SectionC: Physical Landscapes of the UK-Coasts Flashcards
backwash definition
the water that rolls back down a beach after a wave has broken
fetch definition
the distance in the direction of the prevailing wind that air or water can travel continuously without obstruction
swash definition
the waves washing up the beach
waves definition
formed when wind blows over the sea
what are coasts
coasts are where the sand meets the sea. The fetch of the waves cause the swash and backwash
characteristics of a constructive wave
created in calm weather, strong swash, these waves build up the beach
characteristics of a destructive wave
created in stormy conditions, this wave drags material away from the beach eroding it, they are created when the wind is strong and has been blowing for a LONG time, strong backwash, these waves have lots of energy
erosion definition
erosion involves the removal of material and the haping of landforms
abrasion coasts
is the sandpaper effect of the material rubbing agaisnt the cliff-face
hydraulic action coasts
the sheer force of the waves smashing into the cliff, trapped air forced into cracks so rock will fall
attrition coasts
rock fragments carried by the sea knock against each other causing them to become smaller and rounder
traction
large pebbles rolling along the seabed
saltation
small pebbles bouncing along the seabed
solution
dissolved chemicals often derived from limestone or chalk
suspension
particles carried within the water
if sub-aerial processes are greater than cliff-foot processes then the cliff will have…
a more gentle gradient as the mechanical/chemical weathering acting on the top of the cliff is acting faster than the waves at the bottom
if sub-aerial processes are weaker than cliff-foot processes then the cliff will have…
a steeper gradient as the sea is wearing the cliff away faster than the mechanical or chemical weathering
mechanical weathering
this is the process of breaking big rocks into little ones
chemical weathering
this is when there is a chemical change on rocks usually as a result of rainwater being acidic
biological weathering
this would include the effect of animals and plants on the landscape
example of mechanical weathering
freeze-thaw
how does freeze-thaw work
water collects into the small cracks in the surface when the temperature drops the ice expands by 9% which widens the cracks in the rocks, this is called freeze-thawing where eventually the rocks will break away from the cliff
example of chemical weathering
acid rain
where has acid rain occurred - case study
white cliffs of dover
what are the white cliffs of dover made from
limestone
how does acid rain work
rainwater becomes slightly acidic as carbon dioxide dissolves in it, some rocks are easily chemically weathered e.g. limestone and chalk
why are limestone and chalk easily chemically weathered
as they are made up of calcium carbonate
Beachy Head case study
wet winter of 2000 chalk became saturated with water, the water froze as the temperature dropped, in April 2001 this caused a rockfall
mass movement definition
mass movement is the downward movement or sliding of material under the influence of gravity
what do mass movement and weathering have an impact on
the coastal system
where does the material from mass movement go
it is carried away by waves and deposited further along the coast
what are the three types of mass movement
rock fall, landslide, rotational slip
rock fall description
fragments of rock break away from the cliff face, usually in glaciated areas due to freeze-thaw
landslide description
occurs when the land is sloped, bands of rock are layered diagonally along the slope, when the ground is saturated/weathered material can be weakened, this will result in the rock sliding downwards due to gravity
rotational slip description
permeable rock (gravel) sits on top of the impermeable rock (clay), the gravel allows water to soak into the ground which adds weight to the boulder clay, weathering such as freeze-thaw weakens the cliff, the cliff collapses in a rotational movement and slumps downwards
another name for rotational slip
slumping
why does deposition take place
waves enter an area of shallow water, little wind, waves enter a shallow area e.g. a bay, there is a good supply of material
what is wave refraction
where friction with the sea bed causes the wavefront to become distorted (bending and changing direction)
give two ways that wave refraction occurs at headlands and bays
the waves converge at headlands and diverge at bays
what is longshore drift
longshore drift is the movement of material along the beach. The prevailing wind makes the waves hit the beach at an angle. The waves pick up the material and the swash is at a 45-degree angle. Gravity deposits the material then the force of the backwash dragged by the wave back into the sea at 90 degrees. This process is repeated and builds up the beach but occurs in a zig-zag motion
discordant coastline
bands of different rock type
concordant coastline
bands of the same rock type
differential erosion
rocks eroding at different rates
EXAM QUESTION- Explain the formation of headlands and bays (6 marks)
headlands and bays are formed on a discordant coastline which is where bands of hard and soft rock e.g. chalk and clay create a coastline. Destructive waves erode the less resistant rock first then followed by the more resistant rock- this is called differential erosion. The processes of erosion that occur are hydraulic action (sheer force of the water eroding the cliff-face) and abrasion (the sandpaper effect where rocks rub against the cliff-face). The more resistant bands are now left as headlands and the less resistant are bays. The less resistant bands erode at a faster rate will retreat backwards. As constructive waves hit the newly-formed bay they will lose their energy as they have entered a sheltered area and deposit materials to build up the beach
how is a wave-cut platform formed
on a concordant coastline destructive waves attack the cliff between the low and high tide mark, a wave cut notch is created which undercuts the cliff, weathering (freeze-thaw) weakens the top of the cliff, the over-hanging rock will collapse, the backwash carries the rubble towards the sea forming a wave cut platfomr, this process repeats and the cliff continues to retreat
formation of headlands, caves, arches, stacks and stumps
