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Geography > Rivers and river management > Flashcards

Rivers and river management Flashcards

1
Q

What is a drainage basin?

A

The area of land that a river drains

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2
Q

What is corrosion/solution?

Erosion

A

Rocks being dissolved in water

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3
Q

What is hydraulic action?

Erosion

A

The sheer force of the river against a surface

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4
Q

What is attrition?

Erosion

A

Stones in the river banging against each other

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5
Q

What is abrasion?

Erosion

A

When large rocks roll along the river bed leading to erosion.

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6
Q

What is solution?

Transport

A

Chemicals being transported by the water

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7
Q

What is saltation?

Transport

A

Rocks being bounced along the river bed.

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8
Q

What is suspension?

Transport

A

Sediment being carried in the body of the rivers and not being dropped.

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9
Q

What is traction?

Transport

A

Large rocks being rolled along the bottom of the river.

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10
Q

What is the hydrological cycle?

A

The movement of water from land, to sea, to air.

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11
Q

What is groundwater flow?

A

Movement of water through the rock layer

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12
Q

What is throughflow?

A

Movement of water through the soil layer.

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13
Q

What is overland flow/surface run-off?

A

Movement of water over land.

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14
Q

What is transpiration?

A

Water evaporated from the surface of vegetation.

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15
Q

What is infiltration?

A

Water soaking from the surface into the soil.

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16
Q

What is percolation?

A

Water soaking from the soil layer into the rock layer.

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17
Q

What is evaporation?

A

Water heated and turned into water vapour.

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18
Q

What is condensation?

A

Water cooled and turned back into water droplets.

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19
Q

What is interception?

A

Trees catching the rainwater.

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20
Q

What does permeable mean?

A

Rocks that allow water water into it such as sandstone and limestone.

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21
Q

What does impermeable mean?

A

Rock that doesn’t take in water such as granite, slate and clay.

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22
Q

What does saturated mean?

A

When the ground is completely full of water.

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23
Q

What are porous rocks?

A

They have tiny spaces as pores between the grains of rock. Porosity is how much water…

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24
Q

How do humans impact the hydrological cycle?

A

Dams and reservoirs
Urbanisation
Deforestation
Farming and industry

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25
Q

How do dams and reservoirs effect the hydrological cycle?

A

Increased surface storage
Increased evaporation
The water in the river in front of the reservoir is decreased.

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26
Q

How does urbanisation effect the hydrological cycle?

A

Impermeable surfaces such as concrete and tarmac
Water cannot infiltrate which re-educated the amount of groundwater stored.
Water flows over the surface as surface runoff, which can lead to flooding.

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27
Q

How does deforestation impact the hydrological cycle?

A

Prevents interception
Means water hits the ground with more force, possibly leading to erosion.
Water is less likely to infiltrate so there will be more surface run-off, this might lead to flooding.

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28
Q

What is a flood hydrograph?

A

A graph to show how a river reacts to a rainfall event.

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29
Q

What is the base flow?

A

The average or normal flow of the river.

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30
Q

What is river discharge?

A

The volume of water flowing through a given point on a river at a given time.

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31
Q

How do you calculate discharge?

A

River velocity x cross sectional area

Cross sectional area is the width of the river x the average depth

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32
Q

What does a river regime show?

A

How river discharge changes throughout the year/seasons.

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33
Q

What is a v-shaped valley?

A

Found in the upper course of a river.
Started by vertical erosion of the river downwards.
The sides of the river valley then break down due to weathering.
Over time, the weathered rock falls into the river, causing the Valle sides to become v-shaped.

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34
Q

How are water falls formed?

A

Formed in the upper course of the river.
The river erodes the less resistant rock first (which is under the more resistant rock). This creates an overhang. As the river flows over the water fall and into the plunge pool, erosion occurs which makes the plunge pool larger. Eventually, the overhang above the plunge pool collapses and a result of undercutting. This way the waterfall retardants upstream creating a gorge.

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35
Q

How are meanders formed?

