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Geography Paper 2 - UK Geographical Issues > Rivers > Flashcards

Rivers Flashcards

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1
Q

Course of a river

A

the path of a river as it flows down hill

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2
Q

What do rivers form as they flow downhill?

A

Channels and valleys

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3
Q

Describe the upper course of a river

A

gradient - steep

valley and channel shape - v-shaped valley, steep sides narrow, shallow channel

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4
Q

Describe the middle course of a river

A

gradient - Medium

valley and channel shape - gently sloping valley sides wider, deeper channel

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5
Q

Describe the lower course of a river

A

gradient - gentle

valley and channel shape - very wide, almost flat valley, deep channel

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6
Q

Vertical erosion

A

deepens the river valley (and channel) making it V-shaped
dominant in the upper course of the river
high turbulence caused the rough angular particles to be scraped along the river bed - causing intense downwards erosion

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7
Q

Lateral erosion

A

widens the river valley (and channel) during the formation of meanders
dominant in the middle course and lower course

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8
Q

What determines the change in the shape of the valley and channel?

A

it depends on wether erosion or deposition is having the most impact (is the dominant process)

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9
Q

Freeze-thaw weathering

A

happens when temperature alternates above and below 0°c (freezing point of water)
water gets into rock that has cracks - when water freezes it expands which puts pressure on the rock
when water thaws it contracts which releases pressure on the rock
repeat freezing and thawing - widens cracks and causes rock to break up

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10
Q

Four processes of erosion

A

Hydraulic action
Abrasion
Attrition
Solution

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11
Q

Hydraulic action

A

force of the water breaks rock particles away from the river channel

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12
Q

Abrasion

A

eroded rocks picked up by the river scrape and rub against the channel - wearing it away
most erosion happens by abrasion

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13
Q

Attrition

A

eroded rocks picked up by the river smash into each other and break into smaller fragments
edges get rounded off as they rub together
further material travels more eroded it gets - attrition causes particle size to decrease between river source and its mouth

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14
Q

Solution

A

river water dissolves some types of rock such as chalk and limestone

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15
Q

Four processes of transportation

A

Traction
Suspension
Saltation
Solution

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16
Q

Traction

A

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

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17
Q

Suspension

A

Small particles like silt and clay are carried along by the water

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18
Q

Saltation

A

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

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19
Q

Solution

A

Soluble material are dissolved in the water and carried along

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20
Q

Deposition

A

when a river drops eroded material its transporting

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21
Q

When does deposition occur?

A

when a river slows down (loses velocity)

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22
Q

Why does a river slow down and deposit material?

A

1) volume of water in river falls
2) amount of eroded material in the water increases
3) water is shallower (inside of a bend)
4) river reached its mouth

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23
Q

Where are waterfalls and gorges found?

A

upper course of a river

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24
Q

How does a waterfall form?

A

1) when a river flows over an area of hard rock followed by an area of softer rock
2) softer rock is eroded (by hydraulic action and abrasion) more than the hard rock - creates a ‘step’ in the river
3) as water goes over the step it erodes more and more of the softer rock
4) steep drop is eventually created - this is called a waterfall

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25
Q

How does a gorge form?

A

1) once a waterfall forms the hard rock is eventually undercut by erosion - becomes unsupported and collapses
2) collapsed rocks are swirled around at the foot of the waterfall where they are erode the softer rock by abrasion - this creates a plunge pool
3) over time more undercutting causes more collapses - the waterfall will retreat leaving behind a steep-sided gorge

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26
Q

How are interlocking spurs formed?

A

1) in the upper course of a river - most erosion is vertically downwards
this creates steep-sided V-shaped valleys
2) the rivers aren’t powerful enough to erode laterally - have to move around the high hillside that are in their paths on either side
3) hillsides that interlock with each other as the river moves around them are called interlocking spurs

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27
Q

Where do rivers develop meanders (large bends)?

A

Middle and lower courses

in areas where there area both shallow and deep section in the channel

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28
Q

Where is the current faster in a meander?

