River processes and pressures Flashcards

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1
Q

What is the gradient like in the upper course?

A

Steep

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2
Q

What is the discharge like in the upper course?

A

Small

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3
Q

What is the depth like in the upper course?

A

Shallow

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4
Q

What is the channel shape like in the upper course?

A

Narrow, steep sides

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5
Q

What is the velocity like in the upper course?

A

Quite fast

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6
Q

What is the valley shape like in the upper course?

A

Steep sides

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7
Q

What features are found in the upper course?

A

Waterfalls, interlocking spurs

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8
Q

What is the gradient like in the lower course?

A

shallow gradient

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9
Q

What is the discharge like in the lower course?

A

Very large

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10
Q

What is the depth like in the lower course?

A

Deep

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11
Q

What is the channel shape like in the lower course?

A

Flat floor, gentle slopping sides

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12
Q

What is the velocity like in the lower course?

A

Very fast

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13
Q

What is the valley shape like in the lower course?

A

Flat, gentle slopping sides

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14
Q

What features are found in the lower course?

A

Meanders, floodplains, levees and ox-bow lakes

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15
Q

What is the gradient like in the middle course?

A

Less steep

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16
Q

What is the discharge like in the middle course?

A

Large

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17
Q

What is the depth like in the middle course?

A

Deeper than the upper course

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18
Q

What is the channel shape like in the middle course?

A

Flat, steep sides

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19
Q

What is the velocity like in the middle course?

A

Fast

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20
Q

What is the valley shape like in the middle course?

A

Flat, steep sides

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21
Q

What features are found in the middle course?

A

Meanders and floodplains

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22
Q

What are the four main processes of erosion?

A

Hydraulic action
Abrasion
Attrition
Solution

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23
Q

What is hydraulic action?

A

The force of water on the bed and banks of the river removes material

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24
Q

What is attrition?

A

The load that is carried by the river bumps together and wears down into smaller, smoother pieces

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25
Q

What is abrasion?

A

Material carried by the river rubs against the bed and banks and wears them away

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26
Q

What is solution?

A

Some rock minerals dissolve in the river (limestone and chalk) and are carried along in the flow

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27
Q

What are the four main types of transportation?

A

Traction
Saltation
Suspension
Solution

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28
Q

What is traction?

A

Large boulders roll along the river bed

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29
Q

What is saltation?

A

Smaller pebbles are bounced along the river bed, picked up the dropped as the flow of the river changes

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30
Q

What is suspension?

A

Finer sand and silt particles are carried along in the flow, giving the river a brown appearance

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31
Q

How are waterfalls formed?

A

More resistant rocks lies over less resistant rock
Less resistant rock is eroded forming a step
More resistant rock is undercut forming an overhang
Overhang is not supported so rock falls into water
Powerful fall of water erodes plunge pool with fallen rocks
Waterfall retreats upstream

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32
Q

How are interlocking spurs formed?

A

The river naturally flows from side to side, around ridges in valley sides (spurs). These spurs become interlocking with those on the other side of the valley

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33
Q

What are meanders?

A

Bends in the river’s course

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34
Q

Where are meanders found?

A

Lower course

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35
Q

Where are waterfalls found?

A

Upper course

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36
Q

Where are interlocking spurs found?

A

Upper course

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37
Q

How are meanders formed?

A

As a river bends the current is slower on the inside so it deposits sediment whereas on the outside it is faster so it erodes the bank

38
Q

How does an ox-bow lake form?

A

A river creates a meander, due to the river’s eroding the bank. After a long period of time, the meander becomes very curved, and eventually the neck of the meander becomes narrower and the river cuts through the neck during a flood, cutting off the meander and forming an oxbow lake.

39
Q

Where are ox-bow lakes found?

A

Lower course

40
Q

How are levees formed?

A

When a river floods it deposits the biggest and heaviest particles on the bank forming floodplains
Increased deposition causes the river bed to raise
After many floods the banks build to form levees

41
Q

Where are levees found?

A

Lower course

42
Q

What is a delta?

A

Overtime sediment builds up to create an almost flat area of new land

43
Q

What happens to the river because of deltas?

A

The river moves very slowly over the new flat land so its channel fills up with sediment so it has to split into streams

44
Q

What are the two types of slope processes?

A

Soil creep and slumping

45
Q

What is soil creep?

A

Particles of soil slowly move down the sides of valleys under the influence of gravity

46
Q

What is slumping?

A

Valley sides are eroded by the river making the sides steeper and increasing downward movement of material

47
Q

What can trigger slumping?

A

Heavy rainfall

48
Q

What are the sides like of rivers flowing of resistant rock?

A

Steeper

49
Q

What are the sides like of rivers flowing of less resistant rock?

A

Gentle slopes

50
Q

What is the transportation rate of rivers in a wet climate?

A

It is greater as the energy of water is greater so wet climates transport more material

51
Q

What is the amount of discharge in a wetter climate?

