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Rivers and coasts Flashcards

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1
Q

What are sediment cells?

A
  • Sections of coasts that are mostly closed system and there are 11 of them in England Wales
  • In a state of dynamic equilibrium, input and output constantly changing but remain in balance
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2
Q

What is a positive feedback loop?

A
  • When a coast is taken away from a state of dynamic equilibrium
  • If people walk over a sand dune and the vegetation is destroyed the dune becomes more susceptible to erosion and over time it will completely erode and deposition will stop
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3
Q

What are the littoral zones?

A
  • The littoral zone is the area of the coast where land is subject to wave action. It is constantly changing and varies

Offshore: The area of deeper water beyond the point at which waves begin to break. Friction between the waves and the sea bed may cause some distortion of the wave shape.
Nearshore: The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the wave sufficiently to cause it to break. (breaker zone) There may be a breakpoint bar between the offshore and nearshore zones.
Foreshore: The area between the high tide and the low tide mark.
Back-shore: The area above the high tide mark, affected by wave action only during major storm events.

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4
Q

What is valentines classification?

A
  • The different types of coastlines
  • Advancing coastlines are caused by emerging coasts or high levels of deposition
  • Retreating coastlines could be caused by submergence or erosion
  • Emergent coastlines caused by post-glacial rebound and sea level drop
  • Submergent coastlines caused by emerging coast lines, tectonics and crustal sag
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5
Q

What are the 6 types of erosion?

A
  • Abrasion, sediment is carried along the coastline scraping it and damaging it
  • Attrition, Stones and pebbles hit against each other smoothing each other out.
  • Hydraulic action, air is forced into the cracks of a cliff causing pressurised explosions fracturing the cliff breaking off chunks
  • Solution, mildy acidic sea water can cause alkali rock such as limestone to erode
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6
Q

When are erosion rates highest?

A
  • Waves have a long fetch
  • They approach the cliff perpendicular
  • High tide, more cliff is able to be eroded
  • Heavy rainfall, water permeates through permeable rock weakening cliffs
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7
Q

What are the factors affecting a rocks vulnerability to rock?

A
  • Whether they are clastic or crystalline, clastic means sedimentary meaning cemented sediment particles which are more easily eroded
  • Amount of cracks, fractures and fissures
  • The lithology of a rock
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8
Q

What are the three types of rock, examples of each and their vulnerability to erosion?

A
  1. sedimentary
    - Ex: Limestone
    - Rate of erosion: very fast
    - Structure: Lots of faults and bedding planes
  2. Metamorphic
    - Ex: Slate, schist, marble
    - Rate of erosion, slow
    - Structure, Crystal all face in same direction
  3. Igneous
    - Ex: granite, basalt
    - Rate of erosion, Very slow
    - Structure, Interlocking crystal meaning high resistance
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9
Q

How do cave, arches, stacks and stumps form?

A
  • Occurs on headlands
  • Cave, marine erosion widens faults in the base of headlands
  • Arch, cave widens due to marine erosion and sub-aerial processes eroding either side of the headland
  • Stack, arch continues to widen until it cant support itself detaching from the mainland due to mass movement
  • Stump, Marine erosion attacks the bottom of the stack causing it to fall forming a stump
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10
Q

How do wave cut notches and platforms form?

A
  • Marine erosion (abrasion) attacks the bottom of the cliff forming a wave cut notch, sub aerial erosion weakens the cliff from the top and the cliff face becomes unstable and topples through mass movement leaving behind the smooth platform of unaffected cliff base.
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11
Q

How are retreating cliffs formed?

A
  • New cliff faces are formed through repeated platforms and notches cause a retreating coastline forming new vliff faces
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12
Q

How is a blow hole formed?

A
  • Pothole on the top of a cliff caused by chemical weathering
  • Marine erosion forms a cave in the cliff
  • The two eventually meet and waves travel up the blowhole splashing out the top
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13
Q

What is longshore drift?

A
  • Transports sediment along coasts and sediment cells
  • Waves hit the beach at an angle according to the prevailing winds
  • Waves push sediment up the beach in this direction in the swash
  • Due to gravity wave carries sediment back down the beach known as backwash
  • This moves sediment down the beach over time
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14
Q

What are the different alignments of waves?

