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Geography Yr 8 > Rivers > Flashcards

Rivers Flashcards

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1
Q

Water facts

A

A drop of water may spend over 3000 years in the ocean before evaporating into the air.
A drop of water spends 9 days in the atmosphere before falling back to Earth.
An amazing 96.5% of all water is stored as salt water in the oceans. Just 0.001% is stored in the atmosphere and 0.0002% is stored in the worlds rivers.

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2
Q

Throughflow

A

Is when water in the soil moves down hill

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3
Q

Drainage basin

A

The area of land drained by a river where the water cycle takes place.
A drainage basin is an area of land that is drained by a river and its tributaries. Precipitation falling within the basin finds its way into streams and rivers that flow towards the sea. The drainage basin system is part of the hydrological cycle.

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4
Q

Precipitation

A

Is any form of liquid or solid water particles that fall from the atmosphere and reach the surface of the Earth.

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5
Q

Condensation

A

The process of water vapour turning to a liquid as it is cooled.

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6
Q

Infiltration

A

When water soaks into the soil.

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7
Q

Percolation

A

When water moves vertically through the soil and rock

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8
Q

Channel flow

A

Is the flow of water through in a river

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9
Q

Groundwater flow

A

Is when the water in a rock flows downhill.

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10
Q

Transpiration

A

Evaporation water is heated by the sun and turns into water vapour

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11
Q

Surface runoff

A

When water flows overground(on top of land)

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12
Q

Interception

A

When water droplets collect on trees or plants.

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13
Q

Surface storage

A

When water lies on the ground as puddles or lakes.

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14
Q

Soil moisture

A

Water stored in the soil.

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15
Q

An increase in rainfall?

A

Surface storage would increase.

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16
Q

A decrease in rainfall?

A

Decrease in surface storage because the water would evaporate.

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17
Q

A lot of snow which melted very quickly?

A

Lot of surface storage because the water would melt on the surface there would also be infiltrated and moisture.

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18
Q

Long winter with temperatures below freezing for several weeks?

A

The ground would freeze and there would probably be more overground flow since it wouldn’t be able to go underground.

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19
Q

Warm day following several days of heavy snowfall?

A

There would be less snow since a lot of snow would melt and then evaporate into the atmosphere.

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20
Q

A very hot long dry summer?

A

Not much surface storage or surface runoff since a lot of the water on the ground would’ve evaporated into the atmosphere.

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21
Q

what do all rivers flow in?

A

bowl-shaped depressions or basins

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22
Q

inputs

A

water entering the system

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23
Q

transfers/flows

A

the movement of water through the system

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24
Q

stores

A

water stored in the system

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25
Q

outputs

A

water leaving the system

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26
Q

watershed basin

A

the outer edge of a drainage basin

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27
Q

upper course

A

higher upland areas, with mountains

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28
Q

upper

source:

A

start of the river, always begins in high upland areas like mountains

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29
Q

upper

v-shaped river valley:

A

a deep river valley shaped like a V, formed by erosion

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30
Q

upper

tributaries:

A

a small river that joins a larger river

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31
Q

upper

confluence:

A

where tributaries join each other to form larger river channels, where two rivers join

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32
Q

upper

gorge:

A

narrow, steep-sided river valley

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33
Q

middle course

A

the river becomes less steep and becomes more of a gentle gradient, erosion, water increasing, the river channel has widened probably due to lateral erosion, meanders and ox-box lakes will form

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34
Q

middle

river channel:

A

a landform that contains a river at the bottom of the valley

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35
Q

middle

main river channel:

A

the river will go from being in more upland areas to more gentler river slope areas

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36
Q

middle

meander:

A

a winding curve or bend of a river

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37
Q

lower course

A

wider river channel, deposition due to sand deposits

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38
Q

lower

floodplain land:

A

the river meets the flattest area of land

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39
Q

lower

estuary:

A

a broad flooded valley where a river joins the sea

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40
Q

lower

mouth:

A

the river at the end of the journey just before it meets the sea in flat lowland areas

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41
Q

How does a cross profile of a river change as you go downstream.

