coastal landscapes Flashcards
Spot height
height of land above sea level
What type of rock forms most UK mountains
hard resistant rocks such as granite and slate form the most dramatic mountains in the Uk
Chunks and cracks in limestone
chunks- clints
cracks- grykes
Types of weathering
mechanical:
- freeze thaw
- salt mechanical
Biological:
- all the plant ones
Chemical:
- dissolving rocks due to the slight acidity of water
Uk relief
Scotland and higher elevation+ metamorphic -from the lower palaeozoic (metamorphic rock is impermeable so water sits on top)
Lowland areas more commonly further south are made of chalk and clay which are more porous letting water pass through
How are waves formed
the distance and waves has been blowing and the strength of the wind is called the fetch. the larger the fetch the bigger the wave. it travels in a circular motion towards the shore but as the seabed is less shallow the top speeds up causing the wave to break
Uk’s prevailing wind direction
south west (from the atlantic)- large fetch
Swash and Backwash
Swash- water traveling onto shore (if stronger constructive)
Backwash- water travelling offshore(if stronger destructive)
Constructive Vs destructive waves
c- not tall, less frequent (6-8 a minute) formed by storms often 100s of Kms away
d- 10-14 waves a minute, tall , made by strong winds, have a large fetch
Weathering Vs erosion
weathering is in situ whereas Erosion moves mass
mass movement
the downward movement or sliding of materials under the influence of gravity- can deliver loose materials to beaches to be eroded
Landslide
large blocks of rock moving along a shear surface often lubricated by water
Slumping
rapid mass movement involving huge sections of a cliff moving down-slope alongs a saturated curved segment(often due yo waves undercutting the cliff)
rockfall
fragments of rocks break off a cliff face due to freeze thaw weathering
mudflow
saturated soil moves down a slope
4 different coastal erosion processes
abrasion- throwing sediment at cliff face
hydraulic action- forcing high pressure water into small cracks which expand to create cave
Solution- carbonic acid of water dissolving cliff face
Attrition- rocks hitting each other to become smooth
4 erosion processes that occur in rivers
Traction- large pebbles rolling across river bed
saltation- pebbles pouncing as they are too heavy to be suspended
suspension- particles carried within the water
solution- dissolving particles
longshore drift
when waves approach a coast at an angle they move sediment diagonally across as the coast. because of gravity however the backwashcarries material back down the beach at right angles.
coastal deposition
when the force of a wave is refracted/lost the wave cannot carrie the sediment further hence it is deposited
Concordant vs discordant coastlines
concordant means the same type of rock is found all along the coast which can cause coves and lagoons to form
discordant coastlines are where the rocks alternate between hard and soft rock forming headlands and bays
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.
erosion chain
crack(hydraulic action) →cave(abrasion)→arch(widens) →stack→stump
ecosystems formed due to deposition
mud flats and marshes are found behind spits where there is little flow of water
definition of a beach
an accumulation of material transported and deposited by the sea ( can be made from- sand(often found in sheltered bays), pebbles(larger fetch, high energy waves making it steeper), coral, shell, stones)
deposition landforms
Spit- (e.g. Dawlish Warren spit Devon)- longshore drift- curve due to wind and have mudflat at the back
Bar- a spit formed from one headland to another(Slapton Sands- Devon)
Tombolo- a spit connecting an offshore island with the mainland (Isle of portland- Dorset)
Types of Dunes
embryo dunes
yellow dunes
grey dunes
mature dunes/ woodlands
embryo dunes
are quite fragile and are formed by saltation hitting and obstacle and are a host to salt resistant pioneer plants often having characteristics such as waxy leaves and plants being more scattered/lower-growing plants:
- sea rocket
- salt wort
yellow dunes
have been established for 30-40 years and are the first main ridge that reduce winds. Plants residing on yellow dunes are often salt intolerant and thrive being covered in soil e.g. maram grass
grey dunes
are host to more plants due to greater protection provided due to less salt water having a more grey soil with many planta coexisting with penial plants that last more than 2 years such as grey lichen and heather
mature dunes
take over 250 years to form and in shown by more of the organic matter and deciduous woodlands+shrubs hence stuff like hawthorne
what is a dune slack
the area between 2 dunes that host water and a moist habitat holding moisture loving plants such as rushes
windward sign vs leeward side
windward faces the beach as is les steep
stages of a shoreline management plan
1) no active intervention
2) hold the line- maintain existing defences
3) management realignment- allow the shore to move naturally but directing in certain areas (soft engineering)
4) advance the line- new defences (hard engineering)
soft engineering
work with the natural environment to preserve coast
hard engineering
artificial structures protecting the natural environment
soft engineering strategies
- beach nourishment
- beach reprofiling
- sand dune regeneration
beach nourishment
the movement of sand on a beach either material taken from bay to further down the coast (beach recharge) or sand is moved to an area less at risk of erosion (beach recycling).