A

Middle course of the river.
The current swings to the outside of then bend and concentrates the erosion there. Deposition occurs on the inside of the bed where there is not enough energy to carry load. (It is LATERAL erosion).

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36
Q

What is a slip off slope?

A

Formed in a river on the inside bend. This is because the water has little energy so deposits any material her.

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37
Q

What is a river cliff?

A

Formed on the outside bend in a river. The bank is undercut by LATERAL erosion because the water has lots of energy and the water flow is fastest here.

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38
Q

What landforms do you find in the lower course of the river?

A 
Estuary 
Flood plains 
Meanders
Oxbow lakes 
Mud flats 
Salt marshes
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39
Q

What causes river floods?

A 
Rock and soil type 
Land use
Rainfall 
Relief - if the river valley is steep sided, when it rains the water will flow very quickly into the river leading to floods. 
Weather conditions.
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40
Q

What were the physical causes of flooding in Tewkesbury?

2007

A

Depressions that passed over the UK were very slow leading to huge amounts of rainfall.
This meant the ground was very saturated and couldn’t hold anymore water resulting in large scale floods. The ocean temperature had been rising slowly causing an increase in evaporation and therefore rainfall. Also the confluence of the River Severn and Avon meet at Tewkesbury which leave it vulnerable to flooding. Most of the land around Tewkesbury is flat, low lying floodplain.

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41
Q

What are some human causes of the flooding at Tewkesbury?

2007

A

Urban creep - more and more houses built on flood plains in the last 60 years. People were also paving over their front gardens. This meant that more land is impermeable. Rain water flows straight into the rivers rather than soaking into the soil and this causes flooding.
Field drains in the upland parts of the drainage basin. These drain farmland so that the soil is not too wet for crops, however they allow water to reach the river channel very rapidly.

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42
Q

What were the causes of the Boscastle floods in 2004? (FLASH FLOOD)

A

Over 60mm of rainfall fell in two hours
The ground was already saturated
The drainage basin has many steep slopes, and has areas of impermeable slate causes rapid surface run off.
Boscastle is at the confluence of three rivers. A large quantity of water all attained within a short space of time causing the rivers to overflow.
The flooding coincided with a high tide, Laing the impact worse.

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43
Q

What were some of the causes of the Bangladesh flooding? (SEASONAL FLOOD)

A

Monsoon climate brings heavy rain and snow. Souls are leaches and heavy runoff results in soil erosion.
Spring snow melt
Deforestation means less evapotranspiration. Landslides also occur.
Rivers silt-up due to increased soil erosion. This raises the river bed and reduces the capacity of the channel resulting in increased likelihood of flooding.
80 percent of Bangladesh lies on a huge floodplain and delta, most of which is only 1m above sea level.

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44
Q

What are the economic impacts of flooding?

RIVER SEVERN

A 
Short term 
800 properties flooded 
Damage to possessions 
Property contaminated with dirty sediment 
Loss from business not operating. 
Long term 
Severn Trent water company had to spend £25 million on getting people fresh water and repairing the Mythe Water plant. 
Business out of operation for 8 months. 
£11 million of farm sets crops lost 
Damage to shop products 
Rise ins insurance premiums 
People not able to sell their houses 
Fall in house prices
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45
Q

What are the social impacts of flooding? (RIVER SEVERN)

A

Short term
Schools temporarily closed
Psychological impact of having your house flooded.
150000 homes with no water as Mythe Water treatment flooded.

Long term
Children taught in temporary classrooms while school buildings repaired.
People homeless or in temporary accommodation for up to a year.

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46
Q

What are the environmental impacts of flooding? (RIVER SEVERN)

A

Damage to crops

Layers of contaminated silt on properties.

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47
Q

What are some positives of flooding?

A

Recharging water sources
Agriculture (farming)
Fishery

48
Q

How is recharging water spices a positive impact of flooding?

A

River flood plains evoke inundated with flood water, the water will infiltrate the soil and recharge ground water. The groundwater stores are an important source of drinking water and it can also be essential for agriculture.

49
Q

How is agriculture (farming) a positive of flooding?

