Fluvial Processes

Question 1

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

Answer 1

Engineers
Civil defence
Geomorphologists

Question 2

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

Answer 2

Managment

Question 3

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

Answer 3

Risk mitigation

Question 4

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

Answer 4

Landscape evolution

Question 5

What are 4 fundamental flow characteristics?

Answer 5

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

See if the velocity is constant with time

Question 8

How do you identify a laminar flow?

Answer 8

Reynold’s number is less than 500

Question 9

How do you identify a turbulent flow?

Answer 9

Reynold’s number is more than 2500

Question 10

What is energy the product of?

Answer 10

Force x Distance through which the force acts

Question 11

What 4 things is energy in streams expended in?

Answer 11

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

Question 12

What is the hydraulic radius?

Answer 12

A/P

Question 13

What is shear stress?

Answer 13

The rate of change of vertical velocity

Question 14

What two things can cause resistance to flow?q

Answer 14

Form roughness

Grain roughness

Question 15

What is stream power measured in?

Answer 15

Wm-2

Question 16

What is the equation for stream power

Answer 16

Water density x Gravity x Discharge x Slope

(divided by) Channel width

Question 17

What are two direct methods of bedload measurements?

Answer 17

Sediment traps

Pressure pillows

Question 18

What is an indirect method of bedload measurement?

Answer 18

Acoustic monitoring

Question 19

What are two partial methods of bedload measurement?

Answer 19

Tracers (painted pebbles/ radio pebbles)

Sediment budget- channel cross section change

Question 20

What curve shows bedload measurement?

Answer 20

Hjulström curve

Question 21

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

Answer 21

A critical threshold for entrainment

Question 22

When does bedload transport occur?

Answer 22

Once the critical threshold for entrainment in exceeded

Question 23

What does entrainment represent?

Answer 23

The balance of applied vs resisting forces

Question 24

What creates a vertical pressure gradient?

Answer 24

The velocity difference between the top and bottom of a grain

Question 25

What is eddying?

Answer 25

The movement of water in a circular way

Question 26

What are 3 sources of suspended sediment?

Answer 26

Weathering regime Slope regime (degree of "coupling") Fluid transfer regime

Question 27

What curve looks at suspended sediment?

Answer 27

Suspended sediment rating curves

Question 28

What are two key thresholds for erosion/entrainment?

Answer 28

Particle size, shape and density | Cohesive/ non- cohesive

Question 29

Give two examples of cohesive sediments

Answer 29

Clay | Silt

Question 30

When are cohesionless sediment grains entrained?

Answer 30

When there is a great enough force

Question 31

What are 3 measurement techniques?

Answer 31

Units/parameters Manual/point sampling Automated sampling

Question 32

What loops can be found on suspended sediment rating curves?

Answer 32

Hysteresis loops

Question 33

What is shown on suspended sediment rating curves?

Answer 33

Discharge vs suspended sediment concentration

Question 34

What 3 things control suspended sediment concentration?

Answer 34

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

Question 35

What 3 things affect the degree of turbulance?

Answer 35

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

Question 36

What is diffusion the balance of?

Answer 36

Upward and downward movement

Question 37

What 4 things does the rate of settling depend upon?

Answer 37

Class diameter Specific gravity of clast Grain shape Stokes Law

Question 38

What is the equation for the rate of settling?

Answer 38

Drag coefficient x (Diameter/2)^2

Question 39

What 5 things to do with chemistry determine water quality?

Answer 39

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

Question 40

What 6 physical factors determine water quality?

Answer 40

``` Colour Taste Odour Temperature Suspended sediment Bacterial counts ```