coasts Flashcards
characteristics of constructive waves
-swash: strong
-backwash: weak
-beach slope: gently sloping
-wave strength: low
-wave height: under 1m
-wave frequency: low
characteristics of deconstructive waves
-swash: weak
-backwash: strong
-beach slope: steep slope
-wave strength: strong
-wave height: over 1m
-wave frequency: high
transportation
load is transported by the water, the large and heavier the load the greater the velocity needed to transport it
longshore drift
transport if sediment along a stretch of coastline
deposition
when material that is being transported is dropped by constructive waves
corrosion or solution
chemical reaction- acidity of water dissolves the rock
why are some coastlines more vulnerable to erosion than other
rock type- softer rock is eroded faster than hard rock
why do cliffs form
processes of weathering and erosion with the effect of gravity
what are the features of a cliff
-steep slope
-usually a rock face
-nearly vertical, may be overhanging
wave cut platform
as erosion continues, the wave cut notch becomes deeper and eventually the material above the notch will collapse. If this is a cliff line, then the cliff will retreat inland. This will leave behind a platform of hard rock that was once part of a cliff, but is only exposed at low tide
spit
a beach of sand or shingle linked at one end of land. Found where wave energy is reduced, caused by longshore drift
beach
accumilation of material deposited between low spring tides at high frequency and the highest point reached by storms at high spring tides
features of a beach
backshore
foreshore
off-shore
tombolos def
spits connecting an island to the mainland
bars def
ridges of sand or shingle acrss the entrance of a bay or river mouth
headlands def
areas of more resistant rock jutting out from the coast into the sea
bay def
a broad coastal inlet, often curved and with a beach, between two headlands
stack def
an isolated column of rock at the end of a headland formed after a stack has collapsed
arch def
a rock bridge formed at a headland that has been partly broken through by the sea
cave def
a hollow at the base of a cliff which has been eroded by rocks
what will happen if the coastline alternates between soft and hard rock
differntial erosion will take place resulting in a disconcordant coastline
traction
Large rocks and boulders are rolled along the sea bed by strong waves, usually happens during storms
saltation
Small stones and pebbles are bounced along the sea bed, moving them along the coast
suspension
Sand and silt are carried by water, making the water look murky
coral reef def
formed through the build-up and compression of the skeletons of lime secreting, marine animals called polyps
types of coral reef
barrier
fringe
atoll
condintions for coral reefs to form
temp has to be 22-25 degrees
depth of water had to be less than 25m
water has be clear for lots of sunlight
low salinaty
low sediment
high energy wave action for freshly oxygenated water
exposure to air
where are mangerove swamps found
along coastliens between 30 north and 30 south of the equator.
magrove swamps def
tidal swamps that are dominated by mangroves (shrubs or small trees with numerous tangled roots that grow above ground
adaptattions of mangroves
low oxygen conditions
low salt intake in tree
low water loss
aerial roots to absorb nutrients
the seeds float
roles of mangroves
coastal protection
breeding ground
source of food, medicine and raw materials
managing impacts of coastal erosion
sea walls
revetment
gabions
rock armour
groynes
beach replenishment
assessments on how to defend a coast:
cost-benefit analysis
environmental impact assements
shoreline management plan
wherer do salt marshes form
sheltered bays and estuaries in the protected area behind a spit or tombolo and in brackish water
Holderness coast
-long fetch NE wind, deconstructive waves
-fastest eroding coastline in the world, 2m every year
Holderness coast impacts
-economic impacts for local people, cannot sell their homes since it is too dangerous to live in
-communities being lost
-Bridgeton hotel- lost their jobs due to it collapsing
-farmers have lost areas of their farms lost money
-tourism, golf course
-gas terminal, 25% of the UKs gas supply, 25m from cliff edge, Easington, may need to be moved inland at a huge cost
bar
a bar of sand, can also form offshre due to the action of breaking waves from a beach
lagoon
small body of water is cut off from the sea
may form behind a bar or tombolo
do not last forever and may fill with sediment and form new land
sand dunes formation
-wind blown sand is deposited against an obstruction, such as pebble or driftwood
-as more sad particles are caught, the dunes grow in size forming rows bat right angles to the prevailing wind
-in a proces sof recession, vegetation will eventually colonise and fix the rdiges of the dunes
what do pioneer species have to cope with in sand dunes
-salinity
-lack of moisture as sand drains quickly (highly permaeble)
-wind
-temporary submergence by wind- blown sand
-rising sea levels
what factors influence the distrubution of coral reefs
-temperature
-light
-water
-salinity, 32-42% salt water
characteristics of mangroves
-trees that live on the coastline
-sit in water 0.5-2.5 metres high
- range in small shrubs to trees over 60m high
-numerous tangled roots
-need high levels of humidity (75%-80%)
-need 1500mm to 3000mm of rainfall
-ideal temp of 27 degrees
-filtration system to keep salt out
coastal opportunities
-homes
-shopes
-hotels
-schools
-roads
-restaurants
-nature reserves
-swimming and sports
-industry
-fishing and aquaculture
-tourism
-agriculture
-ports and harbours
coastal hazards
-urbanization and transport
-industry
-agirculture
-fisheries and aquaculture
-tourism and recreation
natural coastal hazard
storm surges and storms tides
beach replenishment
-dumping sand and shingle back into a beach to replace eroded material
-AD: beaches abosrb wave energy, widens beach front
-DD: has to be repeated regulary, expensive, impact sediment transportation
replacing vegetation
-helps stabalise beaches or sand dunes
-reduces wind erosion
-cheap
-hard to protect larger areas of coastline
cliff re-grading
-the angle of the cliff is reduced to reduce mass movement
-prevents sudden loss of large sections of cliff
-doesnt stop cliff erosion
managed retreat
-existing coastal defences are abandoned allowing the sea to flood until it reaches higher land or a new line of defences
-sea wall
-a wall, usually concreate, and curved outwards ti deflect the power of the waves
-most effective at preventing erosion and flooding
-very expensive to build and maintain
groynes
-wood, rock or steel piling buildt at right angles to the shore, which traps beach materal being moved by longshore drift
-slows down beach erosion
-starves other beaches of sand
-need maintanence to prevent wood rot
rip-rap
-large boulders are piled up to protect a stretch of coasts
-cheaper method of construction
-absorbs wave energy
-protects cliffs behind
- boulders can be eroded or dislodged during heavy storms
gabions
wire cages filled with stone, concrete, sand ect
-cheapest form of coastal defence
-cages absorb wave energy
-wire cages can break and they need to be securley tied down
revetments
-slopping wooden or concrete fence with an open plank structure
-works to break the forces of the waves
-traps material behind them
-not effective in stormy condintions
-can make beach inaccessible for people
