Coasts Flashcards
What is a coastal landscape?
A coastal area where you get a combination of geomorphological processes
You also get specific coastal landforms
What are the 4 types of geomorphological processes?
Erosion, Weathering, Transportation/deposition , Mass movement
What type of system do coasts operate as, and what does it mean?
Open- inputs and outputs can change.
What are the sources of energy in a coastal system?
Wind, Waves, Currents, Tides, Low/high energy coasts.
What are wind and waves?
- Wind is created by air moving from areas of high pressure to areas of low.
-It is the primary source of energy for other processes, and is important for erosion/transportation.
-Waves are created by the transfer of energy from wind blowing over sea surface (frictional drag)
-Energy gathered by waves depends on the strength of the wind, length of time it is blowing, and the distance travelled (fetch)
- The further the wind has blown, the more destructive waves created. - creates a high energy coastline
What is a high energy coastline?
What are the characteristics?
-When a coast is exposed to strong, powerful prevailing winds it creates high energy waves.
-The rates of erosion are greater than the rates of deposition.
-It is open and uninterrupted, with a large fetch
-Greater exposure to tropical storms
-erosional landforms form (headlands, cliffs, wave-cut platform)
-Processes tend to straighten the coastline as material eroded from headlands gets deposited as beaches which smooths the coastline
What is a low energy coastline?
What are the characteristics?
-Waves are not powerful
-rates of deposition greater than erosion
-creates constructive waves
-includes depositional landforms (beaches ,spits)
What are characteristics of destructive waves?
-Short wavelength
-High amplitude-high vertical height
-stronger backwash than swash
-Results in a steep beach profile
-high frequency (10/14 per minute)
What are characteristics of constructive waves?
-Build up the beach
-long wavelength
-low amplitude
-strong swash weak backwash
-low frequency (6-8 per min)
What are the 4 factors affecting energy on a coastline?
1- coastal geomorphology
2-tides
3-tidal surges
4-currents
Coastal geomorphology
Headlands attract wave energy, and the waves concentrate there - known as wave refraction
Tides
The periodic rise and fall of the ocean surface, caused by gravitational pull of the moon and sun (although moon has more influence as its nearer)
-Moon pulls tide towards it, creating a high tide
- Spring tide is when you get the highest monthly tidal range - due to the sun, moon, earth being in a straight line
-Neap tide is when twice a month the sun and moon are positioned at 90 degrees to each other- resulting in the lowest monthly tidal range
Tidal surges
-Occasions where weather conditions create much stronger winds which can produce much higher water levels than those at high tide
-Areas affected: East coast of Britain
-Depressions (intense low air pressure systems) over the North sea produce low air pressure conditions that can raise sea levels.
-Strong winds push sea water against coastline
Currents
The general flow of water in one direction, which moves material along a coastline
- caused by wind/ variation in temp
3 types of currents:
1- Longshore drift:
waves hit at an angle and create a general flow parallel to the shoreline
2-RIP currents:
strong currents moving away from the shoreline
3-upwelling:
The movement of cold water from the deep ocean to the surface.
Dense cold water replaces the warm surface water and creates a nutrient rich cold ocean current
What are the 6 types of erosion ?
1- hydraulic action
2-wave quarrying
3-corrosion/abrasion
4-wave cavitation
5-solution
6-attrition
What is hydraulic action?
On a high energy coastline, waves hit the cliff and air gets into the cracks- compresses it. The force of the water exerts pressure and the rocks break off. This is known as wave pounding
What is wave quarrying?
Energy of a wave as it bangs against a cliff is enough to detach bits of rock.
what is corrosion/abrasion?
Bits of rock and sediment being transported by waves which hit the cliffs and rocks, and break bits off and smooth surfaces.
What is wave cavitation?
as waves retreat, the compressed air expands and exerts pressure, causing bits of rock to break off.
what is attrition?
Rocks bang in to eachother and break down
what is solution?
soluble calcium based rocks gradually dissolve by sea water.
Doesn’t happen in fresh water as it has a stable pH, but can occur in areas where both saltwater and fresh water interact
What is the rate of erosion affected by?
-wave steepness
-fetch
-geology
-human activity
-coastal configuration eg. headlands -wave refraction
-sea depth
What are the 6 different types of transportation?
