the coastal system Flashcards
What kind of system is the coastal system?
open as it receives inputs from outside the system and transfers outputs away from the system and into other systems
What kind of system are sediment cells
They are closed systems as sediment is recycled within the sediment cell
What are the sources of energy in a coastal system?
wind
waves
tides
currents
what are the different types of waves
constructive
destructive
what is the effect of wind on waves
A high wind speed and long fetch creates higher and more powerful waves
What are the differences between constructive and destructive waves
Constructive waves have a powerful swash and weak backwash
constructive waves have a low frequency
constructive waves are low and long
constructive waves carry material up the beach and deposit it
Describe the action of tides
Tides are the periodic rise and fall of the ocean surface caused by the gravitational pull of the moon and sun
Tides affect the position at which waves break on the beach - at high tide they break higher up the shore
The land between maximum high and low tide is where most landforms are created and destroyed
Describe the action of currents
A current is the general flow of water in one direction and can be caused by wind or by variations in water temperature and salinity
currents cause material to move along the coast
define sediment budget
The difference between the amount of sand that enters and leaves the system
How does the sediment budget affect the coastline
A positive sediment budget means more sediment enters than leaves the cell and overall, the coastline builds outwards
if the sediment budget is negative then the coastline retreats
How many sediment cells are there in the UK
11
what are the four types of erosion
abrasion
attrition
hydraulic action
solution
what are the four types of transportation
traction
saltation
suspension
solution
what is the difference between marine and aeolian deposition
Aeolian deposition is when sediment carried by wind is deposited and marine is when sediment carried by seawater is deposited
what are the 4 types of sub-aerial weathering
salt weathering
freeze-thaw weathering
chemical weathering
biological weathering
What are the 4 types of mass movement
slumping - material shifts with rotation
sliding - material shifts in a straight line
rockfall
mudflow
describe how cliffs and wave-cut platforms are formed
weathering and wave erosion causes a wave-cut notch to form at the high watermark and this eventually develops into a cave
the rock above the cave becomes unstable and with nothing to support it collapses
wave cut platforms are flat surfaces left behind when a cliff is eroded
describe how headlands and bays are formed
headlands and bays form when there are alternating bands of soft rock, and the soft rock is eroded quickly forming bays and the hard rock left over forms a headland
describe the formation of caves, arches, stacks and stumps
weak areas in rock are eroded to form caves and when caves on opposite sides join to form an arch
the arch continues to experience erosion and weathering and may collapse to form a stack
erosion of the stack will lead to a stump
Give an example of a stack
Loch Bracadale, Scotland
what are the erosional coastal landforms
cliffs and wave cut platforms
caves, arches, stacks, stumps
headlands and bays
Describe how a beach is formed
beaches form when constructive waves deposit sediment on the shore and they are a store in the coastal system
What is the difference between swash and drift aligned beaches
swash aligned beaches may have larger sediment and there is limited longshore drift, so sediment doesn’t travel far along the beach
what are some distinctive features of beaches
berms
cusps
runnells
larger sediment is found towards the top of the beach
what are berms
ridges of sand and pebbles found at high tide marks
what are runnels
grooves in the sand running parallel to the shore formed by backwash draining to the sea
what are cusps
small, curved dips in the beach where the swash comes in
what is a spit and how are they formed
they are a long, narrow strip of land which is formed when the coast suddenly changes direction and littoral drift causes the beach to extend to the sea and a salt marsh may form bhind the spit due to the sheltered environment
What is the difference between a simple and a compound spit
straight spits are simple
Compound spits may have many recurved ends due to several periods of growth
Describe the difference between offshore bars and tombolos
bars are formed when a spit joins two headlands and a lagoon is formed behind it. A tombolo however, is when a spit joins to an island
describe barrier islands
they are long, narrow islands of sand or gravel that run parallel to the shore and are detached from it. They tend to form in areas where there’s a good supply of sediment, fairly powerful waves and a small tidal range
describe the formation of barrier islands
it is not exactly clear how they form but scientists believe they probably formed after the last ice age ended when ice melt cause rapid sea level rise. The rising waters flooded the land behind beaches and transported sand offshore where it was deposited in shallow water forming islands
Describe the formation of sand dunes
sand dunes are formed when sand deposited by littoral drift is moved up the beach by the winds
Sand trapped by driftwood or berms is colonised by plants and grasses stabilising the sand dune encouraging more sand to accumulate forming embryo dunes
