Coasts
- Created by: carlajokic
- Created on: 16-03-18 15:11
coasts intro & definitions
concordant - rock that runs parallel
discordant - bands of run running perpendicular
tide - alternate rise & fall of the sea, twice in lunar day due to the moon & sun
cliffed coast - when the transition from the land to sea is abrupt, low tide reveals a rocky platform
sandy coast - flat coastline, high tide conceals sand but not vegetation dunes
estuarine coast - extensive mud flats & salt marshes, gradual transition from land to sea `
salt marsh formation
1. algal stage - growth on mud, binds particles together
2. pioneer stage - roots stabilise mud, allow further mud accretion (growth)
3. establishment stage - carpet of vegetation established, marsh grows in height
4. stabilisation - the area of salt marsh is now rarely submerged
5. climax vegetation - developed soil profile & marsh is only submerged once or twice a year
things impacting salt marshes
weather sea level human action sediment supply
climate wave type tidal regime
dune formation
-coastal dunes begin with colonisation of embryo dunes (pioneer plants) which stabilise the sand
-roots help this, and plants reduce wind speeds which allows more sand to be deposited
-dead matter is also added which creates soil formation
-embryo dunes then change conditions from harsh & salty, to those that can accomodate other plants
-the more plants, the more sand that builds up & the more stable the dune becomes
embryo dunes --> fore dunes --> yellow dunes --> grey dune --> dune slack
coastal plants:
Halophytes - can tolerate salt water
Xerophytes - can tolerate dry conditions
coasts definitions cont.
psammosere: plant growth occuring on bare sand which creates a new environment
vegetation succession:
evolution of plant communities over time
at each stage the microclimate is altered meaning new plants can grow in the new condition
one plant is then replaced by another
when equlibrium is reached, there is a climax community (no further species)
if human inteference takes place a plagioclimax is reached instead
plagioclimax: human intervention stops the environment developing any further
high & low energy coasts
LOW (east anglian coast)
-constructive waves -lowland coasts
-deposition & transport -beaches & spits
HIGH (atlantic coast, scotland)
-destructive waves -cliffs, rocky landscapes, wave cut platforms
-erosion & transport. -stormy conditions & long fetch
coastal plains:
low lying areas close to the coast, low energy environments
contain marshes & wetlands as they are flat and do not drain
form from sea level change or deposition of sediment
the coast
backshore - area between high water mark and landward limit of marine activity. changes normally take place during storms
foreshore - between high & low water mark and an important zone for marine activity
nearshore - LSD occurs, between the low water mark & where the waves cease to effect the land beneath them
offshore - beyond point of waves impacting land beneath, sediment is deposited
littoral zone: wider coastal zone including adjacent land areas & shallow parts of the sea just offshore
the coast
backshore - area between high water mark and landward limit of marine activity. changes normally take place during storms
foreshore - between high & low water mark and an important zone for marine activity
nearshore - LSD occurs, between the low water mark & where the waves cease to effect the land beneath them
offshore - beyond point of waves impacting land beneath, sediment is deposited
littoral zone: wider coastal zone including adjacent land areas & shallow parts of the sea just offshore
sea level change
change happens daily due to
high/low tides atmospheric pressure winds wave height
long term change as a result of global warming and isostatic readjustment
EUSTATIC is GLOBAL change
ISOSTATIC is LOCAL change
accretion: when sediment is deposited and builds up
post glacial isostatic readjustment: uplift of land following the removal of weight (melting ice sheets)
SUBMERGENT features occur when sea level rises
EMERGENT features occur when sea level falls
sediment cells
along the coast, erosion, transportation & deposition operate in a linked system
sediment cells have sources, transfers and sinks
each cell can be regarded as a closed system
sediment budget = amount of sediment available within a cell
negative feedback: maintaining balance within a system
positive feedback: change in the balance until a new equilibrium is reached e.g. after a storm
sub-aerial processes
mass movement is the downward movement of rock or soil e.g. landslieds & rockfall
frost shattering - freeze thaw, water trapped between rock freezes, expands, and forces the rock to shatter
oxidation - when rocks are exposed to air or water, rusting occurs
solution - dissolving of minerals in water
thermal expansion - rocks expand when when heated and contract when cool, when this process occurs quickly it causes stress which causes the rock to break
acid rain - lower Ph levels in rain can cause some rocks to corrode
coastal landforms
landforms of erosion
headlands & bays
wave cut notches & platforms
cliffs
blow holes
arches, coves, stacks & stumps
landforms of deposition
beaches
recurved & double spits
offshore bars
barrier beaches
beaches
storm beach --> berm --> cusp --> ripple
storm beach: noticeable, semi-permanent ridges found at high tide level
berm: small ridges built up by successive levels of tides & storms
cusps: semi-circular embayments found in the shingle
ripples: formed by waves and tidal currents, ripples along the sand
SWASH ALIGNED BEACH
sheltered, low energy environment, bars are formed, bay beaches e.g. Lulworth cove
DRIFT ALIGNED BEACH
develop when waves approach coast at an angle, backwash at a right angle so that sand drifts along the beach- creates spits e.g. Spurn head, Yorkshire
coastal flooding
caused by storm surges, sea level rise & local factors (e.g. land relief, land use)
LECZ: low elevation coastal zone
adaptation: changing to suit the environment
mitigation: putting in protective measures
storm surges: caused by a drop in atmospheric pressure which allows the sea to swell and create waves, which travel towards the coast and create storm surges
coastal management
hard engineering
groynes
revetments
rip rap
rock armour
sea walls
soft engineering
beach replenishment
cliff drainage & cliff regrading
marsh creation
dune stabilisation
managing the coast
holistic management protecting the coast as a whole instead of segregating specific areas
ICZM: integrated coastal zone management
manages the coast as one, aims to establish sustainable techniques & resolve environmental challenges
Options include:
hold the line advance the line managed retreat do nothing approach
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