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Geography > Theme 2 - 2.2 - Rivers > Flashcards

Theme 2 - 2.2 - Rivers Flashcards

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1
Q

Define tributary.

A

A stream or river which joins a larger river.

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2
Q

Define drainage basin.

A

The area of land drained by a river system (a river and its tributaries).

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3
Q

Define watershed.

A

A ridge or other line of separation between two river systems.

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4
Q

Define confluence.

A

The point at which two rivers meet.

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5
Q

Define infiltration.

A

The movement of water into the soil.

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6
Q

Define interception.

A

The precipitation that is collected and stored by vegetation.

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7
Q

Define infiltration rate.

A

The rate at which water enters the soil.

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8
Q

What factors affect the infiltration rate?

A
  • Intensity of rainfall
  • Permeability of soil
  • The water saturation of the soil
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9
Q

Define throughflow.

A

The downslope movement of water in the subsoil (the upper layer of the ground).

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10
Q

Define evaporation.

A

The process in which a liquid turns into a vapour.

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11
Q

Define overland flow.

A

Overland movement of water after rainfall. It is the fastest way in which water reaches a river.

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12
Q

What increases the amount of overland flow?

A
  • Heavy and prolonged rainfall
  • Steep gradients
  • Lack of vegetation cover
  • Saturated or frozen soil
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13
Q

What is abrasion (or corrasion)?

A

When material rubs against the river banks and bed, wearing them away.

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14
Q

What is attrition?

A

When rocks and material in a river collide, wearing each other away.

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15
Q

What is hydraulic action?

A

When the force of water and air pushes into cracks, wearing the river banks and bed away.

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16
Q

What is solution?

A

When rocks and material are dissolved by ions in the water.

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17
Q

What is groundwater flow?

A

Th movement of water from land to river through rock (the lower layer of the ground). It is the slowest form of water movement.

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18
Q

What accounts for the constant flow of water in river during periods of low rainfall?

A

The groundwater flow.

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19
Q

Define suspension.

A

Small particles are carried by the water flow.

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20
Q

Define saltation.

A

Heavier particles are bounced along the bed of the river.

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21
Q

Define traction.

A

Rolling heavy stones along the river bed.

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22
Q

What are the four processes of erosion?

A
  • Corrasion / Abrasion
  • Corrosion / Solution
  • Attrition
  • Hydraulic Action
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23
Q

What are the four processes of transportation?

A
  • Traction
  • Saltation
  • Suspension
  • Solution
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24
Q

What is the hydrological cycle?

A

The movement of water between air, land and sea.

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25
Q

What are some forms of precipitation?

A
  • Rain
  • Snow
  • Frost
  • Dew
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26
Q

Define evapotranspiration.

A

The combined losses of water by evaporation and transpiration from vegetation.

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27
Q

How does the discharge change as the river flows downstream?

A

It increases.

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28
Q

How does the channel width change as the river flows downstream?

A

It increases.

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29
Q

How does the water depth change as the river flows downstream?

A

It increases.

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30
Q

How does the water velocity change as the river flows downstream?

A

It increases.

31
Q

How does the load quantity change as the river flows downstream?

A

It increases.

32
Q

How does the load particle size change as the river flows downstream?

A

It decreases.

33
Q

How does the channel bed roughness change as the river flows downstream?

A

It decreases.

34
Q

How does the gradient change as the river flows downstream?

A

It decreases.

35
Q

Describe the main change as a river flows downstream.

A 
INCREASES
• Discharge
• Channel width
• Water depth
• Water velocity
• Load quantity
DECREASES
• Load particle size
• Channel bed roughness
• Slope angle (gradient)
36
Q

Remember to learn the hydrological cycle (including terms like throughflow).

A

Pg 36 of revision guide

37
Q

What factors increase the rate of erosion in a river?

A
  • Heavy and sharp load
  • Large velocity and discharge
  • Steep gradient
  • Soft materials are easier to erode
  • Solution increases with water acidity
38
Q

How do humans sometimes interfere with erosion in a river?

A

Interfering with the natural flow of a river (e.g. by building a dam) results in an increase in the rate of erosion.

39
Q

When does deposition occur?

A

When the river’s energy or velocity decreases, so that it can no longer carry its load.

40
Q

Give some examples of when deposition might occur.

A
  • Water spills onto the floodplain during a flood
  • Water gets trapped behind a dam
  • Water enters a lake or sea
  • Vegetation slows down the river
  • Gradient becomes gentler
41
Q

What is the cross-profile of a river?

A

The shape of the cross-section at a certain point.

42
Q

What is the long-profile of a river?

A

The change in gradient from source to mouth.

43
Q

What are the main river processes?

A
  • Erosion
  • Deposition
  • Transport
44
Q

How does the cross-profile of a river change from upper to lower course?

A

Upper course: Steep sides + V-shaped

Lower course: Flatter sides + Wider

45
Q

Name some landforms caused by erosion, deposition and both.

A 
EROSION
• Waterfalls
• Gorges 
• Potholes
DEPOSITION
• Levées + Floodplains
• Deltas
EROSION + DEPOSITION
• Meanders + Oxbow lakes
46
Q

What causes steep V-shaped valleys in the upper course?

A

Vertical erosion -> Creates unstable sides -> These sides collapse -> Creates a narrow and V-shaped valley

47
Q

What are interlocking spurs?

A

Protruding hillsides, which a river is forced to wind around.