1-traction
2-saltation
3-suspension
4-solution
5-longsore drift
6-aeolian
what is traction
large boulders that roll along a sea bed
what is saltation?
small rocks that bang along the sea bed
what is suspension?
small material that floats in the water
what is solution?
material that gets dissolved in the water
what is longshore drift?
the movement of sediment along a coastline due to the prevailing wind coming in at a zig zag motion
(comes in at 45 degrees (swash that moves material up the beach), leaves at 90 degrees (backwash that moves material down the beach))
what is aeolian transportation?
transportation by wind
can happen in 2 ways:
1-surface creep- wind rolls sand grains along surface
2-saltation- wind is strong enough to lift grains into the air at heights up to 1 metre
what is deposition?
when the velocity of wind and water decreases due to a decrease in energy so material eroded gets deposited.
In high energy environments:
-sand is easily transported away so leaves behind larger pebbles and rocks (shingle beaches)
In low energy environments:
-small clay particles fall to the sea bed and form mudflats
what is sub-aerial weathering?
the break down of rock which weakens the cliff and makes it vulnerable to erosion
what is physical weathering?
Freeze thaw: on hard rock coastline
when water enters the joint of a rock and freezes. when frozen, it expands by 10%
Overtime, repeated freeze-thaw weakens the cliff and fragments of rock break off
What is chemical weathering?
salt crystallisation:
-when waves refract, the water splashes back onto the top of the cliff. When the water evaporates it leaves behind salt crystals . These corrode the rock and exert pressure and it breaks off.
The salt crystals can also dissolve in rainwater to form acid rain
What is biological weathering?
when plants grow on top of a cliff, the roots can cause parts of the rock to break off
-if animals burrow on top of cliff, it weakens the rock structure
What is mass movement?
the movement of material down a coastline (which is influenced by gravity)
-can be slow(soil creep) or fast (weak geology)
-at a cliff, the weight of the rainfall or weak geology is the main cause of collapse
What is slumping?
occurs on weak, unconsolidated clay, where permeable rock lies on top of impermeable rock.
-The bedding plane is curved, not flat.
-heavy rainfall saturates the soil, lubricates the bedding plane and leads to the rock slumping.
-leaves a scar
What is a landside?
-rock moving rapidly down a planar surface (where the bedding plane is parallel to the ground and not curved)
-rainfall lubricates it and reduces friction, and the force of gravity pushes material down a slope.
What is rockfall?
Happens along a hard rock coastline,
-rock at the top of the cliff are weathered (freeze-thaw) and break off
What is mudflow?
mud flows downhill, usually over unconsolidated rock after heavy rain
what is soil creep?
the slow movement of individual soil particles downhill.
What is runoff?
Where overland flow occurs down a slope and takes along small material
What are the 3 erosional landforms?
1- cliffs
2-wavecut platforms
3-caves, arches, stacks
How is a cliff formed?
processes: erosion, weathering, geology
-formed in oceans, canyons, mountains
-soft rock breaks off from hard rock and leaves a cliff
How is a wave cut platform formed?
processes: erosion (abrasion, corrosion, hydraulic action), geology
-sea attacks a weakness in the base of the cliff, and creates a wave cut notch.
As the notch becomes bigger, the cliff retreats and collapses due to gravity. Material from collapsed cliff gets transported, and leaves a wave cut platform.
How is a cave/arch/stack formed?
processes: weathering, erosion (hydraulic action, wave cavitation)
energy is concentrated on the headland due to wave refraction
Joints in the headland get eroded, and over time joints form a cave
Erosion cuts through cave and forms an arch. The roof of arch falls due to a lack of support and from gravity and sub-aerial processes.
It then leaves a stack
What are the 7 depositional landforms?
1-mudflats/saltmarsh
2-simple/compound spit
3-tombolo
4-offshore bar
5-barrier beach
6-sand dunes
7-beaches
1-How is a mudflat formed?
Processes: deposition (longshore drift)
-Forms at the end of a spit, in sheltered areas
-2 particles combine to form large deposits, due to being heavier (flocculation)
Particles gradually build up and form an inter-tidal mudflat, and continues to rise above sea level
Halophytic vegetation (very adapted to environment) grows and colonises the mud, which traps further sediment.
2-How is a simple/compound spit formed?
processes: longshore drift
-it is found over the mouth of a river
-due to longshore drift, there has been a change in the wind direction or coastline which leads to material depositing where the sea and river meet.
Doesn’t cross the whole mouth due to the energy in the river
3-How is a tombolo formed?
processes: longshore drift
-a spit+ +that has formed between a small island and the mainland.
-May not be visible at high tide
-example: Chesil beach -links isle of Portland to the mainland and is 30km long
4-How is an offshore bar formed?
