Coasts Flashcards
what is a system?
a process or collection of processes that transform inputs into outputs.
define: elements
attributes
relationships
elements-parts that make up a system
attributes-characteristics of the elements
relationships-associations that occur between elements and attributes
what is an open system?
a system in which both mass and energy are allowed to transfer across the system boundary. There may also be a flow of matter in or out of the system
what is a closed system?
may be a flow of energy in or out of the system but no matter flow takes place across the system boundary(fixed with mass)
what is a isolated system?
no interaction between the system and its surroundings(its theoretical)
define input.
material or energy moving into the system from outside e.g. geology
define output.
material or energy moving from the system to the outside e.g. evaporation
define energy.
power or driving force e.g. wind
define stores/components.
parts of a system e.g. beach, sea
define flows/transfers.
the links or relationships between the components e.g. wind/water transport
define positive feedback.
where a flow /transfer leads to increase or growth e.g. constructive waves build up beach
define negative feedback.
where a flow/transfer leads to a decrease or decline e.g. erosional processes
define dynamic equilibrium.
the state of balance within a constantly changing system e.g. sediment, types of waves
what is a costal system?
a series of linked elements affecting the coastal zone through which energy and material circulate.
what is a sediment budget?
the net sum value between quantities of input and output of sediment in a system excess=positive budget deficit=negative budget no difference=neutral budget
what is a sediment cell?
a section of coastline where sediment is recycled
what is a sediment sink?
sediment is lost to the system by transfer to a location beyond further access
what is dynamism?
the degree of change taking place in a system in terms of scale and/or rate
what is the backshore?
the area between the high water mark(HWM) and the landward limit of marine activity. Changes normally take place her only during storm activity.
what is the foreshore?
the area lying between the HWM and the LWM.(most important area for marine processes in times that are not influenced by storm activity)
what is the nearshore (aka inshore)?
area between LWM and the point where waves cease to have any influence beneath them
what is the offshore?
the area beyond the point where waves cease to impact upon the seabed and in which activity is limited to deposition of sediment
what is prevailing wind?
wind that consistently blows from the same direction and generates more high energy waves thank condition where the wind direction is constantly changing
what is fetch?
the distance the wind has been blowing over a body of water. greater fetch=greater wave energy
what is abrasion?
where the waves uses material it carries to wear away landscape features
what are orbital waves?
waves that occur in the open sea as there is little horizontal movement of water
what are elliptical motions?
occurs when water becomes shallower and the circular orbit of the water particles changes to an elliptical shapes
characteristics of destructive waves.
- high, plunging waves +short wavelength
- weak swash strong backwash
- beach loss
- beach has steeper beach profile ,over time flattens
characteristics of constructive waves.
- low surging waves = long wavelength
- strong swash, weak backwash
- beach gain
- gentle beach profile, buildup over time
what is wave refraction?
when waves approach a coastline that is not a regular shape they are refracted and become increasingly parallel to the coastline
where are rocky coasts generally found?
high- energy environments
what are high- energy environments?
-places where rate of erosion exceeds rate of deposition e.g. headlands, cliffs, wave cut platforms
where are sandy coasts generally found?
in low-energy environments
what are low-energy environments
where the rate of deposition exceeds the rate of erosion e.g. beaches, spits
what are tides?
tides are caused by the effect of gravity from the moon and to a lesser extent the sun, as tide rises and falls so does sediment it carries
define spring tide.
earth, moon and sun align at a full moon and new moon and gravity of both combine create higher high tides and lower low tides
define neap tide.
when moon is at first/last quarter and sun and moon pulling at right angles to each other which creates lower high tides and higher low tides
define ocean currents.
the continuous predictable directional movement of seawater driven by gravity, wind ,water and density. Horizontal movements=currents vertical movements=upwellings/downwellings.
define rip currents.
forms when waves break near the shoreline piling up water between the breaking waves and the beach .one way water is retuned to sea is via rip current which is a narrow stream of water moving swiftly away from the shore, often perpendicular to the shoreline.
define longshore current.
waves hit coastline at an angle generating a flow of water running parallel to the shoreline. Transports sediment as well.
define upwelling.
movement of cold water from deep in ocean to the surface. The more dense cold water replaces the warmer surface water and creates nutrient rich cold ocean currents.
state the sources of sediment.
- streams or rivers flowing into the sea
- estuaries
- offshore and banks
- material from biological origin
what is a sediment cell?
