Coasts Flashcards
explain sedimentary rocks
- they are clastic meaning they are made up of cemented sediment particles rather than interlocking crystals
- formed in stratas (layers) with joints which provides weaknesses and makes limestone permeable along with other jointed sediemntary rocks whereas other ones are porous due to the presence of air spaces
- rocks that are younger erode faster than the others as they are softer and weaker, older sediment is buried deeper and is subject to more intense compaction with strongersedimentation- making them more resistant
- forms scree at the base due to mass movement
- limestone erosion rates: 1-2cm/yr, chalk erosion rate: 1-100 cm/yr
- example: Old Harry, Purbeck, Dorset (chalk)
give examples of areas from the most resistant rock to the least resistant rock
most resistant: IGNEOUS- Land’s End, South Cornwall (granite)
resistant rock: METAMORPHIC- St Ives, Cornwall (slate)
resistant sedimentary rock: SEDIMENTARY- Blackers hole, south Purbeck, Dorset (Limestone)
least resistant rock: Holderness, NE Coast, (boulder clay)
explain the cave-arch-stack-stump sequence
- the headland protrudes out into the sea as it is more resistant which means wave energy is concentrated on it due to wave refraction
- wave action attacks weaknesses in the headland due to abrasion and hydraulic action leading to cavitation
- this widens cracks into crevices and into caves
- caves can be eroded to form blowholes as the ceiling collapses
- marine erosion deepens the caves until they connect up andan arch is created and erosion continues and the roofof the arch becomes unstable from the widening of the arch due to weathering and other sub-aerial processes
- the arch eventually collapses by blockfallto form a stack
- continual undercutting and HA in the joints at the base of the stack creating a stump like Old Harry’s wife
what are the 5 different types of mass movement?
landslide
slumping
mudflow
rockfall
soil creep
describe how the differential erosion of alternating and contrasting rocks affects the coastline?
This leads to a series of different landforms forming along the coastline and differing rates of recession. Higher rates of erosions will lead to the formation of bays whilst areas with more resistant rock will simply see faults and joints. It produces complex cliff profiles through the variety of different rock types. Headlands are likely to coincide with resistant rocks and will be characterised by relatively slow rates of recession.
explain the conflicts and winners + losers occurring in the sustainable management of blackwater estuary, essex
conflicts
- the west mersea fisherman were concerned that sediments could choke and kill oysters and water sea level changes could remove oyster habitats
- the RSPB were concerned about the increased erosion and flooding of their site opposite the farm which could change bird habitats
- conflicts have been resolved as research showed that the oysters and bird habitats actually improved as a result, farmers were compensated for land
winners:
- Environmental winners: Water quality in the estuary has improved because of expansion of reef beds that filter and clean the water, Important bird and oyster nurseries were enhanced
- Economic winners: Additional income streams from ecotourism and wildlife watching were enhanced
- Social winners: New paths and walkways were created for leisure activities
losers:
- local residents downdrift, reduces the volume of water travelling up the essex estuaries and creeks which could flood settlements
- led to the flooding of Abbot’s hall farm which led to socio-economic losers as farmers lost their agricultural land, however their land was bought for market value
explain the approach of managed realignment in Abbotts Hall farm, blackwater estuary, Essex
- they have adopted a ‘finding space for water’ philosophy which involves managed retreat
- coastal squeeze due to future sea level rise and storm surges make maintaining flood embankments unsustainable
- landowners and farmers have discussed giving up land to sea
- a CBA concluded that since the soil quality and land value were low, it was not worth maintaining the embankments
- it was the largest coastal realignment project in europe, costing £645,000, CHEAP
- the Essex Wildlife Trust purchased the Abbot’s Hall estate in Essex on Blackwater estuary and converted more than 84 hectares of farmland into salt marsh and greenland through 5 breaches in the embankments, farmers were compensated
- it is sustainable as the 49 ha of additional mudflats and saltmarshes absorb incoming higher seas and storm surges without any local damage
- new wetland bird habitats created, wading birds return for feeding and nesting
- CBA showed that sea wall was not cost-effective, soil quality poor
describe the essential features of the back shore
- It is a part of the beach above the high-tide mark and abutting the cliff base. It is only affected by exceptionally high tides and during severe storms. On the backshore we see a storm beach and pebbles.
- area between the high water margin and the landward limit of marine activity. Changes only happen here in storm events.
what is geological structure?
refers to how the rock is arranged on a macro-scale and looks at the arrangement of different rock types in relation to each other.It looks at the rock strata, deformation and presence of faulting.It looks at the rock strata, deformation and presence of faulting.
how can geological structure influence cliff profiles?
Geological structure largely influences cliff profiles in terms of the landforms that form as a result. If it is a discordant coastline then they are to see headlands and bays but if it is a concordant coastline they will see haffs and coves. Geological structure closely relates to the resistance of the rock and so it determines the rate of coastal recession in the different areas also.
what is rotational slumping?
common where softer rock overlies harder rock, it causes rotational scars, repeated slumping creates a terraced cliff profile
- A rotational scar is a fresh, curved, unweathered and unvegetated rock surface on the cliff face.