A

The river channel becomes wider and deeper, with the valley becoming wider and flatter.
Sides become less steep compared with the V-shape upstream
In reality there are many variations
The changes downstream are due to the amount of water flowing in the river. As tributaries flow into the main channel from other parts of the drainage basin the river becomes bigger. With more water there is more energy and more ability to erode making the channel further wider and deeper
The changes in the cross profile are due to this channel erosion broadening and flattening the base of the valley.
Together with weathering and mass movement, these processes make the sides of the valley less steep

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42
Q

Erosion process

A

Erosion is the process of water wearing away the land. The river erodes as it carries materials in its water. The more energy the river has, the faster it can erode.

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43
Q

Transportation process

A 
The sediments(load) are transported.
Transportation is the process of water carrying rocks and sediment downstream.
The material a river transports is called it’s load. The size and total amount of load that can be carried will depend on the river’s state of flow – its velocity. The more energy a river has, the larger the load it can carry. After a rainstorm in high-flow rivers often look very muddy because they are flowing fast and transporting a large amount of sediment. At low flow, when the rivers are usually clearer, very little sediment is being transported.
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44
Q

Deposition definitions and processes

A

Deposition is the processes where material being transported by a river is dropped. Deposition of sediment occurs when river decreases velocity. It no longer has enough energy to erode or transport sediment so the load is deposited. Sediment is deposited on the river bed and the banks and at the river’s mouth
Larger sediment tend to be deposited first in the upper course of the river. They are only transported very short distances, mostly by traction, during periods of very high-flow
Finer sediment is carried further downstream, mostly held in suspension. This material will be deposited on the river bed or the banks, where velocity is slowed by friction
Dissolved material stays in the water, it will end up in the sea or lake.

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45
Q

Summarise what happens to the processes as you move down the river:

A

Erosion occurs in the upper course which causes v-shaped valleys and waterfalls to form. There are four types of erosion: abrasion, attrition, hydraulic action and solution. In the middle course, erosion, deposition and transportation occur. There are four types of transportation which are suspension, traction, solution and saltation. Deposition mostly occurs in the lower course of the river. Deposition occurs when a river decreases velocity.

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46
Q

Rivers long profile

A

Erosion is the main process in the upper course
Both erosion and deposition occur in the rivers middle course
Deposition wins out in the lower course as it loses energy

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47
Q

The river valley, in cross section

A

In the upper course, the river erodes downwards. The result is a v-shaped valley.
Now the banks are being eroded, so the channel is getting wider. A floodplain forms, where the river floods time after time.

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48
Q

River courses

A

Upper course - mostly erosion landforms e.g. waterfalls
Middle course - mostly erosion and deposition landforms e.g. meanders and transportation
Lower course - mostly deposition landforms e.g. levees

49
Q

Why are histograms useful in geography?

A

Histograms are useful in geography because they help us to compare the quantity or frequency of categories in a data set and they are easy to draw and interpret.

50
Q

6 rules for histograms

A
  1. There are no gaps between the bars because histograms display continuous data.
  2. The categories have to be plotted along the x-axis
  3. The y acid represents the number of things(e.g. pieces of sediment) in each category
  4. Label the x and y axis
  5. Give the graph a title
  6. Plot a single bar for each category on the graph
51
Q

How to interpret histograms

A
  • look for obvious peaks
  • look for any odd bars
  • compare with other histograms
52
Q

Landform

A

Anything that has been created through physical processes e.g. beaches are formed by the process deposition.

53
Q

V - shaped valley formation

A

A small stream will naturally follow small depressions in the landscape.
Over time, weathering and gravity wear away the steep valley sides, forcing material into the stream, which it uses to cut the valley steeper.
As the small stream flows down steeply, the bed load will erode downwards and scrape away the bottom of the channel (vertical erosion).
This vertical erosion deepens the valley, making the sides steeper and exposed.