Pros:
wider beaches attract tourists and reduce costs of maintaining costs of artificial defences while blending with the natural environment
cons:
needs constant maintenance at £300,00 per 100 metres quite expensive
beach reprofiling
reshapes existing beach to act as a buffer between land and sea
pros:
could save over £95 million over 26 years while looking natural and making residents feel safe
cons:
bulldozers restrict access to the beach and major reprofiling can be expensive and the steep crests it creates may deter tourists
sand dune regeneration
planting marram grass on sand dunes stabilises them and helps them develop which is good because they are a great buffer against the sea
pros:
they protect the land behind them and can be done relatively cheap (200-2000 per 100m) and helps develop and maintain habitats. And can create areas for recreation.
Cons:
- time consuming
- can be damaged by storms
hard engineering strategies
- sea walls
- groynes
- rock armour
- gabions
sea walls
concrete barrier that reflect the energy of the wave back into the ocean often placed at the bass of the cliffs
pros:
- sense of security
- last for many years
- do not stop movement of sediment and saves it for further down the beach
cons:
- unnatural and expensive (500-1000 perm metre
Groynes
stops longshore drift beach so is still present
pros:
- more tourists
- cheaper (150,000 for 200m)
cons:
- unnatural
- increases erosion else where as starving the beach further down
Rock armour
absorb the energy of the wave by forcing it to beak- protecting the cliff
pros:
- relatively cheap (200,000 per 100m)
- useful for fishing
cons:
- makes beach harder to access and less attractive
- expensive to import rocks- often from Norway and Sweden
Gabions
works about the same as rock armour
pro:
- cheap- £11,000 per 100 metre and quick to install as a quick fix solution
cons:
- unattractive
- due to rust only lasts 5-10 years
managed retreat
where you allow low lying land to be flooded by taking down the sea wall so defences can be improved further inland. It creates a natural marsh habitat and improves costal engineering (only viable in lower value land)
Medmerry managed retreat
located in west sussex it is mainly used for farming and caravan parks. It cost 28 million pounds as in 2013 it was decided that building a new sea wall was too expensive. A salt marsh was formed as a natural buffer to the sea and protected the surrounding farmlands while establishing new species such as choral grass and sea larven
pros of managed retreat
pros
- takes pressure away further down the course
- cheaper long term
- conserves/enhances local environment
cons of managed retreat
cons:
- relocation required (6 villages in north Norfolk destroyed)
- short term cost are high (28 million in west sussex vs 0.2 million for a new shingle beach
- large amounts of agricultural land lost
- bird numbers (of cranes and billerns) would initially decline
why might managed retreat not be feasible
- it only works in low lying land
- physical and human geography needs to be considered
- needs to be low value land
- unique/high biodiversity should be preserved
5 Ws Lyme regis
- located in south coast of Dorset in the south of england
- it is a popular tourist town renowned for its prehistoric coastline which is known for its fossils
- in summer population goes from 4000-15000
- it has the largest coastal landslide in europe
are landslides good for lyme regis
- most of the coast is formed by landslides
- brings out fossils increasing funding via tourism
- creates new species habitats and eco systems
- puts fortune seekers at risk due to the lack of precautions
- only really an issue when they damage property
- deposition on the beach acts as a shock absorber
lyme regis preservation phase 1
new sea wall in the 1990s
-2003-2004 1.4 million pound emergency
to stabilise the cliff main jobs were:
- stabilising rock armour
- drainage
-beach reprofiling
lyme regis phase 2
2005-2007
22 million pounds
- extend rock armour at the cobb
- build a new sea wall and promenade
- new sand and shingle beach to act as shack absorber (and for tourists)
phase 3
tried to stop landslip but costs outweighed pros
phase 4
2013-2014
19.5 million
- 390m new sea wall in front of the existing one
- extensive nailing piling and drainage to protect 450 homes
why did Lyme regis need protection
- prone to large storms
- quarrying in 19th century removed 90 ft of the cliff face
- pressure on the sands clays at the top of cliff cause to slide over limestone
- drainage systems cant cope
- Black Venn europe’s largest active landslide
-2008 - 1300ft of cliff slipped between lyme regis and charmouth exposing old landfill - 60 million already spent of it
success in lyme regis
- new beaches result in more visitor
- withstood recent storms
- secured 390m of coastline between church cliff and east cliff
- 480 homes saved
problems with Lyme regis
- perceived traffic and littering increase due to tourism
- construction noisy and ugly
- spoils natural landscape
- sea wall may interfere with ecosystem
- prevents fossils from being revealed decreasing the amount of tourists
