river landscapes Flashcards

1
Q

what is a course?

A

the path of the river as it flows downhill

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2
Q

rivers have a _____ upper course, a ______ ________ middle course and an almost ______ lower course

A

steep
gently sloping
flat

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3
Q

what does the long profile of a river show you

A

how the gradient of the river changes

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4
Q

what can rivers form as they flow down hill

A

channels and valleys

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5
Q

what does the cross profile do?

A

shows you what a cross section of the river looks like

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6
Q

what are the two types of river erosion

A

vertical or lateral

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7
Q

can vertical and lateral erosion happen at the same time?

A

yes but one is usually more dominant than the other

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8
Q

what does vertical erosion do?

A
  • deepens the river valley and channel making it V-shaped
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9
Q

where is vertical erosion dominant

A

in the upper course of the river

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10
Q

what does lateral erosion do?

A
  • widens the river channel and valley
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11
Q

where is lateral erosion dominant

A

in the middle and lower course of the valley

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12
Q

what are the four processes or erosion in rivers

A
  • solution
  • abrasion
  • hydraulic action
  • attrition
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13
Q

what is hydraulic action

A

when the force of the river water colliding with the rocks breaks rock particles away from the river channel

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14
Q

what is abrasion?

A

eroded rocks picked up by the river scrape against the channel causing it to wear away - most erosion happens by abrasion

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15
Q

what is attrition

A

eroded rocks picked up by the river crash into each-other and break into smaller fragments and the edges get rounded off - attrition causes particle size to decrease from source to mouth

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16
Q

what is solution ( erosion)

A

river water dissolves some types of rock e.g limestone and chalk

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17
Q

what are the 4 different types of river transportation?

A
  • solution
  • saltation
  • traction
  • suspension
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18
Q

what is traction

A
  • large particles like boulders are pushed along the river bed by the force of the water
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19
Q

what is saltation

A
  • pebble sized particles are bounced along the river bed by the force of the water
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20
Q

what is suspension

A

small particles like slit and slay are carried aloong by the water

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21
Q

what is solution ( transportation)

A

soluble material e.g limestone dissolve in the water and are carried along.

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22
Q

what is deposition

A

when a river drops the material is carrying

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23
Q

when does deposition occur

A

when the river looses velocity and energy

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24
Q

why does the river slow down

A
  • volume of water falls
  • amount of eroded material increases
  • water is shallower e.g on teh inside of a bend
  • the river reaches its mouth
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25
Q

where are waterfalls and gorges found

A

in the upper course of a river

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26
Q

where do waterfalls form

A

where a river flows over an area of hard rock followed by an area of soft rock

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27
Q

how are waterfalls formeed

A

the softer rock is eroded more than the harder rock creating a ‘step in the river’
as the water flows more the step is eroded more
eventually a ‘ steep drop’ is created which is a waterfall

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28
Q

what type of erosion is used to erode the soft rock in the formation of a waterfall

A

abrasion and hydraulic action

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29
Q

what does fluvial mean

A

another word for river

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30
Q

how is a gorge formed

A

after the formation of a water fall:

  • the hard rock is undercut by erosion and becomes unsupported and eventually collapses
    the collapsed rocks swirl around the foot of the waterfall and erode the soft rock by abrasion which creates a deep ‘ plunge pool’
  • over time more undercutting causes more collapse. the waterfall retreats leaving a steep sided gorge
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31
Q

give an example of a waterfall

A

high force waterfall on the river tees, county durham

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32
Q

why are interlocking spurs created

A

in the upper course of the river most erosion is vertical as the river lacks the power to erode laterally so the have to wind around the hillsides that stick out into their paths.

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33
Q

what is the interlocking spur

A

the hillsides that interlock with each other as the river winds around them

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34
Q

where do meanders and ox-bow lakes form

A

in the middle to lower course of the river where the channel as both deep and shallow sections.

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35
Q

how are meanders formed

A
  • the current is faster on the outside of the bend because the river channel is deeper
  • the causes more erosion to happen on the outside of the bend forming river cliffs
  • the current is slower on the inside because the river channel is shallower
  • so eroded material is deposited on the inside of the bend creating slip-off slopes
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36
Q

how are ox-bow lakes formed

A

oxbow lakes come from meanders

  • erosion on the outside bends cause them to get closer
  • until there only a small amount of land between the bends called the ‘neck’
  • the river breaks through the neck, usually during a flood.
  • and then the river flows along the shortest course
  • deposition eventually cuts off the meander forming an ox-bow lake
  • ox-bow lakes eventually dry up back into land
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37
Q

what is a flood plain

A

a flood plain is the wide valley floor on either side of a river which occasionally floods

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38
Q

what happens when a river floods

A

the water slows down, loses energy and deposits the material that its transporting which builds up the flood plain

