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AS Geography > Hydrological Systems > Flashcards

Hydrological Systems Flashcards

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0
Q

Define source (of a river)

A

Start of a river - usually on high ground

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1
Q

Define a drainage basin

A

An area of land drained by a river and its tributaries

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2
Q

Define tributary

A

Smaller river that joins the main river

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3
Q

Define Confluence

A

Where two or more rivers meet

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4
Q

Define watershed

A

A ridge of high ground that forms the boundary between two drainage basins

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5
Q

Define mouth (of a river)

A

The end of the river where it meets a sea or a lake (usually quite wide)

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6
Q

Define precipitation

A

All forms of moisture that reach the Earths surface (e.g rain, snow, dew)

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7
Q

Define evaporation

A

The transformation of water droplets into water vapour by heating

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8
Q

Define (evapo)transpiration

A

Loss of water from a drainage basin into e atmosphere from the leaves of plants

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9
Q

Define channel storage

A

The water stored in a river

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10
Q

Define surface storage

A

Total volume of water held on the Eaths surface in lakes, ponds, puddles

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11
Q

Define groundwater storage

A

Storage of water underground in permeable rock strata

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12
Q

Define Interception storage

A

Total volume of water held on the surface of vegetation

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13
Q

Define Through fall

A

The water that drips off of the leaves of plants

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14
Q

Define Stem flow

A

Where precipitation flows through the arms of the plants to the ground

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15
Q

Define secondary interception

A

The movement of rain water from big plants to smaller plants

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16
Q

Define groundwater flow (base flow)

A

Deep movement of water through the underlying rock strata (horizontal)

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17
Q

Define through flow

A

The movement of water downslope within the soil layer

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18
Q

Define the water table

A

The level below which the ground is saturated with water

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19
Q

Define percolation

A

The gravity flow of water within the soil

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20
Q

Define infiltration

A

The downward movement of water into the soil surface

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21
Q

Define surface runoff (overland flow)

A

Movement of water over the surface of land

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22
Q

Define capillary action

A

Upward movement or water in soil (commonly through the roots of plants)

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23
Q

Define channel flow

A

The movement of water within the river channel

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24
Q

Define antecedent precipitation

A

Already existing precipitation that can cause additional saturation

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25
Q

Define zone of saturation

A

Ground below the water table that fractures and fills with water

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26
Q

Define infiltration capacity

A

The max rate at which a soil in a given condition will absorb water

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27
Q

What is the water balance?

A

Balance between inputs and outputs of moisture in the soil

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28
Q

What is soil moisture deficit?

A

When most of the water in the soil has been used up

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29
Q

Define soil moisture recharge

A

When the water in the soul is being replenished

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30
Q

Define soils moisture drawdown

A

When the stores of water in the soil are being used and their levels are lowering

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31
Q

What is soil moisture excess

A

When the soil stores are full (and overflowing)

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32
Q

Define Peak discharge

A

The point where there is the highest volume of discharge

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33
Q

Define peak rainfall

A

The highest amount of rainfall

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34
Q

Define falling/recession limb

A

When discharge slows down or decreases

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35
Q

Define base flow

A

Water that reaches the channel largely through slow through flow and from permeable rock below the water table

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36
Q

What is discharge?

A

The volume if water flowing in a river per second measured in cumecs

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37
Q

Define rising limb

A

When discharge increases or speeds up

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38
Q

What is lag time?

A

The time difference between peak rainfall and peak discharge

39
Q

What is antecedent flow rate?

A

The discharge before the storm event

40
Q

What is hydraulic action?

A

Movement of sediment by the frictional drag of the moving water

41
Q

What is abrasion (corrasion)?

A

Rubbing or scouring of the bed and banks by the sedimentary material carried along by the rivers

42
Q

Define attrition

A

Reduction in size of the sediment particles as they collide with each other the bed and the banks

43
Q

Define Corrosion (solution)

A

Rocks dissolve into the water and are carried away

44
Q

What are the 4 types of erosion?

A

Hydraulic action
Abrasion (corrasion)
Attrition
Corrosion (solution)

45
Q

Why does deposition occur?

A

A river deposits when it is no longer competent or has the capacity to carry all of it’s load (no energy to carry sediment)

46
Q

Name 5 causes of deposition

A 
River enters a sea or lake
Landslide - sudden increase in volume
Shallow water - eg. Inside of meander
Confluence - change of velocity
Low flow - not enough energy to carry sediment
47
Q

Name all the processes of transportation

A

Traction (bed load)
Solution (dissolve)
Saltation
Suspension

48
Q

Define traction

A

Large rocks and material that are too heavy to be picked up by the current may roll along or slide along the river bed

49
Q

Explain the transportation process of solution

A

Where rivers run through area of carbonate rocks and weak acids that act on more soluble rocks and gradually remove material in solution

50
Q

Explain the process of saltation

A

Material ranging from pebbles to sand grains may be temporary lifted and bounced along the floor in a hopping motion

51
Q

Explain the process of suspension

A

Usually comprises of very small particles (fine muds, clay, sand etc.) which are carried along by the water.

52
Q

what is the long profile

A

It shows how from the source to mouth the balance between erosion transportation and deposition changes throughout the course of the the river

53
Q

Why is the long profile concave?

A

Vertical erosion and downcutting dominates initial stages of rivers course and lateral erosion near the mouth causing a concave structure

54
Q

Define river competence

A

Max size (calibre) a load of a river is capable to carry

55
Q

Define river capacity

A

Total volume of sediment a river can transport

56
Q

What is the Hjulstrom curve?

