1. Executive Summary
This document reports on the design of a project of urban hydraulic structures in Davis,
CA. The designed structures are a drainage channel, gutter, storm sewer inlets and pipe, a
culvert and a detention pond. These structures are designed to a peak runoff from a 10-year
storm in Davis. This peak runoff is obtained from a composite water shed consisting of two
surfaces, a playing field (grass) and a school yard (concrete). The runoff from the water shed
enters into a drainage channel which then goes through a culvert into the detention pond,
which is located 4000 (ft) away. The channel is not only meant to endure the peak runoff but
also is meant to be environmentally friendly and be an asset to the community. Adjacent to the
channel, is a residential area of 40 homes and a road. The gutter and sewer drainage system
will run parallel to the drainage channel and connect with it 3500 (ft) downstream. A culvert is
designed to get the discharge from the drainage channel through road crossing and into a
detention pond. The detention pond is designed to detain the runoff and release the water at
predevelopment rate.
2. Estimation of Peak Runoff
1. Purpose:
The purpose of this assignment is to estimate the peak runoff of a School Yard and Playing field
that share a brick Channel (See Figure 3). The channel was designed for a 10-year storm in
Davis. Six estimations were made: Velocity Method, Wong’s Formula, Kerby’s Formula, FAA
Formula, Morgali and Linsley’s Formula, Chen and Yen and Chow’s Formula. Using Wong’s
Formula, two methods were to be used. One method was treating the water sheds individually
and the other was using a composite water shed. Though it was not required, both of these
methods were used for each formula to get a wider array of results.
2. Methods finding tc
a. Velocity Method
𝑉𝑟𝑢𝑛𝑜𝑓𝑓 was to be found for each surface first, with a given S (Table 1), using Figure 2. (2) was
used, with known values of 𝑉𝑟𝑢𝑛𝑜𝑓𝑓 and L (Table 3), to find 𝑡 𝑐. To find 𝑡 𝑐 𝑡𝑜𝑡𝑎𝑙 for each
watershed, 𝑡 𝑐 (brick) was added to the other two values 𝑜𝑓 𝑘𝑛𝑜𝑤𝑛 𝑡 𝑐 (Table 3). See Sample
calculations for clarification.
*See Table 3 for results
b. Wong’s Method
(3) Requires the use of specific units so, conversions are required (Table 2). With known values
(Table 1, Table 4) and with equations (1) and (3) an explicit formula can be obtained with
𝑡 𝑐 𝑎𝑠 𝑎 𝑓𝑢𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡 𝑐. Iterations are required to obtain 𝑡 𝑐 𝑓𝑜𝑟 𝑒𝑎𝑐ℎ 𝑠𝑢𝑟𝑓𝑎𝑐𝑒. See sample
calculations for clarification.
*See Table 4 for results
c. Yen and Chow’s Formula
Like Wong’s method, conversion are required (Table 2). Known values (Table 1, Table 5)
inserted into (4) give 𝑡 𝑐 𝑓𝑜𝑟 𝑒𝑎𝑐ℎ 𝑠𝑢𝑟𝑓𝑎𝑐𝑒.
*See Table 5 for results
d. Kerby’s Formula
This formula requires no iterations and uses (5) with known values from (Table 1, Table 6). Also
conversions were needed (Table 2).
*See Table 6 for results
3. e. FAA Formula
Requires the same steps as Kerby’s Formula but using (6) and (Table 7)
*See Table 7 for results
f. Morgali and Linsley’s Formula
Requires the same steps as Wong’s Method, including iterations but, using (7) and (Table 8).
