coasts

what is eustatic change?

a global change in sea level resulting from an actual fall or rise in the level of the sea itself

what is isostatic change?

local changes in sea level resulting from the land rising or falling relative to the sea.

caused by the weight of ice pushing earth’s crust down, when it melts the ground begins to rise again.

what are tectonic changes?

land being shifted up or down due to plate movements.

is tectonic uplift or downthrust short medium or long term?

short

is isostatic change short medium or long term?

medium

is continental separation and collision short medium or long term?

long

is thermal expansion short medium or long term?

short

is global warming and ice melting short medium or long term?

medium

what is isostatic readjustment?

the slow uplift of land after the immense weight of ice sheets from an ice age melts, causing the crust to rise from the mantle’s depression. this can create emergent landforms.

what impact has isostatic adjustment had on the coastline of the uk?

the north of england is rising as the ice sheets that once covered the ground have melted, causing the ground to rebound and rise. this also causes the south of uk to begin to sink.

what has happened to sea levels since the last ice age 10,000 years ago?

sea levels have dramatically increased since the last ice age as the glacial ice has melted, flooding the land and resulting in a eustatic sea level rise.

what implication does the potential melting of the Antarctica ice have on future sea levels?

it poses a massive threat to future sea levels as the entire continent holds enough ice to rise sea levels by over 58 metres if it melted completely. although this is unlikely, even the partial collapse of glaciers such as the thwaites glacier could add several metres to the sea level. this could potentially displace many coastal cities.

what is thermal expansion and what impact does it have on sea level?

as heat from the green house effect is absorbed, ocean temperatures rise and water expands. this is because the water molecules spread out which increases it’s volume and density. this contributes to sea level rise and may cause coastal flooding.

give an example of changes in relative sea and land with tectonic activity

• 2004 boxing day tsnuami sumatra

• cause significant vertical movement of the crust which caused parts of the coastline to drop

• areas of land which were above sea level were permanently flooded forming a submerged coastline, leaving a ria.

what is a ria?

• former river valley drowned by rising sea levels

• created by rising sea levels drowning river valleys

• the floodplain of a river will vanish beneath the rising waters, but on the edges of the uplands only the middle and upper course valleys will be filled with sea water

• leaves higher land dry leaving a ria

• example: kingsbury estuary on south devon coast is a 6m long ria

what is a fjord? how is it formed?

• drowned glacial valleys- a section of a glacially eroded valley flooded by the sea

• typically found on coasts of norway, south western new zealand + greenland

• they have steep valley sides and are fairly straight and narrow

• typical u shaped cross section

• formed when the sea drowned the lower part of glacial valleys that were cut to a much lower sea level

• example: sognefjord noway

what is a dalmation coast? how is it formed?

• long narrow islands running parallel to the coastline and seperated from the coast by narrow sea channels called sounds

• they are produced by sea level rise flooding the coastline with the geological structure of folds aligned parallel to the coast

• example: dalmation region of croatia has a limestone coastline stretching 520km nw-se

what are raised beaches? how are they formed?

Raised beaches are ancient shorelines, featuring wave-cut platforms and beaches, now located above current sea level, formed primarily by the rebound of land after ice ages (isostatic uplift) as ice sheets melted, lifting the crust faster than sea levels rose (eustatic rise)

what are relict cliffs? how are they formed?

Relict cliffs are steep slopes, often with features like old caves, arches, and wave-cut notches, that were formed by marine erosion when sea levels were higher but are now abandoned inland, sitting above the present-day high tide mark. They form when sea levels fall (due to ice melting or land uplift) after a period of active coastal erosion, leaving these fossilized features exposed on emerged land, known as raised beaches. 

what is a marine platform? how is it formed?

A marine platform (or wave-cut platform) is a flat, gently sloping rock surface at the base of a cliff, formed by coastal erosion, where waves attack the cliff, undercutting it to create a notch, causing collapse and retreat, leaving the platform exposed at low tide. These platforms are formed through repeated wave action (hydraulic action, abrasion) undercutting the cliff base, which eventually collapses, leaving a smooth, wide ledge as the cliff retreats landward over time. 