54
Q

What are interlocking spurs?

A

Interlocking spurs are slopes that form either side of the valley.

55
Q

How are interlocking spurs formed?

A

They are formed because at this stage of the river it small in width. Its main work is eroding the channel vertically and has no energy to do anything else so the river uses the easiest course rather than eroding the slopes.

56
Q

Waterfalls

A

Warterfalls occur when there’s a sudden change in the composition of a rock from a resistant to a softer rock. The river erodes the weaker rock more quickly than the more resistant rock. The resistant rock is undercut creating an overhang.

57
Q

headward erosion

A

waterfall retreating

58
Q

What happens to the harder rock in a waterfall?

A

The harder rock can’t take the weight and collapses.

59
Q

undercutting of softer rock

waterfalls

A

undercutting of softer rock by hydraulic action and abrasion creating an overhang.

60
Q

What is a gorge?

A

A gorge is a narrow steep sided valley that is usually found immediately downstream from a waterfall.

61
Q

How is a gorge formed?

A

Gorge formed by a retreat due to headward erosion.

62
Q

Plunge pool

A

A deep area of water at the base of a waterfall.

63
Q

Where are meanders?

A

In the middle and lower course.

64
Q

Meander formation

A

Where a river meets layers of hard and soft rock. When it meets hard rock it moves around it.

65
Q

Meander

A

A bend in the river

66
Q

The inside bend

A

The slowest and where the mist deposition occurs = slip off slopes

67
Q

Outside bend

A

has more erosion as it has a high velocity = river cliff

68
Q

Is the outside bend or the inside bend steeper?

A

Deeper on the outside bend because of erosion, shallower on the inside bend due to deposition because of decreased velocity.

69
Q

Oxbow lake

A

In the lower course of the river meander bends become even more extreme and gradually the neck of the meander narrows eventually forming distinctive features known as ox-bow lakes.

70
Q

Deposition

A

The processes where material being transported by a river is deposited.

71
Q

When does deposition occur?

A

Deposition occurs when a river loses energy.
This can be when a river enters a shallow area (this could be when it floods and comes into contact with a floodplain) towards its mouth where it meets another body of water.

72
Q

Oxbow lakes formation

A

As erosion continues, the neck of the meander is worn away. It gets narrower and narrower.
Then, during flooding the river takes a shortcut straight across the neck.
Soon the loop of the meander gets sealed off. It turns into an oxbow lake.
In time the lake will get covered with weeds and fill with soil and disappear.

73
Q

Lower course landform

Floodplains

A

The flat land beside a river.
Forms when a river floods, deposits a lot of sediment making the land very fertile.
Can also be formed by large looping meanders.

74
Q

Lower course landforms

Levees

A

Levees are raised river banks.
They are formed naturally by deposition in a flood.
OR
Artificially to hold more water and reduce flood risk.

75
Q

Lower course landforms

Deltas

A

When a river reaches a lake/sea the water slows down and loses the power to carry sediment.
Sediment is deposited at the mouth of a river.
Some rivers drop so much sediment that waves and tides can’t carry it all away, it builds up in layers forming a delta.
The Nile delta in Egypt.

76
Q

Lower Course Landforms

Estuaries

A

An area where a freshwater river or stream meets an ocean (saltwater).
The water is tidal - rises and falls each day.
Deposition is the key process and helps it to build a mud flat.

77
Q

long profile

A

a long profile is a line representing the river from its source to its mouth

78
Q

cross profile

A

a cross profile shows a cross section of a rivers channel and valley at a certain point

79
Q

upper course landforms

A

v-shaped valleys
interlocking spurs
waterfalls
gorges

80
Q

middle course landforms

A

meanders

oxbow lake

81
Q

lower course landforms

A 
estuaries
delta
floodplains
levees
mud flats
82
Q

braided river

A

a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, aits or eyots

83
Q

river disharge

A

River discharge is the volume of water flowing through a river channel. This is the total volume of water flowing through a channel at any given point and is measured in cubic metres per second (cumecs).