*See Table 8 for results
3. Process in finding 𝑸 𝒑
𝑡 𝑐 𝑡𝑜𝑡𝑎𝑙 𝑤𝑎𝑠 𝑓𝑜𝑢𝑛𝑑 𝑓𝑜𝑟 𝑒𝑎𝑐ℎ 𝑤𝑎𝑡𝑒𝑟𝑠ℎ𝑒𝑑 𝑏𝑦 𝑎𝑑𝑑𝑖𝑛𝑔 𝑡 𝑐 ( 𝑏𝑟𝑖𝑐𝑘) 𝑡𝑜 𝑡ℎ𝑒 𝑜𝑡ℎ𝑒𝑟 𝑡𝑤𝑜 𝑠𝑢𝑟𝑓𝑎𝑐𝑒𝑠.
Given values of 𝑡 𝑐 𝑡𝑜𝑡𝑎𝑙, (1) was used to find i for both water sheds. Given values of 𝐶𝑖 (Table
1), calculated values of i and using (8) 𝑄 𝑝 can be found for each watershed separately. When
using the composite method C can be found with given 𝐶𝑖 𝑎𝑛𝑑 𝐴𝑖 (𝑇𝑎𝑏𝑙𝑒 1)combined with (9).
𝑄 𝑝 (composite) is obtained by using values of C and 𝐴𝑡𝑜𝑡𝑎𝑙 . Conversions from feet to acres is
needed for (8) (Table 2).
*Composite method and Separate method were used for all six methods giving a total of 12 𝑄 𝑝
*These steps are used for each method and do not vary as long as time is in minutes. (See
Sample Calculations for Clarification)
4. Assumptions
Assumptions made when using the above mentioned methods are:
a. All coefficients for Brick are assumed to be the same as Concrete
b. Width of Brick Channel is zero
c. No water lost due to evaporation or absorption
5. Conclusion
An average 𝑄 𝑝 was found. The 𝑄 𝑝 with the lowest relative error to the average was found
using Wong’s method, when each watershed individually (Table 9). The variation between each
method can be seen in (Figure 3). Using Wong’s equation is recommended because it gives a
𝑄 𝑝 closest to the average value.
4. Appendix A: Results in Tables and Graphs
Table 1: W. Shed data
Concrete Playing fields Brick
L (ft) 900.000 1300.000 2300.000
L (m) 274.320 396.240 701.040
S 0.010 0.020 0.030
A (ft2) 2070000.000 2990000.000 0.000
A (acres) 47.521 68.641 0.000
Ci 0.900 0.250 0.700
C 0.516 0.516 0.516
Atotal
(acres)
116.162
Table 2: Conversion
factors
0.305 (m/ft)
43560.000 (ft/acre)
25.400 (mm/in)
60.000 (s/min)
Table 3: Velocity Method
Concrete
Playing
fields
Brick
5. Vrunoff (ft/s) 2.000 0.950 3.500
tc (min) 7.500 22.807 10.952
tc total (min) 18.452 33.759
i (in/hr) 1.034 0.810
Qpi = CiiA (ft3/s) 44.239 13.897
Qp total (ft3/s) 58.136
Qp = CiAtotal
(ft3/s)
48.531
Table 4: Wong's Formula
Concrete
Playing
fields
Brick
C wong 3.000 1.000 3.000
k 0.500 0.000 0.500
ν (m2/s) 8.74E-07 8.74E-07 8.74E-07
tc (min) 14.972 44.967 16.984
tc total 31.956 61.952
i (in/hr) 0.829 0.616
Qpi = CiiA (ft3/s) 35.456 10.565
Qp total 46.021
Qp = CiAtotal
(ft3/s)
36.896
6. Table 5: Yen and Chow's (1983) Simplified Formula
Concrete
Playing
fields
Brick
n 0.014 0.040 0.014
tc (min) 10.711 20.365 13.526
tc total (min) 24.237 33.891
i (in/hr) 0.930 0.808
Qpi = CiiA 39.759 13.873
Qp Total 53.633
Qp = CiAtotal
(ft3/s)
48.450
Table 6: Kerby's (1959) Formula
Concrete Playing fields Brick
Nk 0.02 0.400 0.020
tc (min) 9.411 38.502 11.285
tc total (min) 20.696 49.787
i (in/hr) 0.990 0.682
Qpi = CiiA (ft3/s) 42.328 11.696
Qp (ft3/s) 54.024
Qp = CiAtotal
(ft3/s)
40.845
7. Table 7 : FAA formula
Concrete