- The detached slope section, often with vegetation intact on top of the slump, forms a beach or terraced cliff profile.
- Slumping is facilitated by the presence of water, which adds weight (increasing the gravitational force) as well as lubricating it, reducing friction.
explain the two different cliff profiles
steep and unvegetated cliffs
- produced where marine erosion dominates
- there is little or no debris at the base as it is broken by attrition and transported offshore or along the coast
shallow and vegetated cliffs
- they have a convex profile (curved like the interor of a circle)
- there is debris at the base becuase sub-aerial processes slowly move sediment downslope, but marine erosion is unable to rmeove it from base
- produced where there is little active marine erosion
explain the beach profile
- storm beaches result from high-energy deposition of very coarse sediment during the most severe storms
- berms typically of shingle/graves, result from summer swell wave deposition
- the middle area of the beach is mainly sand, but the sand is coarser where berms/ridges have been deposited than in channels and runnels
- offshore ridges formed by destructive wave erosion and subsequent deposition of sand and shingle offshore.
explain the SMP in chittagong and why they are so vulnerable
a coastal climate resilient infrastructure project (2012) supported by the Asian Development Bank (ADB) aims to ‘climate-proof’ the area
- 1.5m rise in sea level would flood 22,000km sqaured and displace 15 million people
- 40% of farmland will be lost (salt water intrusion and directly)
- mangroves dissapearing, reducing protection from surges
- funnelling bay of bengal
this involves:
- improving road infrastructure for farmers and markets through raising embankments to 60cm above normal flood levels and making them resilient to CE
- creating new market areas with sheds raised on platforms above the expected 2050 sea level
- constructing, improving or extending 25 tropical cyclone shelters, taking account increase in cyclone magnitude
- training in climate resilience and adaptation measures
- it was loaned US$60 million by the IFAD and project was rated as satisfactory
how does lithology affect resistance? (explain 3 types)
1) mineral composition
- some rocks contain reactive minerals eaisly broken by chemical weathering, e.g. calcite in limestone
- other minerals are more inert that chemically weather more slowly
2) rock type
- sedimentary rocks are clastic (sediment particles compacted together) and these are often reactive and easily chemically weathered
- igneous rocks are crystalline with strong chemcial bonding
- rocky coasltines differ in resistance
3) structure
- rocks with fissures or air spaces erode more easily
what is it and explain the formation of a wave-cut platform
it is a flat rock surface exposed at low tide, extending out to sea from the base of a cliff
1) wave action at the base of the cliff between high and low tidemeans that hydraulic action and abrasion undercuts the clif to form a wave cut notch
2) this continues and the cliff above the notch is left unsupported and eventually collapses
3) the cliff retreats leaving a wave cut platform which is the base of the cliff that is left
4) this process maintains a steep cliff profile
what does porous, permeable and pervious mean?
permeability- the ability for water to be infiltrated into the rock
pervious- where there are joints and bedding planes leading to percolation, e.g. limestone
porous- small air pockets and holes in the rock allowing for the percolation of water, e.g. chalk
what does the morphology of discordant coasts lead to
the altering of the distribution of wave energy and rate of erosion through wave refraction
what are discordant coastlines?
- this is where the rock starts runs perpendicular to the coast forming headlands and bays - example: the isle of Purbeck’s eastern coast leading to headlands at peril point and durlston head, swanage bay has formed
explain the successful sustainable ICZM in Namibia as part of climate change policy
- long stretch of coastline of varying value
- it is called the skeketon coast due to Benguela current causing thousands of shipwrecks
- Namib desert runs all the way along the coast creating very inhospitable currents
Namibia’s national policy on climate change launched in 2013:
- emphasisd sustainable adaption measures to reduce vulnerability
- it aims to strengthen the governance of the coastline, improve QOL and maintain ecosystems
how is coastal management changing?
it is increasingly using the concept of littoral cells to manage extended areas of coastline. throughout the world, countries are developing schemes that are sustainable and use holistic ICZM strategies
- littoral cells are natural subdivisions of the coastlines containing sediment sources, transport paths and sinks.
there are 11 littoral cells in the Uk which are relatively closed systems, there are some transfers between however so managing large sections as a whole is more sensible
the second round of SMPs in 2004 changed many HTL strategies to MR and do nothing perhaps due to the fact that they were not aware of the rapid recession rates that were to happen due to climate change.
what is pore pressure?
it is the pressure that the water exerts on the rock when the pores are full
what were the different management strategies put into place in Namibia in the 3 different areas and what was the benefit and drawback of this SMP?
