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PCT1 revision > Geography PC1 revision ( river ) > Flashcards

Geography PC1 revision ( river ) Flashcards

1
Q

Upper course

A

Gradient: Steep gradient
Velocity: Low velocity
Features: Water falls, gorges and rapids
Channel: Narrow and shallow channel

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2
Q

Middle course

A

Gradient : More gentle gradient
Velocity : Faster velocity
Features : Meanders, Ox bow lakes, floodplains
Channel : Wider and deeper channel

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3
Q

Lower course

A

Gradient : Flat gradient
Velocity : Fastest velocity
Features : Floodplains , deltas, estuaries
Channel : Widest and deepest channel

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4
Q

Long profile

A

The gradient of the river from source to mouth

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5
Q

Cross profile

A

The side to side cross section of a river channel or valley

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6
Q

Lateral erosion

A

Sideways erosion on the outside of a meander bend

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7
Q

Vertical erosion

A

Downward erosion of a river bed

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8
Q

Abrasion

A

Rocks carried by the river wear down the river bed and banks

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9
Q

Attrition

A

Rocks smash together and break into smaller pieces

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10
Q

Hydraulic Action

A

Force of the river causes air to be trapped in cracks and weakens the bank

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11
Q

Solution ( Types of erosion )

A

Alkaline rocks such as limestone are dissolved by slightly acidic water

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12
Q

Saltation

A

Particles bouncing down the river bed

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13
Q

Solution ( Types of transportation )

A

Soluble particles are dissolved into the river

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14
Q

Suspension

A

Fine solid material held in the water while it is moving

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15
Q

Traction

A

Rolling of boulders and pebbles along the river bed

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16
Q

Gorge

A

The narrow steep-sided valley formed as waterfall retreats

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17
Q

Potholes

A

A circular or cylindrical hold in the riverbed

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18
Q

Waterfall

A

Sudden descent of a river over a vertical or step slope in its bed

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19
Q

Rapids

A

Area of shallow, fast-flowing water in a stream.

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20
Q

Meander

A

Pronounced ( Khúc cua ) bend in a river

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21
Q

Ox bow lake

A

Arc shaped lake cut off a meander

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22
Q

Deltas

A

A fast, low lying deposit of sediment, found at a river’s mouth.

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23
Q

Levees

A

Embankments of sediment along a river

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24
Q

Floodplain

A

The flat area forming the valley floor on either side of a river channel

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25
Q

Upper course landforms

A
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26
Q

Waterfalls formation

A
  • alternating layers of soft and hard rocks
  • soft rocks erode more quickly than the hard rock
  • due to hydraulic action
  • plunge pool form due to the collapse of soft rocks
  • then no support for the hard rock
  • the hard rocks started to collapse
  • repeats overtime
  • water retreats to form a gorge
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27
Q

How are potholes formed?

A
  1. abrasion and hydraulic action creates a hole in the river bed
  2. holes get bigger so pebbles/rocks may fall inside
  3. abrasion makes the hole deeper
  4. hydraulic action creates a swirling motion
    making the holes deeper and cylindrical
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28
Q

middle course landforms

A

…

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29
Q

Meanders features

A
  • Inside bend = slow current
  • more friction = more deposition
  • outside of the bend = quicker current less friction
  • hydraulic action ( erosion ) take place
  • river cliffs form due to more energy
  • overtime meanders move across the land
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30
Q

Oxbow lakes formation

A
  • Two outside bends move towards each other
  • the necks cut through
  • new routes are formed
  • deposition cuts off the old bend during a flood event
    then oxbow lakes are formed
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31
Q

Gorge Characteristics ( upper course )

A
  • Very narrow valley
  • Steep, high valley sides
  • Downstream of a waterfall
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32
Q

Gorge Formation

A
  • Soft rock erodes quicker than hard rock
  • The hard rock/overhang collapses
  • The waterfall retreats, creating a steep-sided gorge.
33
Q

Lower course land forms

A

…

34
Q

how are floodplain forms?

A
  • They are created of migrating meanders which latterly erode
    this is why the floodplain is very wide
  • when there are floods they deposit layers of silt to form alluvium
  • this built up over time which is why floodplains are very flat
35
Q

how are leaves formed?

A

During low flow conditions deposits occurs

water flow over the channel and onto the floodplain during a flood

deposition of sediment ( rocks, materials etc…) sediments occurs on the river banks - ( bờ sông)

built-up after many floods ( the height of the banks can be raised to 2m tall)

36
Q

how are deltas form?

A

the river meets sea = Deposition occurs at the mouth

sediments are deposited = new land will be formed in the middle of the main channel

then the river splits into distributaries and flows around the new land

more deposition due to low velocity

layers of sediment build the delta out to the sea

vegetation can begin to grow, trapping more sediment =>
raising the delta above sea level.