A

Outside of the bend - the river channel is deeper (there’s less friction to slow down the water)
so more erosion (abrasion and hydraulic action) take place on the outside of the bend forming river cliffs

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29
Q

Where is the current slower in a meander?

A

Inside of the bend - river channel is shallower (there’s more friction to slow down the water)
so eroded material is deposited on the inside of the bend forming slip-off slopes

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30
Q

How does a meander form into an ox-bow lake?

A

erosion causes the outside bend to get closer until there’s only a small bit of land left between the bends - called neck
river breaks through this land - usually during a flood
the river flows along the shortest course
deposition eventually cuts off the meander - forming an ox-bow lake

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31
Q

Flood plain

A

the wide valley floor on either side of a river which occasionally gets flooded

32
Q

What happens when a river floods onto a flood plain?

A

water slows down and deposits the eroded material that it is transporting
this builds up the flood plain (makes it higher)

33
Q

How do meanders effect flood plains?

A

meanders migrate across the flood plain - makes it wider
meanders migrate also down stream - flattens out the valley floor
deposition that happens on the slip-off slopes of meanders -builds up the flood plain

34
Q

Where are flood plains, levees and deltas found?

A

Lower course of a river

35
Q

Levees

A

natural embankments along the edges of a river channel

36
Q

How are levees formed?

A

during a flood - eroded material is deposited over the whole flood plain
heaviest material is deposited closest to river channel - as it gets dropped first when the river slows down
over time the deposited material builds up - creating levees along the edges of the channel

37
Q

Deltas

A

low lying areas where a river meets the sea or lake

38
Q

How are deltas formed?

A

rivers are forced to slow down when they meet the sea or a lake - causes them to deposit the material they are carrying
if the sea doesn’t wash away the material - it builds up and the channel gets blocked
this forces the channel to split up into lots of smaller rivers called distributaries
eventually material builds up so much that low-lying areas of land called deltas are formed

39
Q

Sediment load

A

material carried by a river

40
Q

What 3 factors help shape river landscapes and affect sediment load?

A

Climate
Geology
slope processes

41
Q

Rivers in wetter climates have…

A

higher discharge as there is more water entering the river channel

42
Q

How does higher river discharge affect erosion?

A

increases rate of erosion
if a river has higher volume of water it has more power to erode river banks and bed
this adds material to rivers load

43
Q

How does higher river discharge affect the landscape?

A

shapes the landscape
forms:
V-shaped valleys in the rivers upper course (through vertical erosion)
wide flat flood plain in the lower course (through lateral erosion)

44
Q

How does higher river discharge affect transportation?

A

transportation increases

because the river has more energy to carry material

45
Q

How does higher river discharge affect weathering?

A

weathering increases the river sediment load and can affect the shape of the landscape
for example freeze thaw weathering makes rockfall more likely

46
Q

Rate of erosion of rivers flowing through hard rock

A

Slower rate - hard rock is more resistant

this means river will have low sediment load

47
Q

Rate of erosion of rivers flowing through softer rock

A

Higher rate

adds more material to rivers sediment load

48
Q

valley sides for landscapes with more resistant rock

A

steeper valley sides

49
Q

valley sides for landscapes with less resistant rock

A

gentle sloping valley sides

50
Q

How does vertical erosion effect rivers?

A

makes valley sides steeper - increases movement of material down slopes

51
Q

How does mass movement affect rivers?

A

can add large amounts of material to rivers load
more likely during cold weather - freeze thaw weathering loosens material
and during periods of intense rainfall - saturated ground becomes heavier and less stable

52
Q

Soil creep

A

when soil particles move down slope due to gravity
caused by the expansion and contraction of soil
water adds weight to soil and makes it expand - causes it to move down the slope
when soil dries out it contracts
adds lots of fine material to rivers load

53
Q

River discharge

A

the volume of water that flows in a river per second

measured in cumecs - cubic metres per second

54
Q

Storm hydrographs

A

show the changes in river discharge around the time of a storm

55
Q

Peak discharge

A

highest discharge in the period of time you’re looking at

56
Q

Lag time

A

delay between peak rainfall and peak discharge

happens because most rainwater doesn’t land directly in the river channel - there’s a delay as rainwater gets to the channel
gets there by:
flowing quickly over land - surface runoff
soaking into the ground (infiltration) flowing slowly underground

57
Q

Rising limb

A

increase in river discharge as rainwater flows into the river

58
Q

Falling limb

A

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

59
Q

How does increases surface runoff affect lag time and a Storm Hydrograph?