1) Skeleton coast in the Namib desert with isolated rural settlements and many wildlife areas
LOW COST MANAGEMENT OPTIONS
- prevent future development of coasal buffer zone experiencing recession
- conserve wetland habitats
- stabilise and protect sand dunes
- reduce poverty so people are able to prepare themselves (build better homes)
2) Small tourist settlements like Henties Bay
MODERATE COST OPTIONS
- beach nourishment
- protecting Kelp beds and restoring sand dunes
- rehabilitation of wetland ecosystems
- early warning systems for residents of high tides
3) Larger settlement important for industryand trade like Walvis bay
EXPENSIVE OPTIONS
- sea walls
- relocation of vulnerable communities
- raising of infrastrcture (ports and roads)
- building barrages and barriers
positive:
- they managed to effectively split resources to meet the needs of the population through building sea walls around industrial areas that could not move and using sustainable forms of protection
negative:
- however the limited protection in which this soft engineering offered meant that it led to the forced relocation of the rural settlements, displacement in community leading to fall in lived experience
what are destructive waves like?
- they degrade a beach
- high waveheight, low wavelength
- backwash > swash
- drags sediment back to sea
- scours beach
- 13-15 break/minute
- high energy
- causes cliff retreat
- plunging breaker
- steep beach
what is rockfall/blockfall?
- most likely to occur when strong, jointed and steep rock faces/cliffs are exposed to mechanical weathering or marine erosion,happens on slopes over 40 degres
- once broken away, it can form scree at the bottom of the cliff
blockfalls- similar to rock falls but here a large block of rock falls away from the cliff as a single piece.
what is mudflow?
Flows occur when unconsolidated fine grained sediment, e.g. silts and clays, mix with large volumes of water. They’re common in weak rocks such as clay or unconsolidated sands. They become saturated, lose their cohesion, and flow downslope.
- difference between a slide and a flow is that in a slide the material remains intact but in a flow the material becomes jumbled up
examine the influence of dips on cliff profiles
Landward dipping- they are relatively steep and stable, decreasing recession rates
Seaward dip- high angle produces low-angle profile with one rock layer facing the sea, low angle produces steep face with overhanging rocks
Horizontal dipping- vertical profiles with notches where weaker strata have been eroded, reflecting weathering and small scale mass movement
describe the essential features of the nearshore
- it isthe zone extending seaward from the low water line beyond the surf zone, it defines the area influenced by the nearshore or lowshore
- Shallow water close to the tide line but covered by water at normal low tides Here we see the formation of ridges and runnels.
explain folds
- they are bends in rocks formed by pressure during tectonic activity which makes rocks buckle and crumple - the main two types are anticlines and synclines - folden rock is often more heavily fissured and jolted, meaning they are more easily eroded, also increases erosion by increasing angle of dip and causing joins through the stretching along anticline crests an compressed in syncline troughs
explain the differential erosion on cliffs due to their complex profiles
- groundwater flows through the permeable sands but cannot through the impermeable clay. water flow along the sand/clay interface weakens the material leading to slumping
- poor water pressure (the internal force within cliffs exerted by groundwater) in the saturated layers pushes rock particles apart, reduces fractions and lubricates lines of weaknesses
- wave cut notches are created by erosion of the weak coal layers with more resistant siltstone overhanging the coal below
- the resistant rock creates a ‘bench’ feature at the cliff base
what might influence how vulnerable a cliff is to mass movement?
- lithology and structure of a cliff can determine mass movements it is vulnerable to
- weathering processes cancontribute to the loosening of cliff faces so that mass movements are more likely
- water from rainfall is often a key cause of mass movements
- angle of the slope will also affect vulnerability
what is a CBA and how is it difficult?
it is worked out by seeing if the benefits outweigh the costs and so a value of the land is a key consideration in the decision making process
- it is controversial as the value of property is dependant on how at risk it is as a home, at very high risk it could be worth norhing whereas a very similar house which is safe could be worth £300k
- some human costs (worry, stress) and environmental costs (value of biodiversity) are very hard to quantify in financial terms
what is landward dipping strata?
produces steep profiles on 70º-80º as downward gravitational force pulls loosened blocks into place, very stable with few rock falls
when it develops horizontal joints it will encourage weathering and mass movement
what is a terraced cliff profile?
this where the cliff profile is stepped due to lithology or fractures in the rock.
- it can often form after slumping
what is a wave-cut platform?
a curved indentation of about 1-2m high extending along the base of a cliff. it forms between the high and low tide marks, where destructive waves impact against the cliff.
explain faults
- formed when he stress of pressure not which a rock is subjected, exceeds its internal strength (causing it to fracture). the faults then slip along fault planes. - it significantly increases erosion since faulted rocks are much more easily jointed - huge forces are involved in faulting and displacing them and therefore either side of the fault line, rocks are often heavily fractured example: in bantry bay in cork in the republic of Ireland there is a major fault which runs SW-NE down the centre of the bays. the limestone is weakened allowing rapid fluvial erosion
how are waves created?
waves are created through friction between the wind and water surface, transferring energy from the wind into the water. this generates ripples, which grows into waves whedn the wind is sustained.
what is differential erosion
where cliffs are composed of differing lithology, leads to different sections of a cliff eroding/receding at different rates. it can also be produced when there are alternating permeable and non-permeable strata
they may form a ‘bench’ feature at the cliff base and further up overhanging sections until they collapse by mass movement.