84
Q

load

A

everything the river carries

85
Q

bedload

A

whats carried along the floor of the river

86
Q

Physical Causes of Flooding:

A
  • heavy rain
  • impermeable rock (water can’t soak through/ be taken in/percolate
  • tributaries
  • hard dry soil (rain can’t infiltrate)
  • steep slopes
  • saturated soil(impossible to take in more water)
  • snow melting
87
Q

Causes of flooding:

steep sides

A

If the surrounding land is steep/ mountainous then water will flow down the sides (and end up in the river) faster.

88
Q

Causes of flooding:

dry soil

A

If the weather has been hot/dry the ground gets ‘baked’ and the rain can’t soak in very quickly. So it flows overground to the river.

89
Q

Causes of Flooding:

Building on or near floodplains

A

We often build on or near to the floodplain. The rain can’t soak through the surfaces (e.g. concrete) and instead gets to the river faster through drains.

90
Q

Causes of Flooding:

saturated soil

A

If there has been a lot of rain over a period of time the ground gets ‘saturated’ and can’t hold any more water.

91
Q

Causes of Flooding:

cutting down trees

A

Trees catch rainwater(interception). When we chop them down, we prevent this from happening. Water then ends up in the river faster.

92
Q

Causes of Flooding:

impermeable rock

A

The type of rock is important. Some are permeable and let water through, others are impermeable and don’t.

93
Q

Causes of Flooding:

heavy rainfall

A

Heavy rainfall. Quite simply too much water ends up in the river causing the river to burst its banks.

94
Q

Causes of Flooding:

snow melting

A

When snow starts to melt, a large volume of water finds its way to the river.

95
Q

Human Causes of Flooding:

A
  • cutting trees(can’t soak water, interception), deforestation
  • concrete floors(not able to soak water)
  • building on or near a drainage basin and floodplains(water can’t infiltrate)
96
Q

SEEP

A

Social, Environmental, Economic, Political

97
Q

When does flooding occur?

A

Flooding occurs when rivers discharge is greater Han the discharge it was designed to carry.

98
Q

Hard Engineering:

A

Hard engineering involves using man-made structures to prevent or control natural processes from taking place.

99
Q

Dam and Reservoirs
How it works?
Negative Impacts (cost):
Postive Impacts:

A
  • When rainfall is high water is stored in a reservoir, behind a dam. This means water that would have once flowed downstream and flooded a town is now held and slowly released(decreasing discharge).
  • Large areas of land have to be flooded to make way for a reservoir meaning many people would have to be be moved from their homes. Vey expensive. £1 billion per dam.
  • They can have multiple purposes, for example many dams don’t just stop flooding they can also be used to generate power or store water in periods of water or draught.
100
Q

Channel Straightening
How it works?
Negative Impacts (cost):
Positive Impacts:

A
  • cutting through meanders to create a straight channel, this speeds up the flow of water along the river
  • £4700 per metre. Disrupts wildlife. Unnatural. May increase flood risk further downstream.
  • speeds flow and prevents the banks from collapsing
101
Q

Embankments
How it works?
Negative Impacts (cost):
Positive Impacts:

A
  • A raised riverbank. Raising the level of a river bank allows the river channel to hold more stare before flooding occurs.
  • They are made of concrete which some people may think is too expensive, stops water seeping into the ground, doesn’t look natural and can cause worse flooding if it isn’t properly maintained.. £1152 per metre
  • Prevents the flooding of valuable property. Mud dredged from the river can be used and it is more sustainable and looks more natural. Helps the river hold more water.
102
Q

Flood Relief Channels
How it works?
Negative Impacts (costs):
Positive Impacts:

A
  • Excessive water flows away into the flood relief channel and reduces the threat of flooding.
  • £12,000 per metre. Requires regular maintenance.
  • Reduces flood risks. New habitats of aquatic life. Bypass urban and high-value life.
103
Q

Soft engineering

A

Involves adapting to a river and working with natural processes, it is cheaper but less effective than hard engineering. It doesn’t involve building artificial structures.
Aims to reduce/slow the movement of water.

