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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
What value is generated from a lumped model
A single value
26
What is a distributed model
Thinking about the catchment as a series of grid squares
27
What is the back box model
Process lumped model
28
What is a white box model
Process distributed model
29
What is a DTm
Digital terrain model
30
What are the attributes of a dtm
Slope, aspect. Altitude
31
What areas can you get data for that you couldn’t before
Lidar and satellite data
32
What are some key soil catchment variables
type and association | Derived characteristics
33
What are some key geology catchment variables
Type | Derived characteristics
34
What key catchment land use variables are there
Vegetation cover | Management practices
35
What key catchment artificial factors are there
Storm drains sewers
36
What are | Some important catchment inputs o
Precipitation, suspended/dissolved load, pollutants
37
What are some important river outputs
Discharge, water vapour, groundwater recharge/transfer, suspended dissolved load. Pollutants
38
Why do some models struggle with accuracy
Stores of water, can be very variable
39
Name a GIS based catchment model
Lisflood (Paul bates)
40
What are gis data layers used to represent
Catchment characteristics. Inputs and outputs, water stored in a system, flows within a system
41
What are calculations between layers in GIS based catchment models used to do
Represent relationships model processes predict response
42
What model is lisflood
Gis distributed model
43
What are the natural sources of solutes
Atmosphere, biosphere, rock and soil weathering (60%)
44
What are the controls on solute supply
Lithology, sedimentary rocks 5x that of crystalline Time water is in contact with rocks, hydrology
45
What are the main solutes in the river system
Hydrogen carbonate, sulfate, calcium, silicon dioxide, they make up 80% of all solutes
46
What is suspended material
Small grains that are kept in the flow
47
Where does suspended sediment come from
Surface sources but also under water through flow
48
How much sediment is delivered to channel from catchment
Only 15%, most from t he channel itself
49
What is the sediment budget
The quantitative statement of the rates of sediment production transit and discharge
50
What are the three elements needed to construct a sediment budget
Transport processes, storage elements, identification of linkages amoungst transport processes
51
What is the equation for the sediment budget
O=I + AS O = catchment sediment yield I = sediment inputs AS = change in sediment storage
52
What are the main hill slope processes release sediment
Gullying, mass movement, sheet wash, erosion
53
What has the majority of work been measuring sediment budgets
Small steams eg bed traps
54
How does Chernobyl help in dating soils
Isotopic dating of soils using radio active readings
55
Why is measuring sediment budgets difficult
Great variety of processes operating and wide areas where they occur
56
What is the USLE
Universal soil loss equation, empirically derived equation
57
What was the USLE designed for
Designed for just small plots
58
What is A in the USLE
Soil loss per unit area
59
Name an example of a numerical flood method
CAESAR coulthard et al
60
What does coulthards model show
More human contact and deforestation linked with more sediment into the river streams
61
What can sediment aggregation and degradation occur in response to
Increase or decrease in supply, water division or climate change, channel straightening, land use change, floods or other sudden inputs
62
How can land use changes impact the sediment budgets
Agriculture intensification or abandonment, commercial forestry, urbanisation, mining
63
Which industry presents a big challenge to sediment budgets
Forestry
64
How do you start forestry cycles
Removing natural cover and improving the drainage, much flashier regime, more sediment in the system
65
What happens at the end of the forresty cycle
Cut down trees lead to lots of run off and added sediment in the system
66
If the river shows and equilibrium what can be said about the river system
It is in balance
67
what controls catchment runoff
regional climate, topography, geology, soils, vegetation and land use
68
Was is the nature of sediment delivery
Normally highly pulsed
69
When can sediment enter the river directly
When river banks erode
70
Where does the bulk of a rivers sediment come from
Headwaters
71
what performs the drainage of earths land
stream networks
72
what are stream reaches embedded into
stream networks
73
what are network patterns
the spatial arrangement of river channels in the landscape
74
what is the pattern of most drainage systems
dendritic
75
what is the angle of stream junctions downstream
below 90 degrees
76
who created stream order
strahler
77
which channel shape is treelike, with no preferred channel orientation, acute intersection angles
dendritic
78
what can channel junctions be termed
nodes
79
what is drainage basin magnitude
the amount of exterior links a channel contains
80
what is the londitudinal profile of a stream
plot of the elevation versus length
81
what is the normal shape of a stream longitudinal profile
concave
82
what is a streams base level
the elevation of the stream near the river mouth
83
what is a distributary channel
one that slpits of into multiple channels, like deltas or alluvial fans
84
what is the drainage density of a stream system
total length of streams, divided by the area
85
what are exorheic systems
ones that drain into the sea//ocean
86
what are endorheic systems
rivers drain into the inland seas, or wet lands, which is then evaporated
87
what did Vorosmarty use to find out basin sizes and river stream orders
STN-30p
88
compared with UNESCO sizes, how much did the STN-30p differ in size
=13%
89
how many true first order streams are there worldwide
14,500,000
90
what are the only 2 6th order (true 11th) streams
Amazon and Lena
91
what is the average length of a 1st order stream
0.78km
92
how many second order streams are there
4,150,000
93
what percentage of global rivers are exorhiec
87%
94
What are the 4 causes of convexities in river longitudinal profile
Local rock formations, coarse sediment, tectonic uplift, drop in base level
95
What is a knick point
Pronounced steepening convexities
96
What happens to sediment size as we go doenstream
It decreases
97
What 2 processes reduce grain size over distance
Grain breakdown by abrasion, selective transport of finer sediments
98
what is the difference with Anabranching reaches compared with braided rivers
anabranching rivers are fixed in position
99
what is the shape of a normal cross section shape
concave but asymetrical
100
What was the main control on sediment concentration in the Yorkshire stream tested by naden and cooper
Land cover and use
101
What is a rill
A shallow channel cut into the soil by the erosive action of flowing water
102
What is the larger stage up from rills
Gullies
103
How are rills initiated
When water erodes topsoil on hillsides
104
What is over come to lead to rill creation
Soil shear stress is over come by water shear stress

Year 3 Rivers And Sediment (12 decks)

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