uk's physical & coastal landscape Flashcards
what causes waves
wind blows over the waves sources - friction w/ the wind
why are some waves stronger than others
- strength of the wind
- how long the wind has travelled for
- distance travelled > fetch
what are the two types of waves
- constructive
- destructive
how does the wave type affect the coastline?
- constructive waves build up a beach > flat, wide, beaches
- destructive waves take away > steeper beaches
characteristics of destructive waves
- backwash is stronger than swash
- takes away material
- short wavelength
- high frequency
- longer wave height
- circular orbit
- high energy waves - found in exposed areas
characteristics of constructive waves
- swash is stronger than backwash
- deposits material
- longer wavelength
- shorter frequency
- short wave height
- eliptical orbit
- low energy waves found in sheltered bays + spits
what are the 3 coastal processes?
erosion, transportation, deposition
what are the 4 types of erosion
abrasion, hydraulic action, attrition, solution.
what is abrasion
the waves throw pebbles and rocks against the cliffs, wearing them away
what is hydraulic action
the force of waves traps air in cracks. this processes is repeated over time until the air pressure breaks off pieces of rock
what is attrition
the pebbles and rocks are worn away as they crash against each other
what is solution (erosion)
chemicals in the water break down the rock the rock
what are the 4 types of transportation
solution, suspension, saltation. traction
what is solution (transportation)
material dissolved in the water
what is suspension
material that is held in the water
what is saltation
material is bounced along the seabed
what is traction
heaviest material is rolled along the sea bed
longshore drift
Waves approach the coast at an angle because of the direction of prevailing wind. The swash will carry the material towards the beach at an angle. The backwash then flows back to the sea, down the slope of the beach. The process repeats itself along the coast in the zigzag movement.
deposition
When the river loses energy, it drops any of the material it has been carrying
what are the factors leading to deposition
- waves starting to slow down and lose energy
- shallow water
- sheltered areas, e.g. bays
- little or no wind
weathering
breaking down of rock in situ
types of weathering
mechanical and chemical
freeze thaw weathering
Water enters cracks in the rock. When temperatures drop, the water freezes and expands causing the crack to widen. The ice melts and water makes its way deeper into the cracks. The process repeats itself until the rock splits entirely.
carbonation
Rainwater and seawater can be a weak acid. If a coastline is made up of rocks such as limestone or chalk, over time they can become dissolved by the acid in the water.
mass movement
the downward movement of rock or soil due to gravity caused by the weathering of the rock and heavy rainfall.
sliding
A slide occurs when a portion of the soil or rock along a steep slope suddenly gives away and moves downhill, usually aided by heavy rainfall. Sliding mass movement occurs on slopes weakened by weathering such as landslides, rockslides, and mudslides.
slumping
In slumping, the soil or rock debris moves downhill along a concave or curved plane in a rotational manner. The upper part of the slump moves vertically downward, but the lower part moves outward, forming what is known as a toe at the bottom of the slump area.
rockfalls
A rockfall is the fastest moving type of mass movement where rocks break away from the cliff face and fall, bounce or roll downslope. Rock falls are typical in areas that experience freeze-thaw mechanical weathering, which causes chunks of rock to lose contact with the cliff face and fall
discordant coastline
bands of differing rock types run perpendicular to the coast
concordant coastline
bands of differing rock types run parallel to the coast
formation of bays and headlands
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
formation of wave cut platform
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
what are the two types of coastal management
- soft - working with nature
- hard engineering - working against nature
what is soft engineering
schemes that work with natural processes to reduce the effects of flooding and erosion
what is hard engineering
man made structures built to control the flow of the sea to reduce flooding and erosion
advantages and disadvantages of soft engineering
often cheaper as you are working with nature
can be less effective
advantages and disadvantages of hard engineering
often expensive
can be more effective
description of sea wall
hard engineering - a barrier between waves and land
- usually made out of concrete, modern versions have a curved face they reflect and absorb wave energy back out to sea and so reduce the waves erosive power.