Playing
fields
Brick
Cr 0.900 0.300 0.900
tc (min) 10.746 41.013 11.916
tc total (min) 22.662 52.929
i (in/hr) 0.955 0.663
Qpi = CiiA (ft3/s) 40.843 11.371
Qp total (ft3/s) 52.214
Qp = CiAtotal (ft3/s) 39.711
8. Table 8: Morgali and Linsley's Formula
Concrete
Playing
Fields
Brick
n 0.014 0.040 0.014
tc (min) 25.053 50.908 29.559
tc total (min) 54.613 80.468
i (in/hr) 0.653 0.543
Qpi = CiiA (ft3/s) 27.932 9.318
Qp total (ft3/s) 37.250
Qp = CiAtotal (ft3/s) 32.541
Table 9: Relative Error to the Average
Qp Relative error
Velocity Separate 58.136 0.272
Composite 48.531 0.062
Wong Separate 46.021 0.007
Composite 36.896 0.192
Yen Separate 53.633 0.174
Composite 48.450 0.060
Kerby Separate 54.024 0.182
Composite 40.845 0.106
FAA Separate 52.214 0.143
Composite 39.711 0.131
Morgali Separate 37.250 0.185
Composite 32.541 0.288
Average 45.688 0.000
9. Figure 1: Slope vs Runoff Velocities for Various Surfaces (Meadows, Chapter 2)
10. 1 2
Velocity Method 58.136 48.531
Wong's Formula 46.021 36.896
Yen and Chen's Formula 53.633 48.450
Kerby's Formula 54.024 40.845
FAA Formula 52.214 39.711
Morgali Formula 37.250 32.541
Average Qp 45.688 45.688
0.000
10.000
20.000
30.000
40.000
50.000
60.000
70.000
Qp(ft3/s)
1= Separate
2= Composite
Figure2: Comparison of Qp
Velocity Method
Wong's Formula
Yen and Chen's Formula
Kerby's Formula
FAA Formula
Morgali Formula
Average Qp
15. Drainage Channel
Introduction:
This report will discuss the development of a channel designed for a 10 storm from a Davis
California water shed. The channel will convey the runoff of the water shed to a detention
pond that is 4000 feet away. This channel is designed to be environmentally friendly and
aesthetically pleasing. With that in mind, the channel has to certain requirements.
Requirements can be seen in Table 1 below
Table 1: Constraints,
excavated volume and
footprint
Constraints Actual
Fr < .8 0.16
V < 7 (ft/s) 1.14
Yn < 5 (ft) 3.41
V (ft3) 516349
Foot Print
(ft2) 14000000
Procedure:
Flow master was used for calculations of water depth and velocity. The trickle channel was
designed at 10% peak flow which was given to be 55 (cfs). At 10% peak flow, and desired
dimensions (can be seen in table 2), water elevation was 1.96 ft. This calculation leads to the
design height of the trickle channel to be 2 ft.
Table 2: Trickle
Channel
SS 0.5
B (ft) 3
Height (ft) 2
Yn (ft) 1.96
n (rip rap) 0.069
16. Flood plane was designed at a 100% peak flow. Flow master used Lotters method to find the
combined Manning’s coefficient. Normal depth plus 1 foot water board came to be 4.41 feet.
Because of this water depth the channel was designed at a depth of 4.5 feet. See figure 1 for
clarification. Cross section was designed using Auto Cad. The details of the flood plain can be
seen below in table 3.
