Chapter 13

Question 1

Where does channel flow come from?

Answer 1

from direct
precip, overland flow, soil
throughflow, or seepage from
groundwater.

Question 2

What is energy?

Answer 2

the fundamental motive force

Question 3

How much energy is used overcoming
frictional drag of the channel margin? What is it converted to? What is a major component of kinetic energy?

Answer 3

More than 95% of energy is used overcoming
frictional drag of the channel margin. Converted
to heat and lost to surroundings
* Velocity is a major component of kinetic energy
and is closely related to discharge

Question 4

influent channel

Answer 4

above the water table: losing water (can be dry during a dry season if it is feeding groundwater and is being fed only by precipitation)

Question 5

effluent channel

Answer 5

below the water table: gaining water (gaining water from groundwater)

Question 6

What does a hydrograph show?

Answer 6

-direct and indirect runoff; rising limb, recession curve

Question 7

How does impervious surfaces affect the hydrograph?

Answer 7

-additional impervious surface shortens the time and raises the peak

Question 8

Why does lag time occur

Answer 8

-lag occurs because it takes time for infiltration to occur before water begins to peak

Question 9

the larger the drainage area the ___

Answer 9

larger the discharge

Question 10

Channel dynamics

Answer 10

-resistance to flow is not only at the channel boundary but also within the fluid mass itself
-laminar flow: parallel flow lines
-turbulent flow: water travels obliquely to the general direction of flow (well mixed, more activity is going on and particles are changing more often, tends to move water faster (due to increased velocity, faster dissipation of energy than laminar flow) ; higher velocity = turbulent flow

Question 11

laminar flow

Answer 11

the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing

Question 12

turbulent flow

Answer 12

-turbulent flow: water travels obliquely to the general direction of flow (well mixed, more activity is going on and particles are changing more often, tends to move water faster (due to increased velocity, faster dissipation of energy than laminar flow) ; higher velocity = turbulent flow

Question 13

hydraulic radius

Answer 13

-measure of channel efficiency
Amount of water in contact with channel cross section
-amount of water in contact with channel cross section
-Higher hydraulic radius means more efficient channel
-R= A/2d+w

Question 14

a wide shallow channel is ___ than a compact one

Answer 14

-a wide, shallow channel is less efficient than a more compact one

Question 15

How can the flow of fluid in an open channel be expressed?

Answer 15

Flow of fluid in an open channel can be
expressed as a balance between the impelling
forces and resisting forces
-Manning equation
-velocity is function of channel roughness (n), hydraulic radius (R), and slow (s)
-n varies from 0.03 to 0.10 in natural streams
-easier to measure it today

Question 16

Stream power

Answer 16

-rate at which energy is expended
-increased mass and velocity of water result in greater capacity for work
-stream power is rate at which energy is expended
-most work is carried out at times of high discharge

Question 17

How can material in the channel be carried? (3 ways)

Answer 17

bed load: rolling along the channel floor
-suspended load: carried in suspension in the water (floating down the stream)
-solution load: minerals dissolved in the water (could be salts dissolved or oxygen dissolved in the water)

Question 18

At higher discharge: sediment concentration is __ and solute concentration is __

Answer 18

-sediment concentration is higher (figure a)
-solute concentration is lower (figure b)

Question 19

Stream power and critical power threshold

Answer 19

-power is greatest at higher gradients
-Downcutting: stream power > critical power
-lateral erosion
-alluviation: stream power < critical power

Question 20

alluviation

Answer 20

the process by which deposits of clay, silt, sand, or gravel occur in rivers, estuaries, or along shores of lakes or seas where velocity decreases
-process of depositing sediment

Question 21

Discharge equation

Answer 21

Discharge (Q) = wdv (m3 s−1 where Channel width (w)
* Channel depth (d)
Velocity of flow (V) (m s−1

Question 22

channel form changes

Answer 22

change in channel form that increases hydraulic radius makes discharge more efficient
-energy dissipation of stream: how energy in the streams is moving from faster waters to slower moving waters