-A spit that has developed across 2 headlands and results in a lagoon.
-It is formed due to destructive waves depositing sediment through their strong backwash
-Act as a sediment sink and absorbs wave energy
5- How is a barrier beach formed?
-formed as an extension of a spit - spit develops across whole bay and forms barrier beach
By long shore drift- leads to material deposited in a bay
-results to a lagoon
Can’t happen in an estuary for to force of water
-gets colonised by vegetation (mangroves) which can colonise the land and help stabilise the beach, and trap further sediment.
6-How is a sand dune formed?
-due to the movement of sand
-as a result of onshore wind, wind from the sea blows the sand to the back of the beach
-sand is transported through surface creep, aeolian transportation, traction, suspension and saltation
-vegetation such as maram grass help stabilise the land as they are highly adapted to the environment
-over hundreds of years, the height, size and amount of vegetation increases the further inland you go, known as dune succession.
7-How is a beach formed?
-where the land meets the sea
2 types of beaches:
-Sand- gentle
-Shingle- steep
-beaches can be swash aligned or drift aligned:
-Swash- a low energy environment
-drift- longshore drift- waves approach at an angle
Features of a beach?
cusp- a mark left which shows how far a wave has travelled up a beach
runnel-marks in sand parallel to beach which are formed by backwash that is drained by the sea
berms- a raised area of land that is sloped and made of sand and shingle, and can be seen at high tide
How have sea levels changed over the last 10,000 years?
sea levels stabilised around 3000 years ago- in 20th century, sea levels rise at 10-80 cm per year
what is eustatic sea level change?
this is the global rise or fall in sea level. sea level rises when ice melts- through the melting of ice sheets or thermal expansion
sea level falls when water freezes- gets locked away in glaciers
During glacial periods, ice freezes and during interglacial periods, ice melts
what is isostatic sea level change?
the regional/ local change on sea levels as the height of the land increases/decreases
can be due to:
post glacial adjustment- during the glacial period, ice weighed the land down. now that glaciers are melting, the land is rebounding and also decreasing sea levels in the process- known as isostatic recovery
-accretion- areas build up due to deposition
what is tectonic sea level change?
the regional rise or fall in sea level as a result of tectonic processes
what is an emergent coastline?
a stretch of coastline that is exposed due to a fall in sea level or a rise in the height of the land
what is a raised beach?
a wave cut platform or a beach that is above sea level
due to isostatic rebound- ice melts so the height of land increases
what is a marine platform
sea attacks a base of cliff
due to erosion, forms a wave cut notch
notch gets bigger and cliff retreats and eventually collapses due to weathering weakening it and a lack of support and gravity
leaves a marine platform
What is a submergent coastline?
a coastline that gets flooded by ocean water due to a rise in sea level
how is a ria formed?
the rising sea level floods a narrow river valley
its deepest at the mouth and gets shallow further inland
the floodplain disappears as the rising sea level only leaves the high land to be seen
how is a fjord formed?
a fjord is formed as a glacier retreats it plucks( picks up debris) ehich steep ends valley floor and sides in a v- shaped valley and the water fills the valley floor. as sea level rises, it floods the deep glacial valley and creates a natural inlet and harbour.
it is deepest in the middle section, and shallowest where the glacier was
an example is sogne fjorden in norway, which was 160 km long
how is a dalmatian coastline formed?
narrow valleys parallel to the coastline get flooded and leave long narrow islands.
example is dalmatian coast in croatia
recent climate change?
sea level stabilised around 3000 years ago
after the industrial revolution, sea level ruse by over 230 mm
which is enough to overcome some coastal defences and create storm surges
as the world warms, more eustatic sea level change
predicted climate change?
ipcc predicts that by 2100, sea level will have risen by upto 1m higher than it is now
this leads to more coastal erosion and flooding, which can destroy some coastal cities
it can also salinise aquifers in low lying regions
Maldives
a sids and lecz - no where is 3 m above sea level, and 80% is less than 1 m above sea level
made up of 1192 islands
90% of income comes from tourism
impacts of climate chnage :
as oceans warm up, indian ocean warming up the fastest- leads to more coastal erosion and storm surges which can damage infrastructure and put off tourists
also contaminate ground water and soil so becomes infertile for 5 years
Hard engineering?