What 2 ways are there in which the volume of the oceans is increasing?

• thermal expansion

• melting ice sheets and glaciers

Why is sea level change prediction so difficult? what is the range in predictions?

• uncertainties in future greenhouse emissions

• complex climate system responses

• model limitations

• from 0.6 m to 1.9 m by 2100

what are the aims of coastal management?

1. to provide defence against and mitigate the impact of flooding

2. to provide protection against and mitigate the impacts of coastal erosion

what are groynes?

• wooden structures placed at right angles to coast where LSD occurs

• they reduce movement of material along coastline and hold the beach in place

• causes material down the coast to be missing

• example: groynes in withernsea

what are sea walls?

• thick concrete or rock encasements of shore front. they may have a recurved top to assist deflection of waves back to sea

• they are effective

• long lasting- 20-30 years

• protects settlements from floods

• they are expensive to construct

• maintenance is needed to prevent undercutting and fracturing beneath foundation

• example: sea wall in hornsea

what are gabions?

• steel mesh cages containing boulders of rubble and covered with plates with steel or concrete

• implemented swiftly

• more effective than sea walls

• absorbs energy and reduces erosion

• relatively cheap

• looks ugly

• high maintenance

• houses rodents

• deteriorate over time

what is hard engineering?

making a physical change to the coastal landscape using resistant materials, like concrete, boulders, wood and metal

What is soft engineering?

using natural systems for coastal defence, such as beaches, dunes and salt marshes, which can absorb and adjust to wave and tide energy

what are revetments?

• steel cages containing boulders of rubble and covered with plates of stone or concrete

• more effective than steel walls

• implemented swiftly

• ugly

• may reduce beach access

• requires regular maintenance and repair

what is rock armour?

• large boulders piled on beaches where erosion is likely

• cheap

• absorbs wave energy

• long lasting

• little maintenance

• natural looking kind of

• can restrict shore line access

• may be hazardous to people climbing on them

• high transport costs

what is cliff fixing?

• driving iron bars into cliff face

• stops slumping

• stabilises cliff and absorbs some wave power

what are offshore break waters?

• man made islands, bars or reeds just offshore to cause waves to break

• least “hard” method- it’s relocating a natural process

• islands may form habitats

• might need regular replenishment if material is eroded swiftly

• construction material may contaminate water

what is a barrage?

• large structures built to prevent flooding on major estuaries

• acts as a dam and prevents incursion of seawater

• large scale = expensive

• example: Thames Barrier

What are the main advantages and disadvantages of hard engineering? 

advantages:

• long lasting

• effective over planned lifespan

disadvantages:

• structures can be expensive to build and maintain

• defence in one place can have consequences for another area of the coast

• structures are often an eyesore, spoiling the landscape and physically disrupting natural habitats

what is beach nourishment?

• the addition of sand or pebbles to an existing beach to make it higher or wider

• sediment is usually dredged from nearby sea bed

• relatively cheap and easy to maintain

• looks natural and blends in with existing beach = increases tourist potential

• needs constant maintenance because of LSD and erosion

What is cliff regrading and drainage?

• reducing gradient of slope to help stabilise it

• drainage removes water to prevent landslides and slumping

• can be effective on clay or loose rock where other methods will not work

• drainage is cost effective

• regrading effectively causes cliff to retreat

• drained cliffs can dry out and lead to collapse

What is dune stabilisation?

• marram grass can be planted to stabilise dunes

• areas fenced in to keep people off newly planted dunes

• maintains a natural coastal environment

• provides important wildlife habitats

• relatively cheap and sustainable

• time consuming to plant marram

• people may respond negatively to being kept off certain areas

what is marsh creation?

• a form of managed retreat, by allowing low-lying coastal areas to be flooded by the sea

• relatively cheap

• creates natural buffer to powerful waves

• creates important wildlife habitat

• agricultural land is lost

• farmers and landowners need to be compensated

What is cost benefit analysis and why is it used?

carried out before a coastal management project is given the go-ahead. costs are forecast and then compared with the expected benefits .