Table 3: Flood Plain
SS (left) 1
Top Width (ft) 37.5
A (ft2) 86.13
Bottom Width (ft) 25
SS (right) 4
Figure 1: Cross
Section of Channel
17. Vegetation:
The channel is not only to be functional in the sense of moving the water but also is to be
pleasing to the eye and environmentally friendly. Rip Rap (150 mm) was used for the trickle
channel because it looks natural and will protect the channel when under constant flow. The
flood plain, however, on the left side consists of larger brush and bushes such as Woolly Blue
Curls and California buck wheat. This side of the channel would be for looking only and will be
very concentrated with plants. The right side of the flood plan is more for recreational use in
the off season. The sloped area will have short grass (Torrey’s Melic Grass). The flat part will
be a place for walking and will have Manzanita trees. The flat area will also have a variety of
flower such as the Humboldt Lily and the Red Columbine. Manning’s Coefficient for each
section can be seen below in table 4. Pictures of vegetation can be seen in the Appendix.
Table 4: Manning’s
coefficient
surface n
heavy bush 0.045
short grass 0.03
trees and plants 0.06
rip rap 0.069
Meander Rating Curve and Channel Depth:
In order to preserve a natural look, the channel will not be straight. There will be two big
curves with an equal radius of curvature of 1750 ft. Each curve will be a quarter circle that and
small straight segment at the beginning and end of channel (see figure 2)
18. 4
Figure 2: Birds Eye View of Channel
Due to meander the water will rise a bit. The value is so small it does not affect our design. R is
much greater the Base width so there will not be any problems due to meander and velocity.
The depth of the flow channel at 3500 feet is the slope multiplied by 3500 feet plus the original
depth of the channel 4.5 feet. The depth of the channel at 3500 feet is 8 feet. An analysis of
normal depth vs. flow was made using excel and flow pro the results can be seen below in
Figure 3. As can be seen in the figure even at double capacity the channel will still not over flow
due to the free board requirement of 1 foot.
19. Figure 3: Water Surface Elevation vs. Discharge
Costs:
The costs of the project will consist of maintenance, volume of excavated area, foot print, labor
and materials used. Table 5 shows the specifics of footprint and excavated volume.
Table 5: footprint and
volume
A (ft2) 86.13
L (ft) 5995
V (ft3) 516349
R (ft) 1750
Distance (ft) 4000
Foot Print
(ft2) 14000000
20. Using Perimeter of a half circle the Length of the Channel could be found. Perimeter multiplied
by cross sectional area gives excavated volume. The Diameter of the circle curve multiplied by
the Distance the channel travels horizontally gives the footprint.
Justification:
Cross section was chosen to be irregular because it gives a natural look to the channel. The
steeper side is meant to be more for wildlife such as bugs and animals while the less steep side
can be more for recreation for human beings. Rip rap was used for the trickle channel the
trickle channel can be full all throughout the year. Meander was chosen to be 2 sets of quarter
circles for simplicity in the calculations of the footprint and perimeter. Also curves were chosen
to give a less man made look to the channel. Straight channels do not happen in nature.
Benefits of the flowers chosen were mainly for their appearance. The flowers are very pleasing
to look at and like all plants chosen for this channel they are native to California. The Humboldt
Lily and Red Columbine bloom during different months giving the area different colors during
different parts of the year. The Manzanita tree was chosen to give shade to people using the
area. These trees are a good size for shade and are not overly large. The bushes used on the
left side of the channel were picked mainly because they can survive when submerged in water
for short periods of time, which will be the case. Also the bushes make the steeper slope more
stable so the dirt does not slide. Both the Blue Curl and the Buckwheat require very little
maintenance which is the reason for putting them on the less accessible side of the channel.
Melic Grass was chosen because also it is a low maintenance plant. It was placed on the right
side because it is short and kids can play on the slope of the channel.
24. Gutter and Inlet Design
Introduction:
This design consists of a gutter inlet system to capture the runoff from a 10 year storm.
There are 40 identical homes that are on one side of the gutter drainage channel and a road
that is tree lined on the other side. The tree lining makes it so that there can be clogging. Hard
constraints have to be met. Gutter width has to be greater than spread.
