coasts end of yr Flashcards
(25 cards)
Constructive wave
shallow beach
swash stronger than backwash
more material is moved up the beach
elliptical cycle
Destructive wave
weak swash strong backwash
more material is moved back into the beach
circular motion
tall waves high frequency
Processes of erosion:
hydraulic action: when the force of the water gets in the cracks of rocks and breaks them
attrition: when rocks hit other rocks and make them smaller and smoother
abrasion: when the waves pick up smaller pebbles and hurl them at the cliff
corrosion: the dissolving of rocks due to chemicals in the water
weathering: the breakdown of rocks which is caused by freeze-thaw and the growth of salt crystals, by acid rain and by the growth of plant roots
erosion: the wearing away of rocks by wind and rain
mass-movement: the removal of cliff-face material under the influence of gravity in the form of rock falls, slumping and landslides
longshore drift
Longshore drift is the process where material is transferred along the coastline in the direction of the wind. The prevailing wind causes the swash to go at an angle and the backwash comes back down straight in a zigzag manner. This is how sediment is moved.
Formation of a wave-cut platform
▶ during high-tide processes of erosion such as hydraulic action this causes the base of a cliff to erode which causes a wave-cut notch to form
▶ the notch then grows and over time it gets bigger meaning it cannot support the cliff above and then collapses
▶ this is a repeating process and leaves behind a wave-cut platform
Depositional landforms
are produced on coastlines where mud, sand and shingle accumulate faster than they can be moved away by the waves
this usually happens along stretches of coastline dominated by constructive waves (where the swash coming onto the beach is stronger than the backwash)
fetch
the distance a wave travels between two coastlines
Processes of transportation:
▶ traction: when big rocks roll along the seabed
▶ saltation: when rocks are being picked up by the waves and they bounce along the seabed
▶ suspension: where the material floats in the water
▶ solution: when the material dissolves in the water due to corrosive processes
Formation of headlands and bays:
On a discordant coast, there are alternative bands of hard rock and soft rock
▶ soft rock erodes faster, usually made up of clay, and leaves behind a bay
▶ hard rock more resistant like limestone leaving behind a headland
Cave, arch, stack, stump
On a headland, a large crack is formed, the crack grows into a cave by hydraulic action and abrasion. The cave becomes larger and breaks through the headland forming an arch. The arch is eroded and collapses leaving a tall rock stack. The stack is eroded forming a stump.
Beach:
beaches are made of sand and shingle which come from a number of sources
▶ most of it is material that has been eroded elsewhere and is being moved along the coast by longshore drift.
▶ some comes from offshore as a result of waves picking it up from the sea bed and rolling it towards the land
▶ from the opposite direction, rivers feed mud and silt into the coastal zone via their estuaries. The deposition of this river material then takes place at the head of sheltered bays
formation of a spit
spits are long narrow beaches of sand or shingle that are attached to the land at one end
▶ longshore drift moves materials along the beach. when it reaches a shallow slacks, the waves have less energy and they deposit some of the load on the sea bed
▶ this material builds up over time and rise above the sea water
Tombolo:
tombolos are spits that have continued to grow seawards until they reach and join an island
▶ the formation of a tombolo is the result of not only longshore drift but also probably of constructive waves and sand being rolled towards the shore
Bar:
▶ if a spit develops in a bay, it may build across it and link the two headlands to form a bar
▶ formation of a bar is only possible if there is a gently sloping beach and no sizeable river is entering the bay
▶ in this way bars can straighten out the coast and any water on the landward side is trapped to form a lagoon
Factors affecting the coastline
- geology: if it is concordant or discordant as one is most likely to form cliffs and the other will form headlands and bays
rock type; hard or soft rock - sea level changes – low lying coasts will be drowned by rising sea levels
Soft Engineering
Strategy 1: beach nourishment and reprofiling
cheap
natural appearance
natural defence (absorbs wave energy) then
tourism
off-shore dredging: coral damage
large storms increase costs
constant maintenance
beach closure lose money
soft wngingerring 2
Strategy 2: dune regeneration (plant grass)
cheap
natural barrier quite a lot of beauty
ecological benefits providing habitats for species
time consuming & too much space
easily damaged by storms fragile, delicate
need to be carefully managed
soft engineering 3
Strategy 3: managed retreat
sustainable
natural buffer
saltmarsh ecosystem
increased tourism
can be expensive
loss of agricultural land
impact on locals
ecosystem loss
what is hard engineering
Hard engineering is using concrete structures to defend against natural erosionHard engineering is using concrete structures to defend against natural erosion
sea walls
Sea Walls
expensive
unnatural
high maintenance
prevents erosion by providing a barrier which reflects wave energy
provides a pathway (promenade) so tourists can walk along the beach (attracts tourists)
groynes
expensive (£20,000 per groyne)
made of wood, breaks easily
deprives another area (down drift) of beach material
stops longshore drift, prevents material being taken away
helps beaches decrease damage of waves
Gabions
cheap
looks ugly
merges into landscape
supports a cliff and provides a buffer against erosion
dissipates the waves (slows them down)
rock armour
imported so expensive
takes up space
doesn’t fit in well with local geology
more natural
slows down waves
can also protect other hard engineering