advantages and disadvantages of sea wall
advantages:
- effective
- prevents erosion
- acts as a barrier
- can act as a promenade/cycle path
- can last for many years
disadvantages:
- expensive to build (£5000/m)
- strong backwash erodes beach
- expensive to maintain
- can restrict access to the beach
assessment of sea walls
good for densely populated areas, will have to be built higher due to rising sea levels
description of rock armour
hard engineering - large rocks creating a physical barrier
- as water enters the gap pressure is released so the waves have less power
advantages and disadvantages of rock armour
advantages:
- cheaper than a sea wall (£1000 - 3000/m)
- gaps disperse energy
- fairly cheap
- built quickly
disadvantages:
- unattractive and restricts access to the beach
- expensive to import
- can need maintenance
assessment of rock armour
appropriate for towns + densely populated areas
description of gabions
hard engineering - steel wire mesh cages filled w/ pebbles/rocks
- placed against cliffs so that the waves enter the cages which absorbs energy reducing erosion
advantages and disadvantages of gabions
advantages:
- low cost + low tech (£110/m)
- accessible for diff. levels of economic development
- reduces erosion
- quick + easy to build
- vegetation can grow over them - looks natural
- can last 20-25 years
disadvantages:
- if damaged, dangerous for bird life + for humans
- ugly to look at
- cages can corrode so maintenance needed
assessment of gabions
good options for coastal residents
description of groynes
hard engineering -structures (wooden or stone) built at right angles to the beach
- reduces LSD so beach grows larger
advantages and disadvantages of groynes
advantages:
- creates wider beaches
- encourages tourism
- fairly cheap (£5000 each)
- can last up to 40 years
disadvantages:
- prevents material from being transported down the coast and so starve these areas of sediment which increases erosion in areas
- hazard to windsurfers
assessment of groynes
good for touristic areas affected by LSD
description of beach nourishment
SE - replacing or adding of sand or pebbles on a beach
- a beach is the best form of natural defence as it absorbs wave energy
advantages and disadvantages of beach nourishments
advantages:
- creates wider beaches
- stops erosion
- natural
- blends in w/ environment
disadvantages:
- can kill sponges and corals in sea bed when taking materials
- costs are high £2 mil
- has to be repeated
storms can remove material
assessment of beach nourishments
good for touristic areas
description of beach reprofiling
SE - artificially reshaping of a beach using existing beach material`
advantages and disadvantages of beach reprofiling
advantages:
- costs spread over time
- looks relatively natural
disadvantages:
- has to be done twice a year
- causes disruption
- cost can be 200k/year
- bulldozers are noisy
- beach can look unnatural
- beach habitats can be disrupted
assessment of beach reprofiling
good for touristic areas affected by LSD
- work with groynes
description of dune regeneration
SE - artificial creation of new sand dunes or regeneration of existing dunes
- plant fences to encourage sand to build up behind them and marram grass to stabilise the dunes
- sand dunes act as a barrier and absorb wave energy
advantages and disadvantages of dune regeneration
advantages:
- effective protection from the sea
- low cost
- works w/ natural environment
disadvantages:
- restrict access to the beach
- involves removal of sea-buck thorn to be effective - more expensive
assessment of dune regeneration
good for areas with low population density
description of managed retreat
SE - area of the coast is allowed to erode and flood naturally
- usually in area considered to be of low value
- encourages the development of salt marshes which store water in times of flood
advantages and disadvantages of managed retreat
advantages:
- reduces pressure of flooding further along the coast
- very cheap
- conserves natural coastal habitats
disadvantages:
- land can be lost
- relocation costs can be high
- locals feel ‘let down’ and communities can be broken up
assessment of managed retreat
good for areas w/ low value land.
