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GEO1020 > Fluvial Processes > Flashcards

Fluvial Processes Flashcards

1
Q

Who is the knowledge of water and sediment behaviour within river channels important to? (3)

A

Engineers
Civil defence
Geomorphologists

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2
Q

Why is knowledge of water and sediment behaviour within river channels important to engineers?

A

Managment

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3
Q

Why is knowledge of water and sediment behaviour within river channels important to civil defence?

A

Risk mitigation

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4
Q

Why is knowledge of water and sediment behaviour within river channels important to geomorphologists?

A

Landscape evolution

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5
Q

What are 4 fundamental flow characteristics?

A

Uniform/ non- uniform flow
Steady/ unsteady flow
Laminar/ turbulent
Tranquil/rapid

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6
Q

How can you identify if a flow is uniform or not?

A

Look at the velocity and see if it is constant within the cross-section

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7
Q

How do you tell if the flow is steady or not?

A

See if the velocity is constant with time

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8
Q

How do you identify a laminar flow?

A

Reynold’s number is less than 500

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9
Q

How do you identify a turbulent flow?

A

Reynold’s number is more than 2500

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10
Q

What is energy the product of?

A

Force x Distance through which the force acts

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11
Q

What 4 things is energy in streams expended in?

A

Overcoming viscous shear and turbulence (internal friction)
Boundary friction
Channel erosion
Sediment transport

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12
Q

What is the hydraulic radius?

A

A/P

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13
Q

What is shear stress?

A

The rate of change of vertical velocity

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14
Q

What two things can cause resistance to flow?q

A

Form roughness

Grain roughness

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15
Q

What is stream power measured in?

A

Wm-2

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16
Q

What is the equation for stream power

A

Water density x Gravity x Discharge x Slope

(divided by) Channel width

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17
Q

What are two direct methods of bedload measurements?

A

Sediment traps

Pressure pillows

18
Q

What is an indirect method of bedload measurement?

A

Acoustic monitoring

19
Q

What are two partial methods of bedload measurement?

A

Tracers (painted pebbles/ radio pebbles)

Sediment budget- channel cross section change

20
Q

What curve shows bedload measurement?

A

Hjulström curve

21
Q

In terms of bedload entrainment, what is velocity used to define?

A

A critical threshold for entrainment

22
Q

When does bedload transport occur?

A

Once the critical threshold for entrainment in exceeded

23
Q

What does entrainment represent?

A

The balance of applied vs resisting forces

24
Q

What creates a vertical pressure gradient?

A

The velocity difference between the top and bottom of a grain

25
Q

What is eddying?

A

The movement of water in a circular way

26
Q

What are 3 sources of suspended sediment?

A

Weathering regime
Slope regime (degree of “coupling”)
Fluid transfer regime

27
Q

What curve looks at suspended sediment?

A

Suspended sediment rating curves

28
Q

What are two key thresholds for erosion/entrainment?

A

Particle size, shape and density

Cohesive/ non- cohesive

29
Q

Give two examples of cohesive sediments

A

Clay

Silt

30
Q

When are cohesionless sediment grains entrained?

A

When there is a great enough force

31
Q

What are 3 measurement techniques?

A

Units/parameters
Manual/point sampling
Automated sampling

32
Q

What loops can be found on suspended sediment rating curves?

A

Hysteresis loops

33
Q

What is shown on suspended sediment rating curves?

A

Discharge vs suspended sediment concentration

34
Q

What 3 things control suspended sediment concentration?

A

Size of particles (settling velocity)
Degree of turbulence
Sediment availability

35
Q

What 3 things affect the degree of turbulance?

A

How uniform the distribution of grains is
Mixing (diffusion)
Pulses of turbulence (eddies)

36
Q

What is diffusion the balance of?

A

Upward and downward movement

37
Q

What 4 things does the rate of settling depend upon?

A

Class diameter
Specific gravity of clast
Grain shape
Stokes Law

38
Q

What is the equation for the rate of settling?

A

Drag coefficient x (Diameter/2)^2

39
Q

What 5 things to do with chemistry determine water quality?

A 
pH
Alkalinity (hardness)
Ions in solution (anions, cations)
Oxygen-reduction potential or dissolved O2
Organic species
40
Q

What 6 physical factors determine water quality?

A 
Colour
Taste
Odour
Temperature
Suspended sediment
Bacterial counts

GEO1020 (16 decks)

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