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rivers

las1365 Inglés 98 fichas

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  1. 1human causes of floodingploughing
    grazing animals
    dams
    bridge supports
    tarmac
    sewers
  2. 2soft engineering-AFFORESTATION trees planted to take up water
    -RIVER RESTORATION restore river to its original state QUAGGY
    -CONTOUR PLOUGHING ploughing at high angles to natural slope
    -FORECATS AND WARNINGS CARLISE 2005
  3. 3hard engineeringDAMS large walls built across a river creating a lake behind
    CHANNEL STRAIGHTENING meanders removed by building artificial cut throughs MISSISSIPPI
    LEVEES embankments built along the river so it has more water
  4. 4what is hydraulic radiusthe measure of a river channel's efficiency
  5. 5high drainage density=more likely to flood-steep slopes
    -lack of vegetation
    -many streams
    -urbanisation
    -thin soil
    -hard impermeable rock (clay)
  6. 6low drainage density=less likely to flood-gentle lsopes
    -rural areas
    -few streams
    -forest
    -deep soil
    -soft, permeable rocks
  7. 7outputs of a riverEVAPORATION: water to water vapour
    TRANSPIRATION: evaporation from plant leaves
    EVAPORATION: both above together
  8. 8flows of a river-surface run off: flowing over land
    -through flow: through soil
    -base flow: feeds into rivers through banks and beds
    -discharge: river taking water out of the drainage basin
    -infiltration: water soaking into the soil
    -percolation: seeping through rocks under soil into water table
  9. 9flows of a river-groundwater flow: water flowing slowly below water table
    -throughflow: water dripping from leaves
    -stem flow: water running down plant stem/tree trunk
  10. 10field capacitymax amount of water soil can hold
  11. 11capacitytotal amount of load that is carried
  12. 12competencemax size of load that a river is able to carry
  13. 13soil moisture utilisationsoil water used by people and plants, reducing amount remaining in soil and river channels
  14. 14rechargereplacement of water lost from soil during drier periods
  15. 15stores of a riverINTERCEPTION
    SURFACE STORAGE, puddles ponds lakes
    VEG STORAGE stored by plants
    GROUNDWATER STORAGE soil moisture/rocks
  16. 16inputs of a riverSOLAR INSOLATION energy from the sun
    PRECIPITATION water coming from the atmosphere
  17. 17hydrological cyclecirculatory system by which water is transformed between oceans, atmosphere and land
  18. 18drainage densitytotal length of all streams in drainage basin DIVIDED by total area of drainage basin
    stream DIVIDE area
  19. 19hydrographgraph showing variations in river discharge over a period of time, often produced for a storm of flood
  20. 20river regimeexpected seasonal pattern of discharge over the year at one particular point
  21. 21deltalandform produced by the deposition of sediment at the mouth of a river as it enters the sea/lake
  22. 22urbanisationthe process by which the proportion of people in towns and cities increase
    leads to rocks that water cannot infiltrate=surface run off
  23. 23drainage basinan area of land drained by a river and all of its tributaries
  24. 24flood abatementschanging land use up stream to reduce flooding downstream
  25. 25hjulstrom curvemodel determines whether a river will erode, transport or deposit sediment
  26. 26dynamic equilibriumwhen inputs and outputs of the drainage basin system are equal (balanced)
    DOESNT HAPPEN VERY OFTEN
  27. 27percolationwater moves downwards through the soil into rocks
  28. 28infiltrationwater on ground surface enters the soil
  29. 29rejuvenationoccurs when sea level changes
    EUSTATIC: height of land changes due to rise/ fall of sea level (glaciation)
    ISOSTATIC: land rises relative to sea as a result of crustal movement (ice cap weight removed)
  30. 30dischargethe volume of water in a river passing a measuring point in a given time
    measured in m3/sec
  31. 31flood plainflat, low lying area of the valley floor which floods from time to time
    built up by deposition of alluvium over years
  32. 32erosion typesSOLUTION: water dissolved rocks
    SALTATION: bounced along river bed
    ABRASION: wearing away river bed and banks by rocks hitting them
    HYDRAULIC ACTION: water dislodges sediment from the bed and banks
    ATTRITION: rocks collide against each other
    TRACTION: rolled along river bed
  33. 33physical causes of floodingthin soil
    steep slope
    drainage density
    lack of vegetation
    impermeable rock
  34. 34upper sectionsteep gradient
    high velocity
    vertical erosion
    narrow river
    friction (rough channel)