however, the overall rate of recession is determined by the resistance of the weakest rock layer
explain joints
- (vertical cracks), these are fractures caused either by contraction as sediments dry out or by earth movements during uplift - they are fractures created without displacement and occur in most rocks, dividing rock strata up into blocks with a regular shape - jointing increases erosion rates by creating fissures which marine erosion processes such as HA can exploit example: in bantry bay, the limestone is heavily pointed, leading to more rapid fluvial and marine processes in adjacent sandstones
what are beach profiles like in winter?
destructive waves scour beach winter and create offshore bars and flatter beaches
- destructive waves occur at a higher frequency
- berms are eroded by plunging waves and high-energy swash
- strong backwash transports sediment offshore (offshore bars are made)
- destructive, high-energy waves dominate in the winter, lowering angle of beach profile and spreading shingle over the whole beach
what is integrated coastal zone management?
ICZM takes a holistic approach to a coastline and it required cooperation from stakeholders so conflict is inevitable
it dates from the Rio Earth summit in 1992 and it has three main features:
- that the entire coastal zone needs to be managed rather than individual towns or cities
- the importance of the coastal zone to people’s livelihoods and well-being
ICZM works well with the concept of sediment cells, each cell can be managed as a holistic unit.
- this is normally present along a long coastline, e.g Namibia (sea level rise different along coast, economic value differ)
the main 4 things it should incorporate are:
- plan for the long term
- involve all stakeholders and ensure that they have a say in any policy decisions
- follow an ‘adaptive’ approach to unforseen changes
- try to work with natural processes rather than against them
explain cliff drainage and its pros and cons
if the cliff consists of a permeable layer above an impermeable layer it can become unstable after heavy rain due to pore pressure. so by inserting pipes to take out the water that has percolated through, saturation is prevented and it is less likely to slump
example: Barton-On-Sea, Hampshire
advantages:
- drainage is cost-effective
- In-cliff drainage reduces pore-water pressure and mass movement risk
disadvantages:
- not aesthetically pleasing
- can weaken the cliff when inserted, they dry out leading to them to collapse,disturbing the cliff stability
- cannot prevent weathering and subsequent rock fall
what is lithology?
refers to the physical characteristics of the rock. igenous, metamorphic, sedimentary and unconsolidated rock each have different characteristics.
it also influences geological structure on ameso (medium scale) and micro scale (some types of rocks are more likely to have joints and bedding planes)
explain igneous rocks
- their crystalline structure (interlocking cystals) means they are well connected and impermeable with few lines of weaknesses (resistant)
- these rock types create rocky coastlineswith steep profile cliffs
- erosion rates: 0.1-.0.3 cm/yr
- e.g. granite, basalt
- example: lands end, Cornwall (granite)
what are the strategies used to help and adapt in sustainable coastal management?
1) educating communities to understand why change is needed and how to adapt
2) monitoring coastal change and adapting to unexpected trends
3) creating alternative livelihoods before existing ones are lots to the sea
4) managing natural resources (fish,farmland,water supplies) to ensure long-term productivity
5) managing flood and erosion risk where possible, managed retreat and soft engineering
6) adapting to rising sea levels by relocating, alternative building methods and water supplies
what is the relief of an area affected by?
the relief or height and slope of land is also affected by geology and geological structure. there is a direct relationship between rock type, lithology and cliff profiles
which area suffers from the greatest waves?
the southwest due to the long fetch along the atlantic
what are the different types of biological weathering explained
rock boring
clams and molluscs bore (dig) into rock to make their homes. they can also secrete acids that dissolves rocks. sedimentary rocks in the intertidal zone are vulnerable.
-piddocks drill depressions into sock rocks by rotating their shell equipped with sharp edges
- effects: holes and weaknesses created are vulnerable to erosion and further weathering
plant roots
- tree and plant roots growing into cracks can slowly widen them and cause them to break apart. important process on vegetated cliff faces.
- seeds falling into cracks in rocks can germinate, nourished by rainwater and nutrients from wind-blown sediment.as the plant grows its roots expand and thicken,tree roots exert sufficient tensional force to widen the crack
- effects: eventually angular fragments of rock break away as cobble or boulder-sized sediment, rock falls
seaweed acids
- some seaweed species like kelp contain pockets of sulphuric acid that can burst on rocks and dissolve them
- when the cells break sulphuric acid attacks rock minerals like calcium carbonate leading to a chemical reaction similar to carbonation
- effects: leads to crumbling of the cliff as sections are no longer bonded together
what is a cliff profile?
the height and angle of a cliff face, plus its features such as wave cut notches or changes in slope areas
what are the different types of mechanical weathering explained
freeze thaw
- water gets into the cracks and freezes and expands up to 9%. this exerts pressure on the cracks which loosens and breaks apart rock. most vulnerable are well jointed rocks, only happens when daily temperatures fluctuate around zero degrees.