A sediment cell is a largely self-contained stretch of coastline. They are regarded as closed systems as sediment is not usually transferred from one to the other. In reality, some sediment does get transferred between neighbouring cells.
what is a sediment budget?
the balance between sediment added to and removed from the coastal system;
the coastal sediment budget is like a bank account. When more material is added than is removed, there is a surplus of sediment and the shore builds seaward.
what is geomorphology?
the study of landforms, their processes, form and sediments at the surface of the earth
what is the difference between marine processes and sub-aerial processes?
marine process operate on a coastline and are connected with the sea whereas sub-aerial processes
includes processes that slowly break down the coastline by weakening the rocks and allow erosion to happen more easily.
what is the rate of costal erosion affected by?
- wave steepness and breaking point(steep= h energy)
- fetch
- sea depth(steeply shearing seabed creates higher and steeper waves)
- costal configuration
- beach presence
what is mass movement ?
mass movement is the downhill movement of sediment that moves because of gravity.
state and explain the 4 types of mass movement
Rockfall-Bits of rock fall off the cliff face, usually due to freeze-thaw weathering
Mudflow-Saturated soil (soil filled with water) flows down a slope
Landslide-Large blocks of rock slide downhill
Rotational slip-Saturated soil slumps down a curved surface
define weathering.
the breaking down/wearing away of rock in situ
what is the difference between concordant and discordant coast?
concordant-rock structure is parallel to the coast and the hard bands of rock protect softer rock from erosion
discordant-bands of differing rock type that is perpendicular to the coast (headlands and bays occur here)
formation of wave cut notch.
the waves attack the base of the cliff and it is eroded by abrasion and hydraulic action creating an dent at the base.
formation of wave cut platform.
as the base get attacked even more the cliff on top becomes unstable and cracks start to develop and the cliff collapses causing cliff retreat and leaving a wave cut platform.(example Great tor-Wales)
formation of a cave.
begins with a crack in a headland and the crack is widened by hydraulic action and abrasion and over time it begins to open up and form a cave.
formation of an arch.
forms when a cave extends back wards to meet the other side and the conjoining of caves will create a hole through the whole headland.
formation of a stack
arch widens and sub -aerial processes help weaken rock which causes the arch to collapse leaving a stack(example, old harry, Dorset )
formation of a stump.
base of a stack attacked causing it to collapse leaving a smaller portion called a stump
what is a swash aligned beach?
beaches that are generally orientated parallel to the incoming wave crests and experience minimal longshore drift. They can be found on an irregular coastline.
what is a drift-aligned beach?
beaches that are generally oriented parallel to the direction of dominant longshore drift and have a considerable amounts of sediment transported long distances along them. Initially develop where a section of coastline is fairly regular
what is a spit?
an elongated narrow ridge of land which is formed as longshore drift moves and the deposits sediment.as a spit develops a sand dune can develop.
what is a tombolo?
a spit that links an island to the main land
what is a bar?
when a spit develops across a bay where there is no strong flow of water
what is an offshore bar?
where a ridge of beach material that remains semi-submerged accumulates seaward of the breaker zone
what is a barrier beach?
Barrier Beaches are narrow and elongate beaches situated parallel to the shoreline and are separated from mainland by a body of water.
what is a sand dune?
accumulations of sand shaped into mounds by the wind
what are the important inputs in sand dunes?
- plentiful supply of sand
- strong onshore winds
- a large tidal range
- obstacle to trap sediment
- vegetation growth to encourage further growth of the dune
what are the steps in the formation of sand dunes?
first dunes, embryo dunes-suitable for colonisation by grasses and stabilises.
foredunes-upward growth of embryo dunes(initially yellow due to them containing little organic matter can reach up to 20M)
-Over time, tough plants known as PIONEERS such as Marram grass take root on the dune, their root systems helping to stabilise the sand and fix it in place.
As these plants die off they add nutrients and humus to the sand dune improving the soil, so more complex plants can move in, such as brambles.
-dune slack-hollows form often from blowouts and sand is removed until water fills in
mature dune-woodlands/forest
what is a mudflat?
low lying area of the shore that is submerged at high tide and composed of silt and clay
how are mudflats formed?
mudflats only develop on shorelines that are not exposed to powerful waves. They develop on estuaries, flow of fresh water is slow and sea water flows into river mouth with each high tide and out with each low tide.
salt water flows gently into estuary and meets equally slow moving river which is also carrying lots of fine silt and clay
as 2 flow meet the fine particles settle out suspension by flocculation.particles aggregate together and form larger particles which sink to the bed
what is a salt marsh?
a coastal ecosystem found between land and open salt water or brackish water that is regularly flooded by the tides
how are salt marshes formed?
