# Exam 2 CB ```CLOSED NEIGHBOR - CLOSED NOTES - CLOSED BOOK
Exam 2
Part 1
CVEG 3223
Fall 2004
Name _____________________________
(Each question is worth 2 points)
1. If an engineer calculates a runoff estimation from any of the available methods and he or she gives the
answer to 4 or more significant digits (e.g. 123.4 cfs or 1234.5 cfs or 123.456 cfs etc.) does this make the
engineer look very intelligent or does it indicate that they simply don’t understand the field of hydrology?
___ Very Intelligent
___ Clueless

P  0.2S2  give and what are the units of
2. What answer does the SCS Rainfall-Runoff equation  Q 

P  0.8S 

a.
b.
3. Name three accepted methods for estimating Peak Runoff.
a.
b.
c.
4.
Explain what C and CN tell us as they are used in their associated runoff estimation equations.
5.
A rainfall hyetograph shows (use “X” to mark all correct answers):
___
___
___
___
___
a. the total volume of rainfall for a storm event;
b. the cumulative volume of rainfall with time over the duration of a storm event;
c. the variation of rainfall over a watershed for a storm event;
d. the intensity or volume of rainfall with time over the duration of a storm event;
e. none of the above
6.
In hydrology, why do we calculate the time of concentration for a watershed?
7. What is the graph below used for?
100
Percent of Point Rainfall for Given Area
24 hr duration
90
12 hr duration
6 hr duration
80
3 hr duration
2 hr duration
70
1 hr duration
60
30 min duration
50
0
50
100
150
200
250
300
Area (mi2)
8. Given the site below, what is the time of concentration at the following points?
Point C
Point D
Point E
tc = _________
tc = _________
tc = _________
Subbasin 1
A = 5 acres
C = 0.5
tc = 7 min
Subbasin 3
A = 6 acres
C = 0.3
tc = 14 min
Subbasin 2
A = 6 acres
C = 0.4
tc = 11 min
C
E
D
inlet to
channel
(typical of 3)
Channel 1
t travel = 2 min
Channel 2
t travel = 4 min
350
400
9. Explain how the following type of equation is developed.
Q  2.35A 0.41SL0.17 RI 2  32.04 ST  8 0.65 13  BDF  0.32 IA 0.15
10. The equation Q  CAh 0.5 is typically used to model:
___ flow through an orifice
___ flow in a pipe
___ flow over a weir
___ flow in an open channel .
11. Hydrologic soil groups (A, B, C, &amp; D) are used primarily to take into account what soil
characteristic?
12. What would you expect to happen to the runoff characteristics of an area after it is developed (roads
and buildings are constructed)?
(“X” ALL that probably apply)
___ The total amount of runoff would increase.
___ The time of concentration would decrease.
___ The velocity of the runoff would decrease.
___ The peak runoff flowrate would increase.
___ None of the above
13. What is the key underlying model used to calculate time of concentration for sheet flow, shallow flow
and channel flow? (Hint: we ain’t talkin’ about, v = L/t – which is NOT a model)
14. If you needed to analyze the frequency of the mass of a pollutant that is transported past a point in a
stream during storm events, would it be reasonable to use the statistical methods outlined in Chapter 5
(plotting pollutant yield vs exceedence probability)? Why not or why?
___ Yes
___ No
Because -
15. In the City of Fayetteville Stormwater Management and Erosion Control Plan Submittal Procedures,
the Final Drainage Report Checklist gives 30 items that must be included in a Final Drainage Report for
any development. What are the general categories of information that those thirty items would fall into.
(I have given you 10 spaces; but, you do not necessarily need all ten). If a category name you list is not
self evident as to what type of information would go into that category, give some examples.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
16. Beside each type of surface, write the corresponding letter (a, b, c, or d) for the most probable
Manning’s n value:
A. ___ Dense underbrush
a. biggest n (0.8)
B. ___ Glass
b. almost biggest n (0.2)
C. ___ Bare earth, concrete
c. almost lowest n (0.1)
D. ___ Long grass
d. lowest n (0.01)
17. Draw a line in the general direction (trending upward, flat, trending downward, middle pointed
upward, middle pointed downward, middle pointed to the right, middle pointed to the left) you would
expect for a typical DDF curve.
Precipitation (in)
10
1
0.1
0.01
0.1
1
10
100
Duration (hrs)
18. In developing the SCS Rainfall-Runoff relation, the total rainfall was separated into three
components. Place an “X” beside any of the following that are those components.
___ antecedent soil-moisture
___ initial abstraction
___ direct runoff
___ base flow
19. Which of the following are factors in directly estimating CNs for urban land uses? Place an “X”
beside any of the following that apply.)
___ soil type
___ percent imperviousness
___ percent of unconnected imperviousness
___ percent of the watershed that is sewered
___ time of year
___ all of the above
20. Delineate the drainage basin for the point A (yellow dot) in the map below.
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