coasts Flashcards
sediment cells
Coasts can be split into sections called sediment cells which are often bordered by prominent headlands.
how many sediment cells are in the uk?
11
coastal inputs
marine:
-waves
Atmosphere:
-wind
humans:
-pollution
coastal outputs
-currents
-riptides
-evaporation
coastal transfers
-longshore drift
-erosion
hydraulic action
water crashing against the coastline causing material to be dislodged and carried away by the sea.
corrosion
a process of chemical erosion.
attrition
rocks hit against each other
abrasion
rocks carried by the sea are picked up by strong waves and thrown against the coastline.
coastal stores
-beaches
-dunes
-spits
rivers as a sediment source
-account for majority of sediment
sediment sources
-rivers
-cliff erosion
-wind
sediment budget
the balance of inputs and outputs in the coastal system
littoral zone
area of land between the cliff’s or dunes on the coast and the
sea.
short term factors impacting the littoral zone
-tides
-storm surges
long term factors impacting the littoral zone
-changes in sea level
-human intervention
wave formation
• Wind blows across the sea surface.
• Energy from the wind is transferred to the water.
• The water moves in a circular motion.
• as the water gets more shallow waves grow in height
factors effecting wave energy
-strength of wind
-duration of wind
constructive wave characteristics
-long wavelength
-6-9 per min
-strong swash, weak backwash
destructive wave characteristics
-short wavelength
-25 per min
-weak swash, strong backwash
spring tide
-highest high tide, lowest low tide
-occur when the sun and the moon are in
alignment, so their gravitational forces work with each other
neap tide
-lowest high tide and the highest low tides -when the sun and the moon are
perpendicular to each other, so their gravitational forces work against each other
rip currents
powerful underwater currents occurring in areas close to the shoreline on some
beaches
wave refraction
waves bend as they hit the coastline at an angle, causing uneven distribution of energy and influence coastal shaping through erosion and deposition.
wave quarrying
This is when breaking waves hit the cliff face to directly pull away rocks from a cliff face
factors effecting erosion
-Waves
-Beach Size and Presence
- Rock type
longshore drift
-Waves hit the beach at an angle determined by the direction of the prevailing wind
-The waves push sediment up the beach in the swash
-The wave then carries sediment back down the beach in the backwash
-This moves sediment along the beach over time
mechanical weathering
freeze thaw:
-Water enters cracks in rocks and then the water freezes and expands in volume causing cracks to develop
Salt Crystallisation:
-As seawater evaporates, salt is left behind. Salt crystals will grow over time, forcing the cracks to widen.
chemical weathering
carbonation:
-rainwater is slightly acidic
Oxidation:
-When minerals become exposed to the air they become oxidised which
increases volume causing the rock to crack.
biological weathering
Plant Roots:
- Roots of plants growing into the cracks of rocks, which exerts pressure,
eventually split the rocks
Birds:
-Some birds such as Puffins dig burrows into cliffs weakening them
soil creep
The movement of soil particles downhill.
mass movement
movement of material down a slope under the influence of gravity
mudflow
An increase in the water content of soil can reduce friction, leading to earth and mud to
flow over underlying bedrock.
landslide
when a
block of intact rock moves down the cliff face very quickly
slump
Contrary to a landslide, the slope is curved, the land collapses under its
own weigh
Wave-cut Notch
-Erosion is concentrated around the high-tide line creating a wave-cut notch
- As the notch becomes deeper the cliff face becomes unstable and collapses
- This leaves behind a platform of the unaffected cliff base
swash aligned beach
Waves break parallele to the coast
drift aligned beach
Waves approach at angle, so sediment travels along the beach, which may form
a spit.
spit
-Occur when the coast suddenly changes direction
-Longshore drift continues to deposit material in line with the coast but at sea
-Changes in wind direction lead to a curved end ( spit)
-Area behind the spit is mudflats and saltmarshes
barrier beach/ bar
-Occurs when a beach or spit extends across a bay to join to headlands
-Traps water forming a lagoon which is separated from the sea
tombolo
-Bar that connects the mainland to an offshore island
offshore bar
-An offshore region where sand is deposited , as the waves don’t have enough energy to carry the sediment to shore. They absorb wave energy
sand dunes
-Wind blows sand landwards from beach
-Dunes develop as a process of a vegetation succession: roots hold sand together
Isostatic sea level change
- when the land rises or falls relative to the sea
-localised change
-EG. tectonic activity
Eustatic sea level change
-affects sea level across the whole planet.
-may be due to thermal expansion/contraction
Contemporary Sea Level Change
-Since 1880 sea levels have
increased by around 23cm
hard engineering examples
-groynes
-sea wall
-rock armour
-revetments
groynes
Timber protrusions that
trap sediment from LSD
groynes pros and cons
- build up the beach
- cost effective
x visually unappealing
x increases erosion down shore
sea wall pros and cons
- highly effective
-tourism benefits
x expensive to construct and maintain
x visually unappealing
rock armour
Large rocks that reduce wave
energy
rock armour pros and cons
- cheap
x don’t fit natural geology
x can be a safety hazard
revetments
Wooden or concrete ramps that
help absorb wave energy
revetments pros and cons
-cheap
x visually unappealing
x need constant maintenance
soft engineering examples
-beach nourishment
-dune stabilisation
-managed retreat
beach nourishment
Sediment is taken from offshore
sources to build up the existing beach
beach nourishment pros and cons
-cost effective
-looks natural
x needs constant maintenance
x dredging may have consequences on habitats
dune stabilisation
Marram grass planted. The roots
help bind the dunes, protecting land behind
dune stabilisation pros and cons
- cost effective
- creates a habitat
x planning is time consuming
managed retreat
Type of managed retreat
allowing low-lying areas to flood
Integrated Coastal Zone Management
- environmental protection is prioritised over economic development
- must involve all stakeholders
- In 2013 the EU adopted a new initiative which promotes the use of ICZM’s
managed retreat pros and cons
- creates a habitat
x farmers have to be given compensation
Shoreline Management Plans (SMPs)
-There is an SMP for each UK sediment cell.
-Different factors are considered when choosing a management options: The economic value of
assets that could be protected, the technical feasibility and the
ecological and cultural value of land
