Rivers Flashcards

1
Q

What is the rivers course?

A

the path of a river as it flows downhill

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2
Q

What are the three courses of a river?

A

upper, middle, lower

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3
Q

what do rivers form as they flow downhill?

A

channels and valleys

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4
Q

What does the long profile of a river tell you?

A

how the gradient changes over different courses

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5
Q

What does the cross profile of a river show you?

A

what a cross section of the river would look like

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6
Q

Describe the upper course of a river?

A
  • steep
  • v-shaped valley
  • steep sides
  • narrow, shallow channel
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7
Q

Describe the middle course of a river?

A
  • medium gradiant
  • gently sloping valley sides
  • wider deeper channel
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8
Q

Describe the lower course of a river?

A
  • gentle gradient
  • very wide
  • very flat valley
  • very wide, deep channel
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9
Q

what can erosion be? two things

A

lateral or vertical

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10
Q

What is vertical erosion?

A
  • deepens river valley making it v-shaped
  • dominant in upper course of river
  • high turbulence causes rough rocks to be scraped along river bed causing intense downward erosion
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11
Q

What is lateral erosion?

A
  • widens river valley during formation of meanders

- dominant in middle and lower courses

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12
Q

What are the 4 processes of a river?

A

hydraulic action, abrasion, attrition, solution

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13
Q

What is hydraulic action?

A

the force the water breaks rock particles away from the river channel

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14
Q

What is abrasion?

A

eroded rocks picked up by the river scrape and rub against the channel causing it to wear away

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15
Q

What is attrition?

A

eroded rocks picked up by the river smash into each other and break into smaller fragments . their edges become rounded as they rub together

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16
Q

What is solution?

A

river water dissolves some type of rock

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17
Q

What are the 4 processes of transportation?

A

traction, saltation, suspension and solution

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18
Q

What is traction?

A

large particles like boulders are pushed along the river bed by the force of water

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19
Q

What is suspension?

A

small particles like silt and call are carried along the water

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20
Q

What is saltation?

A

pebble sized materials are bounced along the river bed by the force of water

21
Q

What is solution?

A

soluble materials dissolve in the water and are carried along

22
Q

What is deposition?

A

when a river drops the eroded material its transporting

23
Q

where are waterfalls and gorges found?

A

in the upper course of the river

24
Q

Explain how a waterfall is formed?

A
  • river flows over area of hard rock and then soft rock
  • the soft rock is eroded more then hard rock creating a step in the river
  • as water goes over step it erodes more and more of softer rock
  • steep drop eventually created and waterfall formed
  • hard rock eventually undercut by erosion, becomes unstable and collapses
  • collapsed rocks are swirled around at foot of waterfall where they erode soft rock by abrasion making a plunge pool
  • over time more undercutting and collapsing occurs
  • waterfall retreats leaving a steep gorge
25
Q

Where do waterfalls form?

A

were river flows over an area of hard rock followed by soft rock

26
Q

Explain how interlocking spurs occur?

A
  • in upper course, mostly vertical erosion creating steep v-shaped valley
  • rivers arnt powerful enough to erode laterally, they have to wind around the high hillsides that stick out wither side
  • the hillsides that interlock with each other as river winds around them are called interlocking spurs
27
Q

What are some soft engineering methods to reduce the effect of flooding?

A

flood warning, preparation, flood plain zoning, planting trees, river restoration

28
Q

what are flood warnings?

A

environmental agency warns people about possible flooding through TV, radio, internet and newspapers

29
Q

What is preparation for floods?

A

buildings modified to reduce the amount of damage a flood could cause.
people make plans if a flood occurred
keep items needed in accessible place

30
Q

What is flood plain zoning?

A

restrictions prevent buildings on parts of a flood plain that are likely to be effected by flood

31
Q

What does planting trees do for floods?

A

planting in river valley increases interception of rainwater and also increases lag time

32
Q

What does river restoration do for floods?

A

making rivers more natural, removing man made levees so flood plains can flood naturally

33
Q

What are the benefits of flood warnings?

A
  • impact of flooding is reduced

- give people time to move possessions upstairs, put sandbags in position

34
Q

What are the disadvantages of flood warnings?

A
  • don’t stop flood from happening

- people may not hear or have access to warnings

35
Q

What are the benefits of preparation?

A
  • impact of flooding is reduced
  • buildings less damaged
  • people know what to do
  • less likely to worry about threat
36
Q

What are the disadvantage of preparation?

A
  • doesnt guarantee safety from a flood
  • false sense of security
  • expensive to modify buildings and homes
37
Q

what are some advantages of flood plain zoning?

A
  • risk of flooding is reduced
  • impermeable sufaces arnt created
  • impact of flooding is reduced - no buildings to damage
38
Q

What are some disadvantages of flood plain zoning?

A
  • expansion of urban area is limited

- no help to areas that have already been built on

39
Q

What are some advantages of planting trees?

A
  • dishrag and flood risk are reduced

- vegetation reduces soil erosion in valley and provides habitats to wildlife

40
Q

What are some disadvantages of planting trees?

A

-less land for farming

41
Q

What are some advantages of river restoration?

A
  • less risk of flooding downstream because discharge is reduces
  • little maintenance
  • more habits for wildlife
42
Q

What are some disadvantages of river restoration?

A
  • local flood risk can increase
43
Q

Name a place that needed flood management?

A

banbury

44
Q

Describe banbury?

A

in cotswold hils about 50km north of Oxford.
population of around 45000 people.
most of town on a floodplain of river cherwell and river thames

45
Q

How has Banbury been effected by flooding?

A
  • 1998 flooding led to closure of towns railway station, shut local roads and caused 12.5 mill of damage
  • more then 150 homes and buisnesses were effected
  • in 2007 town was hit again by flooding
46
Q

What has been done in banbury to reduce risk of flooding?

A
  • 2.9km earth embankment was built parallel to M40 motorway to create flood storage, 4.5 meters tall and is capable of 3 million cubic meters of water
  • flow control structures to control rate of flow downstream, excess water backs up behind structure filling resourvoire
  • raising A361 road in the flood storage area and added drainage
  • earth embankments and flood-walls to protect property and businesses ( Pro-drive)
  • new pumping station to transfer excess rainwater into the river below the town
  • Biodiversity action plan, habitat with ponds, trees and hedgerows to absorb and store excess water
47
Q

social benifits of flood management scheme?

A
  • raised A361 will be open during flood
  • quality of life for locals improved with new footpaths and green areas
  • reduced levels of anxiety through fear of flooding
48
Q

What are some economic benefits of flood management scheme?

A
  • cost was £18.5 million

- by protecting 441 houses and 73 properties benefits are over £100 millon

49
Q

enviromental benefits + downsides of banbury flood scheme?

A
  • 100000 tonnes of earth were required to build embankment
  • biodiversity action plan created
  • part of floodplain deliberaterly allowed to flood