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AQA Geography > Rivers > Flashcards

Rivers Flashcards

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1
Q

What does erosion form in the upper course of the river?

A

Interlocking spurs
Waterfall & Gorges

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2
Q

What does erosion in the middle course of the river form?

A

Meanders
Ox-Bow lakes

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3
Q

What does erosion in the lower course of the river form?

A

Levee
Flood Plain
Estuary

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4
Q

Interlocking Spurs

A
  1. Vertical erosion creates steep-sided, v-shaped valley
  2. Freeze thaw weathering widens the valley
  3. Hillsides interlock with each other as river winds around them
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5
Q

Waterfall and Gorge

A
  1. Water runs over alternating of hard rock on top and soft rock below
  2. Erosion breaks down rocks
  3. Hydraulic action wears away soft rock - less resistant, soft rock undercuts hard rock = overhang
  4. Hard rock is left unsupported and collapses into river bed
  5. Rocks are transported downstream or abrasion wares away ar river bed = plunge pool
  6. This process repeats and waterfall retreats backwards → steep-sided gorge.
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6
Q

Meanders

A
  1. Fastest velocity swings round the outside bend of a meander which erodes bank - forming a river cliff = water is deep = less friction
  2. On the inside of the bend, velocity is lower and deposition occurs - slip of slope
  3. Over time lateral erosion of outside bend widens river
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7
Q

Ox-Bow Lake

A
  1. On the inside of the bend flow is slower so sediment is deposited
  2. The neck of the river grows sharper
  3. The neck of the river breaks through, river takes shortest course straight
  4. Meander becomes sealed off as a result of deposition — oxbow lake
  5. Ox bow lake can dry up - vegetation grows leaving a scar
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8
Q

What is a levee?

A

A raised bank next to the river bank

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9
Q

Levee

A
  1. During a flood water passes over a surface —> increases friction = slows flow
  2. Heavy material deposited early, lighter sediment travels downstream
  3. Levee gradually gets higher after more floods = more deposition
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10
Q

Floodplain

A
  1. Build up of sand, silt and clay (deposition + transportation) leads to formarion of a flat piece of land either side of the levees.
  2. Every time a river floods, deposition builds up the floodplain.
  3. width of flood plain is derermined by amount of lateral erosion.
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11
Q

Estuary

A
  1. An estuary is where the river meets the sea
  2. When sea retreats, volume of water is reduced
  3. Less water means river deposits silt to form mudflats (important for wildlife)
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12
Q

Physical factors affecting flood risk

A

Relief - Steep slopes means water runs quickly
Soil saturation - Soil can no longer absorb water
Rock type - Impermeable rock means water is not absorbed
Rainfall - Rainstorms can lead to flash floods
Basin Size - Amount of water a river can store

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13
Q

Human Factors affecting Flood risk

A

Deforestation - Trees intercept water
Urbanisation - Building areas in risk of flooding - impermeable rock
Agriculture - soil is left unused + exposed = surface run off

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14
Q

What do hydrographs show?

A

The relationship between precipitation and discharge

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15
Q

What is river straightening?

A

Widens, Deepens, Straightens course to carry more water

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16
Q

Pros and cons of river straightening?

A

+ Increases basin size of river

  • Speed of river increases
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17
Q

Pros and cons of embankments?

A

+ More water held in river without flooding banks

  • Expensive/Less attractive/Disrupts ecosystem
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18
Q

What is embankments?

A

Raised river banks so water is contained within channel

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19
Q

What is Flood relief?

A

Another channel is built, moves water away from settlements

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20
Q

What are Dams & Reservoirs?

A

Large concrete barrier that holds back flow

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21
Q

Pros and cons of Flood relief

A

+ Effective depending on flood severity

  • Where channel meets river flooding occurs
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22
Q

Pros and cons of Dams & Resovoirs

A

+ Generates energy/Attracts tourists

  • Expensive/traps sediment/habitats ruined/people displaced
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23
Q

What are the three types of flood warning?

A

Flood watch - Flooding of low land and roads

Flood warning - Threat to homes & Businesses

Severe flood warning - EVACUATE

24
Q

What is planting trees?

A

A method of interception

25
Q

Pros and cons of Planting trees

A

+ Slows flow of water towards river

  • Takes space, long time to grow
26
Q

What is flood plain zoning

A

Holds water during flood events
Protects people and houses

27
Q

What is River Restoration

A

Move debris + Logs
Natural methods - beavers

28
Q

pros of River restoration

A

Debris and logs slow down flow of water

29
Q

What is the river case study?

A

The Jubilee River Flood Channel

30
Q

What is the Jubilee river flood channel?

A

Acts as a flood relief channel for the River Thames

31
Q

What does the Jubilee river flood channel do?

A

controls and diverts water during times of high flow
Reduces flood risk

32
Q

How much did the Jubilee river flood channel cost?

A

110 million

33
Q

What are the social impacts of the Jubilee river flood channel?

A

Paddle boarders where promised navigable river - In reality it is two dangerous to cross

Concrete weirs are ugly when river is at normal flow

Some properties are protected others are not - 3,000 homes in Eaton + Windsor (affluent areas)

34
Q

What are the economic impacts of the Jubilee river flood channel?

A

Small business are under pressure - can’t open during floods and insurance is to expensive
Most expensive flood relief scheme in the UK
Additional repair damage

35
Q

What are the environmental impacts of the Jubilee river flood channel?

A

Extensive flooding where channel joins Thames - roads, buildings, fields, habitats and the environment suffered

Algae collects behind the weirs and slows water flow

36
Q

Disadvantage of the Jubilee river flood channel

A

The Thames experiences higher discharge due to the merging of the channels upstream

37
Q

When was there serious flooding of the Jubilee river flood channel

A

2014

38
Q

Upper course characteristics

A

Steep-Sided walls

Narrow channel

Fast flow

39
Q

Lower course Characteristics

A

Shallow sides

Wider channel

40
Q

Lower course characteristics

A

Flat

Wide channel

41
Q

What does Bradshaw model show?

A

Velocity, width, depth increase downstream

42
Q

Why is heaviest material deposited first

A

Requires more energy

43
Q

Where is the most deposition and why

A

Lower course
River slows down as it loses its energy

44
Q

Lateral erosion

A

Sideways erosion of river banks

45
Q

Vertical erosion

A

Downwards erosion of river bed

46
Q

Hydraulic Action

A

Force of river causes air to be trapped in cracks

47
Q

Abrasion

A

Rocks wear down the river beds and banks

48
Q

Attrition

A

Rocks bash against each other = smooth

49
Q

Solution

A

Soluble particles are dissolved in river

50
Q

Traction

A

The rolling of boulders and pebbles along the river bed

51
Q

Saltation

A

Particles bouncing down the river bed

52
Q

Suspension

A

Fine solid material held in water

53
Q

Solution

A

Soluble particles dissolved into river

54
Q

What are upper course characteristics of the river Severn?

A

V-shaped valley

Waterfalls

Meanders - Kempsey in Worcestershire

55
Q

What are lower course characteristics of the river Severn?

A

Meanders - Gloucestershire

Large Mouth

Mudflats & Sandbanks

AQA Geography (10 decks)

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