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Geo > Topic 3 > Flashcards

Topic 3 Flashcards

1
Q

What is a river system?

A

A number of small streams and rivers join to form a river system.

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2
Q

What is the definition of a river?

A

It is a body of water flowing downslope in a defined channel from a source to a mouth.

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3
Q

What is a drainage basin?

A

The area drained by a river system or stream network.

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4
Q

What is a catchment area?

A

The drainage area supplies water to a river. It could be from rainwater or from underground water that seeps into the river.

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5
Q

What determines the size of a drainage basin?

A

The origin of underground water.

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6
Q

What is surface runoff?

A

Rainwater flowing over the surface

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7
Q

Describe drainage basin

A

It collects precipitation, allows water to infiltrate or seep underground to become groundwater, and stores water in lakes, wetlands and underground.

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8
Q

Precipitation that does not infiltrate underground or flow over the surface gets stopped by?

A

Evaporation, intercepted by vegetation or be transpired as water vapour.

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9
Q

What is a watershed?

A

High ground separates one drainage basin from the adjacent basin.

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10
Q

What are stream or river network?

A

Individual streams and rivers that are connected

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11
Q

What is a tributary?

A

Individual river channels form the stream network.

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12
Q

What is a confluence?

A

The point where one river in a network joins another.

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13
Q

What is interfluves?

A

Ridges of high ground between individual channels.

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14
Q

Name the important watershed in South Africa?

A

Drakensburg.
Witwatersrand.
Mountains that form the Orange River System.

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15
Q

What is overland flow

A

Rainwater flowing over the surface

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16
Q

What is channel flow

A

Water flowing in a river channel

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17
Q

What is throughflow

A

Water flowing through the soil

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18
Q

What is permeable rocks

A

Rocks that allow water to seep in.

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19
Q

What is groundwater

A

Underground water

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20
Q

What is groundwater flow

A

Water flowing through underground rocks

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21
Q

Factors that influence how much water how much surface runoff or how much will become infiltrated underground

A

Relief
Soil type
Rock type
Soil moisture
Vegetation
Rainfall
Land use

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22
Q

Impermeable rock

A

Rock without pore spaces or cracks through which water is able to pass

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23
Q

What is water table

A

Upper surface of the groundwater

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24
Q

What is base flow?

A

Groundwater that seeps into a river

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25
Q

Types or rivers and an example in South Africa

A

Permanent rivers: receive ground water all year, water table is always above the bed or the river. All year. Eastern side of country for example the uThukela River(Tugela River)

Periodic rivers: receive ground water only in rainy season when water table is above river bed, only flow with base flow for 5-6 months after the rain periods. Rivers that flow in winter in the Cape (Palmiet river) in summer is found on the plateau (Vaal River)

Episodic rivers: never supplied with groundwater they only flow after rain, water rapidly seeps into the riverbed as it is above the water table. Often used as roads or runway for light aircrafts. Northern Cape and on western side (Molopo River)

Exotic rivers: Flow all year round, supplied with water at source but very little is added as they flow. River that gets water from source but then runs through deserts and arid areas (The Orange River)

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26
Q

Drainage patterns that depend on the geology or topography of the are where they are found

A

Radial: A radial drainage pattern develops on a dome where streams flow outwards and downhill.

Trellis: A trellis drainage pattern forms on inclined strata that are unequally resistant to erosion or parallel-fold mountains.

Rectangular: Igneous rock that has joints and cracks gives rise to a rectangular drainage pattern.

Centripetal: Streams flowing into a central pan or low-lying are develops a centripetal pattern.

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27
Q

Patterns that depend on the geology or topography of the are where rivers are found.

A

The rock structure and gradient of the land where water flows. They develop in less resistant rock, in joints and cracks or steeper gradients. This is where rivers are formed.

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28
Q

Patterns that develop independently of the rock structure or gradient.

A

The rock is the same throughout and so there are no weaker areas in which the water would erode a channel. The gradient is uniform so there are no steeper sides where the water to be flowing more quickly to carve out a channel.

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29
Q

Examples of drainage patterns that develop independently or rock structure or gradient

A

Dendritic: Tree-like appearance. Tributaries join the stream at less than 90*. Most common type forms on areas with similar hardness of rocks and similar gradients.

Parallel: develops on the surface of a slope that slopes uniformly but is fairly steep. Flow downslope nearly parallel to each other.

Deranged: Develop on surfaces of land that are covered by ice sheets or glaciers, small streams, swamps and lakes, with no apparent drainage pattern.

