Rivers Flashcards

1
Q

What percent of the worlds water is found in seas and oceans?

A

97%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a drainage basin?

A

The area of land drained by a river

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the catchment area?

A

The area within the drainage basin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the watershed?

A

The boundary between two or more drainage basins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where are watersheds usually found?

A

The edge of highlands surrounding a drainage basin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a confluence?

A

The point at which two rivers or streams join together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a tributary?

A

A stream or smaller river which joins a larger river

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe a cross section of the land near to the source of a river

A

V-shaped valley Narrow and shallow river

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the name of the process that causes a river to erode downwards?

A

Vertical erosion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name the four main forms of erosion

A

Hydraulic action Solution Attrition Abrasion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Explain hydraulic action

A

The force of the river causes air to be trapped in cracks of the bank. This pressure weakens the banks and slowly causes them to wear away

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Explain abrasion

A

Erosion caused by the rubbing of materials carried by rivers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Explain attrition

A

Erosion caused when rocks and boulders transported by rivers and waves bump into each other and get smaller

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does attrition do to the size of the rocks?

A

Smaller Smoother Rounder

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Name the four different transport processes in rivers

A

Solution Suspension Traction Saltation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain solution for erosion and transportation

A

Small pieces of rock and minerals are dissolved in the river and then carried along

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Explain suspension

A

Fine, light materials are carried along the water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Explain saltation

A

Small pebbles and stones bounce along the river bed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Explain traction

A

Larger rocks and boulders are rolled along the river bed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is required for traction to occur?

A

High energy level in the river

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where are energy levels usually at their highest in a river?

A

In the lower course

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What causes deposition?

A

The river losing energy : Inside of a meander

Estuary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where is deposition the most common?

A

Near to the mouth Shallow areas Low volume of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Name the upper course features

A

-V shaped valleys -Interlocking Spurs -Rapids -Waterfalls -Gorges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Name the features of the middle course

A

-Wider, shallower valleys -Meanders -Oxbow lakes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Name the features of the lower course

A

-Wide, flat bottomed valleys -Floodplains -Levees -Deltas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Why do interlocking Spurs occur?

A

The river avoids areas of hard rock due to its low energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How does a waterfall occur?

A

-A layer of hard rock above a thicker layer of soft rock causes the soft layer to erode faster -The soft rock slowly undercuts the hard rock due to it eroding faster and a steep edge is created -This overtime develops to be a waterfall as the height difference increases -Eventually the overhanging rock falls and the waterfall slowly retreats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How do Rapids form?

A

Ridges of hard rock cause an uneven slope. This creates Rapids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Why does water travel faster in the middle course compared to the upper course?

A

The channel has been widened and deepened and therefore less friction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Why do meanders form?

A

-The river erodes laterally -Deposition on inside -Erosion on outer side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What happens on the inside bend of a meander?

A

-The river flows slower -Material is deposited -More friction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What happens on the outside bend of a meander?

A

-Water erodes and undercuts the bank -Most energy -Less friction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the result of meanders being cut off?

A

An oxbow lake

35
Q

When is an oxbow lake most to form?

A

In times of flood

36
Q

What happens when oxbow starts to form?

A

-Sediment builds up, blocking it from the rest of the river -Over time the stagnant water could be replaced by land as sediment is deposited

37
Q

What is it called when a meander is replaced by land?

A

Meander scar

38
Q

What happens to interlocking Spurs if they occur in the middle course?

A

Bluffs (Truncated Spurs) are created

39
Q

What are created by floods in the middle course?

A

Levees

40
Q

What is the material which is deposited in the event of a flood?

A

Alluvium deposits

41
Q

What is precipitation?

A

Rainfall

42
Q

What is interception?

A

When trees and plants catch rainfall.

43
Q

What is infiltration?

A

When water on the surface enters the ground.

44
Q

What is percolation?

A

The gravity flow of water in soil.

45
Q

What is infiltration?

A

When water on the surface enters the ground.

46
Q

What is throughflow?

A

Sideways flow of water under ground.

47
Q

What is transpiration?