What is meant by tangible and intangible costs and benefits?

tangible- where costs and benefits are known and can be given a monetary value

intangible- where costs can be difficult to assess but are important (e.g visual impact of a revetment)

what coastal management has been used in holderness?

• Bridlington is protected by a 4.7 km long sea wall.

• Hornsea is protected by a sea wall, groynes and rock armour.

• Coastal management at Withernsea has tried to make the beach wider by using groynes, and also uses a seawall to protect the coast.

• Mappleton is protected by rock groynes.

• Spurn Head is protected with groynes and rock armour.

why does holderness need coastal management?

• coastline is rapidly eroding at 1.8 metres a year

• cliffs are made up of a less resistant boulder clay that slumps when wet

• naturally narrow beaches give less protection to beaches as it doesn’t reduce power of waves

• powerful waves: waves travel long distances along north sea (long fetch) which means they will increase in energy

What was the medmery managed realignment scheme?

• high tides threatened to breach single beach, 300 homes were at risk

• water treatment works and a main road needed protecting

• constructed an inland flood bank that’s 7km long

• 15 year project

• 60,000 tonnes of rock from norway imported to consolidate the flood defences

what is dynamic equilibrium?

the maintenance of balance in a natural system, despite it being in a constant change of state

what is weathering?

the breakdown of rocks over time, leading to the transfer of material into the littoral zone, where it becomes input to sediment cells

what are the three types of mechanical weathering?

• freeze thaw

• salt crystallisation

• wetting and drying

what is freeze thaw weathering

• water enters cracks in rocks and the water freezes overnight during the winter

• as it freezes water expands by around 10% in volume which increases the pressure acting on a rock, causing cracks to develop

• over time the cracks grow, weakening the cliff making it more vulnerable to other processes of erosion

what is salt crystallisation

• as sea water evaporates, salt is left behind

• salt crystals will grow over time, exerting pressure on the rock, which forces the cracks to widen

what is wetting and drying

• rocks such as clay expand when wet and then contact again when they are drying

• frequent cycles of wetting and drying at the coast can cause these rocks and cliffs to break up

what are the different types of chemical weathering

• carbonation

• oxidation

• solution

what is carbonation

• rainwater absorbs co2 from the air to create a weak carbonic acid which then reacts with calcium carbonate in rocks to form calcium bicarbonate, which can be easily dissolved

• acid rain reacts with limestone to form calcium bicarbonate, which can also be easily dissolved allowing erosion

what is oxidation

• when minerals become exposed to the air through cracks and fissures, the mineral will become oxidised which will increase it’s volume (contributing to mechanical weathering) causing the rock to crumble

• most common oxidation within rocks is iron minerals becoming iron oxide, turning the rock rusty orange after being exposed to the air

what is solution (weathering)

when rock minerals such as rock salt are dissolved

what are the types of biological weathering

• plant roots- roots of plants grow into cracks of rocks, which exerts pressure eventually splitting the rocks

• birds- some birds such as puiffins dig burrows into cliffs weakening them making erosion more likely

• rock boring- many species of clam secrete chemicals that dissolve rocks

• seaweed acids- some seaweeds contain pockets of sulphuric acid, which can dissolve rock’s minerals

• decaying vegetation- water that flows through decaying vegetation and then over coastal areas will be acidic, causing chemical weathering

what is mass movement

movement of material down a slope under the influence of gravity.

can be categorised into four main areas: creeps, flows, slides and falls

what is the type of mass movement dependent on?

• cliff/slope angle

• rock type

• rock structure

• vegetation

• saturation of ground

• presence of weathering

what is soil creep

• the slowest but most continuous form of mass movement involving the movement of soil particles downhill

• particles rise and fall due to wetting and freezing and this causes the soil to move down the slope

what is solifluction

• occurs mainly in tundra areas where land is frozen

• as the top layers thaw during summer (lower layers still stay frozen due to permafrost) the surface layers flow over the frozen layers

what are mudflows

• increase in the water content of soil can reduce friction, leading to earth and mud to flow over underlying bedrock, or slippery materials such as clay

