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Year 3 Rivers And Sediment > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What does a river remove from the catchment

A

Water and sediment

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2
Q

Name some variations in channel dimensions

A

Grain size, water quality, river width, flow, slope

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3
Q

How could a desert effect river morphology

A

Flashy flows, mostly runoff, periodic rain, greatly changing hydrograph

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4
Q

What is the name for when plants and animals change the natural system to suit themselves

A

Ecosystem engineers

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5
Q

Why can the hydrological cycle and hydrograph differ around the world

A

Soil, rainfall, evaporation ect

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6
Q

What is the main split between flows in the hydrological cycle

A

Underwater vs overland

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7
Q

What is common with groundwater flow

A

Water travels more slowly, more steady store

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8
Q

What does overland and underground run off change

A

The hydrograph

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9
Q

What is antecedent precipitation

A

If rainfall falls into already wet ground more water can be released

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10
Q

What effects surface runoff

A

Land use, vegetation, soil, basin shape, evlevation, slope topography

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11
Q

What concerning the catchment can effect hydrographs

A

Catchment shape

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12
Q

Why can steepness change channel hydrograph

A

Faster flow more flashy and peaked hydrographs

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13
Q

How can land use, namely urbanisation effect hydrographs

A

Runoff on hard surfaces can create peaky and flashy hydrographs

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14
Q

How can we predict what sort of flows a catchment will generate in the channel

A

Flow records, empirical approaches, physically based models

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15
Q

What are flow records

A

Gauging data from minimums and maximums, USA and uk large historical record

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16
Q

What are empirical approaches

A

Devised for when no gauges in the stream system, uses key characteristics to work out flow

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17
Q

What factors can we use in empirical approaches to model river flow

A

Catchment area, stream frequency, effective rainfall, soil type, slope, lake storage

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18
Q

What letter do we always use for discharge

A

Q

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19
Q

Name an empirical report used to predict river flow

A

Flood studies report

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20
Q

What factor is C in the flood studies report

A

Regional multiplier

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21
Q

What do empirical approaches give you

A

Estimates of what the empirical approach might be

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22
Q

What is the problem with empirical methods or flow records

A

Only says what is in the past or what has been

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23
Q

What are the two main groups of catchment based models

A

Spatial representation and process representation

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24
Q

What is a lumped model

A

Treating the catchment as one entity

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25
Q

What value is generated from a lumped model

A

A single value

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26
Q

What is a distributed model

A

Thinking about the catchment as a series of grid squares

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27
Q

What is the back box model

A

Process lumped model

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28
Q

What is a white box model

A

Process distributed model

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29
Q

What is a DTm

A

Digital terrain model

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30
Q

What are the attributes of a dtm

A

Slope, aspect. Altitude

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31
Q

What areas can you get data for that you couldn’t before

A

Lidar and satellite data

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32
Q

What are some key soil catchment variables

A

type and association

Derived characteristics

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33
Q

What are some key geology catchment variables

A

Type

Derived characteristics

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34
Q

What key catchment land use variables are there

A

Vegetation cover

Management practices

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35
Q

What key catchment artificial factors are there

A

Storm drains sewers

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36
Q

What are

Some important catchment inputs o

A

Precipitation, suspended/dissolved load, pollutants

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37
Q

What are some important river outputs

A

Discharge, water vapour, groundwater recharge/transfer, suspended dissolved load. Pollutants

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38
Q

Why do some models struggle with accuracy

A

Stores of water, can be very variable

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39
Q

Name a GIS based catchment model

A

Lisflood (Paul bates)

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40
Q

What are gis data layers used to represent

A

Catchment characteristics. Inputs and outputs, water stored in a system, flows within a system

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41
Q

What are calculations between layers in GIS based catchment models used to do

A

Represent relationships model processes predict response

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42
Q

What model is lisflood

A

Gis distributed model

43
Q

What are the natural sources of solutes

A

Atmosphere, biosphere, rock and soil weathering (60%)

44
Q

What are the controls on solute supply

A

Lithology, sedimentary rocks 5x that of crystalline

Time water is in contact with rocks, hydrology

45
Q

What are the main solutes in the river system

A

Hydrogen carbonate, sulfate, calcium, silicon dioxide, they make up 80% of all solutes

46
Q

What is suspended material

A

Small grains that are kept in the flow

47
Q

Where does suspended sediment come from

A

Surface sources but also under water through flow

48
Q

How much sediment is delivered to channel from catchment

A

Only 15%, most from t he channel itself

49
Q

What is the sediment budget

A

The quantitative statement of the rates of sediment production transit and discharge

50
Q

What are the three elements needed to construct a sediment budget

A

Transport processes, storage elements, identification of linkages amoungst transport processes

