, flow of water out of estuary stops spit reachign the other side
What are the factors and processes in the origin and development of tombolos?
Where a spit connects to an an island
What are the factors and processes in the origin and development of offshore bars?
ridge of material running parallel to the coastline, caused by desgtrctive waves with strong backwash
What are the factors and processes in the origin and development of barrier beaches?
Develops in same way to a spit but where flow of water from river is less powerful and therefore joins to headland on th either side, creating a lagoon
What are the factors and processes in the origin and development of barrier islands?
similar to offshore bars but always exposed, created after the last ice age left behind material
What are the factors in origin and development of sand dunes?
- Plant succession
- Needs
What is plant succession?
where plants gradually make an area more hospitable for other plants which then take over
What are the needs for development of sand dunes?
large supply of sand, therefore large tidal range, exposed to wind to dry & entrain
What is the development of sand dunes?
- Embryo dune
- Foredune
- Yellow dune
- Grey dune
- Mature dune
What is the process of the development of sand dunes?
- Sand accumulates against an object e.g. driftwood
- Behind the barrier wind drops so more sand is deposited and pioneer plants able to tolerate harsh conditions (salt water, inundation, dry, lack of nutrients, windy) colonise e.g. sea rocket
- Marram grass, with long tap roots to get water, colonise dunes making them more stable
- Decaying plants add humus to the soil which allows other plants to colonise.
- Soil developed which allows a range of different plants to colonise and eventually trees to develop as the climax vegetation
What are the factors in the development of estuarine mudflat/saltmarsh environment?
- estuaries, low wave/river energy, sheltered areas, low lying and flat, behind spits which create a Halosere
- Mudflats - deposition of fine silts and clays
- Saltmarsh - area of coastal grassland that is regularly flooded
What are the processes involved in the development of estuaries and mudflat/saltmarsgg environments?
- Mud is deposited close to high-tide line, dropping out of the water by flocculation - tiny individual particles of clay stick together which enables them to sink
- Pioneer plants such as eelgrass and spartina colonise the transition zone between high and low tide. These plants can tolerate inundation by salty water and they also help to trap deposits of mud.
- The mud level rises above high tide and lower saltmarsh develops with a wider range of plants that no longer need to be so well adapted to salty conditions.
- Soil conditions improve and the vegetation succession continues to form a meadow.
- Shrubs and trees will colonise the area as the succession reaches its climatic climax.
What was the sea level 20,000 years ago?
120m below current level
What was the sea level 10,000 years ago?
50m below current level until 7,000 years ago
What is Eustatic change?
A global change in sea level as a result of change in input and stores e.g. input of snow stored as ice which decreases ocean store & melting of ice decreases store of ice and increases flow to oceans.
What is isostatic change?
a local change in sea level caused by land weighed down by weight of ice (isostatic subsidence), once ice melts land rebounds (isostatic recovery) - acts like a sea-saw
What is tectonic change?
changes in level of the land and/or sea bed as a result of tectonic activity e.g Nea Zealand in 2016 after 7.8 earthquake, seabed rose by 0.5-2m along a 20km stretch of South Island, however areas on North Island coastline is subsiding by 5mm a year.
What is thermal expansion?
Hot water expands
- responsible for up to 50%
What is a submergent coastline?
One which has a rising sea level
What is an example of a submergent landforms?
- Ria
- Fjord
What is a emergent coastline?
One which has a falling sea level
What are some example of an emergent coastline?
- Raised beach
- Relict cliff
What is a Ria?
A drowned river valley
As sea levels rise they flood the river valley, leaving only the high land visible
What is Fjord?
A drowned glacial valley
As sea levels rise U-shaped valleys left by glaciers are submerged
What are some features of Fjords?
- Steep valley sides and are fairly straight and narrow
- They have a u-shaped cross section with hanging valleys on either side
- At the mouth they have a shallower section called a threshold
- This is thought to be due to reduced glacial erosion as the glacier came into contact with the sea
What is a raised beach?
Areas of former wave-cut platforms and
their beaches which are at a higher level
than the present sea level
What is an example of a raised beach?
Raised beaches are common in Scotland.
The Isle of Arran is a good example.
What are relict cliffs?
An old cliff displaying features such
as caves, arches and stacks.
How have sea levels changed over the years?
- Rising sea level has been happening quite
slowly in recent millenia – 1-2mm per year - Rate has increased recently to 4-5mm per year
- Future predictions are uncertain: between 0.3
and 0.5m increase by 2090
What have been the impacts of present and predicted sea level rise?
- Coastal flooding: particularly low-lying areas and increased erosion, eg Holderness
- Southeast Britain is at greatest risk of flooding due to combined eustatic change and subsidence
What are some examples of areas that are likely to be impacted by flooding due to sea levels changing?
- London
- Hull
- Middlesborough
What are the impacts of present and predicted sea level rise on fresh water sources?
- Impact on underground water resources
- Intrusion of salt water beneath the land could contaminate freshwater stores
- Abstraction points would have to be moved upstream/inland
What are the environmental impacts of present and predicted sea level rise?
- Coastal habitats threatened - wetlands and salt marsh
- Ecosystems can adjusr but depends how fast the sea level rise is
- Also, coastal squeeze may occur in salt marsh
What are socio-economic impacts of present ad predicted sea level rise?
- More developments are occuring on at risk areas
- Insurance is expensive - which may dissuade people from moving into these areas
What is hard engineering?
a very traditional and in many ways outdated approach to coastal management
and it involves man made structures that aim to prevent erosion
What are the positives of hard engineering?
They are often very effective
at preventing erosion in the desired area
What are the negatives of hard engineering?
