Hydrological Systems Flashcards

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0
Q

Define Abrasion (corrasion) (erosion)

A

The rubbing or scouring of the bed and banks by the sedimentary material carried along by the river

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1
Q

Define Hydraulic action (erosion)

A

The movement of sediment by the frictional drag of moving water

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2
Q

Define Attrition (erosion)

A

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

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3
Q

Define Corrosion (erosion)

A

Rocks dissolve in water and are carried away

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4
Q

Define Traction (transportation)

A

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

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5
Q

Define Solution (transportation)

A

Rivers run through an area of carbonate rocks. Weak acids may act on more soluble rocks and gradually remove material in solution. This dissolves the material

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6
Q

Define Saltation (transportation)

A

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

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7
Q

Define Suspension (transportation)

A

This usually comprises of very small particles from fine clays and muds to sand. The particles are carried along by the water. This usually forms the bulk of sediment transported by rivers. More turbulent rivers can carry more suspended load

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8
Q

Why does deposition occur?

A
  • there’s shallow water
  • river enters a lake/sea
  • doesn’t have the capacity or energy to carry it’s load
  • reduction in gradient
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9
Q

What’s the long profile?

A

Balance between erosion, transportation and deposition changes throughout the course of the river

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10
Q

Why is the long profile concave?

A

Source is in the high mountains and river wants to get to sea level by vertical and lateral erosion

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11
Q

Define River competence

A

The maximum size of load it can carry

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12
Q

Define River capacity

A

The maximum volume of load it can carry

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13
Q

What is the Hjulstrom curve?

A

The relationship between velocity and competence

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14
Q

What influences erosion, transportation and deposition?

A

Energy of a river

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15
Q

3 things which contribute to a rivers energy

A
  1. Mass of water
  2. Height above sea level
  3. Gradient of the river
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16
Q

What influences a rivers energy?

A
  1. Altitude (potential energy)
  2. Steepness/gradient (kinetic energy)
  3. Gravity
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17
Q

What is Velocity?

A

The Speed and direction in which a body of water flows

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18
Q

Factors which influence velocity

A
Channel roughness
Channel shape (hydraulic radius)
Channel slope (gradient)
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19
Q

What is hydraulic radius?

A

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

=cross-sectional area / wetted perimeter

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20
Q

Factors which effect the shape of a v-shaped valley

A
  1. Climate
  2. Geology
  3. Vegetation
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21
Q

What is a waterfall?

A

A sudden fall of water that occurs where there are rapid changes nk gradient in the rivers course

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22
Q

What’s a pool? (Meanders)

A

A dip in the river bed

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23
Q

What is a riffle? (Meanders)

A

A mound of sediment/ an area of deposited sediment

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24
Q

What are braided rivers?

A

They have multiple channels and islands of sediment inbetween the channels

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25
Q

What causes braiding?

A

Fluctuation in discharge levels, low river velocity and by the river losing capacity and competence

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26
Q

What are levees?

A

Natural raised embankments made up of sand and mud deposits built up along either side of the flood plain of a river

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27
Q

What is a floodplain?

A

The area that would naturally be affected by flooding if a river rises above it’s banks

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28
Q

What is a delta?

A

Low-lying plain or landform that occurs at the mouth of a river near the ocean

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29
Q

What is rejuvenation?

A

An increase in the energy of a river cause by either a fall in it’s base level (sea level) or an uplift of the land

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30
Q

Define Isostatic change

A

(Ice melting)

Changes in uplift of land relative to the sea level as a result of crustal movements

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31
Q

Define Eustatic change

A

(Water freezing)

Change in relative height of the land and the sea may also result from a rise/fall in sea level

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32
Q

What is a knick point?

A

A sudden break in the gradient along the long profile of a river. They can be shown by waterfalls

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33
Q

What is a river terrace?

A

A remnant of a former floodplain which has been left at a higher level after rejuvenation

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34
Q

What is an incised meander?

A

Rivers have cut deeply into the landscape (Grand Canyon)

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35
Q

What is Flood frequency?

A

How often a flood occurs

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36
Q

What is Flood recurrence?

A

How often a flood of a certain magnitude occurs

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37
Q

How do you calculate flood recurrence?

A

T=n+1

M

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38
Q

What is flooding?

A

A river exceeds bankfall level

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39
Q

Natural causes of flooding

A
  • vegetation
  • drainage density
  • soil depth
  • slope
  • rock type
40
Q

Human causes of flooding

A
  • ploughing
  • impermeable areas of Tarmac
  • dams
  • sewers
  • grazing animals
41
Q

What is hard engineering?

A

Building artificial structures such as dams, aimed at controlling natural processes

42
Q

What is soft engineering?

