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IGCSE geography > 2.2 Rivers > Flashcards

2.2 Rivers Flashcards

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1
Q

Opportunities of living near a river

A
  • abundant water supply
  • fertile soil
  • water for transport (e.g. trading, fishing, tourism)
  • leisure and tourism (more job opportunities)
  • navigation
  • lower house prices
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2
Q

5 management for river flooding

A
  • dams
  • widen, deepen, straighten river to carry more water
  • plant more trees to block water from overflowing
  • naturally letting it flood to prevent flooding in other areas
  • planning policies (warnings and evacuation procedures)
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3
Q

2 hazards of rivers

A
  • Spread of diseases (e.g. Malaria)

- Flooding –> deaths, loss of homes, infrastructure destroyed, shortage of food and water, fires

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4
Q

Definition of ‘drainage basin’

A

Area drained by the river

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5
Q

Definition of HEP

A

Hydroelectric power

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6
Q

4 causes of flooding

A
  • Steep channel –> causes fast surface run-off
  • Drainage basin with impermeable rock –> rock does not absorb any water
  • Drainage basin in an urban area –> impermeable concrete/flooring
  • Deforestation, over-cultivation, population pressure –> causes soil erosion –> increase in amount of sediment
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7
Q

Hydraulic action

A

The force of flowing water alone breaking off material from the bed and banks of a river

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8
Q

Abrasion (corrasion)

A

Pebbles and rocks rub against the bed and banks of the river (like sandpaper), causing them to crack and break off

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9
Q

Attrition

A

Material that wear each other away as they smash into each other

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10
Q

Corrosion (solution)

A

Acids in the river dissolving material (limestone)

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11
Q

Vertical erosion

A

the wearing away and deepening of the river bed

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12
Q

Lateral erosion

A

the wearing away and widening of the sides of the river

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13
Q

Describe the profile of the upper course of the river

A
  • Steep slopes
  • Thin river channel
  • Steep v-shaped valley
  • Deep in places
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14
Q

Describe the profile of the middle course of the river

A
  • shallow slopes towards the mouth
  • wider river channel
  • v-shaped valley
  • river begins to meander
  • deeper channel
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15
Q

Describe the profile of the lower course of the river

A
  • almost at sea level
  • gently sloping to its mouth
  • wide, shallow valley
  • large floodplain
  • meanders
  • wide channel
  • deep and smooth sides
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16
Q

Describe the landform of the upper course

A
  • More roughness, turbulence and friction
  • Steep slopes = vertical erosion
  • Shallow river bed
17
Q

Describe the landform of the middle course

A
  • meanders

- oxbow lakes

18
Q

How are meanders formed?

A

Helical flow of water causes lateral erosion, forming bends
Fastest current is forced to the outer bank
Deposition in the inner bank as current slows + more friction

19
Q

Hazards of living near rivers

A 
Spread of diseases
- Malaria 
Flooding
- Deaths
- Loss of homes
- Infrastructure destroyed
- Shortage of food + water
Fires
20
Q

Opportunities of living near a river

A
  • Abundant water supply
  • Water for transport (trading, tourism and fishing)
  • Leisure and tourism –> more job opportunities
  • Fertile soil
  • Lower house prices
  • Navigation
  • Electricity for power stations
21
Q

Factors that influence the shape of the river

A 
The rate of vertical erosion
The rate of lateral erosion by weathering and erosion
The geology of the valley
The climate of the valley
Time
22
Q

How are waterfalls formed?

A
  • River flows over hard rock onto soft rock
  • Soft rock at the bottom erodes more quickly
  • The soft rock erodes until a plunge pool is created
  • Hard rock will form an overhang, forming a waterfall
  • Over time, the overhang becomes bigger, until the hard rock is no longer supported by the soft rock underneath
  • The overhang falls, forming a gorge
23
Q

How are oxbow lakes formed?

A
  • Erosion continues in meandering river → causing it to become more narrow
  • The curves eventually curve and join together → forms a circular river
  • Substances deposited on the inner banks
  • As deposition continues, new land is formed
  • The meandering section falls apart from the river → creates an oxbow lake
24
Q

How are deltas formed?

A
  • Occurs where a river carrying large amounts of sediment meets a lake or the sea → causes rivers to lose energy + deposit material
  • Usually occurs where the rate of deposition by the river and tides is far more than the sea currents can remove
  • Rate of flow slows down towards the mouth
  • Deposition of material on the river bed occur
  • When ocean calms, more sediment piles up → forms new land
  • Deltas form where river mouths are blocked with sediment, causing the main river channel to split into hundreds of smaller channels
25
Q

Causes of flooding

A

Steep channel: causes fast surface run-off

Drainage basin with impermeable rock: x percolation through rock layer → surface run-off

Drainage basin in an urban area: impermeable concrete/flooring

Deforestation, over-cultivation, population pressure: causes soil erosion

Increase in amount of sediment, decrease in cross sectional area

26
Q

How are levees formed?

A

Formed when river floods
Heavy materials are deposited first when flooding → they require more energy
Deposited at channel edges
As more floods occur, the material builds up, creating a side barrier —> levees

27
Q

How are flood plains formed?

A

Area of deposited material found beside the river → where river flood exceeds the discharge
When rivers flood, they deposit material in the water
Water also erodes the bottom of the land
As they deposit material to the sides → creating a barrier + river erodes the land
Flood plain is formed
Lateral erosion allows the river to meander
Creates a wide valley floor → floodplain

28
Q

Management of flooding (hard engineering)

A
  • Dams across the river to control the amount of discharge → water held back in reservoirs
  • River engineering: widen/deepen/straighten river to carry more water, change river direction → does not run-off to land
29
Q

Management of flooding (soft engineering)

A
  • Afforestation → planting trees nearby to increasing interception → block water
  • Managed flooding: allow river to flood naturally to prevent flooding in other areas
  • Planning: policies to protect areas near rivers, installing a system of sirens and warnings and evacuation procedures, a store of sand for emergency use, temporary, moveable metal barriers that can be put up quickly

IGCSE geography (9 decks)

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