A

The flow of water up a plant and, eventually, its evaporation.

48
Q

What can cause flooding?

A

• A steep-sided channel • A lack of vegetation or woodland • A drainage basin, consisting of mainly impermeable rock • A drainage basin in an urban area • Heavy rainfall

49
Q

What can cause river erosion?

A

• Stream bed lowering• Saturation of banks• Redirection and acceleration of flow • Removal or disturbance of protective vegetation • Bank soil characteristics such as poor drainage or seams of readily erodible material within the bank profile• Wave action generated by wind or boat wash;• Excessive or inappropriate sand and gravel extraction• Intense rainfall events (e.g. cyclones).

50
Q

What are the advantages of living near a river or a delta?

A

• Fertile soil • Fishing • Tourism • Protection against hurricanes (only delta) • Sand and gravel for construction

51
Q

What are the two main ways river flooding can be managed?

A

Hard-engineering Soft-engineering

52
Q

What are some examples of hard engineering?

A

• Dams • River engineering

53
Q

What are some examples of soft engineering?

A

• Afforestation • Managed flooding • Planning

54
Q

What is the Bradshaw model?

A

A graphic representation of the change of characteristics as you go downstream

55
Q

What is the cross section?

A

A profile of the shape of the river channel

56
Q

What is the channel width?

A

The measuremeant from one bank to the other, either present flow or bankfull flow

Increases going downstream

57
Q

What is the mean depth?

A

Water’s surface to the river bed across the entire width

Increases going downstream

58
Q

What is the discharge of a river?

A

Volume of water which flows past a point in a given time.

Usually measured in cubic meters/second (cumecs) and increases going downstream

59
Q

What is the wetted perimeter?

A

The surface of the channel bottom and sides in direct contact with water

60
Q

What is the hydraulic radius?

A

Measure of a channel flow efficiency

cross-sectional area / wetted perimeter

Increases going downstream

61
Q

How does the channel bed roughness change as you go downstream?

A

Decreases: due to ersosional processes which increase due to a higher discharge

62
Q

How does turbulance and friction change as you go downstream?

A

Decreases: due to the smaller particle size

63
Q

What is evaporation?

A

When water particles heat up to a point where they become a gas

64
Q

What is the source?

A

The place where the river begins

65
Q

What is the mouth of a river?

A

Where the main river meets the sea/ocean/lake

66
Q

What is drainage denisty?

A

Total length of the rivers / area

67
Q

What type of rock underlys high drainage denisty?

A

Non-porous hard rocks such as clay

68
Q

What does high and low drainage density look like?

A
69
Q

What drainage density is more likely to flood?

A

High Drainage density

70
Q

What is groundwater flow?

A

Water flowing through rocks underground

71
Q

What is surface storage?

A

Water which is stored in rivers, lakes reservoirs etc.

72
Q

What is a rivers load?

A

The material which the river is carrying

73
Q

What is a meander scar?

A

The feature left behind when the water in an ox-bow lake dries up

74
Q

What are natural levees?

A

A raised river bank formed by deposition

75
Q

What are man-made levees?

A

Artificial raised banks to increase the channel capacity and reduce flood risk

76
Q

What is a floodplain?

A

An area of land around a river channel which is formed during times of flood when deposition occurs

77
Q

Why is alluvium useful?

A

Rich with minerals and is essential for fertile lands

78
Q

What is the bluff line?

A

Outer limits of the floodplain

79
Q

What is the strand line?

A

Outer limit of floodplain where material is left

80
Q

How is a delta formed?

A

A delta is formed when the river deposits its material faster than the sea can remove it

81
Q

Name and give an example of 3 types of deltas

A
  • Bird’s foot delta (Mississipi)
  • Arcuate delta (Nile)
  • Cuspate delta (Ebro)
82
Q

What is flocculation?

A

Salt from the sea causes the load from a river to join together and heavier so it is more likely to be deposited

83
Q

What are the disadvantages of living near/on a delta?

A
  • Risk of flood
  • Mosquitos (malaria, dengue)
  • Dirty and polluted water
  • Rising sea levels
  • Defences cost