humans intervene to try stop coastal erosion by absorbing the waves energy
sea wall
a wall along a coastline
+ve
reduces coastal erosion
has a curved end to reflect wave energy
reduce insurance premiums
can be used as a promenade which is a tourist attraction
-ve
very expensive to build and maintain-£6000/m
curved end reflects wave energy and creates a strong backwash which will erode somewhere else
looks unnatural
example: holderness coast
area of bridlington protected by a 4.7km long sea wall
revetment
a wall made from sandbags which reduces coastal erosion
+ve
cheap to maintain
reduces coastal erosion
-ve
looks unnatural
needs alot of maintainance
expensive to build
gabion
a cage of rocks which absorb wave energy
+ve
reduces coastal erosion
-ve
ugly
dangerous
rock armour
where you place large rocks infront of a cliff
+ve
absorbs wave energy
if use local geology, will fit in with the natural environment
cheap and easy to maintain
-ve
rocks can move during storms
can affect access to beach
can look unnatural if not using local geology
groynes
wooden planks put in the sea to trap sediment and stop longshore drift
+ve
makes beaches wider and steeper which reduces coastal erosion
cheap
-ve
looks unnatural
can starve beaches further down of sediment, which can increase erosion- terminal groyne syndrome
offshore breakwater
concrete sloped surface which reduces the power of the waves, so when it reaches the shore the energy of the waves is reduces
+ve
energy of waves is reduced so reduces coastal erosion
-ve
looks ugly
can get damaged in storms
soft engineering
a more natural and sustainable approach to coastal management
beach nourishment
you add sand to a beach
+ve
natural
cheap
build bigger beaches which attracts more tourists
-ve
needs constant maintenance
example:
dutch sand engine in holand
netherlands is vulnerable to coastal erosion as it has 350km of coast, and 50% of its population is below sea level
project to move sand in a natural pattern, reduce coastal erosion and make wider beaches
beach stabilisation
plant vegetation to stabilise the sand
+ve
looks natural
sustainable and cheap
reduces coastal erosion
-ve
takes a long time to grow
affect access to the beach
dune stabilisation
create sand dunes along a coast
+ve
looks natural and is sustainable
marsh creation
this is where you allow low lying areas to flood and overtime creates a saltmarsh or wetland
+ve
cheap
natural
creates a habitat for wildlife
creates a buffer zone as saltmarsh will absorb wave energy, so waves wont reach the sand
-ve
agricultural or farming land may get lost so they need to be compensated
cliff regrading and drainage
regrading- where you reduce the angle of a cliff to make it less steep
-drainage- you remove water to reduce slumping and landslides
+ve
effective on cliffs with clay or loose rock
drainage is cost effective
-ve
regrading means the cliff retreats
draining too much can dry cliff out and lead to collapse
what is a sediment cell?
is a closed system usually between 2 headlands
you get erosion, deposition transportation within each sediment cell
sediment doesnt usually move from one cell to another
humans can interfere with a sediment cell and create an imbalance which leaves some areas vulnerable to coastal erosion
what is a sediment budget
the balance between inputs and outputs of sediment
balance between erosion and deposition
can be affected by events or humans
what are sediment sources?
where the sediment comes from - rivers cliffs or wind
What is a shoreline management plan?
was set up in 1995 by the environment agency and aims to protect coastlines more holistically, by looking at the whole sediment cell not just specific areas
theres 22 smps, but 11 sediment cells across england and wales
does a coat benefit analysis based on an assessment with risks of how an area can be affected by coastal erosion and flooding, then local agencies work together to make a plan
not totally sustainable, but more
aims to be technically sustainable, economically viable and environmentally acceptable
theres 3 goals:
long term - over 100 years
medium term
short term
has a live document which is continuously reviewed and updated
4 methods:
hold the line
advance the line
retreat the line
do nothing
smps sustainability?
they seek to manage the coast as well as balancing the needs in a sediment cell
provide a large scale assessment- find out the most sustainable method
take into account the needs of people and the environment
cost is a huge factor- see if an area is worth protecting
the sussex smp
The sussex coast is locates on the south coast of england, and is part of spm4
It has a large residential area and tourism industry
it is heavily defended by hard engineering, however this creates problems further down and the cost of protection is set to rise from 3-5 million to 6-10.
The environmental agency are looking for a way to meet the needs of the sediment cell, and make it economically sustainable to protect in the future.
