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Role of
deposition in
formation of
landforms
- Deposition
- Occurs when water not
enough energy so drops
particles
- In areas where swash brings
material up beach but backwash not
enough energy to bring down again
- Occurs when water not
enough energy so drops
particles
- Rowen spit
- Spit doesn't form
from change in
direction of coast
- Instead, LSD deflected by tidal
flow and into deeper water
- Waves don't break -> no swash/backwash
- Material is deposited
- Material is deposited
- Waves don't break -> no swash/backwash
- Spit increased in size by LSD, waves and wind
move sediment along coast and big swash, small
backwash mean sediment is deposited, increasing
the length
- Curved end
- SW winds and wave refraction
- destructive energy dissipates as waves refract
into bay allowing constructive waves to build up
curved end
- destructive energy dissipates as waves refract
into bay allowing constructive waves to build up
curved end
- SW winds and wave refraction
- Biggest particles deposited out of 3
landforms as subjected to highest
wave energy, so pebbles on spit as
well as sand
- Spit doesn't form
from change in
direction of coast
- Sand dunes
- Situated on Rowen spit and Barmouth beach
- Develop where strong offshore winds and
a low gradient near shore slope
- Sand is deposited in this environment and starts to
build up
- Sand is deposited in this environment and starts to
build up
- Marram grass establishes and roots hold sand in
place, allowing consolidation and growth
- Forms a more effective wind break starting a positive
feedback loop: sand is deposited so dunes get higher, which
means more sand is trapped and dunes get higher and so on
- Forms a more effective wind break starting a positive
feedback loop: sand is deposited so dunes get higher, which
means more sand is trapped and dunes get higher and so on
- Human processes can encourage
deposition and so, growth of sand dunes
- 1972 causeway built across Bar Bach channel
- Caused a large amount of deposition behind the
causeway, facilitating the development of sand dunes
- Caused a large amount of deposition behind the
causeway, facilitating the development of sand dunes
- 1972 causeway built across Bar Bach channel
- Sand dunes are effective form of natural coastal management,
during high spring tide they act as natural wall, protecting what is
behind them
- Situated on Rowen spit and Barmouth beach
- Salt marsh
- Area behind Rowen spit sheltered, only open
to tidal flow and some refracted waves
- They carry very fine grained
sediments from river estuary, clay
& silt
- Particles flocculate in salt water to form larger
particles, which are mainly deposited around
high tide, as the flow velocities are low
- Particles flocculate in salt water to form larger
particles, which are mainly deposited around
high tide, as the flow velocities are low
- They carry very fine grained
sediments from river estuary, clay
& silt
- The rate of deposition is highest on mud flats, where flow
velocities are lowest and the low energy means the material is
more likely to be deposited
- From high tide mark, deposition extends seawards,
which expands the mud flats
- From high tide mark, deposition extends seawards,
which expands the mud flats
- Salt marsh builds up higher, frequency of tidal flooding falls
- Allowing vegetation to colonise. The plants (eg spartina) trap
sediment, like marram grass, as energy from water is reduced
- and so more sediment is deposited
- Most vegetation is found in the lowest energy
environment. (Areas only flooded in a high
spring tide)
- Plants which can withstand saline conditions, allow more
deposition as they can withstand tide change
- Most vegetation is found in the lowest energy
environment. (Areas only flooded in a high
spring tide)
- Allowing vegetation to colonise. The plants (eg spartina) trap
sediment, like marram grass, as energy from water is reduced
- and so more sediment is deposited
- Area behind Rowen spit sheltered, only open
to tidal flow and some refracted waves
- Conclusion
- These landforms controlled by the energy the wind and waves have
and so, governed by deposition
- Enhanced greenhouse effect (312 ppm 1960s
to over 400ppm today)
- Results in rising global average temps which means eustatic sea level rise,
due to melting of land based ice and thermal expansion of sea water
- Deposition will change with rising sea levels
- Dramatic sea level rise could mean spit submerged, destroyed
sand dunes and inundated salt marsh
- Gentle sea level rise, effects less severe, salt marsh
and sand dunes could grow and rise with sea level
- Dramatic sea level rise could mean spit submerged, destroyed
sand dunes and inundated salt marsh
- Deposition will change with rising sea levels
- Results in rising global average temps which means eustatic sea level rise,
due to melting of land based ice and thermal expansion of sea water
- These landforms controlled by the energy the wind and waves have
and so, governed by deposition
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