A

The water transports nutrients and sediments onto the surrounding flood plains where it is then deposited as a layer of alluvium. As this is rich in nutrients, it helps to enrich the surrounding soil. Rice paddies are flooded deliberately to take advantage of this natural fertilisation process.

50
Q

How is flooding a positive for fishing?

A

A river basin is an ecological unit of interconnecting upstream spawning habitats with downstream rearing habitats for a variety of species and other aquatic systems. Seasonal habitats on the flood plain, created by variable flow regimes, are essential for various stages of the life cycle of species. Floods provide an ecological trigger for both the spawning and migration of certain species.

51
Q

What is hard engineering?

A

Generally defined as a controlled disruption of natural processes using man made structures.

52
Q

What is soft engineering?

A

Use of ecological practices to reduce erosion and achieve stabilisation while enhancing habitats and saving money.

53
Q

What are some examples of hard engineering?

A

Dams
Flood shelters
Embankments or levees
River straightening

54
Q

What are dams?

A

Walls built across river valleys to control the amount of water in the river. The prevent flooding and produce electricity. However, they are expensive and the reservoir floods large amounts of land.

55
Q

What are flood shelters?

A

Concrete shelters built to house people safely during times of flood.

56
Q

What are embankments and levees?

A

Walls put either side of the river to keep it in its channel. If they fail they can make flooding worse. Also make flooding worse further downstream.

57
Q

What is river straightening?

A

Meanders are straightened so that the river moves through towns more quickly and doesn’t flood. They do however sometimes make flooding worse downstream.

58
Q

What are some example of soft engineering?

A 
Do nothing
Flood warning system 
Managed flooding 
Floodplain zoning 
Afforestation
59
Q

What is floodplain zoning?

A

Restricting certain activities to certain areas. Building houses would not be allowed on land that is frequently flooded.

60
Q

What are flood warning systems?

A

Use of satellite imagery to detect storms and warn people of flooding so they can evacuate.

61
Q

What is managed flooding (wetland creation)?

A

Allowing certain areas to flood where it doesn’t matter, to take pressure off the river.

62
Q

What is afforestation?

A

Planting trees means there is more interception and rainfall takes longer to reach the river, so stops flooding.

63
Q

What are some sustainable solutions to flooding?

A

Householders should be encouraged not to pave over their gardens.
Make homes flood proof eg putting sockets higher up the walls and using yacht varnish to make wooden floors water proof.
Restoring old peat bogs in the upper part of the river. Bigs act like sponges and soak up water meaning less water reaches the river.

64
Q

What is the source?

A

The area in which the river begins.

65
Q

What is the mouth?

A

Where a river ends its journey, flowing into the sea or a lake.

66
Q

What is a tributary?

A

A smaller river that joins a larger river.

67
Q

What is the confluence?

A

The point at which two rivers join.

68
Q

What is the watershed?

A

The boundary between two drainage basins marked by a ridge of high land.

69
Q

What is a drainage basin?

A

The area which is drained by a river and its tributaries.

70
Q

What is drainage density?

A

The total length of all streams in the basin divided by the total area of the basin.

71
Q

In what ways do people affect the hydrological cycle?

A

Buildings, towns and cities
Dams and reservoirs
Farming
Deforestation

72
Q

How do buildings, towns and cities affect the hydrological cycle?

A

more interception
more surface run off
less infiltration
less groundwater flow

73
Q

How do dams and reservoirs affect the hydrological cycle?

A

Less surface run off
more evaporation.
lower channel flow infront of the dam
more surface storage.

74
Q

How does framing affect the hydrological cycle?

A

more transpiration
more vegetation storage
permeable - ploughed soil - more infiltration
water can be removed from rivers to water crops.

75
Q

How does deforestation affect the hydrological cycle?

A 
less transpiration 
less interception 
more surface run off - no trees to slow down the rain
less infiltration. 
less groundwater flow.
76
Q

What is the river discharge?

A

the volume of water flowing through a given point on a river at a given time.

77
Q

How do you calculate river discharge?