A
  • Swash aligned, wave crests approach parallel to coast meaning little longshore drift
  • Drift aligned, sediment travels far up the beach due to significant angle of waves
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15
Q

What are the different types of deposition?

A
  • Gravity settling, waves energy becomes low and sediment is deposited starting with the largest pieces
  • Flocculation, Particles clump together due to chemical attraction and sink due to high density.
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16
Q

How do spits form?

A
  • A spit is a long strip of deposited material
  • Longshore drift occurs and the waves lose energy usually behind a headland depositing sediment
  • This creates a spit and over time the prevailing wind will change causing a hooked end
  • The water behind it will form a salt marsh strengthening the spit
  • The length will be capped depending on surrounding currents and estuaries preventing deposition
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17
Q

How do bars form?

A
  • A spit stretches across a bay over time uniting two headlands forming a lagoon behind it and due to it being a low energy area it may become a salt marsh
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18
Q

How do tombolos form?

A
  • A beach or bar that connects to an islan due to wave refraction from the island reducing wave velocity May be covered at high tide
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19
Q

How do cuspate forelands form?

A
  • Occurs on triangle shaped headlands
  • Longshore drift on each side forms beaches and when they meet form a cuspate foreland
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20
Q

How do offshore bars form?

A
  • Waves dont have enough energy to carry sediment to the beach
  • Formed when the wave breaks early scouring the seabed depositing its sediment
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21
Q

How do sand dunes form?

A
  • Prevailing winds blow sediment to the back of the beach
  • Require large amounts of sand and a large tidal range so the sand can dry and is light enough to be carried by the wind to the back of the beach
  • Embryo dunes, Upper beach area where sand begins to accumulate around a small obstacle
  • Yellow dunes, as the dune gets bigger vegetation may begin to strengthen the dune which is the tallest one over the whole process
  • Grey dunes, sand develops into soil with lots of moisture and nutrients as vegetation dies enabling more growth
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22
Q

How do dune slacks form?

A
  • ## Water becomes trapped between dunes allowing moisture loving grass such as willow grass
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23
Q

How does health and woodland form?

A
  • Sandy soils develop allowing less brackish plants allowing the growth of woodland
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24
Q

What factors affect the stability of depositional landforms?

A
  • Major storms can transport major amounts of sediment
  • Depositional landforms rely on continuous amounts of sediment meaning a change in dynamic equilibrium can influence landforms
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25
Q

What is weathering?

A
  • Weathering is the breakdown of rocks (mechanical, biological or chemical) over time, leading to the transfer of material into the littoral zone, where it becomes an input to sediment cells.
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26
Q

What are the different types of physical weathering?

A
  • Freeze-thaw (Frost-Shattering): Water enters cracks in rocks and then 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 these cracks grow, weakening the cliff making is more vulnerable to other processes of erosion
  • Salt Crystallisation: As seawater evaporates, salt is left behind. Salt crystals will grow over time, exerting pressure on the rock, which forces the cracks to widen. Salt can also corrode ferrous (materials that contains iron) rock due to chemical reactions
  • Wetting and Drying: Rocks such as clay expand when wet and then contract again when they are drying. The frequent cycles of wetting and drying at the coast can cause these rocks and cliffs to break up
27
Q

What are the different types of chemical weathering?

A
  • 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 then be easily dissolved. Acid rain reacts with limestone to form calcium bicarbonate, which is then easily dissolved allowing erosion.
  • Oxidation: When minerals become exposed to the air through cracks and fissures , the mineral will become oxidised which will increase its volume (contributing to mechanical weathering), causing the rock to crumble. The most common oxidation within rocks is iron minerals becoming iron oxide, turning the rock rusty orange after being exposed to the air.
  • Solution: When rock minerals such as rock salt are dissolved.
28
Q

What are the different types of biological weathering?

A
  • Plant Roots - Roots of plants growing into the cracks of rocks, which exerts pressure, eventually splitting the rocks. Research Angkor Wat for more information on this, even though it is not coastal!
  • Birds - Some birds such as Puffins dig burrows into cliffs weakening them and making erosion more likely.
  • Rock Boring - Many species of clams secrete chemicals that dissolve rocks and piddocks may burrow into the rock face
  • Seaweed Acids - Some seaweeds contain pockets of sulphuric acid, which if hit against a rock or cliff face, the acid will dissolve some of the rock’s minerals. (e.g. Kelp)
  • Decaying Vegetation - Water that flows through decaying vegetation and then over coastal areas, will be acidic, thus causing chemical weathering
29
Q

What is mass movement and what influences it?

