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IGCSE Geography Edexcel > Rivers > Flashcards

Rivers Flashcards

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1
Q

What is the difference between the hydrological cycle and the drainage basin

A
  • Hydrological cycle is a closed system, where water is constantly recycled
  • Drainage basin is an open system
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2
Q

define drainage density

A

the number of tributaries in a drainage basin

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3
Q

what influences drainage density

A

permeability of the rocks/soil under the surface
* impermeable = water can’t infiltrate = high drainage density
* permeable = throughflow or groundwater flow = low drainage density

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4
Q

how does temperature affect surface run-off

A

high temp = increased evaporation, less surface runoff

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5
Q

how does precipitation affect surface runoff

A
  • more precipitation
  • more runoff
  • water doesn’t have time to inflitrate
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6
Q

how does rock type affect surface runoff

A
  • impermeable rocks, rapid runoff
  • permeable, reduced runoff, infiltration
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7
Q

define channel network density

A

the system of surface and underground channels that collect and traansport the percipitation that falls on the drainage basin

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8
Q

state the 3 stores in the hydrological cycle

A
  1. atmosphere: water vapour/droplets in clouds
  2. land: ice sheets, glaciers, lakes, groundwater, resovoirs
  3. the sea
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9
Q

what does a river regime demonstrate

A

the variations in a river’s discharge throughout the year

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10
Q

what does a storm hydrograph represent

A

changes in river discharge after a storm event

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11
Q

what can affect a river regime

A
  1. levels of precipitation
  2. temperature changes throughout the year
  3. evapotranspiration
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12
Q

what is base flow

A

normal discharge

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13
Q

define peak rainfall

A

highest rainfall during a storm

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14
Q

define peak dischage

A

highest discharge during the storm event

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15
Q

define lag time

A

time between peak rainfall and peak discharge

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16
Q

what is the receeding limb

A

river discharge returning to normal

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17
Q

what is river discharge measured in

A

cumecs (m^3/s)

it is the river volume

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18
Q

what are the three main processes in shaping landforms

A
  1. erosion
  2. transporation
  3. deposition
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19
Q

define weathering

A

the breakdown of rocks in situ

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20
Q

how does physical weathering occur

A

changes in temperature

freeze-thaw and exfoliation

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21
Q

how does chemical weathering occur

A

rocks disintegrate in slightly acidic rainwater

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22
Q

how does biological weathering occur

A

rocks broken by the roots of plants

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23
Q

define mass movement

A

weathered material moves downhill because of gravity

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24
Q

define slumping

A

slope eroded by river, undercutting slope causing large-scare movement of material down

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25
Q

define soil creep

A

gravity causes weathered material to slowly move down the river

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26
Q

define erosion

A

the wearing away of material by force of water or other materials

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27
Q

hydraulic action

EROSION

A

force of water removes material from bed/banks of river

28
Q

corrosion (solution)

EROSION

A

rocks dissolved in slightly acidic water

29
Q

abrasion

EROSION

A

materials scrape away at banks and bed

30
Q

attrition

EROSION

A
  • like ATTRACTION
  • materials hit eachother, pieces become rounder and smaller
31
Q

solution

TRANSPORTATION

A

material dissolved

32
Q

suspension

TRANSPORTATION

A

light material carried in the river

33
Q

saltation

TRANSPORATION

A

material too heavy to be suspended, bounces up and down

34
Q

traction

TRANSPORTATION

A

larger rocks roll across river bed

35
Q

where is vertical erosion found, and what does it do

A
  • upper course
  • inc. river depth + valley
  • river erodes DOWNWARDS
36
Q

where is lateral erosion found, and what does it do

A
  • middle and lower course
  • inc. width of river + valley
37
Q

define deposition

A

when a river no longer has enough energy to carry material

38
Q

why/where does deposition occur

what causes a river to deposit material

A
  1. reduced discharge: lack of percipitatio, abstraction upstream
  2. decreased gradient
  3. slower flow on inside of river bed (meander)
  4. at the mouth
39
Q

how is river material deposited

in order of size

A
  1. bedload: heaviest, deposited first
  2. alluvium: finer load, deposits last
  3. dissolved materials: carried out to sea
40
Q

what factors affect river proccesses

A
  1. wet climate: more weathering, more mass movement, more discharge, more powerful erosion and transportation –> more load deposited downstream
  2. less resistant rocks weathered and eroded more rapidly
  3. gentler slopes means reduced river energy, deposits load
41
Q

what is a long profile

A

changes in the river gradient from source–>mouth

42
Q

characteristics of upper course

A
  • low velocity
  • large bedload
  • vertical erosion
  • steep valley sides, shallow channel
  • rough channel bed
  • most erosion
43
Q