A

Lag time - reduced

discharge increases and the hydrograph will be steeper - more water gets into the river in a shorter period of time

60
Q

How does geology affect runoff?

A

water cant infiltrate impermeable rock - more runoff

61
Q

How does rock type affect runoff?

A

more impermeable soils cant absorb as much water as sandy soils - increases surface runoff
shallower soils become saturated more quickly than deeper soils

62
Q

how does slope affect runoff?

A

steeper the slope, the less infiltration - higher the surface runoff

63
Q

How does drainage basin affect lag time and discharge?

A

Circular drainage basins - shorter lag time and higher discharge than narrow basins
this is because water reaches the main river channel at the same time
Narrower basin - water from the far end of the basin takes long time to reach the main channel

64
Q

How do antecedent condition affect runoff?

A

previously wet or very cold weather can increase runoff

because water cant infiltrate saturated or frozen soil

65
Q

How does urbanisation affect runoff and discharge?

A

water cant infiltrate impermeable surface (concrete/tarmac)- more runoff
gutters and drains quickly take runoff to rivers - rapidly increases discharge

66
Q

How does deforestation affect runoff and discharge?

A

trees take up water from ground and store it which reduces runoff
cutting them down - increases runoff and causes more water to enter river channel - increases discharge

67
Q

Two main factors in the UK increasing risk of flood

A

Increased frequency of storms -
consequence of climate change
more periods of wet weather means ground is more saturated - makes floods more likely

Land use change -
as population grows - more pressure to expand urban areas which leads to increase in impermeable surfaces
removing vegetation and permeable surfaces - eater than would have been stored in the soil/plant/tree now flow downstream quickly
development (houses) on floodplains - areas are more prone to flooding

68
Q

Threats of flooding to people (5)

A

1) killed or injured by flood water
2) infrastructure (roads/bridges/rail lines) damaged or destroyed
3) flood water contaminated with sewage - lack of clean drinking water
4) homelessness
5) businesses forced to shut due to flood damage and disrupted power supplies - leads to loss of livelihoods

69
Q

Threats to the Environment (4)

A

1) flood water contaminated with sewage and rubbish can pollute rivers - damage wildlife habitats
2) farmland ruined due to silt and sediment deposited after flood
3) river banks eroded causing huge changes to river landscape
4) force of flood water can uproot plants/trees and standing flood water causes those that survive to die

70
Q

Hard engineering examples

A

Flood walls
embankments
flood barriers (flood gates)
flood barriers (demountable)

71
Q

Soft engineering examples

A

Flood plain retention

River restoration

72
Q

Flood walls

A

artifice barriers built along river banks
designed to increase the height of river banks - allowing the river channel too hold more water
very expensive, not asthetically pleasing

73
Q

Enbankments

A

high banks that area built along or near the river banks
stop river flooding into built-up areas during a flood
protects building and infrastructure on the flood plain
expensive
risk of severe fooding in water rises above level of enbankment

74
Q

Flood gates

A

such as Thames Barrier
built on river estuaries to stop flooding from storm surges/high tides
can be shut when there is a surge forecast to prevent flooding and protect large areas if land - Central London
very expensive to build
need to maintained regularly

75
Q

Flood plain retention

A

strategy involves maintaining rivers flood plain - by building on it
helps slow flood water down and maintain flood plains ability to store water
no money has to be spent
restrict development and cant be used in urban areas

76
Q

River restoration

A

involves making the river more natural - by removing man-made levees so that the flood plain can flood naturally
less risk of flooding downstream as discharge is reduced
river is left in natural state - little maintenance required

Geography Paper 2 - UK Geographical Issues (5 decks)

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