37
Q

Drainage Basins system and processes

A

Nah

38
Q

sources

A

is the start of a river

39
Q

Drainage Basin

A

the area is drained by a river - (khu vực được thoát nước bởi một con sông)

40
Q

tributary

A

where smaller streams join a larger river

41
Q

confluence

A

The point at which two rivers meet

42
Q

watershed

A

the boundary of the drainage basin

43
Q

watershed

A

the boundary of the drainage basin

44
Q

mouth

A

where rivers meet the sea

45
Q

Discharge

A

The amount of water / volume a river is carrying

46
Q

Groundwater flow

A

Very slow water movement deep below the ground

47
Q

Infiltration

A

When surface water is absorbed into the soil

48
Q

Interception

A

When water droplets collect on trees and plants

49
Q

Throughflow

A

Movement of water downhill through the soil

50
Q

Surface run off

A

The movement of water across the land

51
Q

Percolation

A

Water moving downwards through the soil into rocks below

52
Q

Transpiration

A

Water vapour released by trees and plants

53
Q

Hard engineering

A

Building of artificial structures to reduce, disrupt or stop the impact of river processes

54
Q

Flood

A

Occurs when river discharge exceeds river channel capacity and water spills over the floodplain

55
Q

Soft engineering

A

The use of the natural environment surrounding the river to work with the natural processes

56
Q

Dam and reservoirs

A

Large structures which regulate (control) river flow. high rainfall = water can be stored in the reservoir (big lake). It can then be released when the rainfall is low

57
Q

Embankments

A

Raised river banks. Raising the level = river channel can hold more water before flooding

58
Q

Flood relief channels

A

A manmade river channel constructed to by-pass (go around) an urban area. High rainfall = sluice gates (barriers which control water flow) open to allow excess water to flow away into the flood relief channel and reduce the threat of flooding

59
Q

Channel straightening

A

Cutting through meanders to create a straight channel. This speeds up the flow of water along the river so it passes through a location quickly, reducing the risk of flooding.

60
Q

Flood plain zoning

A

This involves putting building restrictions (rules) in place on floodplains that are at risk of flooding. Areas at risk can be kept clear of building impermeable surfaces.

61
Q

Flood warnings

A

Developing a system of alerting people to the risk of flooding.People then have time to plan, prepare or even evacuate if a flood is likely to occur.

62
Q

Planting trees

A

Planting more trees helps to increase the amount of interception and transpiration. They help to slow down the time it takes for water to enter a river.

63
Q

River restoration

A

Where the course of a river has been changed artificially, it can be restored to its original course. This reduces the discharge of the river, making it less likely to flood.

64
Q

Alluvium

A

A deposit of clay, silt, sand, and gravel left by flowing streams in a river valley or delta, typically producing fertile soil.

( Đất bồi )

65
Q

Silt

A

Fine sand, clay, or other material carried by running water and deposited as a sediment, especially in a channel or harbor.
( Phù sa )

66
Q

Case Study: The River Ganges, Bangladesh, LEDC- (2007)

A

…

67
Q

What were the causes of the flood? ( Bangladesh)

A

…

68
Q

physical Factors (1)

A

Snow Melt from glaciers of the Himalayas,

69
Q

(2)

A

Low lying country – 80% lies on floodplains of the Ganges

70
Q

(3)

A

Bangladesh and Meghna rivers, the average height of land 6m…Monsoon climate with 80% annual rainfall falling

71
Q

Humans factors

A

Rapidly increasing population (162m), building on floodplains
= impermeable surfaces.

72
Q

(3)

A

Deforestation in Nepal in the upper course of the Ganges,

73
Q

What were the impacts/hazards of the flood?

A

…

74
Q

social

A
  • 11,000km of roads were damaged, blocking communication routes
  • 1,100 deaths, 10.5 million were made homeless.
  • 100,000 people caught water-borne diseases like cholera due to flood water
  • 44 schools were destroyed, 4,444 closed
  • 20% of factories closed, losing jobs and income.
75
Q

economics

A
  • Rice crops were devastated twice in 2007, causing $290m of damage

farmers did not have time to recover their losses and replant

47% of the population rely on farming for their jobs but were unemployed as 2.2m acres of cropland was flooded

76
Q

How was the river managed?

A
  • Increased efforts to reduce deforestation in Nepal and the Himalayas
  • 2500 stilted shelters, raised above 2m, were built for people, crops and animals.
  • Flood warning systems installed in villages through speakers
77
Q

part (2)

A
  • Flood action plan– A $100m system of 7,500km huge embankments and levees were built along the river, reinforced by concrete.
  • 3200 drainage canals cleared to allow floodwater to drain away more efficiently.
  • 55 flood monitoring stations were installed to give locals 72 hours notice of impending
78
Q

What are the opportunities of living in a delta/floodplain / near a river? (Why do people live there?) ( part2)

A
  • The flat floodplains of the delta are veryfertile. Rice and Jute are grown as the two main crops
  • 47% of the population are employed in agriculture (farming and fishing)
  • They help meet the demand for water – Particularly for irrigation of crops
  • The rivers naturally improve water quality by naturally filtering out excess sediment and nutrients

PCT1 revision (12 decks)

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