What kind of sere is a sand dune
psamosere
What is a plagioclimax
when a climatic climax isn’t reached due to human intervention such as a golf course
What are sand dunes an example of
Succesion
Describe the formation of mudflats and salt marshes
mudflats and saltmarshes form in low energy, sheltered environments e.g., behind spits
as silt and mud are deposited by the river or tide mudflats develop and are colonised by vegetation that can survive halophytic conditions and long periods of submergence by the tide
the plants trap more silt and sediment and gradually the mudflat builds upwards to create an area of saltmarsh that remains exposed for longer and longer between tides
Give 6 examples of depositional landforms
beaches
spits
tombolos and bars
barrier island
mudflats and saltmarshes
sand dunes
define eustatic change
when the sea level itself rises or falls
deine iostatic change
when the land rises or falls relative tothe sea
Describe how eustatic change occurs
glacial melting or thermal expansion
describe how isostatic change occurs
isostatic recovery - when glacial ice melts and the land lifts to readjust due to the reduced weight of the ice on the land
What is the difference between isostatic and eustatic change
eustatic is global and is the change in water
isostatic change occurs locally and is the change in the land relative to the sea
give evidence of sea level change
global sea level is rising by around 2mm each year
increasing temperatures are likely to cause increases in sea level and sea level is predicted to rise by 8-16mm per year by 2100
How can eustatic change impact coastlines
submergence of low lying islands
changes in coastlines - 8000km2 of Bangladesh will be lost
increased coatal erosion
give examples of emergent coastlines
raised beaches
sea-level fall can lead to exposed wave-cut platforms
relict cliffs- cliffs above raised beaches are no longer eroded by the sea
Give examples of submergent coastlines
Rias - flooded river valley e.g., Milford Haven in Wales
Fjords - drowned glacial valleys
Dalmation coasts- valleys are flooded leaving islands parallel to the cast e.g., Croatio
What is the difference between rias and fjords
Rias are flooded river valleys whereas fjords are drowned glacial valleys
Rias generally have a long and wide cross profile whereas fjords are narrow and straight sided
Rias become shallower inland but fjords are very deep inland
what are the 4 options for coastal management
hold the line
advance the line
do nothing
managed retreat
define hold the line
maintain the existing coastal defences
define advance the line
build new coastal defences further out to sea
define managed realignment
allow the shoreline to move but manage the retreat so it causes the least damage
what is the difference between hard and soft engineering
Hard engineering involves built structures whereas soft engineering involves coaxing natural processes along
describe how a sea wall works
the wall reflects waves back out to sea preventing erosion of the cast and flooding
What are the disadvantages of sea walls
they are expensive to build and maintain and create a strong backwash which erodes the under wall
describe how a revetment works
they are slanted structures built at the foot of a cliff and absorb wave energy preventing cliff erosion is relatively cheap to maintain
what are the disadvantages of revetments
expensive to build and creates a strong backwash
Describe how gabions work
gabions are rock-filled cages which absorb energy and are quite cheap
What are the disadvantages of gabions
ugly
describe how ripraps work
they are boulders piled up along the coast which absorb wave energy and are fairly cheap
What are the disadvantages of rip raps
they can shift in storms
Describe how groynes work
groynes are fences built at right angles to the coast and traps material deposited by littoral drift creating wider beaches and gives greater protection from floods and erosion and they are quite cheap
what are the disadvantages of groynes
they deplete further along the beach of sediment making it more prone to erosion and flooding
describe how breakwaters work
concrete blocks or builders deposited of the coast forcing waves to break offshore so theyre erosional power is less when they reach the beach
What are the disadvantages of breakwaters
they are expensive and can be damaged in storms
describe how earth banks work
They are mounds of earth that act as a barrier against flooding
What are the disadvantages of earth banks
expensive and can be eroded
Describe how tidal barriers work
Built across river estuaries and contain floodgates that can be raised to prevent flooding from storm surges
What are the disadvantages of tidal barriers
theyre very expensive
Describe how tidal barrages work
dams built across river estuaries and thier main purpose is to generate electricity and water is trapped behind it at high tide
prevent flooding at storm surges
What are the disadvantages of tidal barrages(dams)
very expensive and can disrupt sediment flow
what are the 6 soft engineering defences
beach nourishment
beach stabilisation
dune regeneration
land use management
creating marshland
coastal realignment - allowing the sea to flood the land and breaching the defence
Define SMP
shoreline management plan
the coastline is split into stretches by sediment cells and for each cell a plan is devised for how to manage different areas with the aim of protecting important sites without causing problems elsewhere