- effects: creates angular rock fragments at the base of the cliffs called scree and a jagged cliff face. also can contribute tolarge rock falls.
salt crystallisation
- salt spray or waves hitting cliffs makes them wet with seawater. this evaporates and leaves salt in cracks on the cliff. overtime, salt crystals form and grow, exerting pressure on the cracks and pores which loosens and breaks apart rocks. most vulnerable are well jointed rocks (limestone) and porous rocks (sandstone). happens most in hotter climates
- effects: creates angular rock fragments at the base of cliffs called scree. some rock faces crumble away.
wetting and drying
- rocks rich in clay expand when they get wet and contract when they dry. this repeated process causes them to crack and break apart
- effects: cracks form in cliffs so they become vulnerable to slumping.
what did the CBA show in Happisburgh?
- they chose the ‘no active intervention’ in the immediat efuture as defending the area would have an impact on the wider coastal management plan. it would block LSD and cause further erosion downdrift.
- longer term plan is managed realignment
- the median cost of building defences here is £6 million. this is very close to the value of property that could be saved and much higher than the compensation costs payable to local residents
- coastal managers argue that the area should be seen in the wider context of the whole SMP, further justifying the decision not to defend the village
what are the positives and negatives and winners and losers of the SMP in. chittagong
positives:
social winners- helped alleviate poverty by 10% by generating income opportunities
reduced disaster risk, road flooding 5 days a year rather than 20
environmental winners- environmental enhancement through growing trees
negatives:
- disturbance of people and habitats especially during construction
- conflicts with environmentalists over the permanent removal of natural vegetation
- relocation of 200 people by road realignment
- slow progress on road embankments
winners:
farmers, local community seeking jobs,market sellers
losers:
community who are relocated and disturbed by construction , environmentalists through removal of natural vegetation
what are micro features?
- small-scale features such a scales and wave-cut notches which form part of a cliff profile - the location of these micro-features are often controlled by the location of faults and/or strata which have a high amount of joints and fissures
what is the funnelling effect?
when the land is in a triangle shape and so it becomes narrower and shallower towards the coast it means that wave height increases as the volume of water is in a smaller space. this is seen at the bay of bengal in bangladesh
explain the positives and negatives and winners and losers in Happisburgh
positives:
- the gov started providing grant aid of £5000 to assist with demolition costs and £1000 for relocation costs
- they obtained a gov allocation of £3 million partly because of its emphaiss on ICZM and stakeholder engagement
- all but caravan park were able to relocate due to difficulties of finding an alternative site
- the community remains the same size and profits from the sale of the new houses will be used in the future to buy properties of those under threat from CE
negatives
- by 2105, the shoreline may recede by 200m with a loss of a further 50 homes, caravan sites and property losses totalling £6m
- in 2003, the lifeboat and beach access ramp were lost, prompting concerns for their tourism
- house values are very low and people cannot afford to move elsewhere
- there is no national system of compensation but campaigning led to pathfinder project where people along beach road were offered half the non blighted value of their home to help them relocate, houses now demolished to create buffer, all but one took it
- there could be a promontary effect where erosion comes either sides and comes round the back
- the existing rip rap will have limited effect on the rate of recession in the short term
winners:
- those who have successfully relocated
social winners: originally there was no national system of compensation but those along beach road were offered half the non blighted value of their home to help them relocate through the pathfinder project, £1.4 million set aside for ‘purchase and lease-back’
losers:
social losers: those who are closest to cliff face who cannot afford to relocate
economic losers: businesses relying on tourism industry after seeing in 2003 the beach access ramp and lifeboat being lost to sea
social losers: local residents initially until they campaigned and were offered half the blighted value of their homes
- local council, large costs of relocating
how do cliffs vary in morphology?
they vary in their morphology depending on lithology and weathering are actively eroded by wave action or they are affected by sub-aerial processes
how are erosional processes influenced by wave type, size and lithology?
- most effective during high energy storm events with large destructive waves
- most effective in winter, in high energy storms
- faster when the tide is high
- sedimentary rocks with joints are more vulnerable to HA and abrasion
- limestone and chalk vulnerable to solution
what are constructive waves like?
- they aggrade a beach
- low waveheight, long wavelength
- swash > backwash
- brings sediment back to the sea
- builds beach up
- 6-8 break/minute
- low energy
- spilling breaker
- flat beach
what are rates of recession influenced by?
1) geology
2) lithology
3) weathering
4) mass movement
- how reactive minerals in the rock are when exposed to chemical weathering
- whether rocks are clastic (less) or crystalline (more resistant)
- the degree to which rocks have cracks, fractures and fissures
how is weathering and erosion different?
erosion also involves the transport of sediment away from the cliffs, the erosion occurs by an external agent
what is sustainable coastal management?
- management that meets the need of the present and future (environmental, social and economic)
it is increasingly based on adaptation strategies due to increasing recession rates
what are landslides?
rocks that have jointed or having bedding planes parallel to the slope are susceptible to landslides. increased water leads to less friction, leading to sliding
what is soil creep?
the slowest form of mass movement, an almost continuous process, it is a very slow downhill movement of individual soil particles
what does wave size depend on?