• water can get trapped within the rock increasing pore water pressure, which forces rock particles apart and therefore weakens the slope

• pore water pressure is an important energy source for determining slope stability and refers to the pressure of groundwater held within soil or rock

• mudflows represent a serious threat to life as they can be very fast flowing

what is rockfall

• occurs on sloped cliffs (0ver 40°) when exposed to mechanical weathering, though mostly occurs on vertical cliff faces and can be triggered by earthquakes

• leads to scree (rock fragments) building up at the base of the slope

what are landslides

• heavy rainfall leads to water between joints and bedding planes in cliffs (which are parallel to the cliff face) which can reduce friction and lead to a landslide

• occurs when a block of intact rock moves down the cliff face very quickly along a flat slope

• can be dangerous

how is a wave cut notch/ platform formed

• erosion attacks the base of the cliff, creating a notch of eroded material between high tide height and low tide height

• as notch becomes deeper (and sub-ariel weathering weakens cliff from top) the cliff face becomes unstable and falls under its own weight through mass movement

• this leaves behind a platform of the unaffected cliff base beneath the wave- cut notch

how are caves, arches, stacks and stumps formed ?

• sequence appears on pinnacle headlands

• marine erosion widens faults in the base of the headland, widening over time to create a cave

• cave will widen due to both erosion and weathering, eroding to the other side of the headland creating an arch

• arch continues to widen until it is unable to support itself, falling under its own weight through mass movement, leaving a stack as one side of the arch becomes detached from the mainland

• marine erosion attacks the base of the stump, eventually the stack will collapse into a stump

what is flocculation

clay particles clump together due to chemical attraction and then sink due to their high density

how are spits formed?

• spit is a long narrow strip of land which is formed due to deposition

• LSD occurs along coast line, but as waves loose energy they deposit their sediment

• over time this creates a spit

• over time the prevailing wind will change direction causing a hook to appear

• sheltered area behind spit turns into a salt marsh

what are bars?

a spit which over time crosses a bay and links up two sections of the coast- water within bay is called a lagoon

what is a tombolo?

bar or beach that connects mainland to an offshore island and is formed due to wave refraction off the coastal island reducing wave velocity, leading to deposition of sediments

explain how sand dunes are formed and the different stages

sand dunes occur when prevailing winds blow sediment to the back of the beach and therefore the formation of dunes requires large quantities of sand and a large tidal range. this allows the sand to dry, so that it is light enough to be picked up and carried by the wind to the back of the beach. frequent and strong onshore winds are also necessary.

1. embryo dunes- upper beach area where sand starts to accumulate around a small obstacle e.g drift wood

2. yellow dunes- as more sand accumulates and the dune grows, vegetation may develop on the upper and back dune surfaces, which stabilises the dune. the tallest of the dune succession.

3. grey dunes- sand develops into soil with lots of moisture and nutrients, as vegetation dies, enabling more varied plant growth

4. dune slack- water table rises closer to the surface, or water is trapped between hollows between dunes during storms, allowing the development of water loving plants e.g willow grass

5. heath and woodland- sandy soils develop as there is greater nutrients content, allowing for less brackish plants to thrive. trees will also grow e.g willow with the coastal woodland becoming a natural windbreak to the mainland behind

what factors are causing the rapid rate of erosion in holderness?

• long fetch

• powerful waves

• weak and unconsolidated till cliffs

• extensive mass movement

• narrow beaches= cliff vulnerable to wave attack and undercutting

• lack of coastal defences

flamborough head

• no active intervention- resistant chalk of headland erodes slowly

• frequent rockfalls as sea is actively eroding base of cliff

• cliff retreating has left wave cut platforms, stacks and stumps

hornsea

• rapid rates of erosion so hard engineering structures have been put in place

• holiday resort with a promenade and hotel frontage

• groynes have been repaired and new ones were built at a cost of £5.2 million

• steel doors guard entrance to beach

• old sea wall has been raised slightly

• + groynes seem locally effective, relatively low cost, acceptable visually

• - trapping of sand may cause scour at mappleton, groynes rarely work on their own

mappleton

• in 1786 the village was 3.5 km from sea, 1988 sea was on its doorstep

• in 1991 scheme was implemented at a cost of £2.1 million supported by EU funding (largely unsuccessful)