A

Works with the natural processes of the river. A sustainable approach to managing the river without using artificial structures

43
Q

Define Dams and reservoirs

A

Large concrete constructions whose purpose is to hold back the flood waters and release them gradually

44
Q

Define Straightening channels

A

The process of removing meanders from rivers

45
Q

Define Levees and embankments

A

Often made of earth, these constructions increase the height of the river banks

46
Q

Define Diversion spillways/relief channels

A

Artificial channels that branch off the main channel often used to bypass Urban areas

47
Q

Define Dredging

A

The process by which river channels are made deeper by digging into the bed

48
Q

Define Permeable surfaces

A

This includes the use of grass, gravel and porous bricks

49
Q

Define Flood walls

A

Brick or concrete constructions that are found on river banks or in front of properties and businesses

50
Q

Define Basins and ponds

A

Man made areas created for storing water. The former are only filled with water during the high discharges and the latter are always full

51
Q

Define Flood forecasting and warning

A

Close monitoring of weather and river responses allows the environment agency to prepare local residents and businesses

52
Q

Define Floodplain zoning and land use management

A

Area are categorised according to the level of risk abs human activities are controlled as a result

53
Q

Define Naturalisation of channels

A

Meanders are reintroduced to straighten channels

54
Q

Define Wetland and river conservation

A

Encouraging ponds and marshes to be left untouched and encourage the natural state of the river and it’s surroundings

55
Q

Define Swales

A

These are long shallow channels that allow water to infiltrate gradually. They are usually found either side of roads and have vegetation

56
Q

Define Filter strips

A

These are gently sloping areas of vegetation (usually wild grass). Often found at the side of roads

57
Q

What is a Source?

A

Start of the river

58
Q

Define Drainage basin

A

An area of land drained by a river and it’s tributaries

59
Q

What is the Mouth?

A

End of the river and meets sea/lake

60
Q

Define Tributary

A

A smaller river that joins a main river

61
Q

Define Confluence

A

Where two or more rivers meet

62
Q

Define Watershed

A

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

63
Q

Define Precipitation

A

All forms of moisture which reaches the earths surface

64
Q

Define Evaporation

A

The transformation of water droplets into water vapour by heating

65
Q

Define Transpiration

A

The loss of water from a drainage basin into the atmosphere from the leaves of plants

66
Q

Define Channel storage

A

The water in a river

67
Q

Define Surface storage

A

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

68
Q

Define Groundwater storage

A

The storage of water underground in permeable rock strata

69
Q

Define Interception storage

A

The total volume of water held on the surface of vegetation

70
Q

Define Through fall

A

The water dripping off the leaves

71
Q

Define Stem flow

A

Where precipitation flows through stems of plants to the ground

72
Q

Define Secondary interception

A

The movement of rain water from big plants to smaller plants

73
Q

Define Groundwater flow/base flow

A

The deeper movement of water through underlying rock strata (horizontal)

74
Q

Define Through flow

A

The movement of water downslope within the soil layer

75
Q

Define Water table

A

All water the ground can hold before it starts to flood (saturation)

76
Q

Define Percolation

A

The gravity flow if water In the soil

77
Q

Define Infiltration

A

The downward movement of water into the soil from the surface

78
Q

Define Surface runoff (overland flow)

A

The movement of water over the surface of the land, usually when the ground is saturated or frozen or when precipitation is too intense for infiltration

79
Q

Define Capillary action

A

The upward movement if water in soil

80
Q

Define Channel flow

A

The movement of water in the river channel

81
Q

Define Antecedent precipitation

A

Already existing precipitation that can cause additional saturation

82
Q

Define Zone of saturation

A

Ground below water table the fractures in soil and rocks are saturated with water

83
Q

Define Infiltration capacity

A

Maximum rate at which soil in a given condition will absorb water

84
Q

Define Water balance

A

Balance between inputs and outputs of moisture in the soil

85
Q

Define Lag time

A

Difference between peak rainfall and peak discharge

86
Q

Define Soil moisture deficit

A

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

87
Q

Define Soil moisture recharge

A

When the water in the soil is being replenished

88
Q

Define Soil moisture drawdown

A

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

89
Q

Define Soil moisture excess

A

This is when the soil stores are full (overflowing)

90
Q

Define Peak discharge

A

The most discharge which you occur during the storm

91
Q

Define Peak rainfall

A

The highest record level of rain in that day (mm)

92
Q

Define Falling/recession limb

A

Discharge is steadily going down

93
Q

Define Base flow

A

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

94
Q

Define Rising limb

A

Rapid rise in discharge

95
Q

Define Discharge

A

The volume of water passing by a given point every second

96
Q

Define Antecedent flow rate

A

Discharge before the storm event

97
Q

Where and when was the flood in Scotland?

A

River Tay

Mud January 1993

98
Q

What does the flood in Scotland tell us?

A

That we cannot trust historic events to predict when floods will occur