104
Q

Trees
Advantages:
Disadvantages:

A
  • Planting trees in order to intercept rainfall and prevent it from reaching the river, thus reducing the flood risk. Also creates new habitats for wildlife and is very cheap.
  • Cheap and creates nee wildlife. Better for the environment.
  • Takes up space. Not 100% sustainable/reliable.
105
Q

River Restoration
Advantages:
Disadvantages:

A
  • Where the course of river has been change artificially, river restoration can return to its original course. Uses the natural processes and features of a river e.g. meanders and wetlands to slow down river flow and reduce the likelihood of a major flood.
  • Keeps rivers natural. Doesn’t add concrete or artificial structure. Creates more channel space.
  • Lengthy process. Not sustainable.
106
Q

Flood warnings and preparations
Advantages:
Disadvantages:

A
  • Flood warnings and preparations: river and river basins are remotely monitored using satellites and computer technology. Instruments check rainfall and check river levels. Computer models used to predict discharges and identify areas at risk from flooding.
  • Keeps areas alert and gives people enough time to protect themselves or move.
  • Not 100% reliable. Doesn’t stop or reduce flood risk.
107
Q

Floodplain Zoning
Advantages:
Disadvantages:

A
  • Floodplain zoning restricts different land uses to certain locations on floodplains. Areas close to the river and at risk from the flooding can be kept clear of high value land uses such as housing and industry. Instead these areas can be used for pasture, parkland, playing fields etc. Reduces losses caused by flooding. Can be difficult to implement on floodplains that have already been developed causing prices to fall.
  • Keeps expensive property safe in low flood risk areas. Makes use of areas by river safety. Causes land price to fall. Difficult to implement on developed floodplains.
108
Q

Where does deposition occur?

A
  • Where the river becomes shallower and friction increases
  • When the river meets a slow moving body of water like the sea and slows down
  • When the river floods and moves across floodplains
  • Where the river changes it’s course and an area of the river is cut off from the moving water.
109
Q

Type of Erosion

Abrasion

A

sand and stones scrape the bed and banks like sandpaper, and wear them away

110
Q

Type of Erosion

Attrition

A

when stones carried by the river knock against each other, gradually making the stones smaller and more rounded

111
Q

Type of Erosion

Hydraulic Action

A

in a fast-flowing river, water is forced into cracks in the bank, over time it breaks up the bank by compressing the air and breaking up the particles.

112
Q

Type of Erosion

Solution

A

Water dissolves soluble minerals from the bed and banks. This helps to break them up. / When the river flows over limestone or chalk, the rock is slowly dissolved. This is because it is soluble in mildly acidic water.

113
Q

Type of Erosion

Vertical erosion

A

gravity pulling the water down that starts to erode on the bottom of the hill creating a v-shaped valley.

114
Q

Type of Erosion

Interlocking spur

A

when the river erodes around the softer rock moving around the harder rock.

115
Q

Type of Erosion

Lateral Erosion

A

erosion of the banks rather than the beds

116
Q

Type of Transportation

Suspension

A

fine, light materials carried along by the river

117
Q

Type of transportation

Traction

A

large boulders and rocks are rolled along the river bed

118
Q

Type of Transportation

Solution

A

minerals are dissolved in the water, this is a chemical change

119
Q

Type of transportation

Saltation

A

small pebbles and stones are bounced along the river bed

Geography Yr 8 (10 decks)

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