• 450m rock revetment to prevent erosion of cliffs

• cliffs regraded to reduce slumping

• nourishment of beach to encourage deposition

• granite boulder groynes extending into sea —> can lead to terminal groyne syndrome

• protects B1242 road

easington

• hold the line short term, do nothing medium and long term

• rock armour and revetments

• gas terminal located here, which will likely run out of gas

• also no interest to tourists because of the gas terminal

withernsea

• another resort

• groynes and sea wall put in place

• cost £6.3 million

• wave return wall built protected by rip-rap and some beach nourishment

• + will hold the line and calms concerns of residents and hotelier, saves seasonal jobs

• - costs have limited the length of the sea wall, rocks have reduced beach access and limited the view, problem of wave noise

spurn head

• officially abandoned in 1995

• managed retreat short term, do nothing medium and long term

• + growing annual costs of protection were saved, some evidence suggests it will repair itself

• - community of life-boat men and coast guards may have to move elsewhere, loss of ‘heritage coast’ site and bird habitat

where is odisha?

odisha is located on the east coast of india and it borders the bay of Bengal.

how long is Odisha’s coastline?

480 km long

what are the main habitats in odisha?

• six major deltas on odisha’s coast- explains why the coastal plain is known as the hexadeltaic region

• almost 1500 km2 of mangrove forest

• chilika lake- a salty lagoon well known for it’s bird life

what portions of the coast are eroding/stable?

odisha’s coast- 47% accreting (deposition) whilst 37% erosion

what threats is odisha facing?

• flooding

• village is loosing land due to soil erosion which swallows up homes and leads to a loss of livelihood. 5/7 villages in odisha have been lost.

• climate change has increased the frequency of storms, which has made 10% of land vulnerable

• water is too saline —> can’t grow crops + locals have to walk to nearby villages to get water

• some people are refusing to leave

what opportunities are there for odisha?

• variety of marine + coastal flora and fauna

• large stocks of fish, marine mammals, reptiles

• huge potential for offshore wind, tidal and wave power

• opportunities for offshore oil and natural gas as well as sea bed mining

• local people are employed in fishing

what were the aims of the ICZM in odisha?

• people involved (stakeholders) - world bank, government india —→ ministry of environment forest and climate change, government odisha, water source department, fisheries department etc…

• mitigate and adapt to issues caused by tropical cyclones and storm surges due to climate change and sea levels rising

what have they done in odisha to make sure the coastline is managed in a sustainable way?

• alternative livelihoods for fisherfolk and women

make people less vulnerable to climate change and become economically secure, 600 self help groups in 72 fishing villages, implemented via fisheries and animals dept. 600 women in industry making things like doormats

• protecting against flooding and erosion (mangroves and hard engineering)

geo- textile tubing used as hard engineering, acts as rip-rap / sea wall to prevent erosion along 500m stretch —> 41k people benefited. also planted mangroves

• creating jobs through ecotourism

6 sites in chilika lake, ecotourism society, 55% rise in employment and income, alligator and turtle patrols

• protecting the heritage of the area

renovation of temples and cultural sites to support and aid tourism

• protecting the wildlife

crocodile and turtle protection by patrols, protection of biodiversity, monitoring of pollution of creeks and coastal water

• the construction of cyclone shelters

mitigation strategies- broadcast warnings, staged evacuations. shelters- also used as classrooms for students and vaccinations. this has protected up to 14,000 people

what impacts did the october 2013 cyclone have on odisha?

• loss of livelihoods- many fishermen experienced damage to boats and nets

• agricultural land was damaged (5000 square km)

• infrastructure damaged

• 44 dead

what was the average width of the mangroves 50 years ago in odisha?

5km

what has led to the considerable loss of mangroves in the last 50 years in odisha?

• agricultural expansion and the construction of paradeep port

why is planting mangroves so sustainable?

• they protect biodiversity

• they grow around 2 feet per year ( much faster than the rate of erosion)