Lecture #4

Question 1

3 characteristics of discharge

Answer 1

• Channel shape characteristics determines how discharge is allocated
• imposed by watershed
• Independant variable

Question 2

What does the shape of the cross section affect?

Answer 2

Width of channel

-square vs. irregular channel

Question 3

What does resistance characteristics affect?

Answer 3

depth and velocity

Question 4

What is the resistance to flow based on?

Answer 4

Characteristics of the channel itself

Question 5

What is the main cause of resistance in the river channel?

Answer 5

The roughness of the bed itself

Question 6

What is the velocity at the bed?

Answer 6

0

Question 7

What is the momentum extraction?

Answer 7

The flow has momentum that is being transferred to the boulder or other object

Question 8

What is the driving force the same as?

Answer 8

Bed shear stress

-Gradient of the channel and the wright of the water acting down the gradient of the channel

Question 9

Where can shear stress act on in the water?

Answer 9

SS is anywhere and there is a shear stress acting on it

Question 10

Where is shear stress 0?

Answer 10

At the surface

-it varies linearly in between

Question 11

What is the vertical velocity gradient?

Answer 11

rate of change of velocity which elevation above bed

Question 12

What happens to the driving force when you increase velocity?

Answer 12

it increases as well

Question 13

Which area has the highest rate of displacement?

Answer 13

Highest at the bed

Steepest gradient

Question 14

As elevation increases, what does that do to the velocity?

Answer 14

Velocity increases too but the rate if increase decreases upwards

Question 15

What are the 2 different states of flow?

Answer 15

Turbulent

Laminar

Question 16

What are Turbulent and Laminar flow defined by?

Answer 16

Reynolds #

-w x v x d/viscosity

Question 17

What flow do you get when Reynolds number is greater than 5000?

Answer 17

Turbulent flow

Question 18

What flow do you get when Reynolds number is less than 2000

Answer 18

Laminar

Question 19

Why is velocity lowered in turbulent waters?

Answer 19

Slow and fast moving water mixes together reducing the overall velocity

Question 20

Where would you find subcritical conditions?

Answer 20

Deep and slow moving water

Question 21

Where would you find supercritical conditions?

Answer 21

Shallow and fast water

Question 22

What number do we use to define subcritical and supercritical conditions?

Answer 22

Froud #

- v/sqrt(g x d)

Question 23

What flow conditions do we get if Frouds # is greater than 1?

Answer 23

supercritical

Question 24

What flow conditions do we get if Frouds # is less than one?

Answer 24

Subcritical

Question 25

What are the 2 methods of transferring sediment material within an Alluvial channel?

Answer 25

Bed load

Suspended Load

Question 26

What characteristic of a particle determines the resisting force?

Answer 26

Particle size

Question 27

What moves the particles down the channel?

Answer 27

Driving force

-we use bed shear stress normally

Question 28

What is the Critical Bed Shear Stress?

Answer 28

Stress at which particles begin to move

Question 29

What happens to critical shear stress as particle size increases?

Answer 29

Critical shear stress needs to increase as well in order to move the particles