    traction& saltation
    abrasion & hydraulic action
    WATERFALLS AND RAPIDS
  35. 35middle sectionless steep
    potential energy=now kinetic
    lateral erosion
    less steep sides
    wider river
    smaller sediment size
    suspension, saltation, abrasion, attrition
    SMALL MEANDERS, SMALL FLOOD PLIAN
  36. 36lower courserelatively flat
    faster flow
    most discharge
    deposits sediment at mouth
    suspension
    MEANDERS, LEVEES
  37. 37rapidscaused by a localised increased gradient along the river or where there are bands of hard and soft rock
    water becomes more turbulent
  38. 38deltasARCUATE: rounded convex outer margin
    CUSPATE: evenly spread material either side of estuary
    BIRD'S FOOT: many sediment bound distributary channels extending in a fan shape
  39. 39how is an incised meander formedsteep gorge cut into meandering channel
    formed when rapid vertical erosion from rejuvenation exceeds normal rate of lateral erosion
  40. 40incised meanders INGROWN, ENTRENCHEDINGROWN- slow and asymmetrical
    ENTRENCHED- fast and symmetrical
  41. 41what does hydraulic radius measuremeasure of rivers channel efficiency
    cross section area DIVIDED wetted perimeter
  42. 42flocculationat an estuary- fresh and salt water mix= chemical settling of clays and silts
    COAGULATION: particles stick together and sink more rapidly
  43. 43turbulenceirregular and rough type of river flow caused by high speed of water/friction with river bed and banks
  44. 44calibresize of particles in a river
  45. 45V shaped valleya river valley with evenly sloped sides in the shape of a V (caused by erosion and weathering)
  46. 463 gorges dam$40bn, 1.5 acres of land
    3 % of china's electricity
    22.5 kilowatts
  47. 473 gorges dam advimproved navigation
    protects 15million people
  48. 48Bangladesh floods key facts-monsoon climate
    -80% of rain fall in 4 months
    -low lying land
    -90% of land is less than 10m above sea level
    -melting snow and ice from the Himalayas in late summer increase river discharge
  49. 49Bangladesh floods when?july and august of 2007
  50. 50Bangladesh floods physical factors-monsoon came suddenly after a very dry, early summer
    -heavy rainfall (Assam 169.5mm 24hrs)
    -900mm in July
    -long duration of heavy rainfall
    -saturated soil, increasing surface run off
    -peak discharges coincided with the Ganges, Brahmaptura
  51. 51Bangladesh floods human activities-deforestation in Nepal & Himalayas
    -less interception, increased discharge
    -growth of urban areas, due to migration, increased surface run off
    -collapse of old earth dams in Madhya etc
  52. 52Bangladesh floods social impacts-over 2000 people died
    -people reluctant to leave their homes,livestock
    -poor transport links, evacuation was slow
    -wells became polluted
    -lack of clean drinking water
    -over 100,000 caught water borne diseases
    -25m homeless
    -112,000 houses destroyed, porous mud
    -4000 schools affected
    -44 schools destroyed
  53. 53Bangladesh floods economic impacts-US$1 billion
    -factories closed, loss of raw material
    -widespread loss of livestock
    -550,000 ha of land could not be planted
    -10,000km road were destroyed
    -debt increased
  54. 54Bangladesh floods environmental impacts-flood deposited fertile silt on the floodplain
    -rivers were polluted with sewage
  55. 55Bangladesh floods human factors which made the impacts worse-Bangladesh is a poor country
    -no flood defenses or warning systems
    -low incomes, little savings and little insurance limited people's ability to recover
    -corrupt officials diverted aid money away from people that need it most
  56. 56Carlisle flood key facts-drainage basin of the river Eden is very large
    -some of the basin has steep sides
    -many streams, lag time short
  57. 57Carlisle flood when?8th January 2005
    flood return interval is about 200 years
  58. 58Carlisle flood physical factors-heavy rainfall on the 6th, 36 hours
    -200mm recorded
    -rain fell on saturated ground
    -very high peak discharge over 1250 cumecs average 52
  59. 59Carlisle flood human activities-large built up area
    -impermeable surfaces,little soil or vegetation, little infiltration, high surface run off
    -drains and sewerage over flowed
    25% of flooding problems was because of overflowing drains
  60. 60Carlisle flood environmental impacts-increased river bank erosion
    -rivers were polluted with rubbish and sewage
  61. 61Carlisle flood social impacts-3 people died
    -over 3000 homeless
    -000s lost personal possessions
    -living in temporary accommodation disrupted lives
    -children lost an education, 4 schools severely flooded