30
Q

What is stream order?

A

The category of a stream in a network is determined by the order of the streams feeding into it.

31
Q

List the stream order

A

First-order streams lowest category with no streams feeding into them. Where 2 streams of the same order in a network join a higher order is formed. Stream order indicates the number of tributaries in the basin and the linking of them.

32
Q

What is discharge?

A

The amount of water flowing in a river channel past a point in a given time

33
Q

What is a stream gauge?

A

Measures the discharge in cubic meters per second

34
Q

What is storm hydrographs

A

When a discharge of a river during and after a rainstorm is recorded.

35
Q

What is discharge dependant on?

A

rain, gradient, soil type, rock type, vegetation and human activities

36
Q

What is the fastest part of a river

A

the point that is not in contact with the channel sides and bed

37
Q

What is laminar flow

A

water flowing in sheets; it does not change level, water flowing over a smooth surface, little friction, fast flow speeds

38
Q

What is turbulent flow?

A

Water flowing in a bubbling motion; it changes levels, the river bed is uneven, a lot of internal friction, slow.

39
Q

Fastest flow speeds

A

Symmetrical channel= middle just below the surface.
Meandering river = Fastest towards the outer banks.

40
Q

What is a longitudinal profile:

A

Visual representation of the gradient down which a river flows

41
Q

What is a transversal profile(cross-profile of the river)

A

Section drawn transversely across the valley at right angles to the river (Cross section)

42
Q

What is upstream?

A

Towards the source

43
Q

What is downstream?

A

Towards the mouth

44
Q

Temporary base level

A

Changes in a gradient along the course of a river where vertical erosion of the river is slowed.

45
Q

Examples of temporary base levels

A

Rapids, waterfalls, lakes and dams

46
Q

What is a permanent base level or ultimate base level

A

Sea level is the lowest level at which a river will erode the land.

47
Q

When will a cross-profile be wider

A

Upstream from a temporary base level. Downstream it will be a steep-sided gorge or ravine, with high vertical erosion, this deepens the channel

48
Q

What is erosion?

A

The wearing away and removal of weathered rock material from the river channel

49
Q

Fluvial landforms

A

Landforms created by a river

50
Q

Spurs

A

Ridges of high ground between individual channels.

51
Q

Rapids

A

A resistant layer of rock causes slight changes in the gradient and turbulent flow. High rainfall and steep gradient. Uneven and rocky

52
Q

Waterfalls

A

A river crosses a horizontal layer of resistant rock, or a layer of resistant rock dipping upstream, and flows down a steep gradient. High rainfall and steep gradient.

53
Q

The resistant layer of rock by a water fall is called

A

The lip or fall-maker.

54
Q

How is a plunge pool formed?

A

Hydraulic action caused by falling water and abrasion of eroded material forms a plunge pool

55
Q

What is Headward erosion

A

It is when a river lengthens its course by cutting back upstream above its original course

56
Q

What is hydraulic action

A

It is the force of the flowing water loosening pebbles stones sand and salt from the sides and a bed of the channel

57
Q

What is abrasion

A

It is particles of sand and silt that are carried by the river scratch and wear away the bed and sides of the channel

58
Q

What is traction

A

Boulders and larger rocks are pushed and rolled along the river bed

59
Q

What is saltation

A

It is when smaller rocks and stones are bounced along the river bed

60
Q

What is suspension

A

Silt and very small particles are carried within the flow of the water

61
Q

What is sheetflow

A

Water flowing downslope in thin sheets

62
Q

Mass movement

A

Movement downslope of weathered material

63
Q

Meanders(Meandering channel patterns)

A

Bends in a river channel

64
Q

Alluvial Fans

A

Deposition as the river flows off the mountains on to the flatter plains

65
Q

Flood Plain

A

Flat valley floor

66
Q

Alluvium

A

Fertile silt deposited by a river

67
Q

Braided streams(Braided channel pattern)

A

Deposits of alluvium form islands in the middle of the channel, splitting the river into separate channels

68
Q

Levees

A

Raised banks of a river

69
Q

oxbow lakes

A

A meander that is cut off when a river takes a new course across the neck of a meander loop

70
Q

Meander scars

A

Dried up oxbow lakes

71
Q

Deltas

A

Deposition by the mouth of the river resulting in deltas

72
Q

Distributaries

A

A single channel divides into a number of smaller channels that do not rejoin; opposite of a tributary

Geo (3 decks)

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