51
Q

What is the equation for the sediment budget

A

O=I + AS
O = catchment sediment yield
I = sediment inputs
AS = change in sediment storage

52
Q

What are the main hill slope processes release sediment

A

Gullying, mass movement, sheet wash, erosion

53
Q

What has the majority of work been measuring sediment budgets

A

Small steams eg bed traps

54
Q

How does Chernobyl help in dating soils

A

Isotopic dating of soils using radio active readings

55
Q

Why is measuring sediment budgets difficult

A

Great variety of processes operating and wide areas where they occur

56
Q

What is the USLE

A

Universal soil loss equation, empirically derived equation

57
Q

What was the USLE designed for

A

Designed for just small plots

58
Q

What is A in the USLE

A

Soil loss per unit area

59
Q

Name an example of a numerical flood method

A

CAESAR coulthard et al

60
Q

What does coulthards model show

A

More human contact and deforestation linked with more sediment into the river streams

61
Q

What can sediment aggregation and degradation occur in response to

A

Increase or decrease in supply, water division or climate change, channel straightening, land use change, floods or other sudden inputs

62
Q

How can land use changes impact the sediment budgets

A

Agriculture intensification or abandonment, commercial forestry, urbanisation, mining

63
Q

Which industry presents a big challenge to sediment budgets

A

Forestry

64
Q

How do you start forestry cycles

A

Removing natural cover and improving the drainage, much flashier regime, more sediment in the system

65
Q

What happens at the end of the forresty cycle

A

Cut down trees lead to lots of run off and added sediment in the system

66
Q

If the river shows and equilibrium what can be said about the river system

A

It is in balance

67
Q

what controls catchment runoff

A

regional climate, topography, geology, soils, vegetation and land use

68
Q

Was is the nature of sediment delivery

A

Normally highly pulsed

69
Q

When can sediment enter the river directly

A

When river banks erode

70
Q

Where does the bulk of a rivers sediment come from

A

Headwaters

71
Q

what performs the drainage of earths land

A

stream networks

72
Q

what are stream reaches embedded into

A

stream networks

73
Q

what are network patterns

A

the spatial arrangement of river channels in the landscape

74
Q

what is the pattern of most drainage systems

A

dendritic

75
Q

what is the angle of stream junctions downstream

A

below 90 degrees

76
Q

who created stream order

A

strahler

77
Q

which channel shape is treelike, with no preferred channel orientation, acute intersection angles

A

dendritic

78
Q

what can channel junctions be termed

A

nodes

79
Q

what is drainage basin magnitude

A

the amount of exterior links a channel contains

80
Q

what is the londitudinal profile of a stream

A

plot of the elevation versus length

81
Q

what is the normal shape of a stream longitudinal profile

A

concave

82
Q

what is a streams base level

A

the elevation of the stream near the river mouth

83
Q

what is a distributary channel

A

one that slpits of into multiple channels, like deltas or alluvial fans

84
Q

what is the drainage density of a stream system

A

total length of streams, divided by the area

85
Q

what are exorheic systems

A

ones that drain into the sea//ocean

86
Q

what are endorheic systems

A

rivers drain into the inland seas, or wet lands, which is then evaporated

87
Q

what did Vorosmarty use to find out basin sizes and river stream orders

A

STN-30p

88
Q

compared with UNESCO sizes, how much did the STN-30p differ in size

A

=13%

89
Q

how many true first order streams are there worldwide

A

14,500,000

90
Q

what are the only 2 6th order (true 11th) streams

A

Amazon and Lena

91
Q

what is the average length of a 1st order stream

A

0.78km

92
Q

how many second order streams are there

A

4,150,000

93
Q

what percentage of global rivers are exorhiec

A

87%

94
Q

What are the 4 causes of convexities in river longitudinal profile

A

Local rock formations, coarse sediment, tectonic uplift, drop in base level

95
Q

What is a knick point

A

Pronounced steepening convexities

96
Q

What happens to sediment size as we go doenstream

A

It decreases

97
Q

What 2 processes reduce grain size over distance

A

Grain breakdown by abrasion, selective transport of finer sediments

98
Q

what is the difference with Anabranching reaches compared with braided rivers

A

anabranching rivers are fixed in position

99
Q

what is the shape of a normal cross section shape

A

concave but asymetrical

100
Q

What was the main control on sediment concentration in the Yorkshire stream tested by naden and cooper

A

Land cover and use

101
Q

What is a rill

A

A shallow channel cut into the soil by the erosive action of flowing water

102
Q

What is the larger stage up from rills

A

Gullies

103
Q

How are rills initiated

A

When water erodes topsoil on hillsides

104
Q

What is over come to lead to rill creation

A

Soil shear stress is over come by water shear stress

Year 3 Rivers And Sediment (12 decks)

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