Define ICZM
Integrated coastal zone management
considers all elements of the coastal system such as economy water and people
it is a dynamic strategy
the environment is viewed as a whole and different uses are considered and levels of authority have an input to the plan
It aims to protect the coastal zone in a relatively natural state whilst allowing people to use it and develop it in different ways
.what are the different types of wind action
surface creep wind rolls or slides sand along the surface
saltation - where wind is strong enough to temporarily lift grains into the airflow to heights of up to one metre for long distances
what are some examples of chemical weathering
solution
hydrolysis
carbonation
acid rain
what kind of waves do bays experience and why
they experience low -energy waves that allow sediment to accumulate because of refraction
what happens when waves are refracted
they become increasingly parallel to the coastline
What are the different types of current
longshore
rip currents
upwelling
what do tidal ranges determine
the upper and lower limits of erosion
what is the difference between a spring and a neap tide
spring tides are the highest and sun, moon and earth are in a straight line
neap tides are 10-30 per cent lower than average and moon is perpendicular to earth and sun
what are the main inputs at a discordant coast
geology and lithology of the coast
nature of waves approaching the coast
direction and strength of prevailing wind
what are the processes at a discordant coast
differential rates of erosion at the coast
wave refraction
deposition in the bay
erosion of the headland
what are the outputs at a discordant coast
the headland and bay
erosional features of the headland
depositional features in the bay
why is the size of a wave-cut platform limited
as the platform continues to grow the waves break further out at sea and have to travel across more platform before reaching the cliff line so there is a greater dissipation of energy
what is a geo
the sea will cut inland along a joint widening the crack to form a narrow steep sided inlet
why is shingle usually at the top of the beach
because water rapidly percolates through shingle so the backwash is somewhat limited in its ability to transport material back down the beach
at what kinds of coasts are swash-alligned beaches found
irregular coastlines where littoral drift is impeded
At what kinds of coasts are drift-alligned beaches found
where coastline is fairly regular or where wave direction is at an angle to the beach
What can occur as a spit matures
sand dunes can develop as deposited sand dries out and is blown landward side of the spit
What is the formation of a barrier beach thought to be
breaching of a spit or by constructive waves pushing a bar towards land
what are some factors that over time have helped to develop the coastline
local tectonic processes
sea level change
climatic change
changing ocean currents and wave regimens
human activity
natural disasters
what are some inputs of a coastal sand dune
plentiful supply of sand
strong onshore winds
large tidal range
obstacle to trap the sand
vegetation growth to encourage further dune growth
describe how an embryo dune is formed
sand is moved inland mainly by saltation and where there is a large tidal range large amounts of sand are exposed at low tides
sand may be trapped by obstacles such as seaweed and driftwood at the back of the beach possibly on the highest berm
Why are embryo dunes suitable for colonisation
accumulating wind blown sand is stabilised by grasses and low hummocky dunes are formed and the presence of plants adds organic matter increasing water retention
how are foredunes formed
upwards growth of embryo dunes raises the height of the dune so they are beyond the reach of all but the highest storm tides
foredunes are originally yellow because they lack organic matter but as vegetation cover increases humus is added to the sand and they look grey in colour
What are dune slacks
depressions within fixed dunes where water table is on or near the surface
why are salt marshes not a permanent feature
changes in sea level
wave action
changes in discharge levels in river
changes to tidal flows
describe the flows of water at a salt marsh
salt water from slow moving sea currents bring large amounts of fine sediments and meets the river which is also carrying its own fine silts and clays
as two flows meet fine particles settle out of the suspension by flocculation where clay particles aggregate to form larger heavier particles that sink to the bed
what are the pioneer plants in a salt marsh
glasswort, sea-bite, spartina
when are raised beaches formed
when isostatic movement is faster then eustatic
how do dalmatian coasts differ from rias and fjords
the flooded valleys run parallel to the coast rather than at right-angles
what are changes in sea level a result of
increased volume of ocean
subsidence of coast
how does rock strata influence coastlines
steepest cliffs tend to form in rocks that have horizontal strata or dip gently inland
whereas rocks that dip towards the coast produce more sloping features
how can run off impact coastlines
may take in the form of a stream emerging in a bay and taking large quantities of load during times of flood
stream cascading over cliff excavating v shaped groove
presence will also assist with many mass movements