A

Relationship between the velocity of the river and competence

57
Q

What influences the rivers 3 processes - transportation, erosion, deposition

A

Level of energy a river possesses

58
Q

What 3 things contribute to a rivers energy?

A

Mass of water
Height above sea level
Gradient

59
Q

Define velocity

A

Speed and direction at which the body of water flows

60
Q

State 3 factors that influence velocity

A

Channel shape (hydraulic radius)
Roughness
Slope (gradient)

61
Q

Define hydraulic radius

A

Ratio of cross-sectional area of the channel and the length of it’s wetted perimeter

62
Q

What 3 things effect the shape of a V-shaped valley?

A

Climate
Geology
Vegetation

63
Q

Define a pothole

A

Circular depression on the river bed carved out of solid rock

64
Q

Define a waterfall

A

Sudden fall of water where there is a rapid change in gradient in the rivers course

65
Q

What is a pool

A

Dip in river bed

66
Q

What is a riffle

A

Mound or area of deposited sediment

67
Q

What is rejuvenation

A

Increase in energy of a river caused by either a fall in its base level or an uplift in land

68
Q

Define isostatic change

A

Land rising relative to the sea as a result of crustal movements

69
Q

Define eustatic change

A

Global changes in the sea levels

70
Q

Define a knick point

A

Sudden bread or irregularity in the gradient along the long profile of a river

71
Q

Define a river terrace

A

Remnant of a former floodplain which has been left at a higher level after rejuvenation of the river

73
Q

How do interlocking spurs form?

A

Rivers take the easiest and quickest route by eroding through soft rock and leaving hard rock protrusions called interlocking spurs
Abrasion and hydraulic action are able to erode the channel vertically but not the lateral banks so the river meanders around the hard rock

74
Q

What are levees?

A

Natural raised embankments made up of sand and mud deposits built up along either side of the floodplain of a river or stream

75
Q

How do levees form?

A

As a river overflows it’s bank during a flood, the velocity of the water falls.
Competence of river suddenly reduced
The thickest and coarsest sediments are deposited at channel edges
Thin and fine sediments deposited over outer floodplain
Over time deposited sediment builds up

76
Q

What are deltas?

A

When a river reaches a lake or the sea the water slows down and loses the power to carry sediment, this sediment is dropped and forms a delta

77
Q

What are the 3 types of delta?

A

Arcuate/fan-shaped: land around river mouth arches out into sea and river splits many times on way to sea, creating a fan effect
Cuspate: land around mouth of river just out arrow-like into the sea
Bird’s foot: river splits on way to sea, each part juts out, like a birds foot

78
Q

Explain formation of deltas

A

Rivers energy and efficiency is reduced as it joins a larger body of water (sea) which decreases the hydraulic radius.
River loses power to carry sediment and drops it at the mouth of the river
Areas of sediment continue to grow creating landforms that rise above water surface

79
Q

Factors influencing formation of deltas

A
  • Amount and type of sediment available
  • Variations in volume of water discharged from river
  • Geometry of Coast
  • Coastal processes
80
Q

What is a floodplain

A

Area that would naturally be affected by flooding if a river rides above it’s banks
Low flat lands used to hold floodwater temporarily

81
Q

Formation of floodplains

A 
Lateral erosion (hydraulic action and abrasion) due to fast velocity 
River erodes valley sides, widening valley floor to create a floodplain
82
Q

Define incised meanders

A

Rivers that have cut deeply into the landscape because they have been deepened by rejuvenation

83
Q

what do we mean by flood frequency?

A

How often does a flood occur?

84
Q

What is flood recurrence?

A

How often does a flood of a certain magnitude (size) occur?

85
Q

what is magnitude-frequency analysis of flood risk

A

Calculating the recurrence interval which shows the no. of years within a flood of a a certain size can be expected

86
Q

How reliable are flood recurrence intervals?

A

Relies on natural events and processes
only based on previous events
only a prediction

87
Q

Name all 6 types of hard engineering flood management techniques

A 
Dams ans reservoirs, 
Straightening channels,
Levees and embankments, 
Relief channels, 
Dredging, 
Flood walls
88
Q

Name all 7 types of soft engineering flood management techniques

A

Permeable surfaces, Basins and ponds, floodplain zoning, naturalisation of channels, wetland conservation, swales, filter strips

89
Q

What are filter strips?

A

Gently sloping areas of vegetation that allow water to infiltrate into the soil

90
Q

define hard engineering

A

building artificial structures such as dams aimed at controlling natural processes

91
Q

define soft engineering

A

A sustainable approach to managing the coast without using artificial structures but using the natural processes of the river

92
Q

What happened at River Tay,Scotland?

A

Major flood in Feb 1990
Flooded again mid-Jan 1993 with record of 2200m3/s
Both floods greater in magnitude than previous high record 52

93
Q

What is a flood

A

When a river exceeds bankfull level and bursts its banks

94
Q

What are the 5 natural causes of flooding?

A

Vegetation - interception, storage, transpiration
Slope - steeper angled means less absorption
Rock Type - infiltration in permeable rock, groundstorage
Drainage density - streams divided by area, lag time
Soil depth - deeper soil absorbs more, less runoff

95
Q

State 5 human causes of flooding

A

Impermeable areas of tarmac - more runoff
Deforestation - less interception etc.
Ploughing - compacts soil so less infiltration
Sewers - directs into river, short lag time
Urbanisation - remove grasslands, less infiltration

AS Geography (4 decks)

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