25. Calculations
Before designing the gutter, time of
concentration (tc) and flow is needed to be
calculated for the watershed of houses and
road. Time of concentration is found using
Wong’s equation (1) combined with the
intensity equation for a ten year storm in
Davis (2):
𝑡𝑐 = (
0.21 ∗ (3.6 ∗ 106
∗ 𝑣) 𝑘
∗ (𝐶 ∗ 𝐿 𝑜
2−𝑘
)
𝑆 𝑜 ∗ 𝑖 𝑛
1+𝑘
)
1/3
(1)
𝑖 =
9.74
(𝑡 𝑑
0.608
+ 3.533)
(2)
tc was found to be 18.3 (min) and C was found to be .632. Through back calculation with
known tc value i is found to be 1.04 (in/hr). Note that conversion to metric were used in (1).
Using (3) flow (Q) is found to be 1.04 (cfs)
𝑄 = 𝐶𝑖𝐴 (3)
With the value of Q known, Flow master is used to calculate spread. Inputs can be found in
Table 1 above and Table 2 below.
Table 1: At a glance
Spread (ft) 1.68
Gutter width (ft) 3
Sw 2%
S Gutter 0.20%
Length between inlets
(ft)
350
Inlet Type Combination in
Sag
Inlet width (ft) 2
Inlet Length (ft) 3
Flowrate /Inlet (cfs) 1.04
Inlet # 4
Inlet Local Depression
(in)
6
Clogging 20%
Curb opening length (ft) 3
Curb height (ft) 0.4
26. Table 2: Initial Values
grass concrete House road gutter
Ci 0.13 0.7 0.4 0.9 0.7
S 0.05 0.05 0.02 0.002
Ai (ft2) 1000 400 2000 3500
C 0.632
Acomp (ft2) 6900
Acomp (acres) 0.158
L (ft) 20 20 n/a 50 350
L (m) 6.096 6.096 15.24 106.68
Cwong 1 3 3 3
kwong 0 0.5 0.5 0.5
v (m2/s) 8.74E-
07
8.74E-07 8.74E-07 8.74E-07
tc (min) 1.45 0.937306 2.147994 16.19682
tc tot (min) 18.3
i (in/hr) 1.04
Q per house (cfs) 0.104
Qtot (cfs) 1.04
Rolling slope is used with 4 total gutters. The spread is 1.68 (ft) which is less than the gutter
width of 3 (ft). Gutter Specs can be found in Tables 1 and 2 and are illustrated in Figures 1,2
and 3 below.
29. Costs
Table 3: Main Cost Items
Volume of excavation/gutter
(ft3)
Maintenance
Equipment
Labor
Material
Earth must be excavated in order to insert the gutter system. This will cost in labor and earth
removal. Equipment costs will be present to excavate and maintain the gutter. Maintenance to
unclog or fix gutter system when needed will cost money. Material in this case is concrete and
this can be a repeated cost if gutter system is ever replaced.
Justification
Rolling slope (illustrated in figure 3) is used because it minimizes the length of the downward
slope. Also it allows the water to flow into one larger inlet from two sides which allows for less
inlets. A slope width of 3ft is a typical width being that it is not abnormally large (over 3ft) nor
small. Four inlets were used as to not have too many inlets. Two would have been a small
amount of inlets to handle this large water shed. Inlet dimensions are in relation to the gutter
width. To keep the inlet from being wider than the gutter two feet was chosen as the width.
Assumptions
It is assumed that the gutter has a relatively tiny area so the area is ignored in our C
calculations. Gutter has the same coefficients as the concrete drive way as well as the asphalt
pavement.
Appendix A: Pictures of Inlets
32. Storm Sewer Design
Introduction:
The sewer starts from below the first inlet of the gutter which was designed in the previous
assignment. The designed sewer connects with drainage channel which was designed in
assignment 2. The sewer brings the runoff 3500 feet from house one to the drainage channel.