A

discharge = river velocity x cross sectional area

final answer is measured in cumecs

78
Q

What is the measurement for river discharge?

A

final answer is measured in cumecs. Cumecs are cubic meters per second.

79
Q

What area will mean there is a long lag time on a flood hydrograph?

A 
gentle slopes 
light rain 
permeable rocks
vegetation
large drainage basin
dry soil
80
Q

What area will mean there is a short lag time on a flood hydrograph?

A 
steep slope - water will flow into the river easily 
heavy rain 
impermeable rocks
ground surface frozen
impermeable surfaces 
man made surfaces 
deforestation
small drainage basin.
81
Q

Name the river erosion processes.

A

Attrition
Hydraulic action
Corrosion
Corrasion

82
Q

What is attrition?

A

When rocks and material carried by the river grind into each other and wear down.

83
Q

What is hydraulic action?

A

When the sheer force of the water wears away the river bank and bed.

84
Q

What is corrosion?

A

When rocks in the river are dissolved by acid. (also solution)

85
Q

What is corrasion? (or abrasion)

A

When small particles of rock carried by the river rubs against the banks of the river. (also abrasion).

86
Q

What are the river transportation processes?

A

Traction
Saltation
Suspension
Solution

87
Q

What is traction?

A

Large rocks and boulders are rolled along the bed of the river.

88
Q

What is saltation?

A

Smaller stones are bounced along the bed of the river in a leap-frogging motion.

89
Q

What is suspension?

A

Fine material, light enough in weight to be carried by the river. This material causes the water to be discoloured.

90
Q

What is solution?

A

Dissolved material transported in the river.

91
Q

What is a river regime?

A

A river regime shows how river discharge changes through the year-seasons.

92
Q

What is weathering?

A

The breaking up of rock material (can be due to wind, rain, chemicals, freeze-thraw, biological etc).

93
Q

What is mass movement?

A

When gravity pulls loose material down a slope (can happen quickly as a rock falls or slowly by slumping or soil creep).

94
Q

How are interlocking spurs created?

A

As the river flows through the valley it is forced to swing from side to side around more resistant areas of rock (spurs). as there is little energy for lateral erosion, the river continues to cut down vertically flowing between spurs of higher land creating interlocking spurs.

95
Q

How are waterfalls formed?

A

Waterfalls form when a band of hard rock lies over a band of softer, less resistant rock is eroded more quickly than the harder, overlying rock, through abrasion and hydraulic action. This causes an overhang to form, which eventually collapses from the weight above it, creating a steep drop. A deep plunge pool will form at the bottom of the waterfall, and the water will continue to erode the soft rock through hydraulic power and abrasion creating another overhand.

Over time the waterfall will recede due to repeated formation and collapse of overhangs, creating a steep-sided gorge.

96
Q

Describe a meander.

A

A meander is a bend in the river. As the water flows around the bend the flow is fastest on the outside, where the river is deeper. Here, the processes of abrasion and hydraulic action erode the outside bank and undercut it to form a river cliff. On the inside of the river bend the flow is slow and the river is shallow. This causes deposition to take place and a slip-off slope is formed.
As the water travels around the meander it moves in a circular motion like a corkscrew. This is called helicoidal flow. It helps erode and undercut the outside end and move the sediment to the inside bend where it is then deposited.

97
Q

How are ox-bow lakes formed?

A

Ox-bow lakes form in the middle course of a river because the river meanders more vigorously.
Continued erosion (eg abrasion) on the outside bend causes the neck of the meander to narrow. Eventually, the neck is broken through to form a straight channel. This often happens during floods when the river is very powerful.
Continued deposition causes the old meander to be sealed off.
Gradually the ox-bow lake will dry out.

98
Q

Causes of the River Valency floods in Boscastle

A

unpredictable
little time between rain fall and the flood
drains couldn’t cope
fast flowing
sudden rain fell 8 bours before the flood
small, steep river
infrequent

99
Q

Causes of the River Ganges floods in Bangladesh

A

snowmelt in the Himalayas.
cyclones
25% of Bangladesh is less than 1m above sea level.
bad drainage systems
slow flow
monsoon- happens over a long period of time
frequent

100
Q

Define hard engineering.

