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Geography GCSE > rivers > Flashcards

rivers Flashcards

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
how are flood plains formed
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
26
what do meanders do
meanders make the plain wider and as they migrate downstream flatten out the valley floor
27
levee
natural embankments along the edges of the river channel
28
how are levees formed
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
29
delta
low lying area where a river meets the sea or a lake
30
how are deltas formed
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
what are 3 types of delta
arcuate/fan shaped cuspate bird's foot
32
arcuate/fan shaped delta and example
land around river arches out into the sea and river splits many times on way to sea, creating a fan effect river Niger
33
cuspate delta and example
land around the mouth of the river just out like an arrow into the dea Ebro delta
34
bird's foot delta and example
river splits up on the way to the sea, each part sticking out into the sea like a bird's foot Mississippi delta
35
how does climate affect river landscapes and sediment load
wetter climate -> higher discharge -> higher rate of erosion -> more sediment in the river's load erosion, weathering and transportation all increase
36
how does geology affect river landscapes and sediment load
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
how do slope processes affect river landscapes and sediment load
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
river discharge
the volume of water that flows in a river per second
39
what is discharge measured in
cumecs m^3/s
40
peak discharge
the highest discharge in the time period you are looking at
41
lag time
the delay between peak rainfall and peak discharge
42
rising limb
the increase in river discharge as rainwater flows into the river
43
falling limb
the decrease in river discharge as the river returns to its normal level
44
what 5 physical factors can affect lag time
``` geology soil type slope gradient drainage basin shape antecedent rainfall ```
45
what 2 human factors can affect lag time
urbanisation | deforestation
46
how does geology affect lag time
water cannot infiltrate into impermeable rocks | so run off increases
47
how does soil type affect lag time
more impermeable soils can't absorb as much water and this increases run off shallower soils become saturated more easily that deeper soils
48
how does slope gradient affect lag time
the steeper the slope, the less infiltration and the more run off
49
how does drainage basin shape affect lag time
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
how does antecedent rainfall affect lag time
previously wet or cold weather makes soil saturated or frozen so water cannot infiltrate and run off
51
how does rainfall travel to the river basin (3)
surface run off throughflow groundwater flow
52
how does urbanisation affect lag time
impermable surfaces like tarmac increase run off gutters and drains increase run off, increasing discharge1
53
how does discharge affect lag time
trees intercept, absorb and store water reducing run off | removal of this increases run off and discharge
54
what are 2 factors increasing risks of river flooding
increased frequency of storms | land use change
55
how is increased frequency of storms increasing risks of river flooding
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
how is land use change increasing the risks of river flooding
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
what are 6 potential threats to the people from river flooding
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
what are 5 potential threats to the environments from river flooding
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
hard engineering
manmade structures built to control the flow of rivers and reduce flooding
60
soft engineering
schemes set up using the knowledge of a river and its processes to reduce the effects of flooding
61
3 examples of hard engineering
flood walls embankments flood barriers (floodgates or demountable flood barriers)
62
flood walls
artificial walls built along river banks
63
embankments
high banks built along or near to river banks
64
floodgates
built on river estuaries to stop flooding from storm surges or very high tides
65
demountable flood barriers
provide temporary protection against flooding
66
2 examples of soft engineering
flood plain retention | river restoration
67
flood plain retention
maintaining a river's flood plain (not building on it)
68
river restoration
making a river more natural such as by removing man made levees so the flood plain can flood naturally
69
evaluate flood walls (1+,2-)
+ increases height of river banks, increasing channel capacity - very expensive - unsightly and block view of river
70
evaluate embankments (2+,2-)
+ 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
evaluate floodgates(2+,2-)
+ can be shut when there is a surge forecast +protect a large area of land - very expensive - need regular maintenance
72
evaluate demountable flood barriers (1+,2-)
+ don't spoil the look of attractive locations - expensive to build - risk if barriers aren't put up in time
73
evaluate flood plain retention (3+,2-)
+ 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
evaluate river restoration (2+,1-)
+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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