- the strength of the wind
- how long has the wind been blowing for
- the length of the fetch
what is a high angle of seaward dip
produces a sloping, low-angled profile with vulnerable rock layers, loosened by weathering. rocks slip down the bedding plane creating an angled cliff face
= talus/scree
how does the size of sediment vary on a beach?
as constructive waves have a weaker backwash can only transport smaller particles down the beach. this leads to the sorting of material with larger, heavier shingle at the back of the beach (storm beach) through the powerful storm waves in extreme high tides having the energy to transport here and the sand drawn back closer to the sea.the backwash onlyhas enough energy to transport down smaller sediment, not aided by the percolation.they also become more angular at the back of the beach and rounder at the front of the beach.
what is cliff regrading and what are the pros and cons
if the cliff lithology is unstable and vulnerable to slumping after heavy rainfall, engineers calculate a stable angle for the particular rock and the cliff is artificially cut back, reducing its angle to make it more stable.
example: Barton-On-Sea, Hampshire
advantages:
- regrading can work on clay or loose rock where other methods won’t work
- allows the build up of the beach
disadvantages:
- very expensive (about £1 million)
- unaesthetically pleasing, not natural, can be disruptive during construction
- cliff line retreats into valuable land when constructed
- not full proof in extreme conditions, other measures needed
what is the difference between macro, meso and micro scales?
macro scale- concordant and discordant coastlines (encourages headlands and bays or coves)
meso scale- (measured on a stretch of cliff) dip of strata (bedding planes), differential erosion from mixed lithology layers
micro scale- (measured on a single cliff) joints, these are vulnerable to HA, freeze thaw, salt crystallisation and bio weathering
how are waves created?
1) waves move across open ocean in circular motion as ocean swell
2) as the waves reach shallower water, when their wave height is less than half the wavelength then friction increases slowing the wave down for the circular oscillations to become more so elliptical
3) as the wavelength decreases due to the shallower water, wave height increases and eventually the wave breaks as the top of the wave is moving faster than the base
4) the waves then lose enrgy and gravity pulls the water back as backwash
what is beach nourishment and what are the pros and cons?
sand is dredged from the seabed and pumped onto the beach to replenish it from the effect of LSD or destructive waves. the beach can be ‘reprofiled’ to recreate its original shape.
example: Pevensey Bay, Sussex
advantages:
- it looks natural and blends in with the existing beach
- it increases tourist potential by creating a bigger beach
- beach absorbs wave energy
disadvantages:
- will need to be done every few years as LSD/destructive waves will continue to remove beach sediment, ongoing costs are high
- can disrupt the marine ecosystem or the natural sediment cycling and deepening offshore so waves have more energy
explain unconsolidated sediment
- they are the least resistant, they are not cemented together in anyway so are very vulnerable to erosion, fast recession rates
- can create slumped coastlines due to mudslides/landslides causing slumping, stepped profile through rotational slumping
- the boulder clay of Holderness coast in Yorkshire retreats at a rate of 2-10 m p.a
- boulder clay erosion rates: 100-1000 cm/yr, sandstone rate: 10-100 cm/yr
what is a low angle of seaward dip
produces a steep profile that may even exceed 90 degrees, creating areas of overhanging rock, vulnerable to rock falls, it encourages weathering and mass movement
explain the sustainable management in Happisburgh
- no active intervention due to promontory effect, blocking LSD for downdrift
- by 2105, the shoreline may recede by 200m and 50 homes will be lost
- they have repeatedly failed to quanitfy for gov grants for coastal defences. managed retreat has been operated which has caused conflict among locals and especially residents of beach road on the coastline
- the gov started proviidng grant aid of £5000 to assist with demolition costs and £1000 for relocation costs
- no national compensation but campaigning led to pathfinder project where £1.4million was set aside for ‘purchase and lease-back’ of 11 houses on beach road to create a buffer zone between the eroding cliff and the main village, people offered half the value of their home to relocate, all but one took it
- they have spent lots of money relocating important sites like the caravan park (450k) and taking out the defences
- lobbying by the CCAG and others have led to a change in the SMPZ policy for them to follow ‘managed realignment’ which allows for some coastal defences if funding can be found
what is soft engineering and what are the 3 methods?
it makes use of natural systems such as beaches, sand dunes and salt marshes to help with coastal defence
beach nourishment
cliff regrading and drainage
dune stabilisation
describe the essential features of the foreshore
the area between the HWM and the LWM. The most important zone for marine processes. Only exception is during storm events (the tidal range), if it is a small tidal range there are fewer processes.
what is horizontal dipping
a vertical or near-vertical profile, notches reflect weathering and small scale mass movement
what are subaerial processes
they are processes that affect the cliff face rather than the cliff foot. they are land-based processes which later the shape of the coastline. they are a combination of weathering and mass movement
what is the fetch?
