Stormwater test two UPDATED ACTUAL
Questions and CORRECT Answers
What is the primary need for flow control in stormwater management? - CORRECT
ANSWER - To let the water stores in detention basins out at a slower rate than it was
flowing in
Which is the least restrictive type of outlet with flow depth: a weir, an orifice, or a pipe? -
CORRECT ANSWER - Weir
If the inlet is submerged and a pipe is very short, it may actually act as what? - CORRECT
ANSWER - An orifice
Why can't we just design the outlet control for the biggest storm? - CORRECT
ANSWER - If you design the outlet for the biggest storm you are not going to stop any
water flow for any storm except the biggest one
What two things must be done by a stormwater conveyance? - CORRECT ANSWER -
•Handle the peak flow without failure •Not have any erosion
If I have steady - CORRECT ANSWER - state flow, the friction force acting upslope is
equal to what other force?- Actually velocity squared
For flow in a channel, what two factors control the resisting friction force? - CORRECT
ANSWER - How rough the surface is, and how much water we have in contact with the
surface!
\Write out the Manning's Equation, and define the terms. - CORRECT ANSWER -
V=(1.49/n)*R^⅔*S^½ V- velocity in ft/s, n-Manning's roughness, S- channel grade in ft/ft, R-
hydraulic radius
, Describe (in words) what the "hydraulic radius" really means. - CORRECT ANSWER -
How much water in your channel is actually touching "stuff"
What is the hydraulic radius for very shallow even flow? - CORRECT ANSWER - Very
shallow even flow will have a large hydraulic radius and a slower velocity
Designing a channel requires solving Manning's Equation and what other equation
simultaneously? - CORRECT ANSWER - Continuity Equation
The pipe flow equation presented in class says that the flow rate depends on the loss coefficient
and what two other Inputs? - CORRECT ANSWER - Cross sectional area and the
difference in water elevation
How do we figure out the flow rate that our channel must handle? - CORRECT
ANSWER - Use the rational method or the TR55 method
The Manning's n roughness values depend on not just the channel material, but what other
channel characteristic? - CORRECT ANSWER - Morphology of the channel
Use of Manning's equation generally assumes that the flow depth is much greater than what other
measurement? - CORRECT ANSWER - Roughness element
Describe a case in which Manning's n can change rather suddenly. - CORRECT
ANSWER - If you have a channel that is lined with grass but the flow rate is so fast that it
lays the grass down flat
How do you change your channel design if the velocity is higher than the permissible velocity
for our soil type and cover? - CORRECT ANSWER - Reduce the slope, make the channel
wider, use a different material
Questions and CORRECT Answers
What is the primary need for flow control in stormwater management? - CORRECT
ANSWER - To let the water stores in detention basins out at a slower rate than it was
flowing in
Which is the least restrictive type of outlet with flow depth: a weir, an orifice, or a pipe? -
CORRECT ANSWER - Weir
If the inlet is submerged and a pipe is very short, it may actually act as what? - CORRECT
ANSWER - An orifice
Why can't we just design the outlet control for the biggest storm? - CORRECT
ANSWER - If you design the outlet for the biggest storm you are not going to stop any
water flow for any storm except the biggest one
What two things must be done by a stormwater conveyance? - CORRECT ANSWER -
•Handle the peak flow without failure •Not have any erosion
If I have steady - CORRECT ANSWER - state flow, the friction force acting upslope is
equal to what other force?- Actually velocity squared
For flow in a channel, what two factors control the resisting friction force? - CORRECT
ANSWER - How rough the surface is, and how much water we have in contact with the
surface!
\Write out the Manning's Equation, and define the terms. - CORRECT ANSWER -
V=(1.49/n)*R^⅔*S^½ V- velocity in ft/s, n-Manning's roughness, S- channel grade in ft/ft, R-
hydraulic radius
, Describe (in words) what the "hydraulic radius" really means. - CORRECT ANSWER -
How much water in your channel is actually touching "stuff"
What is the hydraulic radius for very shallow even flow? - CORRECT ANSWER - Very
shallow even flow will have a large hydraulic radius and a slower velocity
Designing a channel requires solving Manning's Equation and what other equation
simultaneously? - CORRECT ANSWER - Continuity Equation
The pipe flow equation presented in class says that the flow rate depends on the loss coefficient
and what two other Inputs? - CORRECT ANSWER - Cross sectional area and the
difference in water elevation
How do we figure out the flow rate that our channel must handle? - CORRECT
ANSWER - Use the rational method or the TR55 method
The Manning's n roughness values depend on not just the channel material, but what other
channel characteristic? - CORRECT ANSWER - Morphology of the channel
Use of Manning's equation generally assumes that the flow depth is much greater than what other
measurement? - CORRECT ANSWER - Roughness element
Describe a case in which Manning's n can change rather suddenly. - CORRECT
ANSWER - If you have a channel that is lined with grass but the flow rate is so fast that it
lays the grass down flat
How do you change your channel design if the velocity is higher than the permissible velocity
for our soil type and cover? - CORRECT ANSWER - Reduce the slope, make the channel
wider, use a different material