A

Greater discharge

52
Q

What is the amount of discharge in a drier climate?

A

Less discharge as there is more evaporation

53
Q

The greater the discharge the higher the what?

A

The higher rate of transportation

54
Q

What type of weathering is greater in a colder climate?

A

Freeze-thaw

55
Q

When is the erosion rate greater?

A

Where discharge and energy of the river is greater

56
Q

Is the erosion greater in a hotter or wetter climate?

A

Wetter

57
Q

What does the rate of erosion effect?

A

Shape of river valley and amount of sediment

58
Q

What do storm (flood) hydrographs show?

A

How a river responds to a rainstorm

59
Q

How do you find the lag time?

A

The difference in time between the peak of the rainstorm and the peak of the discharge

60
Q

What does the bar graph show?

A

The amount of rainfall in mm

61
Q

What does the line graph show?

A

The rivers discharge

62
Q

What does a shorter lag time and steeper rising limb show?

A

Greater risk of flooding

63
Q

What human activities contribute to flooding?

A

Urbanisation
Land-use change
Building on floodplains
Deforestation

64
Q

How does geology effect flooding?

A

More resistant rock will absorb lees water so run-off will be greater and faster

65
Q

How does soil type effect flooding?

A

More impermeable soil (clay) will absorb less water so run-off will greater and faster

66
Q

How does vegetation effect flooding?

A

Less vegetation will mean the rain will not be intercepted and surface run-off will be greater and faster

67
Q

How does slope effect flooding?

A

Steeper slopes cause faster surface run-off so more water reaches the river quicker

68
Q

How does drainage basin effect flooding?

A

A wide drainage basin with lots if tributaries close together means water enters the river quicker, meaning the rising limb is steeper and the lag time shorter

69
Q

How does antecedent conditions effect flooding?

A

When the ground is more saturated with water, further rain flows as surface run-off

70
Q

What are the threats of flooding on people?

A

Damage to home
Damage to farmland
Death and injury
Damage to businesses

71
Q

What are the threats of flooding on the environment?>

A

Damage to wildlife/ their habitats
Damage to vegetations
Polluted floodwater damaging the land

72
Q

How has climate change increased flooding?

A

Increased frequency of storms
Increased periods of hot/dry weather
Increased periods of extreme cold

73
Q

How does increased storm frequency increase flooding?

A

More periods of heavy rainfall so more rainfall enters the river and more antecedent conditions

74
Q

How does increased periods of hot/dry weather increase flooding?

A

It bakes the soil so when it does rain it can’t be absorbed so it runs as surface run-off

75
Q

How does increased periods of extreme cold increase flooding?

A

Freezes the soil so water runs as surface run-off as it can’t be absorbed

76
Q

What are hard engineering methods for managing flood risk?

A

Embankments and levees
Flood walls
Dams and reservoirs
Flood barriers

77
Q

What are the advantages and disadvantages of embankments and levees?

A

Use natural materials so the look natural

May burst causing widespread flooding

78
Q

What are the advantages and disadvantages of flood walls?

A

Require minimum maintenance

Block the view of the river

79
Q

What are the advantages and disadvantages of dams and reservoirs?

A

Able to regulate and control the flow of water

Very expensive

80
Q

What are the advantages and disadvantages of flood barriers?

A

Can be moved to where needed and quickly erected

Don’t provide long lasting protection

81
Q

What are the soft engineering methods for managing flood risk?

A

River restoration
Washlands
Floodplain retention
Plant trees (afforestation)

82
Q

What are the advantages and disadvantages of river restoration?

A

Can reduce flooding downstream

People living there may not want land use to change

83
Q

What are the advantages and disadvantages of washlands?

A

Restricts economic development

84
Q

What are the advantages and disadvantages of floodplain retention?

A

Provides somewhere for floodwater to go
Restricts economic development
Attractive and provides place for leisure and recreation

85
Q

What are the advantages and disadvantages of planting trees (afforestation)?

A

Increased infiltration

Not suitable fort all locations

86
Q

What are one of the physical causes of flooding in Tewkesbury?

A

Two of the largest rivers in the UK meet in Tewkesbury- the Severn and the Avon

87
Q

What happens before the Severn reaches Tewkesbury?

A

It travels through many mountains and hills so steep slopes cause faster surface run-off

88
Q

Why does the drainage basin effect the Severn and flooding in Tewkesbury?

A

Because lots of tributaries flow into the river before it reaches Tewkesbury

89
Q

Why is the Severn’s discharge often high before it reaches Tewkesbury?

A

Because of snowmelt

90
Q

Why has urbanisation increased flooding in Tewkesbury?

A

Caused the town to grow so there is less permeable surfaces to absorb water

91
Q

Why has building houses increased flooding in Tewkesbury?

A

As houses have been built on a floodplain making them very vulnerable to flooding

92
Q

Why has field drains increased flooding in Tewkesbury?

A

They improve farmland but they move water into the tributaries very quickly