- high cost and have a significant environmental
impact due to the use of concrete and other man-made materials - By reducing erosion in one area of the coastline, they may act to exacerbate erosion elsewhere. Therefore their only impact is
to change where erosion is occuring.
What is a Offshore Breakwater?
Hard Engineering:
A Rock barrier which forces waves to break before reaching the shore
What is a positive of an offshore breakwater?
Effective at reducing waves’ energy
What are negatives of an offshire breakwater?
- Visually unappealling
- Navigation hazard for boats
What is a groyne?
Hard engineering:
Timer or rock protrusions that trap sediment from LSD
What are positives of groynes?
- Builds up beach, protecting cliff and incresing tourists potential
- Cost effective
What are negative of groynes?
- Visually unappealling
- Deprives areas downwind of sediment
increasing erosion elsewhere
What is a sea wall?
Hard engineering:
Concrete structures that absorb and reflect wave energ, with curved surface
What are positives of sea walls?
- Effective erosion prevention
- Promenade has tourism benefits
What are negatives of sea walls?
- Visually unappealling
- Expensive to construct and maintain
- Wave energy reflected elsewhere,
with impacts on erosion rates
What is rip rap?
Hard Engineering:
Large rocks that reduce wave energy, but allow water to flow through
What is a positive of rip rap?
Cost effective
What are negative of rip rap?
- Rocks are sourced from elsewhere,
so do not fit with local geology - Pose a hazard if climbed upon
What are revetments?
Hard Engineering:
Wooden or concrete ramps that help absorb wave energy
What are positives of using revetments?
Cost effective
What are negatives of using revetments?
- Visually unappealling
- Can need constant maintenance, which creates an additional cost
What is soft engineering?
aims to work with and complement the physical
environment by using natural methods of coastal defence
What is beach nourishment?
Sediment is taken from offshore
sources to build up the existing beach
What are positives of beach nourishment?
- Builds up the beach, protecting cliff and increasing tourist potential
- Cost effective and looks natural
What are negatives of beach nourishment?
- Needs constant maintenance
- Dredging may have consequences on local coastal habitats
What is cliff regrading and drainage?
Reduces the angle of the cliff to help stabilise it. A steeper cliff would be
more likely to collapse
What is a positive of cliff regrading and drainage?
- Cliff may collapse suddenly as the cliff is drier leading to rock falls which pose a hazard
- May look unnatural
When is a cost benefit analysis carried out?
Before any form of coastal management takes place
What does the cost benefit analysis include?
The expected cost of:
- Construction
- Demolition
- Maintenance
What is the cost of the coastal management plan then compared to?
The expected benefits of a scheme including:
- Value of the land
- Homes and businesses that will be protected
What are sustainable Coastal Management?
They are holistic strategies
What do holistic strategies mean?
They recognise that all of the different sections of the coastlineare interlinked and function together as a whole
What are ways of managing a coast in a sustainable way?
- Managing natural resources like fish, water, farmland to ensure long term productivity
- Ensuring that there are new jobs for people who may face unemployment as a result of
protection measures. E.g. if a decision is taken that fishing needs to decrease as currently it
is above sustainable levels - Educating communities about the need to adapt and how to protect the coastline for
future generations
What does integrated Coastal Zone Management do?
Manage Large sections of coastline (often
sediment cells) are managed with one integrated strategy
Where does Integrated Coastal Zone Management occur?
between
different political boundaries , which is both beneficial and problematic as decision making is
likely to be a longer process
What does the ICZM recognise?
- the importance of the coast for people’s livelihoods
- that coastal management must be sustainable whereby economic
development is important, but is not prioritised over protection of the coastal
environment
What must ICZM involve?
all stakeholders , plan for the long term and try to work with
natural process and not against them
What does the ICZM recognise about sediment?
that sediment eroded in one location may form a protective beach
elsewhere and therefore a decision to protect one coastal community may not outweigh the
disadvantages of exposing another community to increased erosion
What did the EU adopt in 2013?
a new initiative which promotes the use of ICZM’s across all of
Europe’s coastlines, which recognised the benefits of the ICZM strategy
What has been created for each sediment cell in the UK?
Shoreline Management Plans (SMPs)
What does each SMP help to identify?
which occur within the
coastline area of each sediment cel
What are the four options for each stretch of shoreline?
- Hold the line
- Managed retreat
- Advance the line
- No active intervention
What is hold the line?
Defences are used to maintain the current position of the shoreline
What is managed retreat?
Defences and engineering techniques are used to allow
the coastline to advance inland and create its own natural defences such as salt marshes
What is advance the line?
Defence are built to try and move the shoreline seawards, potentially to
protect an important population centre or tourist amenity
What is no active intervention?
The coastline is exposed to natural processes
What are the different factors considered when choosing a management option?
- Economic value of assets
- The technical feasibility of engineering solutions
- ecological and cultural value of land
When considering coastal management what is their?
Winners and losers
Who are the winners?
Those who benefit - economically e.g. their homes and businesses are protected - environmentally e.g. habitats are protected - socially community ties still remain in place, people still have jobs so less stress and worrying
What are the losers classified as?
those who lose
their property, lose a job, or have to relocate elsewhere
What are the impacts of installing a sea wall?
reflect wave energy downdrift
increasing wave energy and erosion elsewhere on the coastline. Less erosion occurs in these
areas with the sea wall , so there is also less sediment in the areas with increased wave
energy. Less sediment reduces the beach size , so the cliff is more exposed to erosion from
the higher energy waves. Building groynes has the same effect on downdrift areas as longshore
drift can no longer transport sediment away from one stretch of coastline.