A

generally defined as a controlled disruption of natural processes using non man made structures

101
Q

Define soft engineering.

A

use of ecological practices to reduce erosion and achieve stabilisation while enhancing habitats and saving money.

102
Q

Discuss flood gates. long term.

A

Can be opened and closed to access roads. They stop any water from flooding into people homes.

cheaper to run, easy access to rivers and roads, only a few people needed to shut them

May be difficult to close the gates on time.

103
Q

Discuss flood walls. long term

A

Act as a barrier to stop any excess water from flooding into peoples homes.
However, it may remove areas of the floodplain.

104
Q

Discuss compensatory flood storage. long term

A

Provides an area of land that the river can flood onto.

Cheap.

Can’t use the land for anything else.

105
Q

Discuss sustainable urban drainage. long term

A

permeable ground provides a place for water to go.

Reduces surface run off.

106
Q

Discuss large ponds. long term

A

Holds any extra water

cost efficient

safety hazard for young children.

107
Q

Discuss flood prediction. short term.

A

tracking the river enables you to predict flooding. Severity.

108
Q

Discuss personal measures. Short term response.

A

Lighter furniture.
Moving electrical appliances further up the wall.
Home flood gates.
Tiled floors.

Cheaper to repair if the house does flood.

Personal expense eg light furniture may be expensive.

109
Q

Discuss river gauges. Short term response.

A

Provide information and predictions of river flooding. Rainfall.

Accurate predictions allows preparation time.

someone has to man the office 24/7,

110
Q

Discuss flood warning and alerts. Short term response.

A

Flood alert - flood is possible.
Flood warning - flooding is expected.
Severe flood warning - danger to life.

111
Q

Explain embankments (levees) as a management strategy.

A

Hard engineering
High banks built on the river banks.

The high bank stops water spreading into areas where it could cause problems. They can be made from earth which makes them look natural.

Flood water may go over the top. They can also break and burst under pressure causing more problems as the gushing water is focussed.

112
Q

Explain washlands as a management strategy.

A

Soft engineering.
Areas which are allowed to naturally flood, these are on the flood plain.

Water is allowed to naturally flood the flood plain meaning that it is inexpensive and the natural environment is left unspoilt.

If the floodplain is allowed to be flooded, then it cant be used for anything else.

113
Q

Explain dams and reservoirs and a management strategy.

A

Hard engineering.
A large artificial structure designed to hold back water creating a reservoir behind it.

Water is held back before being released slowly to avoid large discharge and flooding. the are often multi-purpose and can provide electric and recreational facilities.

Silt can build up behind the dam reducing capacity. a large area of land is flooded behind the dam which can destroy habitats and homes.

114
Q

Explain channelization as a management strategy.

A

Hard engineering.
Dredging the river (making it deeper) and/or straightening it.

The deeper channel allows more water to run through it, straightening the channel allows water to pass through quicker.

Th river has to be dredged every year, which is expensive. Water that passes through one area quickly can cause areas further downstream to flood.

115
Q

Explain flood relief channels as a management strategy.

A

Hard engineering.
Extra channels built next to river to carry water.

The relief channels take the extra water from the river when needed thus meaning the river is less likely o flood.

Cutting a whole new relief channel can look ugly; they can also be very expensive to build.

116
Q

Explain flood warning systems as a flood management strategy.

A

Soft engineering
River is watched, of the river rises settlements downstream are warned.

people downstream can be warned and prepare to evacuate on the first sign of danger.

it is not always possible to warn people, making it hard to save possessions.

117
Q

Explain land use zoning as a management strategy.

A

Soft engineering.
Areas of land are allocated different role depending on their flood risk.

Major building zones are assigned low risk zones, other land use zones such as sports fields are assigned higher risk zones as when flooded they are less costly.

The areas assigned for each zone may not be best for the public in terms of public use and accessibility.

Geography (10 decks)

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