Different sized pipes will be used for the sewer at each inlet. Due to the accumulation of flow
the pipe sizes will need to increase. At a slope (So) of .0017 the sewer pipe enters into the
drainage channel with 2ft of cover.
Constraints:
1. The sewer pipes must be circular and of different diameters to accommodate the different
flow rates that will occur along its length.
2. The proposed pipe diameters must be available commercially. Commercially available pipe
diameters come in increments of 3”.
3. The ratio of water depth to diameter (y/D) in each pipe should be as close to the “most
efficient” value as possible. Most efficient value is .93. All ratios are at a minimum of .8
4. The minimum cover allowed is 2 ft. This is only applicable to pipe 4.
5. The flow velocity must be greater than 1 ft/s, and less than 10 ft/s. All velocities are at a
minimum of 2 ft/s.
Table 1: Actual Values
Pipe 1 Pipe 2 Pipe 3 Pipe 4
Shape Circular Circular Circular Circular
Diameter D (in) 12 15 18 21
Cover (ft) 2 >2 >2 >2
33. Velocity V (ft/s) 2 2.33 2.56 2.79
Depth to Diameter ratio y/D 0.8 0.82 0.83 0.8
Longitudinal Slope 0.0016 0.0016 0.0016 0.0016
Flow Q (cfs) 1.04 2.08 3.12 4.16
Calculations:
Q was found in the previous assignment. Q was found for 1 inlet so at each inlet Q is found to
be cumulative. This means that at inlet two Q is double and at inlet 3 it is triple and finally at
inlet 4 Q is quadruple. Flow master was used to find the diameters and water depths and in
turn a simple division of y/D was used to find the depth to diameter ratio. Optimal diameters
(Dopt) were found and this number was rounded up to find D as available pipe diameter
(standard D). A Manning’s n of .013 was used for the concrete pipe and a longitudinal slope of
.0016 was used to keep the velocity from dropping below the minimum and keeping it in the
drainage channel at 3500 feet.
Table 2: Results
Q (cfs) n S cm
1.04 0.013 0.0017 1.486
Inlet Q (cfs) Dmin (ft) y (ft) y/D Dopt (ft) Dopt (in) Standard D (in)
1 1.04 0.878492 0.67 0.8 0.92 11.04 12
2 2.08 1.139263 0.93 0.816317 1.139263 13.67116146 15
3 3.12 1.326351 1.1 0.829343 1.326351 15.91620904 18
4 4.16 1.477442 1.18 0.8 1.51 18.12 21
Costs:
Table 3: Costs
materials used
excavation volume
34. Length of pipe (ft)
Pipe 1 700
Pipe 2 700
Pipe 3 700
Pipe 4 1050
Volume of Excavation (ft3)
5171
The excavation volume will be the length of each pipe times it’s cross sectional area plus the
volume excavated for the slope and 2 (ft) cover. The volume excavated due to the slope and 2
(ft) cover will be used to back fill the excavated area that is not filled by the pipe. Materials
used will be concrete. Labor is another cost.
Justification:
.0016 Slope is used in the design because that was the maximum possible slope, with the 2 (ft)
cover, that the sewer could have while still entering into the drainage channel without extra
excavation. Also, when dealing with lower slopes the velocity was very minimal and it was hard
to keep it at a value far from minimum. A 2 foot cover was used because this was the minimum
and having it low requires less excavation.
Concrete was used to design the Channel because it is smooth and sturdy. The smoothness like
the slope will keep the water moving and a relatively quick rate. Once Dmin was found the
diameters were adjusted in order to find a D with a more optimal value. Once y/D was found to
35. be greater than .8 iterations were stopped because .8 is sufficiently close to the overall optimal
value of .93.