A
  • There are several types of mass movement, which tend to be determined by the weight of the sediment and its ability to flow downhill.
    The type of mass movement that occurs depends on:
  • the angle of the slope/cliff
  • the rock’s lithology and geology
  • the vegetation cover on the cliff face
  • the saturation of the ground/ previous weather patterns
30
Q

What are the different types of flowing mass movement?

A
  • Soil creep, soil particles slowly move downhill continuously
  • Soilfluction, In tundra areas, top layer melts in summer flowing over bottom layer of ice
  • Mudflows, Increase in water content reduces friction in soil encouraging mudflows
31
Q

What are the different types of sliding mass movement?

A
  • Occur on sloped cliffs (over 40o ) when exposed to mechanical weathering.
  • Rock slides - Water between joints and bedding planes (which are parallel to the cliff face) can reduce friction and lead to more sliding.
  • Slumps - Occur when the soil is saturated with water, causing a rotation movement of soft materials (such as clay and sand) forming rotational scars and terraced cliff profiles.
32
Q

What are cliff profiles and whaat influences them?

A
  • Cliff profiles are influenced by many factors but the two main characteristics that dominate are:
  • The resistance of the rock to erosion
  • The dip in rock strata in relation to the sea
    Many cliffed coastlines are composite (they have different rock layers) which makes explaining cliff profiles very complex.
    Cliff profiles due to solifluction, rock falls, rock slides and slumping.
33
Q

What are concordant coastlines?

A
  • Rock strata parallel to the coastline
  • Not much erosion
34
Q

What are discordant coastlines?

A
  • Rock strata runs perpendicular to the coast
  • Some rock erodes faster than others forming headlands and bays
  • The bays cause wave refraction focusing erosion on headlands leading to more erosive features
35
Q

What are the different types of coastal vegetation and how do they help?

A
  • Xerophytes – plants that are tolerant of dry conditions.
  • Halophytes (or brackish) – plants that are tolerant of salty conditions.
  • Roots of plants bind soil together which helps to reduce erosion.
  • When completely submerged, plants provide a protective layer for the ground and so the ground is less easily eroded.
  • Plants reduce the wind speed at the surface and so less wind erosion occurs.
36
Q

What is plant succession and an example?

A
  • Long term change in the plant community
  • Pioneer plants begin to grow in mud and sand only brackish plants can grow at this point
  • Saltiness is reduced due to deposition killing the pioneer plant increasing nutrients in the soil
  • New species can colonise because f this
  • Marram grass is a very good example of a pioneer plant:
  • it is tough and flexible, so can cope when being blasted with sand.
  • it has adapted to reduce water loss through transpiration.
  • Their roots grow up to 3 metres deep and can tolerate temperatures of up to 60oC -
37
Q

What is salt marsh sucession?

A
  • Algal Stage - Gut weed & Blue green algae establish as they can grow on bare mud, which their roots help to bind together.
  • Pioneer Stage - Cord grass & Glasswort grow, their roots begin to stabilise the mud allowing the estuarine to grow.
  • Establishment Stage - Salt marsh grass & Sea asters grow, creating a carpet of vegetation and so the height of the salt marsh increases.
  • Stabilisation - Sea thrift, Scurvy grass & Sea lavender grow, and so salt rarely ever gets submerged beneath the marsh.
  • Climax vegetation - Rush, Sedge & Red fescue grass grow since the salt marsh is only submerged one or twice a year.
38
Q

What is a high energy coastline?

A
  • High-energy coastlines are associated with more powerful waves, so occur in areas where there is a large fetch. They typically have rocky headlands and landforms and fairly frequent destructive waves. As a result these coastlines are often eroding as the rate of erosion exceeds the rate of deposition.
39
Q

What is a low energy coastline?

A
  • Low-energy coastlines have less powerful waves and occur in sheltered areas where constructive waves prevail and as a result these are often fairly sandy areas . There are landforms of deposition as the rates of deposition exceed the rates of erosion.
40
Q

What influences the size of a wave?