this is the uninterrupted distance across water over which the wind blows and therefore the distance waves have to grow in size
how can conflicts between players develop over management decisions? give case studies
Blackwater estuary, Essex
- the west mersea fisherman were concerned that sediments could choke and kill oysters and water sea level changes could remove oyster habitats
- the RSPB were concerned about the increased erosion and flooding of their site opposite the farm which could change bird habitats
Chittagong, Bangladesh
- environmentalists concerned about the permanent removal of natural vegetation
- local communities concerned about the fact that 200 people would have to be relocated, breaking up communities
Maldives
- there is conflict over adaption to SLR. Currently the government have prioritised protecting capital city of Malé and its tourism industry but it is not prioritising smaller communities that rely on traditional industries (farming, fishing)
- Smaller communities left to seek help from NGOs and other governments (mangroves for the future educating on the restoration of mangroves and the Japanese gov funding mangrove nurseries, Global environment facility supplying small grants to islanders to help them develop organic farming and move away from coral reef
Happisburgh
They have chosen a no active intervention approach after doing a CBA
- this has caused conflict between local residents and the authorities as people are having to relocate losing their home and community, beach road residents relocated and given half the value of their home but people believe their homes are worth a lot more, shoreline said to recede by 200m by 2105, house values are very low and so people cannot afford to move elsewhere
- lobbying by the CCAG led to a change in policy to allow for some defences if funding is found
what are the different types of chemical weathering
these become greater in hotter and wetter climates
carbonation
- this is where limestone slowly dissolves as it reacts with weak carbonic acid
- This attacks calcium carbonate in limestones, other carbonate rocks and sedimentary rocks with calcite sediment.
- effects: joints and cracks get wider on cliffs and wave cut platforms. this makes them more vulnerable to other weathering and mass movement processes
oxidation
- oxygen combines with iron based minerals in a rock causing a chemical breakdown of the minerals shown by red rusty colour on the rock face. it produces iron oxides and increases in volume, leading to mechanical breakdown.sandstones and shales often contain iron so are vulnerable.
- effects: leads to crumbling of the cliff as sections are no longer bonded together
what are the 4 erosional processes explained?
abrasion- the rubbbing together of hard load, sand paper effect
attrition- rocks bashing into one another breaking them down
hydraulic action- air trapped in cracks and fissures is compressed by the force of the waves crashing against the cliff face. when the wave retreats, pressure is released explosively which can widen cracks and dislodge blocks friom the cliff face
solution- where water in waves dissolves rock minerals
what are the micro features of a cliff and how are they formed?
These are small-scale features such as wave-cut notches, caves, stacks or blow holes. They are normally formed through the presence of faults and strata which have a high amount of joints and fissures.
explain dips
- refers to the angle at which rock strata lie (horizontally, vertically, dipping towards the sea or dipping inland) - its a tectonic feature, sedimentary rocks deposited horizontally can be tilted by faulting and folding by tectonic forces
what is a talus/scree slope?
The angular blockfall debris accumulates at the cliff foot to form atalus scree slope, a fan shaped mound of material.
formed from a blockfall
explain dune stabilisation and what are the pros and cons?
protecting this ecosystem can provide natural protection for the coastline. it is mainly damaged by vegetation removal which can lead to blowouts. strategies include:
- geotextile netting can reduce erosion but still allow water in
- vegetation planting (marram grass) to encourage sand deposition
- fences and boards put up so tourists don’t stand on the dunes, they are given an area to walk on
- afforestation with quick-growing conifers
example: Studland, Dorset
advantages:
- can be very cost effective in the long term
- it provides important wildlife habitats
disadvantages:
- only effective if public access controlled by fences and signs which reduces amenity value
- strong storms can still cause damage
- time consuming to plant marram grass
- people may respond negatively to being kept off certain areas
what is weathering?
the decay and disintegration of rock in situ (where they are) by mechanical, biological or chemical agents.
using cliff profiles explain how recession rates can differ
- recession rate increases if dip is towards so as weathering opens joints and gravity speeds mass movement
- steep dip to the sea increases erosion rate as gravity makes bedding planes unstable and slabs slide downslope. this increases recession rates
- a cliff with landward dipping bedding planes are relatively steep and stable whcih decreases recession rates
- landward dip with well-developed joints will increase recession rates as joints acts as slide planes
what is beach morphology?
the shape of a beach including width and slope (profile) and other features such as berms
why is coastal management increasingly following an ‘adaptation’ policy and what does it involve and lead to ?
- in order to use the latest scientific understanding
- evaluate new coastal developments
- ensure that any necessary developments provide social and economic benefits
- ensure the overall long-term sustainability of coastal areas, will it affect other areas of the coastline?
leading to:
- the high costs of building and maintaining a coastal defence against large-scalel natural processes means that some locations will not be supported by gov funding
- the potential loss of property and cultural heritage has led to conflict between govs and communities
- the UK gov, through the environment agency and Defra encourages local communities and council to adapt themselves, e.g. through the ‘pathfinder initiative’
why does adopting sustainable coastal management often lead to conflict?