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39
Q

what are leeves

A

they are natural embankments along the edge of a river channel

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40
Q

how are levees formed

A
  • during a flood, eroded material is deposited onto a floodplain
  • the Heaviest material is deposited closest to the channel because it gets dropped first when the river loses energy
  • over time the deposited material builds up creating levees along the edge of a channel
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41
Q

where are estuaries found

A

at the mouths of rivers

42
Q

how are mud flats formed

A
  • at river mouths
  • the water is tidal so the river level rises and falls each day
  • when the river floods over the banks of the river it carries silt and and sand onto the valley floor
  • as the tide reaches the highest point water moves slowly so the river has little energy and deposits sediment
  • over time more sediment builds up creating large mudflats
43
Q

what are estuaries

A

estuaries are tidal areas where the river meets the sea

44
Q

what is the name of the river in the river landscape case study

A

River tees

45
Q

what are the land forms on river tees

A

interlocking spur - Calderon snout
source - cross fell in The pennies
water fall - high force

46
Q

what are the land forms in the middle of the river tees

A

Barnard castle - river meanders

47
Q

what land forms are at the end of the river tees

A

seal sands - estuary

48
Q

what is river discharge

A

the volume of water flowing in a river per second mesured in cumers

49
Q

what do hydrographs show

A

they plot the river discharge aftera storm

50
Q

what are the different parts of a flood hydrograph

A
  • peak discharge
  • lag time
  • rising limb
  • falling limb
  • base flow
51
Q

what is the peak discharge in a hydrograph

A
  • the highest point of discharge
52
Q

what is the lag time in a hydrograph

A

the delay between the peak rainfall and the peak discharge

53
Q

what is the rising limb in a hydrograph

A

the increase in river discharge as rainwater flows into the river

54
Q

what is the falling limb in a hydrograph

A

the decrease in river discharge as rainwater flows into the river

55
Q

how does flooding occur

A

when a rivers level rises so much that it spills over the banks

56
Q

why does lag time occur in hydrographs

A

becuase most rainwater doesnt land directly in the river channe. it flows quickly overland or soaks into the ground and flows to the channel

57
Q

what are some physical factors that affect flood risk

A
  • heavy rainfall
  • geology
  • relief
  • prolonged rainfall
58
Q

how does heavy rainfall affect flood risk

A

the water arrives too quickly to infiltrate, so theres alot of surface runoff which increases discharge

59
Q

how does geology affect flood risk

A

some rocks eg. granite + clay soils are impermeable and dont allow infiltration so surface run off is icrease

60
Q

what is surface run off

A

when preciptation runs off the landscape

61
Q

who does prolonged rainfall affect flood risk

A

prolonged rainfall can saturate the soil as there is more time. but any further rain fall cant infiltrate which increases surface run off

62
Q

how does relief affect flood risk

A

if the river is on a steep sided valley water will reach the river quicker as it can flow faster down steep slopes which rapidly increases discharge.

63
Q

what are human factors that affect flood risk

A
  • urbanisation + buildings
  • removing trees
  • climate change + burning fossil fuels
64
Q

how does urbanisation and buildings affect flood risk

A

buildings and roads are often made from impermeable rock like concrete + tarmac so water cant infiltrate + increases surface run off

man made rains also send water directly to river which increases discharge

65
Q

how does removing trees affect flood risk

A
  • trees intercept water on their leaves which then evaporates
  • trees take in and store water from the ground
    so cutting them down increase amount of water going to river
66
Q

how does climate change affect flood risk.

A
  • people burn more fossil fuels that make the atmosphere warmer. the warmer atmosphere can hold more moisture so when it releases it there is heavier rainfall
67
Q

what is the difference between hard engineering and soft engineering

A

hard - man-made structures built to control flow of rivers and reduce flooding

soft- using the knowledge of rivers to reduce the effects of flooding

68
Q

what are different methods of hard engineering to reduce the risk of flooding.

A
  • dams and reservoirs
  • channel straightening
  • embankments
  • flood relief channels
69
Q

what are dams + reservoirs

A

dams - dams are barriers built across rivers

reservoirs - artificial lake that is formed behind the dam

70
Q

what are the benefits of using dams and reservoirs in reducing the risks of flooding?

A
  • store water after heavy rain
  • controls water flow and prevents floods down stream
  • can be used to generate hydroelectric power
71
Q

what are the disadvantages of using dams and reservoirs in reducing the risks of flooding?

A
  • dams are expensive to build
  • creating a reservoir can flood existing settlements
  • material is deposited into reservoir instead of along the rivers course so farmland downstream can be less fertile
72
Q

what is channel straightening

A

meanders are removed by building straighter artificial channels

73
Q

what are the advantages of channel straightening in reducing the risks of flooding?