A
  • The strength of the wind
  • How long the wind has been blowing for
  • Water depth
  • Distance of fetch
41
Q

What are the two types of waves?

A
  • Constructive waves

▪ Strong swash, weak backwash
▪ Low wave height, long wavelength
▪ Low frequency 6-8
▪ Depositional

  • Destructive waves

▪ Strong backwash, weak swash
▪ High wave height, short wavelength
▪ High frequency 10-14
▪ Erosional

42
Q

How can waves on a beach vary?

A
  • ● In summer, constructive waves dominate but destructive waves dominate in winter.
    ● Constructive waves may turn into destructive waves as a storm begins.
    ● Climate change could mean that the UK may become more stormier meaning an increase in destructive waves.
    ● Dams prevent sediment being transported from rivers and entering into the coastal area which means erosion could increase.
    ● Interference with natural processes along the coast (e.g. through human activity) could affect sediment supply across a coastal area.
43
Q

What causes short term sea level change?

A
  • High tide and low tide - a daily phenomena due to the gravitational pull of the Moon. www.pmt.education
  • Wind strength and direction - these can change causing a change in sea level for a couple of minutes or longer
  • Atmospheric pressure - the lower the pressure, the higher the sea levels
44
Q

What causes long term sea level change?

A
  • Isostatic - localised sea level change
    Isostatic sea level change could be due to post-glacial adjustment (glaciers weigh down the land beneath, and so the land subsides until it melts). For example, post-glacial adjustment for the UK after the Ice Age has caused Southern England to subside around 1mm per year and Scotland to rebound and increase around 1.55mm per year.
    Tectonic activity (such as earthquakes and volcanic eruptions) may cause land subsidence, therefore causing isostatic sea level increase.
  • Eustatic rise - Global sea level change
    Eustatic rise is due to thermal expansion. Water expands when it gets warmer, and so the volume of water increases which as a result, sea levels increase. This is due to Global Warming.
45
Q

What is coastalisation?

A
  • Coastalisation is the movement of people towards the coast. Despite having a high flood risk, may people move to the coast due to tourism, high-yield agricultural lands, or housing pressure. Coastalisation can increase the environmental vulnerability of these locals to flooding due to storm surges
46
Q

What causes storm surges?

A
  • Subsidence of the land - through tectonic activity or post-glacial adjustment.
  • Removing natural vegetation - Mangrove forests are the most productive and complex ecosystem in the world. Mangroves also provide protection against extreme weather events like cyclones which are very common in the Bay of Bengal. However, due to pressure for land space, much mangrove forests are destroyed for tourism, local industry, or housing plains.
  • Global Warming - As the surface of oceans get warmer, it is estimated that the frequency and intensity of storms
    will increase, and so the severity of storm surges and flooding is also expected to increase.
47
Q

What are the consequences for coastal communities due to erosion?

A
  • Some areas of the coast may have significantly reduced house and land prices (as the area becomes known to be at
    significant risk). This can lead to economic loss for homeowners and local coastal economies. In the UK, many insurers don’t
    provide home insurance to people living along coastlines that are at extreme risk of erosion or storm surges.
    Storm surges also damage the environment by destroying plant successions and damaging many coastal landforms. Depositional landforms, due to their unconsolidated nature, are most likely to be destroyed. Also, erosion may take place at accelerated rates or higher up along the cliff face, which can increase the risk of collapse.
48
Q

What are the two yypes of engineering?

A
  • Soft engineering, encouraging natural defences to be more effective against erosion
  • Hard engineering, using man made processes to defend against erosion
49
Q

What are the different approaches to managing coastal areas?

A
  • Hold the line – Defences are built to try and keep the shore where it is.
  • Managed realignment – Coastline moves inland naturally but managed.
  • Advance the line – Defence are built to try and move the shore seawards.
  • Do nothing – No defences are put in place and the coast is allowed to erode.
50
Q

What factors decide what defence policies to use?

A
  • Economic value of assets that could be protected is looked at, for example the important natural gas terminal at Easington would be protected however farmland and caravan parks wouldn’t
  • The technical feasibility of engineering solutions, for example a sea wall may not be possible for a certain location.
  • The ecological and cultural value of land. For example, it may be desirable to protect historic sites or SSSI.
51
Q

What is cost benefit analysis?