what is a drainage basin
the area of land drained by a river and its tributaries with a boundary known as the watershed
what are the three stages of a river
upper, middle and lower course
what is the river like in the upper course
- location of teh source
- river volume is small and shallow
- v shaped
what river features are found in the upper course
- v-shaped valleys
- interlocking spurs
- waterfalls
- rapids
what is the river like in the middle course
- river is increasing in colume
- it has become wider and deeper
- the relief of the land around it has reduced
what river features are found in the middle course
- meanders
- ox-bow lakes
what is the river like in the lower course
- the river has reached its highest volume as it nears the mouth
- land is flat as the river is close to sea level
- river channel is at its widest and deepest
what river feautures are found in the lower course
- levees
- estuaries
hydraulic action
water under high pressure cause cracks to force apart and widen in any rocks along the bank and river
abrasion
the rock carried by the river scrape anf bang against the sides of the river and so wear away the channel gradually
attrition
rocks and pebbles hit each other so they then become rounder and smaller
solution
chemicals or acids dissolved in the river channel can dissolve rocks
traction
large, heavy pebbles are rolled along the river bed. This is most common near the source of a river, as here the
load is larger.
saltation
pebbles are bounced along the river bed, most commonly near the source
suspension
lighter sediment is suspended (carried) within the water, most commonly near the
mouth of the river
solution
the transport of dissolved chemicals. This varies along the river depending on the presence of soluble rocks.
what factors lead to deposition in rivers:
- shallow water
- at the end of the river’s journey, at the river’s mouth
- when the volume of the water decreases
watershed
the area of high land forming the edge of a river basin
source
where a river begins
mouth
where a river meets the sea
confluence
a small river or stream that joins a larger riverthe point at which two rivers meet
tributary
a small river or stream that joins a larger river
channel
where the river flows
what is the long profile of a river
a line representing the river from its source (where it starts) to its mouth (where it meets the sea). It shows how the river changes over its course.
what is the cross profile of a river
a cross-section of a river’s channel and valley
at a certain point along the river’s course.
how are waterfalls formed
- The soft rock is eroded quicker than the hard rock and this creates a step.
As erosion continues, the hard rock is undercut forming an overhang. - Abrasion and hydraulic action erode to create a plunge pool
- Over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses. This process continues and the waterfall retreats upstream.
- A steep-sided valley is left where the waterfall once was. This is called a
gorge
.
how are interlocking spurs formed
In the upper course there is more
vertical erosion. The river cuts down into the valley. If there are areas of hard rock which are harder to erode, the river will bend around it. This creates interlocking spurs of land which link together like the teeth of a zip.
how are meanders formed
- As a river goes around a bend, most of the water is pushed towards the outside. This causes increased speed and therefore increased erosion (through hydraulic action and abrasion).
- The lateral erosion on the outside bend causes undercutting of the bank to form a
river cliff. - Water on the inner bend is slower, causing the water to slow down and deposit the eroded material, creating a gentle slope of sand and shingle.
- The build-up of deposited sediment is known as a slip-off slope (or sometimes river beach).
how are oxbow lakes formed
Due to erosion on the outside of a bend and deposition on the inside, the shape of a meander will change over a period of time. Erosion narrows the neck of the land within the meander and as the process continues, the meanders move closer together. When there is a very high discharge (usually during a flood), the river cuts across the neck, taking a new, straighter and shorter route. Deposition will occur to cut off the original meander, leaving a horseshoe-shaped oxbow lake.
what is a floodplain
an area of land which is covered in water when a river bursts its banks.
what is the makeup of floodplains
Floodplains are often agricultural land, as the area is very fertile because it’s made up of
alluvium (deposited silt from a river flood). The floodplain is often a wide, flat area caused by meanders shifting along the valley.
how are levees formed
- Levees occur in the lower course of a river when there is an increase in the volume of water flowing downstream and flooding occurs.
- Sediment that has been eroded further upstream is transported downstream.
When the river floods, the sediment spreads out across the floodplain.
3.When a flood occurs, the river loses energy. The largest material is deposited first on the sides of the river banks and smaller material further away.
4.After many floods, the sediment builds up to increase the height of the river banks, meaning that the channel can carry more water (a greater discharge) and flooding is less likely to occur in the future.
what is an estuary
where the river meets the sea, the river here is tidal and when the sea retreats the volume of the water in the estuary is reduced. When there is less water, the river deposits silt to form
mudflats
which are an important habitat for wildlife.