As can be seen in figure 1, crow aligned was the alignment chosen. The reason for this is that
the cover only has to be checked at the beginning of the pipe being that all pipes further down
will be lower due to the slope. Inlets can be easily designed using the slope as the distance
from inlet to sewer is linear.
Appendix A: Drawings
Figure 1: side view
37. Culvert Design
Introduction:
A roadway is to span the drainage channel from assignment 2 at 3500 (ft). A culvert is designed
to transport the water from the channel to a detention pond on the other side of the road way.
There is a total of 3 culverts of 3 feet each having its invert at the base of the flood plain of the
drainage channel. Horizontally, the culverts are centered on each side of the flood plain and
the center culvert is centered with the trickle channel (see figure 4). The culverts are designed
at a discharge of 65 (cfs).
Constraints:
1. The roadway is level with the top of the drainage channel. Measured from the invert of the
culverts will be at a height of 6 (ft)
2. The exit flow velocity must not be less than 2 (ft/s), or exceed 15 (ft/s).
3. The crown of the culverts must be at distance of least half the diameter from the base of the
roadway. This distance will be 1 (ft)
4. Must allow for at least 1 (ft) freeboard. Height measured from the invert of the culverts will
be 1ft less than the roadway level to account for the freeboard. This will measure to be 5 (ft)
for allowable head water depth.
Table 1: Actual Values
Height of Roadway
(ft)
8
Exit Flow Velocity
(ft/s)
8.79
Distance of roadway
from Crown (ft)
4
Free Board (ft) 1
-Height of roadway is measure from the invert of the culverts (see figure 1 for clarification).
38. Calculations and Design:
Culvert master is used to find the characteristics of flow. Culverts
are placed vertically with inverts in line with the flood plain. Due
to the requirement for a 1 (ft) freeboard the Allowable head
water is made to be 5 (ft). This is calculated by taking the 8 (ft)
channel and subtracting the trickle channel height at the
freeboard. Concrete is the material used in the culvert design so
a Manning’s number of .013 is chosen. All other inputs were
given or decided upon (see justification section). All inputs can be
seen in Table 2. For outputs of Culvert master the datum is taken
to be at the invert of the pipe upstream and downstream.
Outputs can be seen on table 3.
The calculations are done at first with tail water at 0. When tail
water is not zero it affects the head water. If tail water reaches
4.75 (ft) then the water will overflow onto the road. Table 4 and
Figure 4 illustrate the affect the tail water has on the head water.
Costs:
Excavation, Labor and materials are the costs for this project. Table 5 shows a list of the costs
Culverts 3
Diameter of
Culverts (in)
24
Allowable Head
Water (ft)
5
Tail Water (ft) 0
Upstream Invert
elevation (ft)
0
Down Stream
Invert elevation
(ft)
-0.5
Type of beveled
Inlet Entrance
(degree)
45
Manning's
number
0.013
Material concrete
Length of (ft) 40
Discharge (cfs) 65
Table 2: Inputs for culvert
Master
Slope 0.0125
Head Water (ft) 2.89
Velocity (ft/s) 8.79
Exit Depth (ft) 1.46
Table 3: Outputs for
Culvert Master
Tail water (ft) Head water (ft)
0 2.89
2 3.25
5 3.75
6 4.75
Table 4: Tailwater vs Head
Water
39. Table 5: Costs
Volume of fill and
excavation
Materials concrete
Beveling
(degree)
45
Justifications:
Beveling is used in order to decrease losses of energy. The water
flows through the culvert smoother with the beveled inlet. Three culverts were used to
disperse the flow across the channel (blm.gov). Also one culvert was place in the middle
(horizontally) of the trickle channel to help in times of low flow. Ideally this middle culvert
would be lower than the others but Culvert Master does not allow for varied heights of the
culverts. A circular shape was used for the culverts due to the relatively low flow
(engineeringcivil.com). They are the most hydraulically efficient shape and make lining of
culvert cheaper. Concrete is
used because it is strong and
durable.