characteristics of middle course

A
  • deeper than upper course
  • gentle valley sides
  • bedload size decreases
  • lower friction
    * lateral erosion
44
Q

characteristics of the lower course

A
  • deepest
  • flat floodplains
  • widest
  • greatest velocity
  • dominantly deposition
45
Q

how are v-shaped valleys formed

UPLAND LANDFORMS

A
  1. VERTICAL EROSION dominant in upper course
  2. CUTS down into the river bed
  3. WEATHERING+MASS MOVEMENT = valley sides collapse into the river
  4. mass movement adds LOAD, aiding ABRASION
46
Q

how are waterfalls and gorges formed

UPLAND LANDFORMS

A
  1. drop in river bed from one level to another
  2. hard rock overlies soft rock
  3. soft rock erodes quicker, undercutting hard rock, creates plunge pool
  4. development of an overhang of resistant rock, collapses overtime due to gravity
  5. waterfall retreats upstream, leaving** steep-sided gorge**
47
Q

how are interlocking spurs formed

UPLAND LANDFORMS

A
  1. upper course: river starts to meander
  2. erosion happens on outside bend
  3. vertical erosion between spurs, rather than lateral erosion on them
48
Q

how are meanders formed

LOWLAND LANDFORMS

A
  1. lateral erosion dominant in lower courses
  2. meander increases in size
  3. thalweg on outside of river bed = erosion
  4. erosion undercuts banks = river cliff
  5. river bank collapses, meander moves further out
  6. slowest flow is on the inside of bends = deposition
  7. deposition creates slip-off slope
  8. deposition on one side, erosion on other = meander migrates accross valley
49
Q

how are ox-bow lakes formed

A
  1. distance downstream, meander size increases
  2. erosion on outer bends = meander neck
  3. flooding = river cuts through neck forming straighter course for water
  4. flow of water at entry/exit of meander is slower, meaning deposition
  5. meander cut off from main river channel = ox bow lake
50
Q

how are flood plains and levees formed

A
  1. migration of meanders = floodplains
  2. high discharge can cause the river to break its banks (flooding)
  3. increased friction –> reduced velocity –> material deposited along floodplain –> floodplain increases in height
  4. heaviest material deposited nearest to the channel, forms embankments called levees
51
Q

what are the percentages for global water use

A

70% agriculutre: irrigation/livestock
20% industry
10% domestic

52
Q

what is the threshold for water stress

A

below 1700m^3 a year per person

53
Q

what is the threshold for water scarcity

A

below 1000m^3 a year per person

54
Q

how does agriculture affect water quality

A
  • waste water from manure, fertilisers, herbicides, pesticides, soil erosion
  • death of fish + other wildlife due to bioaccumilation
  • eutrophication, poisonous
  • inc. sediment, decreased oxygen levels
55
Q

how does industry affect water quality

A
  • oil spillages
  • water used as coolant, returned to river at high temperatures
  • toxic substances from industrial processes
  • wildlife coated in oil, unable to move/eat/fly
  • organisms cannot survive high temperatures
  • toxins enter food chain
56
Q

how does domestic use of water impact water quality

A
  • untreated sewage
  • leisure - treated with chlorine
  • water used for bathing or washing clothes
  • more nitrogen, more bacteria
  • chemicals are harmful for wildlife
  • chlorine causes chemical burn to wildlife
57
Q

describe the process for cleaning water

A
  1. AERATION: removes dissolved iron and maganese
  2. CHLORINATION: removes biological growth
  3. DISINFECTION: removes bacteria
  4. SEDIMENTATION: removes suspended soils
  5. FILTRATION: removes very fine sediment
58
Q

define flooding

A

when the capacity of the river channel is exceeded

59
Q

what is hard engineering

A
  • building of structures
  • expensive to construct and maintain
60
Q

what do dams and resovoirs do

HARD ENGINEERING

A

control amount of discharge

61
Q

what do levees do

HARD ENGINEERING

A

increase capacity of river channel

62
Q

what do straightened channels do

HARD ENGINEERING

A

river flows more quickly past vulnerable areas

63
Q

what do flood relief channels do

HARD ENGINEERING

A

allow water to flow out of the main channel

64
Q

what does river restoration do

SOFT ENGINEERING

A

restoring rivers (like straightened channels) back to their original regime

65
Q

what does wetland conservation do

SOFT ENGINEERING

A

provide excess water area to go and slow down flow of floodwater

conserves an area of land that can get wet

66
Q

what does floodplain zoning do

SOFT ENGINEERING

A

only certain land uses allowed on flood plains

67
Q

what do flood resistant buildings typically consist of

A
  • homes raised on stilts
  • carpets replaced with tiles
  • power sockets built above level of likely flood

IGCSE Geography Edexcel (2 decks)

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