It is protected due to it having a large residential area, good transport links means that london commuters decide to locate there. It also has a mild beach which attracts many tourists
The areas of Eastbourne, hastings and Brighton need protecting as they are high value assets
The coast is exposed to prevailing winds from the Atlantic, bringing storms and high energy waves
Hard engineering is good at protecting the coast and reducing erosion, however it disrupts west-to-east Longshore drift and creates depleted beaches further down
The south coast is subsiding by 1mm a year due to isostatic rebound
sea level rise means more rain which will rapidly weather cliffs
Brighton
has a population of almost 300,00, 140,000 jobs ,16,000 businesses
use a hold the line policy: groynes, sea wall and regular beach nourishment - 20,000 tonnes of sediment are moved to sustain longshore drift
In the brighton marina, a sea wall was built in the 1970s costed 2.2 million It has increased down drift erosion by 0.3m per year - which is a positive feedback cycle
what is an intergrated coastal zone?
a more holistic way of managing the coastline as many different stakeholders are considered
it aims to manage the coast whilst allowing people to use it
it sees the coast as a whole unit, rather than ignoring one place which can impact another
it takes into account all types of users- locals, visitors
local, national, regional levels of authority all have an input
sundarbans
located on the south east coas of india, and south west coast of Bangladesh
40% in India and 605 in Bangladesh
Largest mangrove forest in the world, found in Delta of the Ganges and River meghna, bordering bay of Bengal
area is 10,000 km
tropical climate with a monsoon season
home to rare species of animals such as Bengal tiger
Opportunities it brings
The mangroves act as a natural barrier -soft engineering against flooding
-also protects the coast from erosion as the roots of the mangroves bind the soil together
-opportunities for trade through fishing and timber
-ecotourism- people are attracted to the wildlife
Risks of development
Due to climate change, sea level is rising by 3-8mm a year due to subsiding land
more flooding
-more cyclones- destroys habitats and displaces wildlife
-Illegal logging for mangroves for development and infrastructure
mangroves are vital to ecosystem as the provide habitats protect the coast and filter water.
challenges
the area is in poverty and is poor- only 1/5 of population has access to electricity so communication is slow
-growing population-more food is needed- more mangrove forests being cut down
-access is difficult- few roads so hard to receive education and healthcare
resilience
being able to cope with challenges;
-provide shelter against flooding and cyclones
-improve access to clean water
-improve electricity-people receive flood warnings faster
-improve food security by providing farmers with subsidies
mitigation
reduce the severity of the event
-3500km of embankments are being built to protect against flooding- gradually being eroded and at risk of being breeched by storms
-reduce severity of event by ngos and governments providing funding for shelters and early warning systems
-improve infrastructure such as roads and hospital and due to NGOS people have access to microcredit so have greater economic stability
-reaforrestation schemes- replant mangroves as they are cheap and quick to grow.
adaption
changing your behaviour to fit the environment
-plant salt resistant crops (rice)-protects against flooding
-increase tourism in the area
-build houses on stilts to adapt to sea level rise
-NGOs provide training and education
government
ministry of environment, forest and climate change- implement environmental policies
NGOs
sundarbans social development centre- focus on health and education of people
however, cant help everyone and only get limited funding
cyclone Aila
2009, cyclone Aila destroyed 100,000 homes and 400km of embankments breached.
the sundarbans embankment reconstruction project- government led rebuilt 5000m of concrete embankments
also built new roads
Odisha
Located on east coast of India bordering Bay of Bengal, around the chilica lake
Coastline is 480km
Population of 47 million
Opportunities to Humans:
Fishing
Tourism- beaches wildlife
Risks;
most people live on coast, at risk of climate change, rising sea levels and coastal flooding
What is the shoreline assessment
Stop hard engineering as it increases problems further down ans starves places of sediment
the Holderness coast
Located on the East Yorkshire coastline, in the North sea
coastline stretches 61km
-coastline is made of chalk and glacial till
-its one of the fastest eroding coastlines in europe-roughly 2 metres a year
-high energy coastline with destructive waves
transportation and deposition
faces alot of longshore drift which gets deposited at Spurn Point- a spit in the Humber estuary
Spit has formed, as well as mudflats and saltmarshes
Protection
holderness coast has population of around 95,000
Easington gas terminal:
critical hub for uks energy supply and considered one of uks most important facilities
Terminal is being developed into a hydrogen hub
how is the holderness being protected
part of SMP2
Authorities have decided to only protect areas that are worth being protected
Bridlington:
has population of over 30,000 aswel as a major fishing harbour
-sea wall and groynes
Hornsea:
sea wall, groynes rock armour
Mappleton:
2 groynes, revetments and rock armour
managed retreat
the holderness is home to many caravan parks and each year they are encourages to gradually move back to reduce the risk of them being destroyed