Appendix A: CAD drawings and
Rating Curves
As discharge decrease the
head water increases. (See
Table 6 for values).
Logically the head water depth
increases with the increase of
flow.
Figure 1: Depth vs Discharge
Discharge (cfs) Head Water (ft)
Design 115.85 6
Max 102.27 5
Overflow 65 2.89
Table 6: Critical Discharges
40. As discharge increases,
downstream velocity
increases as illustrated
in Figure 2. The flow
seams to behave
linearly but after a
certain flow is reached
the slope of the
change in velocity with
respect to discharge
gets larger in
magnitude.
Figure 2: Down Stream Velocity vs Discharge
As discharge increases, downstream depth increases as illustrated in Figure 3. But if the flow
increases greatly the pipe will be completely full of water and cannot increase any more even if
the flow continues to increase.
Figure 3: Downstream Depth vs Discharge
42. Detention Pond Design
Introduction:
The purpose of designing a detention (dry) pond is to detain the total rainfall runoff conveyed
by the drainage channel and the storm sewer. The pond will drain at a predevelopment rate.
Some constraints that would be applied into the design would be that the maximum water
depth must not exceed 4 feet, a minimum free board of 1 feet would be required. Also a
maximum of 2 acres is to be used for the detention pond. A discharge (Qpost) of 65 (cfs) is
used for the design.
Results:
Table 1: At a Glance
Constraint Actual
FootPrint(acres) 2 1.55
Depth(ft) 4 3.7
PondDepthwith1ft
freeboard(ft) 4.7 4.7
D required(ft) 2.47 2.47
Table 2: Pond Parameters
Depth (ft) 4.7
Side Slope 2.5
Area of bottom
(acres) 1.28
Storage (acre-ft) 5.13
Side Length of
Bottom (ft) 236
Side Length of Top
(ft) 260
Area of Top (acres) 1.55
43. Table 3 Orofice
Parameters
Qpre (cfs) 30
Diameter(ft) 2.5
Area(ft2
) 1.94
acceleration of
gravity (ft/s2
) 32.2
The pond is designed as a square with a 2.5 side slope. Using (1) storage was found with given
parameters. Storage was found to be 5.13 (acre-ft). Water depth (y) is found using (2) to be 3.7
(ft). Depth of channel was taken to be 1 (ft) higher than y. With given post development
discharge (Qpre) the orifice diameter is designed to be 2.47 (ft) using (3).
Figure 1: Stage vs Storage
This figure illustrates the relationship between water depth and storage. Both design and max
storage and depth are shown.
0
1
2
3
4
5
6
0 1 2 3 4 5 6 7 8
stage(ft)
Storage (acre-ft)
Stage vs Storage
Depth vs Storage Design Max
44. Figure 2: Post and Pre Development
Figure 2 illustrates the post and pre development discharge vs time hydrographs. The integral
of these curves is the storage.
Justification:
A 2.5 slope is used because it isn’t too steep yet, it keeps the footprint below 2 acres. To help
with implementation and calculations a square base is used.
Appendix A: Drawings
0
10
20
30
40
50
60
70
0 100 200 300 400 500
discharge(cfs)
time (min)
Postand Pre Development
Post Development
Pre development
47. References
Wong, Tommy S. W. "Journal of Irrigation and Drainage Engineering - 131(4):383 - PDF
(ASCE)." Journal of Irrigation and Drainage Engineering - 131(4):383 - PDF (ASCE). ASCE, Aug.
2005. Web. 14 Apr. 2016.
Meadows, M. E., and T. M. Walski. "2." Computer Applications in Hydraulic Engineering. 8th
ed.Waterbury: Haestad Methods, 1997. N. pag. Print.
http://www.blm.gov/bmp/low%20volume%20engineering/J_Ch8_Culvert_Use_Installation_&_
Sizing.pdf:
http://www.engineeringcivil.com/what-are-the-differences-in-applications-between-pipe-
culverts-and-box-culverts.html
