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Geography GCSE > rivers > Flashcards

rivers Flashcards

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1
Q

long profile

A

shows you how the gradient of the river changes over the different courses

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2
Q

cross profile

A

shows you what the cross section of a river looks like

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3
Q

vertical erosion

A

deepens the river valley and channel making it V-shaped
dominant in the upper course
high turbulence causes rough, angular particles to be scraped along the river bed, causing intense downward erosioni

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4
Q

lateral erosion

A

widens the river valley and channel during the formation of meanders
dominant in the middle and lower courses

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5
Q

erosion

A

the wearing away of rock and transportation of it away

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6
Q

what are the 4 types of erosion

A

hydraulic action
abrasion
attrition
solution

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7
Q

hydraulic action

A

force of water breaks rock particles away from the river channel

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8
Q

abrasion

A

eroded rocks scrape and rub against the channel, wearing it down

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9
Q

attrition

A

eroded rocks picked up by the river smash into each other and break down into smaller fragments

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10
Q

solution

A

river water dissolves some types of rock

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11
Q

what are the 4 types of transportation

A

traction
saltation
suspension
solution

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12
Q

traction

A

large particles, like boulders, are rolled/pushed along the river bed by the force of the water

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13
Q

saltation

A

pebble sized particles are bounced along the river bed by the force of the water

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14
Q

suspension

A

small particles like silt and clay are carried along in the water

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15
Q

solution

A

soluble materials dissolve in the water and are carried along

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16
Q

deposition

A

rivers drop eroded material that they are transporting when it loses velocity

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17
Q

what 4 things can cause deposition

A

volume of water falls
amount of eroded material in water increases
water is shallower
river reaches its mouth

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18
Q

what 2 landforms are formed by erosion

A

waterfalls + gorges

interlocking spurs

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19
Q

how are waterfalls and gorges formed (6 = 3+3)

A

form where rivers flows over an area of hard rock followed by an area of soft rock
as soft rock is eroded by hydraulic action and abrasion more than the hard rock, a step forms
over time, as water goes over the step it erodes more and more to form a WATERFALL

gradually the hard rock is undercut, until it becomes so unsupported that it collapses
collapsed rocks swirl around at the foot, eroding the softer rock by abrasion and forming a plunge pool
gradually, as more undercutting occurs, more collapses occur, the waterfall retreats leaving a STEEP SIDED GORGE

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20
Q

how do interlocking spurs form

A

in the upper course, most erosion is vertical, forming steep sided valleys
rivers aren’t powerful enough to erode laterally, so wind around the area of hard rock
the way that rivers wind around these interlocking hillsides if INTERLOCKING SPURS

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21
Q

what what 2 landforms are formed by erosion and deposition

A

meanders

oxbow lakes

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22
Q

how are meanders formed

A

the river bends in its middle course
water flows in a corkscrew pattern known as helicoidal flow, which sends the rivers energy laterally
the thalweg (fastest current) is forced to the outer bend, undercutting the bank and forming a steep cliff which collapses and undercutting continues
helicoidal flow shifts sediment across the channel and onto the inner bank where it is shallower and sediment is deposited to form a point bar

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23
Q

how are oxbow lakes formed

A

continual erosion causes the outside bends on two meanders to get closer
the neck is eventually broken through by erosion, generally during a flood, and the river flows along its shortest course
deposition eventually cuts off the meander, forming an oxbow lake

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24
Q

what 3 landforms are formed by deposition

A

flood plain
levees
deltas

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25
Q

how are flood plains formed

A

wide valley floor on either side of a river that usually gets flooded
when a river overflows onto it, water slows and deposits eroded material, building up the flood plain

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26
Q

what do meanders do

A

meanders make the plain wider and as they migrate downstream flatten out the valley floor

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27
Q

levee

A

natural embankments along the edges of the river channel

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28
Q

how are levees formed

A

when a river floods, eroded material is deposited over the whole flood plain
heaviest material is dropped first
over time, the deposited material builds up, creating levees along the edges of the channel

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29
Q

delta

A

low lying area where a river meets the sea or a lake

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30
Q

how are deltas formed

A

rivers are forced to slow down and so deposit the material they are carrying
if the deposition is faster than the sea can wash sediment away then the channel becomes blocked and so the channel splits up into smaller rivers known as distribuaries

31
Q

what are 3 types of delta

A

arcuate/fan shaped
cuspate
bird’s foot

32
Q

arcuate/fan shaped delta and example

A

land around river arches out into the sea and river splits many times on way to sea, creating a fan effect

river Niger

33
Q

cuspate delta and example

A

land around the mouth of the river just out like an arrow into the dea

Ebro delta

34
Q

bird’s foot delta and example

A

river splits up on the way to the sea, each part sticking out into the sea like a bird’s foot

Mississippi delta

35
Q

how does climate affect river landscapes and sediment load

A

wetter climate -> higher discharge -> higher rate of erosion -> more sediment in the river’s load

erosion, weathering and transportation all increase

36
Q

how does geology affect river landscapes and sediment load

A

rivers flowing through areas of hard rock have a lower sediment load and steep valleys

rivers flowing through areas of soft rock have a higher sediment load and gentle, sloping valley sides