48
Q

Describe the formation of a waterfall.

A
  1. There are bands of different rock - some hard, some soft
  2. The river erodes the soft rock more quickly, undercutting the hard rock and causing it to overhang
  3. Eventually, the overhang is too large and so collapses
  4. The fallen rocks swirl around I t eh plunge pool, causing even more erosion
  5. The process repeats and the waterfall moves upstream
  6. This leaves a steep-sided gorge of recession
49
Q

Describe the formation of rapids.

A
  1. Layers of hard and soft rock are very THIN
  2. Sticking out rock causes change in water depth
  3. Rapids occur here
50
Q

Give an example of a waterfall.

A

High Force waterfall - River Tees

51
Q

Describe the formation of potholes.

A
  1. River water is swirled around irregularities in the river bed, creating vertical eddies
  2. Rocks get swept into the small depressions and abrade the hollow. These rocks are called grinders.
  3. The process continues, enlarging the pothole
52
Q

Define source.

A

The start of a river.

53
Q

Define watershed.

A

The boundary marking out a drainage basin. It is the boundary between two drainage basins.

54
Q

Define percolation.

A

When water moves down through the soil.

55
Q

What are the characteristics of the upper course river valleys?

A
  • V-shaped valleys + Steep sides
  • Interlocking spurs
  • Slumping and landslides
  • Narrow, shallow channel -> Low velocity and discharge
  • Large bed load
56
Q

What are the characteristics of the middle course river valleys?

A
  • Gentler sides with floodplain
  • Wider, deeper channel -> Higher velocity and discharge
  • More suspended sediment
  • First signs of meanders
57
Q

What are the characteristics of the lower course river valleys?

A
  • Gentle sides with wide floodplain
  • Wide, open valley
  • Very wide and deep channel
58
Q

What features can be seen in the upper course of a river?

A
  • V-shaped valleys
  • Interlocking spurs
  • Waterfalls
  • Gorges
59
Q

What features can be seen in the middle course of a river?

A
  • Meanders

* Slip-off slopes

60
Q

What features can be seen in the lower course of a river?

A
  • Oxbow lakes
  • Floodplains
  • Levées
61
Q

Describe the formation of meanders and oxbow lakes.

A
  1. On a bend, water flows fastest on the outside, which causes erosion, while water flows slowest on the inside, which causes deposition to happen
  2. This creates a river cliff on the outside and a slip-off slope (river beach) on the inside
  3. This process repeats until the meander becomes more and more exaggerated
  4. Eventually, the river cuts across the meander’s neck and forms an oxbow lake
62
Q

What is a slip-off slope?

A

A river beach which forms on the inside of a meander by deposition.

63
Q

Give an example of a meander.

A

Meander at Yarm

64
Q

Describe the formation of a levée and floodplain.

A
  1. River floods its banks
  2. Sudden increase of friction -> Reduces water’s velocity
  3. Large, coarse particles deposited close to river -> Form a small bar called a lévee
  4. Small, smooth particles deposited further away -> Form in layers to create a flat floodplain
65
Q

Describe the formation of a delta.

A
  1. When a river reaches the sea, the current may be reduced
  2. The material carried is deposited
  3. This builds up, forcing the river into several distributaries
  4. Eventually, a delta is formed, which sticks out into the sea
66
Q

What are some uses of deltas?

A
  • Provide fertile soil
  • Provide sand and gravel
  • Provide a habitat for many species
  • Protection against hurricanes
67
Q

What are some river hazards?

A
  • Flooding -> Loss of life and property

* River erosion -> Loss of property

68
Q

What are the PHYSICAL causes of flooding?

A 
CLIMATOLOGICAL
• Rain
• Ice melt
• Snow melt
PART-CLIMATOLOGICAL
• Interactions between stream flow and tidal conditions
• Coastal storm surges
OTHER
• Earthquakes
• Landslides
• Dam failure
69
Q

What are the HUMAN causes of flooding (or intensifying a flood)?

A
  • Faster discharge in urban areas -> Due to impermeable surface and many drainage channels
  • Urbanisation -> More people + impermeable surfaces
  • Building on floodplains
  • Dams
  • Changes in vegetation cover -> E.g. Deforestation
  • Human-induced climate change
70
Q

What are some opportunities presented by rivers?

A
  • Source of drinking water
  • Fertile silt for agriculture
  • Communication and navigation
  • Power
  • Fishing
  • Recreation
71
Q

How do dams affect rivers?

A
  • Reduce speed of water flow
  • Control amount of water in a river
  • Cause deposition behind the dam
  • Increase erosion downstream
  • Change ecosystems
  • Increase pressure on rocks -> Earthquakes
72
Q

What opportunities do dams provide?

A
  • Reliable water throughout the year
  • Navigation
  • Hydro-electric power
  • Water for irrigation
  • Safety from flooding
73
Q

How can the impacts of river flooding be managed?

A
  • Building dams or reservoirs to hold back excess water
  • Raising the banks of rivers
  • Dredging the river channel so it can hold more water
  • Diverting streams and creating new flood relief channels
  • Sandbags -> Prevent water getting into houses
  • Building houses on stilts
  • Land use planning -> Not building on floodplains, etc.
  • Afforestation -> Increases interception and reduced overland flow
  • Have insurance cover in vulnerable areas
  • Improved forecasting and warnings
  • River restoration and allowing rivers to flood naturally

Geography (20 decks)

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