A
  • This is an analysis that is carried out before any form of coastal management takes place. The cost involved include construction, demolition, maintenance etc. is then compared to the expected benefits like the value of land saved, homes and businesses protected. Costs and benefits include both tangible and intangible things.
    For a project to be given the go ahead, the expected benefits have to outweigh the costs (according to DEFRAs 1:1 analysis)
52
Q

What is ICZM?

A
  • A coastal area (sediment cell) is managed as a whole. This often involves management between different political boundaries e.g in the UK different councils will have to work and manage coasts together.
  • The ICZM recognises the importance of the coast for people’s livelihoods.
  • The ICZM recognises that coastal management must be sustainable whereby economic development is important but this should come at a cost for the environment.
    The ICZM must involve all stakeholders, plan for the long term and try to work with natural process and not against them.
53
Q

What are shoreline management plans?

A
  • For each sediment cell in the UK, an SMP has been created to help with coastline management. Each SMP identifies all of the activities, both natural and human which occur within the coastline area of each sediment cell. The sediment cells are considered to be closed for the purposes of management, although in reality there will be some exchanges between the different sediment cells. SMP’s are recommended for all sections of English and Welsh coastlines by DEFRA (governing body responsible for majority of environmental protection in the UK). Four options are considered for each stretch of the coastline:
54
Q

What is an offshore breakwater?

A
  • Hard, Rock barrier forcing waves to break before they reach the coast
  • Interferes with boats and Longshore drift
  • Visually unappealing
  • effective at breaking wave energy
55
Q

What are groynes?

A
  • Hard, Wooden protrusions that stop longshore drift
  • Builds up beach increasing tourist potential
  • cost effective
  • visually unappealing
  • Deprives downwind areas of sediment
56
Q

What is a seawall?

A
  • Hard, Concrete structures that absorb and reflect wave energy, with curved surface
  • Effective erosion prevention
  • Promenade has tourism benefits
  • Visually unappealling
  • Expensive to construct and maintain
  • Wave energy reflected elsewhere, with impacts on erosion rates
57
Q

What is rip rap?

A
  • Hard, Large rocks that reduce wave energy, but allow water to flow through
  • Cost effective
  • Rocks are sourced from elsewhere, so do not fit with local geology
  • Pose a hazard if climbed upon
58
Q

What are revetments?

A
  • Hard, Wooden or concrete ramps that help absorb wave energy
  • Cost effective
  • Visually unappealling
  • Can need constant maintenance, which creates an additional cost
59
Q

What is beach nourishment?

A
  • Soft, Sediment is taken from offshore sources to build up the existing beach
  • Builds up beach, protecting cliff and increasing tourist potential
  • Cost effective and looks natural
  • Needs constant maintenance
  • Dredging may have consequences on local coastal habitats
59
Q

What is cliff regrading and drainage?

A
  • Soft, Reduces the angle of the cliff to help stabilise it. A steeper cliff would be more likely to collapse
  • Cost effective
  • Cliff may collapse suddenly as the cliff is drier leading to rock falls which pose a hazard
  • May look unnatural
60
Q

What is dune stabalisation?

A
  • Soft, Marram grass planted. The roots help bind the dunes, protecting land behind
  • Cost effective and creates an
    important wildlife habitat
  • Planting is time consuming
61
Q

What is marsh creation?

A
  • Type of managed retreat allowing low-lying areas to flood
  • Creates an important wildlife habitat
  • Farmers lose land and may need compensation as a result
62
Q

What are some sustainable strategies of coastal management?

A
  • Managing natural resources like fish, water, farmland to ensure long-term productivity.
  • Creating alternative livelihoods before people lose their existing jobs.
  • Educating communities about the need and how to adapt.
  • Monitoring coastal changes and then adapting or mitigating.
  • Managing flood risk or relocating if needed.
63
Q

What are the arguments for no active intervention?

A
  • Coastal managers produce SMP for an entire area so they have to see what kind of impacts other may have if the coast is managed in one specific area
  • Local authorities and DEFRA have had their budgets reduced as central government funding since 2010 has dropped and so they cannot invest in coastal management in all areas, they have to prioritise their funding to the most important places

Geography (14 decks)

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