37
Q

how do slope processes affect river landscapes and sediment load

A

vertical erosion of rivers makes valley sides steeper, increasing movement of materials down slopes
mass movement can add large amounts of material to the river’s load
soil creep can add lots of fine material to the river’s load

38
Q

river discharge

A

the volume of water that flows in a river per second

39
Q

what is discharge measured in

A

cumecs m^3/s

40
Q

peak discharge

A

the highest discharge in the time period you are looking at

41
Q

lag time

A

the delay between peak rainfall and peak discharge

42
Q

rising limb

A

the increase in river discharge as rainwater flows into the river

43
Q

falling limb

A

the decrease in river discharge as the river returns to its normal level

44
Q

what 5 physical factors can affect lag time

A 
geology
soil type
slope gradient
drainage basin shape
antecedent rainfall
45
Q

what 2 human factors can affect lag time

A

urbanisation

deforestation

46
Q

how does geology affect lag time

A

water cannot infiltrate into impermeable rocks

so run off increases

47
Q

how does soil type affect lag time

A

more impermeable soils can’t absorb as much water and this increases run off
shallower soils become saturated more easily that deeper soils

48
Q

how does slope gradient affect lag time

A

the steeper the slope, the less infiltration and the more run off

49
Q

how does drainage basin shape affect lag time

A

more circular basin means shorter lag time and higher discharge as water reaches channel at the same time

in a narrower basin, it takes long to reach the main channel

50
Q

how does antecedent rainfall affect lag time

A

previously wet or cold weather makes soil saturated or frozen so water cannot infiltrate and run off

51
Q

how does rainfall travel to the river basin (3)

A

surface run off
throughflow
groundwater flow

52
Q

how does urbanisation affect lag time

A

impermable surfaces like tarmac increase run off

gutters and drains increase run off, increasing discharge1

53
Q

how does discharge affect lag time

A

trees intercept, absorb and store water reducing run off

removal of this increases run off and discharge

54
Q

what are 2 factors increasing risks of river flooding

A

increased frequency of storms

land use change

55
Q

how is increased frequency of storms increasing risks of river flooding

A

storm frequency in the UK is increasing, this could be due to climate change
storms are becoming more intense with heavier rainfall
more periods of wet weather mean that the ground is more prone to becoming saturated, making flooding more likely

56
Q

how is land use change increasing the risks of river flooding

A

UK population growing so urban areas expanding

leads to an increase in impermeable surfaces which cause rapid surface run off
removing vegetation and permeable surface means that water that would have been stored in soil, plants are trees flows quickly downstream
lots of development on floodplains that are naturally prone to flooding, increases the risk to developed area

57
Q

what are 6 potential threats to the people from river flooding

A

death or injury by floodwater
roads, bridges and rail lines damaged or destroyed
lack of clean drinking water due to pollution of water by sewage
washed away or damaged possessions
homelessness due to inundated or damage properties
loss of jobs due to businesses being forced to shut from flood damage and disrupted power supplies

58
Q

what are 5 potential threats to the environments from river flooding

A

floodwater contaminated with sewage and rubbish polluted rivers, damaging wildlife habitats
farmland can be ruined by silt and sediment deposited
eroded river banks can cause changes to the river landscape
force of floodwater can uproot trees and plants
standing floodwater can cause trees and plants that survive the first wave of water to die

59
Q

hard engineering

A

manmade structures built to control the flow of rivers and reduce flooding

60
Q

soft engineering

A

schemes set up using the knowledge of a river and its processes to reduce the effects of flooding

61
Q

3 examples of hard engineering

A

flood walls
embankments
flood barriers (floodgates or demountable flood barriers)

62
Q

flood walls

A

artificial walls built along river banks

63
Q

embankments

A

high banks built along or near to river banks

64
Q

floodgates

A

built on river estuaries to stop flooding from storm surges or very high tides

65
Q

demountable flood barriers

A

provide temporary protection against flooding

66
Q

2 examples of soft engineering

A

flood plain retention

river restoration

67
Q

flood plain retention

A

maintaining a river’s flood plain (not building on it)

68
Q

river restoration

A

making a river more natural such as by removing man made levees so the flood plain can flood naturally

69
Q

evaluate flood walls (1+,2-)

A

+ increases height of river banks, increasing channel capacity

  • very expensive
  • unsightly and block view of river
70
Q

evaluate embankments (2+,2-)

A

+ stop water from flowing into built up areas during a flood, protecting buildings and infrastructure on the flood plain
+ can be made from earth or other materials so look more natural, less unsightly
- expensive to build
- risk of severe flooding if water level rises beyond or they break

71
Q

evaluate floodgates(2+,2-)

A

+ can be shut when there is a surge forecast
+protect a large area of land
- very expensive
- need regular maintenance

72
Q

evaluate demountable flood barriers (1+,2-)

A

+ don’t spoil the look of attractive locations

  • expensive to build
  • risk if barriers aren’t put up in time
73
Q

evaluate flood plain retention (3+,2-)

A

+ helps to slow floodwaters down
+maintains flood plain’s ability to store water
+ no money has to be spent on flood defences
- restricts development
- can’t be used in urban areas

74
Q

evaluate river restoration (2+,1-)

A

+less risk of flooding downstream as discharge is reduced
+ very little maintenance required
- can increase local flood risk, especially is nothing else is done to prevent major flooding

Geography GCSE (7 decks)

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