A

water leaves area more quickly rather than building up so flood risk is flower

74
Q

what are the disadvantages of channel straightening in reducing the risks of flooding?

A
  • flooding may happen downstream instead
  • faster moving water may cause more erosion downstream
75
Q

what are the advantages of enbankments in reducing the risks of flooding?

A

river can hold more water so floods are less frequent

76
Q

what are enbankments

flood managment

A

raised walls built along river banks

77
Q

what are the disadvantages of embankments in reducing the risks of flooding?

A
  • expensive
    -if they break or water rises above there is a severe risk of flooding
78
Q

what are flood relief channels

A

channels are built to divert water around built up areas or to divert excess water if river levels are too high

79
Q

what are the advantages of flood relief channels in reducing the risks of flooding?

A
  • gates on the channels mean that release of water is controlled
80
Q

what are the disadvantages of flood relief channels in reducing the risks of flooding?

A

increased discharge where relief channel rejoins teh river

81
Q

what are the different types of soft engineering in reducing the risks of flooding?

A
  • flood warning and preperation
  • flood plain zoning
  • planting trees
  • river restoration
82
Q

what is flood warning and preparation

A
  • environment agency issue flood warning through TV or radio etc
  • buildings are modified to minimise damage]
  • sandbags + flood boards prior to floods
83
Q

what are the advantages of flood warning and preparation in reducing the risks of flooding?

A
  • give people time to prepare and place sandbags and move possessions upstairs
84
Q

what are the disadvantages of flood warning and preparation in reducing the risks of flooding?

A
  • doesn’t prevent floods
    -modifying buildings are expensive
  • doesn’t guarantee safety - false sense of security
85
Q

what is flood plain zoning

A

restrictions that prevent building on parts of the flood plain that are likely to get flooded

86
Q

what are the advantages of flood plain zoning in reducing the risks of flooding?

A

flood risk reduced as there are fewer impermeable surfaces

  • impact reduced as no buildings to damage
87
Q

what are the disadvantages of flood plain zoning in reducing the risks of flooding?

A
  • expansion of an urban area is limited
  • cant help in areas with existing buildings
88
Q

how does planting trees reduce the affects of flooding

A

– trees intercept water on their leaves which then evaporates
- trees take in and store water from the ground

89
Q

what are the advantages of planting trees in reducing the risks of flooding?

A
  • flood risk + discharge decreases
90
Q

what are the disadvantages of planting trees in reducing the risks of flooding?

A
  • less land for farming
91
Q

what is river restoration

A

making the river more natural by removing man made structure e.g leeves so the flood plain can flood naturally

92
Q

what are the advantages of river restoration in reducing the risks of flooding?

A
  • discharge is reduced so less risk of water flowing down stream
  • little maintenance is needed + more habitats for wildlife
93
Q

what are the disadvantages of river restoration in reducing the risks of flooding?

A
  • local flood risks can increase
94
Q

why was a flood management scheme need in oxfard?

A
  • oxford sits at the confluence of the river Thames and river cherwell - the proxminity of these river channels means oxfard is prone to flooding
  • the floods restricted people access to work + services
  • prevented tourists vising historic centre
  • damaged the local economy
95
Q

what happened in 2007 in oxfard

A
  • intense flooding + flash floods
  • over 250 homes had to be evacuated
    -A420 road was flooded for 100 metres
96
Q

what was the Oxford flood management scheme called and when was it created

A

oxford flood alleviation scheme
2014

97
Q

what are the different parts of the Oxford flood alleviation scheme?

A
  • span 5km
  • includes hard + soft engineering
  • creating embankments + flood walls using excavated material
  • creating areas of woodland + floodplain meadow to decrease peak discharge
  • increasing water storage in an existing bypass channel.
98
Q

what are the social issues of the Oxford flood alleviation scheme?

positive + negitive

A
  • compulsory purchase orders were send to landowners whose land was need to widen the flood plain - some people did not want to sell their land
  • construction disrupt residents lives - noise pollution
  • improve public footpaths
  • residents will feel more confident that their homes wont flood
99
Q

what are the economic issues of the Oxfard flooding allevation scheme?

positive + negitive

A
  • cost over 150 million pounds in total
  • homes + businesses will be better protected so less risk of expensive damage.
100
Q

what are the enviromental issues of the Oxfard flooding allevation scheme?

A
  • 2000 trees and 2 hectres of grassland removed. they will be replanated but will take a while for vegitation to grow back
  • scheme will create over 20 hectares of new riverside habitats improving biodiveristy.
101
Q

Where does the River Tees flow?

A

from the pennine hills to the northen sea

102
Q

what is the soft rock and hard rock on the high force waterfall in the river tees

A

soft: limestone
hard: dolerite