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DES 602 – Urban Storm Drain Design
Assessment Instrument – Pilot – July 2013
Instructions
This examination is an assessment of knowledge acquired during the DES602
course. Participants may use the course materials to assist in selecting the best
answers to each question.
1) What is “time of concentration?”
A. The time from beginning of rainfall until the peak outflow
B. The time it takes a water drop to travel from the most hydrologically remote
point of a drainage area to the point of interest
C. The travel time through a storm sewer system
D. The time between the beginning of rainfall and the beginning of runoff
2) What is rainfall intensity?
A.
B.
C.
D.
How much rain falls in a given time
How hard it is raining
Depth of rain divided by time of accumulation
All of the above
3) What factors influence ponded width of water on a roadway?
A.
B.
C.
D.
Transverse slope
Longitudinal slope
Inlet spacing
All of the above
4) What is “contributing area?”
A.
B.
C.
D.
Area that is immediately adjacent to the point of interest
Area that is not immediately adjacent to the point of interest
Area where water drains away from the point of interest
Area where water drains to the point of interest
5) How does roadway longitudinal slope influence ponded width?
A.
B.
C.
D.
By increasing or decreasing velocity
By increasing or decreasing area of flow
By increasing or decreasing depth of flow
All of the above
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6) In the Rational Equation, Q=(1/z) C*I*A, the term I is
A.
B.
C.
D.
Rainfall intensity
Contributing area
Rational Coefficient
Dimensional correction coefficient
7) Which of the following may result in increased computed rainfall intensity?
A.
B.
C.
D.
improved flow paths (i.e. drainage ditches)
a land use change from pasture to dense forest
construction of detention ponds
installation of regulatory structures (dams) in the watershed
8) What effect does urbanization have on runoff?
A.
B.
C.
D.
None
Decreased runoff due to increased storage
Increased runoff due to decreased infiltration
Increased runoff due to improved flow efficiency
9) What restrictions exist on the use of the rational equation?
A.
B.
C.
D.
Less than 200 acres
No intensities computed for less than 10 minute duration
Developed watersheds only
A and B
10) What factors influence inlet spacing?
A.
B.
C.
D.
E.
Contributing area
Roadway cross section/transverse slope
Roadway cross section/auxiliary lanes
Roadway longitudinal slope
B, C, and D
11) What is meant by the slope term in Manning’s equation?
A.
B.
C.
D.
The longitudinal slope of the channel
The sideslope of the channel
The friction slope of the energy grade line
A and B
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12) Which inlets are most commonly used on TxDOT projects with curb and gutter?
A.
B.
C.
D.
Curb Inlet type C (IL-C standard)
Combination inlets
Drop inlets
Manholes
13) Why would one want to design for carryover?
A.
B.
C.
D.
Make the best use of inlet efficiency
Inlet efficiency drops off as depth decreases
The most downstream part of the inlet is very inefficient
All of the above
14) At what depth to diameter (d/D) ratio does a circular pipe flowing partially full
reach peak (maximum) discharge?
A.
B.
C.
D.
.5 (half full)
.76
.85
.99
15) What are the lines called that carry accumulated flow in a system?
A.
B.
C.
D.
Hydraulic grade lines
Energy grade lines
Laterals
Trunk lines
16) What does a pump performance curve display?
A.
B.
C.
D.
Depth versus head
Net positive suction head
Discharge versus head
Discharge versus efficiency
17) How should energy and velocity be managed as water proceeds downstream in
a storm sewer?
A. Energy should be conserved as much as possible
B. Velocity should be as high as possible and energy conserved
C. Velocity should not decrease, and the energy grade line should be carefully
managed
D. Energy and velocity should be balanced
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18) At what maximum angle should a conduit join a junction box?
A.
B.
C.
D.
5 degrees
10 degrees
30 degrees
45 degrees
19) Figure 1 is a set of pump performance curves. What is the total dynamic head
added by a pump operating on curve 2 at 12,000 gallons per minute?
Figure 1. Pump Performance Curves
A.
B.
C.
D.
74%
87 ft
51 ft
1450 rpm
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20) What is the purpose of the angle restriction on conduits joining with junction
boxes?
A.
B.
C.
D.
Reduce vortices in the boxes
Reduce inlet/exit losses from the boxes
Control the amount of reinforcing steel compromised
Prevent high-angle pipe end cuts
21) What physical feature should match or drop when crossing a junction?
A.
B.
C.
D.
Flow line
Manhole cover
Conduit soffits
Riser
22) What is needed before one can design and construct a storm sewer outside of
TxDOT right-of-way?
A.
B.
C.
D.
a hydraulic jump
an increase in channel slope
a decrease in channel width
an advanced funding agreement and funds in escrow
23) What is a system curve?
A.
B.
C.
D.
The performance curve of an entire hydraulic system
A curved sewer trunk line formed by “pulling” pipe joints
The combined pump curves of all pumps in a system
A storm sewer system designed for variable performance
24) The D+1 specification on the inlet specifications is
A. A minimum standard, that is the inlet depth should not be smaller than D+1
B. A fixed standard, that is the inlet depth should be exactly D+1
C. A maximum standard, that is the inlet depth should not be larger than D+1
25) Inlet extensions should be set to one side of the inlet because
A.
B.
C.
D.
hydraulics requires the extension to be upstream
structural reasons to prevent inlet box failure from two cantilever portions
hydraulics requires the extension to be downstream
to minimize the angle of the pipe-inlet connection.
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