    -increase in stress related illnesses
  62. 62examples of hard management-dam construction
    -diversion spillways
    -levees
    -channel straightening
  63. 63examples of soft management-afforestation
    -land use
    -wetland and river bank conservation
    -river restoration
    -contour ploughing
  64. 64hard engineeringdefenses are man made structures that reduce flooding. they often alter the rivers natural processes
  65. 65channel straightening How it worksmeanders being removed by building artificial cut-through. water flows faster and out of drainage basin
  66. 66channel straightening adv-less time to navigate
    -made shorter
    -faster
  67. 67channel straightening dis-very expensive
    -flood large areas destroying farmland and habitats
    -some people need to relocate
  68. 68channel straightening EXAMPLESMISSISSIPPI RIVER
  69. 69levees how it works-embankments built along rivers, allowing river to hold more water
    the reduces the likelihood of a river flooding
  70. 70levees adv-flood plain can be built on
    -can be cheap
    -depositing sediment onto the banks -raising their height
  71. 71levees dis-flooding maybe downstream
    -may cause erosion downstream
    -disrupts habitats
    -looks less natural
    -can damage local wetlands
  72. 72levees EXAMPLESRIVER RHONE, FRANCE
  73. 73DIVERSION SPILLWAYS how it workschannels to take excess water elsewhere when very high
    can be taken round important areas
    during high flow periods, sluice gates are opened to allow excess water to flow along
  74. 74DIVERSION SPILLWAYS adv-allows complete control
    -new wetlands
  75. 75DIVERSION SPILLWAYS dis-could cause flooding where it rejoins main river
    -may flood new areas
    -can be costly
  76. 76DIVERSION SPILLWAYS exampleJubilee river, River THAMES 2002
  77. 77dams how it works-huge walls built across rivers, creating g an artificial lake or reservoir behind
    water is caught preventing flooding, and is released slowly
  78. 78dams adv-multi purpose: HEP
    -allows irrigation
    -recreational use of reservoir
  79. 79dams dis-expensive
    -environmentally intrusive
    -severe risk of flooding
  80. 80dams examplesthree gorges dam
  81. 81river restoration how it worksremoving the river from a concrete channel and reintroducing meanders means the river can hold more water
  82. 82river restoration dis-only to be used in certain areas of drainage basin
    farmers have to be happy to oblige
  83. 83river restoration exampleriver quaggy
  84. 84wetland and river bank conservation how it workswetlands are established as they are highly efficient at storing water
    -river banks to prevent erosion
  85. 85wetland and river bank conservation adv-good for natural environment
    animal habitats
    prevent flooding to settlements
  86. 86wetland and river bank conservation distake up a lot of land
    -most fertile land cannot be used
    -cost of removing hard engineering can be costly
  87. 87wetland and river bank conservation exampleriver quaggy
  88. 88contour ploughing how it worksploughing at right angles to the natural slope of the land to create a series of stepped ridges
    -reduces the flow of run off
  89. 89contour ploughing adv-reduces surface run off
    -little maintenance
    -increased water infiltration
    -easily managed
    -cheap solution
  90. 90contour ploughing dis-having to leave space for a large floodplain
    -flooding can still occur
  91. 91contour ploughing exampeextensively in the Us, CANADA< AUSTRALIA
  92. 92where does the river quaggy run throughsoutheast of London
  93. 93history of the river quaggysince the 60s it has been heavily managed with
    artifical channels
    culverts
  94. 94river quaggy soft management scheme purposed by aimslocal community
    QWAG
    -reduce flood risk
    -improve the urban realm
    -restore wildlife
    -create opportunities
  95. 95river quaggy scheme-bring the river above ground
    -cutting a new channel through Sutcliffe park
    -park itself was lowered and shaped to create floodplain
    -culvert still remained underground during flood conditions
  96. 96river quaggy prevention-town of lewisham and greenwich
    -risk of flooding 600 homes
    - holds 85,000m of water
  97. 97why did river quaggy need to be developedincreased urban development in Lewisham and greenwich
  98. 98river quaggy environmental benefits-wetland environment with reed beds
    wild flower meadows
    trees

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Fichas sobre rivers, creado por las1365 el 20/03/2016.
Creado por
las1365 · mar 2016
Actualizado
18 may 2016
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