on a concordant coastline a large crack is opened up by hydraulic action, the crack grows into a cave by hydraulic action and abrasion, the cave becomes larger, the cave breaks through the headland forming a natural arch, the arch is eroded and collapses, this leaves a tall rock stack, the stack is eroded forming a stumps
what is coastal deposition
where the sea loses energy it drops the material it has been carrying. Deposition occurs when the swash is stronger than the backwash and is associated with constructive waves
how is a beach formed
beaches are a build-up of sand, pebbles and cobbles on a wave-cut platform and they are formed by the transportation and deposition of beach material
how is material sorted along the beach
by longshore drift
what is a berm
ridges of material deposited at high tide
what is a storm beach
a ridge of beach material deposited during storm conditions
how is material sorted along with the beach profile
by wave energy
spit- case study
Spurn Head, East Riding of Yorkshire
what is a spit
a narrow band of sand which extends out to sea
how is a spit formed
longshore drift moves sediment along the coast in the direction of the prevailing wind, a change in the coastlines shape causes the waves to lose their energy and deposit the sediment, the deposited material form a band of land called a spit that extends out to sea, as the end of the spit reaches deeper water it is more affected by strong winds and sea currents which curve the end of the spit into a hook, the area behind the spit is sheltered meaning the waters are calm so deposit all their fine material making salt marshes
what is a bar
a band of sand which has joined two headlands, this is formed when a spit has built up across a bay
example of a bar
Orford Ness, Suffolk
what type of coastline must a bar occur on
a discordant, as a bar is sand joining two headlands
vegetation at an embryo dune
sea couch
vegetation at a foredune/yellow dune
marram grass, lyme grass
vegetation at a grey dune
heather, legumes
vegetation at a shrub and woodland
brambles and wild roses
how are sand dunes formed
embryo dunes are formed around deposited obstacles such as seaweed, wood and rocks. When sand is transported up the beach it gets trapped in these obstacles, the dune will develop and become colonised by pioneer plant species which are able to survive the harsh conditions, as conditions become less harsh species begin to grow these dunes are more protected due to new dunes in front, rotting vegetation adds organic matter to the sand making it more fertile, sand dunes develop into shrubs then woodland, the ground is now nutrient-rich
where is Swanage
a seaside town in Dorset on the South coast of England
what is Swanage
a seaside town
erosional landforms in Swanage
headlands and bays (discordant), headlands, caves, arches, stacks and stumps (concordant)
depositional landforms in Swanage
Spit, beach, sand dunes
4 hard engineering strategies for coasts
gabions, sea walls, groynes, rock armour
what are gabions
rock-filled wire cages that support the base of the cliff and a buffer against the sea
gabions cost
5,000-10,000 per metre
gabions advantages
wire cages force the waves to break, increased sediment will slow down the waves
gabions disadvantages
will rust in 5-10 years, look ugly
what are groynes
wooden barriers built at right-angles to the beach to stop longshore drift, this creates a wider beach to absorb wave energy
advantages of groynes
traps sediment from longshore drift, wider beach will reduce wave energy so will have less impact on the cliffs
disadvantages of groynes
can starve areas from other coasts, problem has shifted rather than solved, ugly
groynes cost
£1500 each
what are sea walls
concrete walls. straight walls absorb the wave energy, curved walls reflect the wave energy back to the sea
sea walls cost
£5000-£10,000 per metre
sea walls advantages
the cliffs will be protected, curved reflects, straight absorbs
sea walls disadvantages
expensive, need to constantly be maintained
what is rock armour
large boulders piled on the beach absorb the wave energy so reduces the erosion of the beach pr cliffs
rock armour cost
£200,000 per 100 metres
rock armour advantages
rocks force the waves to break and they absorb the wave’s energy, the increased sediment will slow down the waves
rock armour disadvantages
rocks can be taken from other parts of the coastline or abroad, transport is expensive, the beach isn’t authentic
what are the four soft engineering strategies for coastal management
dune fencing, beach nourishment, dune regeneration, managed retreat
what is dune fencing
fences are constructed along the seaward side of existing dunes to encourage new dune formation
dune fencing cost
£400-£2000 per 100 metres
dune fencing advantages
little impact on nature controls access and protects the ecosystem
dune fencing disadvantages
unsightly, regular maintenance
what is dune regeneration
dunes are covered in matting and vegetation planted to make them more stable
dune regeneration cost
£200-£2000 per 100 metres
advantages of dune regeneration
sand dunes are effective buffers, creates habitats
disadvantages of dune regeneration
damaged by nature and people, time-consuming to plant marram grass
what is beach nourishment
sand is added to the beach to replace sand washed away
advantages of beach nourishment
increase of sediment on the beach so waves will lose energy before reaching the cliff
disadvantages of beach nourishment
needs constant maintenance, short term fix
beach nourishment cost
£500,000 per 100 metres
what is managed retreat
this doesn’t stop coastal erosion, it allows coastal areas to erode and flood naturally, this is usually areas of low- value land
cost of managed retreat
varies
advantages of managed retreat
create wetland habitats, maintain the natural environment, last forever
disadvantages of managed retreat
often unpopular as most of the land flooded is rural and attractive so popular for walking and bird watching etc.
case study for coastal management
Lyme Regis
where is Lyme Regis
South coast of England
how many phases of the Lyme Regis scheme
4 but only 3 went through
what was the main idea of the Lyme Regis scheme
to provide long term protection and reduce the threat of landslides and reduce conflict between property owners and fishermen
what coastal management did they use in the Lyme Regis scheme
emergency nailing, sea walls, beach nourishment, nailing, piling and drainage
how much did the Lyme Regis scheme cost
£43.4 million
positives of the Lyme Regis scheme
more visitors, the harbour is protected
negatives of the Lyme Regis scheme
traffic congestion has increased, spoilt the natural environment