- lower demand for coastal natural resources in order to protect them (loss of income)
- relocation may be needed where engineering solutions are too costly
- some erosion/flooding will always occur, as engineering schemes cannot protect against all threats
- future trends such as SLR may change, creating uncertainty and the need to change plans
what are the 4 possible actions in a SMP?
the hardest part is the decision making process to decide what actions to take. in the UK there are four different management options to follow:
1) no active intervention
- no investment will be made in coastal defences
- letting nature take its course and allowing the sea to erode and flood low-lying land
2) hold the line
- trying to eliminate any further retreat of the coast, involves a mixture of hard and soft engineering
- maintaining the current position of the coastline
3) advance the line (build new coastal defences on the seaward side of the existing coastlines. this usually involves land reclamation.)
- may involve drainage as well as other hard engineering techniques
- extending the coastline out to sea through encouraging the build up of a bigger beach
the choice is generally not straightforward due to a number of factors:
- the economic value of the assets that might be protected
- the technical feasibility of different engineering solutions
- the environmental sensitivity
- the cultural and ecological value of the land that might be protected
- pressure from local communities, developers and environmental groups
4) managed realignment/retreat - involves allowing the coastline to retreat but in a managed way
- removal of existing hard engineering defences and using more natural and sustainable techniques including protection, management or restoration of coastal ecosystems such as salt marshes and sand dunes, e.g. porlock bay
what are beach profiles like in summer?
constructive waves build up the beach in summer creating a steeper beach
- they are steeper in summer, where constructive waves are more common than destructive. wave energy dissipates and deposits over a wide area.
- as the berm builds up, the backwash becomes weaker and only has enough energy to move smaller material, so the beach material becomes smaller towards the shoreline
what are SMP decisions based on?
1) CBA- value of the land (properties and business that would be lost) vs the cost of the proposed management strategies
2) Environmental sensibility throughEIA- short and long term positive and negative impacts on environment: changes to flora and fauna, impacts on water and air quality
3) technical feasibility- it is not possible to hold the line in all areas, e.g. dynamic deposition features such as spits
4) social and political factors- impact, pressure from communities: campaigning and loss of property, business and stress
any decision also needs to be informed by the results of objective investigations, such as a CBA and EIA
explain metamorphic rocks
- they are also well-connected and impermeable
- however they are often folded and faulted so have weaknesses
- these rock types create rocky coasltines with steep profile cliffs (depending on folding and dip) and erode slowly
- erosion rates: 0.5-1 cm/yr
- e.g. marble, slate, schist
- crystalline rocks are resistant to erosion
- example: St Ives, Cornwall (slate)
what are the different players involved in shoreline management plan
- homeowners
- local authorities
- environmental pressure groups
what are cliff profiles influenced by?
- geology, especially the resistance to erosion of the rock
- the dip of rock strata in relation to the coastline
explain the conflicts happening in the Maldives
- the gov have prioritised protecting the capital city Male and its tourism industry over smaller communities that rely on traditional industries (farming, fishing), they have built a large sea wall around the capital
- mangroves for the future is an organisation that promotes sustainable development and is helping the maldives to become more sustainably managed for the future by:
1) educating communities on the importance of maintaining coastal mangrove swamps as a natural defence against coastal erosion and flooding
- the Global Environment Facility (GEF) has provided small grants to islanders to help them develop sustainable and organic farming as an alternative food and income source to coral reef fish (threatened by both overfishing and global warming)
- the Japanese gov have funded mangrove nurseries on the maldives so that damaged mangrove areas can be replanted
how should sustainable management be done?
by taking the area as a whole, taking into consideration each littoral cell and how they interlink. it requires making use of the concept of integrated coastal zone management.
coastal communities face the dynamic nature of the coast’s everyday environment and the threats we face such as rising global sea levels and increased frequency of storms and increased erosion and flooding
what are concordant coastlines?
- this is where rock starts runs parallel to the coast forming bays and coves - example: the souther coast of the isle of purbeck has formed lulworth cove and kimmeridge bay due to its concordant structure§
what is mass movement
the movement of material downslope as the result of gravity. water commonly acts a lubricant in mass movement.
explain an environmental impact assessment (EIA)
any type of coastal management usually requires an EIA
it is a process that aims to identify:
- the long term impacts of building new sea defences or changing a policy from hold the line to no active intervention or managed realignment
- the short term imapcts on the coastal environment of construction
EIA involves assessments of:
- impacts on water movement (hydrology) and sediment flow which can affect marine ecosystems
- impacts on water quality, which can affect sensitive marine species
- possible changes to flora and fauna including marine plants and marine mammals
- wider environmental impacts such as air quality and noise pollution during construction
what are examples of the winners and losers of sustainable coastal management
Winners
1) environmental winners- blackwater estuary, new habitats been created with the wetland, conflicts resolved
2) economic winners- protection of important trade areas, Namibia, different management depending on the area, sustainable, split the resources effectively to protect the area, building sea walls around areas that could not be relocated (walvis bay) and rehousing those who were mobile
Losers
1) social losers originally- no compensation for homes until campaigning by the pathfinder project led to half the blighted value of the homes, all but one accepted it
2) environmental losers- Chittagong, permanent removal of natural vegetation, disturbance to environment during construction