develops from mudflats as mud breaks surface due to deposition and some plants begin to grow(pioneer plants )e.g. cordgrass which is tolerant to seawater and its long roots help hold mud and sediment together.
as material and sediment accumulate it gets covered by the tide less,which plus rain leaches some salt causing less salt concentration
less salt concentration=plants more fertile and grow and grow new species
over time bigger and harder plants grow which form marsh uplands which have trees as well as plants.
define eustatic.
global change in sea level from sea level rising/falling
define isostatic.
global change in sea level from land rising /falling
what is a ria?
a drowned river valley, which are widest and deepest near the sea and get shallow further inland
define submergence coastline
flooding of coastlines from river and glacial valleys e.g. rias ,fjords, Dalmatian coasts
define emergence coastline
isostatic change as land movement occurring faster than eustatic left behind wave cut platforms e.g. raised beaches
what is a fjord?
a former glacial valley drowned by rising sea levels
what happens during a glacial and inter-glacial period?
glacial period-temperature falls, ice sheets, ice caps and glaciers form on land and global eustatic fall in sea level.
continental ice causes localised isostatic depression of land; sea level rises locally
inter-glacial-temperatures rise and ice melts causing a global eustatic rise in sea level and positive change in base level
what is a Dalmatian coast?
where the topography of the land runs parallel to the coastline and becomes flooded by sea level rise
what is a raised beach?
areas of former wave cut platforms and their beaches which are at higher level than the present sea level
what is a marine platform?
where a greater expanse of gently sloping formerly submerged land has been exposed by the lowering of sea levels
what is hard engineering?
making a physical change to the coastal landscape using resistant materials
what is soft engineering?
using natural systems for coastal defence such as beaches which absorb wave/tide energy
what are sea walls and pros and cons etc?
Concrete walls that are placed at the foot of a cliff to prevent erosion. They are curved to reflect the energy back into the sea.
pros:-long life span (50-100yrs), excellent defence
cons; very expensive to build and maintain, destroy habitats
cost:£5000/m
what is rock armour and pros and cons etc?
Large boulders placed at the foot of a cliff. They break the waves and absorb their energy.(off coast called rip-rap)
pros: cheap compared to sea wall, built quickly
cons: rock is expensive to transport, looks different to local geology
cost: £1000-3000/m
what is a gabion and pros and cons etc?
Rocks are held in mesh cages and placed in areas affected by erosion.
pros: cheap; approximately £100 per metre, can last 20-25 yrs
cons: not very strong, restricted to sandy beaches as shingle beach material will degrade quickly
what is a revetment and pros and cons etc?
wooden, steel, or concrete fence-like structures that allow sea water and sediment to pass through, but the structures absorb wave energy. A beach can build up behind the revetment and provide further protection for the cliff.
pros: cheap
cons: short lifespan, destroys habitats
cost: £2000/m
what is a groyne and pros and cons etc?
Wooden or rock structures built out at right angles into the sea.
pros: builds a beach - which encourages tourism, trap sediment being carried by longshore drift.
con: trapping sediment it starves beaches further down the coastline, increasing rates of erosion elsewhere, need regular maintenance
cost: £5000 each
what is beach nourishment and pros and cons etc?
Sand is pumped onto an existing beach to build it up
pros :blends in with existing beach ,bigger beach appeals to tourists
cons: needs to be constantly replaced, sand brought from elsewhere
cost: £3000 per km
what is dune regeneration and pros and cons etc?
Marram grass planted on sand dunes stabilises the dunes and helps to trap sand to build them up.
pros: relatively cheap, maintains natural looking coastline
cons: can be damaged by storm waves , areas have to be zoned off from the public
cost: £2000 per 100m
what are some extra hard and soft engineering methods?
- cliff fixing-prevents landslides and mass movements
- offshore reefs
- barrages
- salt march creation
- land use management
what is a SMP and it aim?
SMPs are designed to identify the most sustainable approach to managing the flood and coastal erosion risks to the coastline and they aim to plan for long, short and mid term.
what are features of a SMP(shoreline management plan)?
- provide assessment of risks to people and to the developed historic and natural environment.
- address risks in sustainable way
what are the 4 management categories in a SMP?
1.managed retreat
2.do nothing
3.hold the line
4.advance the line
British coastline separated into 22 SMPS
what is an ICZM(integrated coastal zone management)?
originated in 1992 from UN earth summit
contributes to sustainable development of coastal zones by an approach that respects the limits of natural resources and ecosystems
coasts are some of the most ecologically productive places in the world and are popular for tourists, settlements and businesses -around 200 million people live near Europe’s coastline
future threats-flooding, erosion , sea level rise
ICZMs are sustainable for generations
