Post on 08-Feb-2018
124 MODERN SEWER DESIGN
Fabricated fittings are hydraulically superior.
1255. HYDRAULIC DESIGN OF STORM SEWERS
CHAPTER 5
The hydraulic design of a sewer system may have to take into account theeffect of backwater (the limiting effect on flows that a downstream sewerhas on upstream sewers), surcharging, inlet capacity and all energy lossesin the system. Whether each, or all, of these factors have to be considereddepends on the complexity of the sewer system and the objectives of theanalysis (i.e., is the sizing of the system preliminary or final?). Further-more, the degree of analysis will also depend on the potential impact shouldthe sewer system capacity be exceeded. For example, would surchargingresult in damages to private property due to the foundation drains beingconnected to the system or is the depth of flooding on a roadway importantbecause emergency vehicles depend on safe access along the street. Bydefining the above factors the user may then select the level of analysiswhich is required.
This section will outline two methods using hand calculations. Both meth-ods assume that all flows enter the sewer system, i.e., that the inlet capac-ity of the system is not a limiting factor. In addition, a listing of variouscomputer models which may be used in the analysis or design of sewersystems is provided.
Flow charts and nomographs such as those presented in Chapter 4 pro-vide quick answers for the friction head losses in a given run of straightconduit between structures (manholes, junctions). These design aids donot consider the additional head losses associated with other structures andappurtenances common in sewer systems.
In most instances, when designing with common friction flow formulaesuch as the Manning equation, the hydraulic grade is assumed to be equalto the pipe slope at an elevation equal to the crown of the pipe. Considera-tion must therefore also be given to the changes in hydraulic grade line dueto pressure changes, elevation changes, manholes and junctions. The de-sign should then not only be based on the pipe slope, but on the hydraulicgrade line.
A comprehensive storm sewer design must therefore proceed on the ba-sis of one run of conduit or channel at a time, working methodically throughthe system. Only in this way can the free flow conditions be known and thehydraulic grade controlled, thus assuring performance of the system.
Making such an analysis requires backwater calculations for each run ofconduit. This is a detailed process which is demonstrated on the followingpages. However, it is recognized that a reasonable, conservative “estimate”or “shortcut” will sometimes be required. This can be done and is alsodemonstrated on pages 134 through 138.
When using the backwater curve approach the designer should first es-tablish the type of flow (sub-critical or supercritical) in order to determinethe direction his calculations are to proceed.— Super critical flow - designer works downstream with flow.— Sub-critical flow - designer works against the flow.— Hydraulic jump may form if there is super and sub-critical flow in the
same sewer.
BACKWATER ANALYSISGiven is a flow profile of a storm drainage system (see Figures 5.1 and
of Storm SewersHydraulic Design
126 MODERN SEWER DESIGN
QA
5.2) where the hydraulic grade is set at the crown of the outlet pipe. Hydro-logical computations have been made and preliminary design for the ini-tial pipe sizing has been completed.
In order to demonstrate the significance of form losses in sewer design,a backwater calculation will be performed in this example with helical cor-rugated steel pipe.
Solution1) Draw a plan and surface profile of trunk storm sewer.2) Design discharges, Q are known; Areas, A are known; Diameters of
pipe, D have been calculated in preliminary design.3) Calculate the first section of sewer line. Note: Normal depth is greater
than critical depth, yn > y
c; therefore, calculations to begin at outfall
working upstream. At “point of control” set design conditions on pro-file and calculations sheet:
Station 0 + 00 (outfall)Design discharge Q = 7.0 m3/s (9)Invert of pipe = 28.2 m (2)Diameter D = l800 mm (3)Hydraulic grade elevation H.G. = 30 m (4)Area of pipe A = 2.54 m2 (6)Velocity = V = 2.8 m/s (8)
Note: (1) Numbers in parentheses refer to the columns on Table 5.2.
Compute:a) ‘K’ value (7): K = (2g) n2 (Derived from Manning-Chezy Formula)
b) ‘Sf’ value (12): S
f = K R4/3
The friction slope (Sf) may also be estimated from Table 5.1 for a given
diameter of pipe and with a known ‘n’ value for the expected flow Q.S
f (12) is a “point slope” at each station set forth by the designer. There-
fore, the friction slope (Avg. Sf) (13) for each reach of pipe L (14), is the
average of the two point slopes Sf being considered.
c) Velocity Head (l0): Hv =
d) Energy grade point, E. G. (11) is equal to H. G. (4) plus the velocityhead (10).
e) Friction loss (15): Multiply Avg. Sf (13) by length of sewer section, L
(14) = Hf (15).
f) Calculate energy losses: Hb, H
j, H
m, H
t, using formulae in text.
g) Compute new H. G. (4) by adding all energy loss columns, (15) thru(19) to previous H. G.Note: If sewer system is designed under pressure (surcharging) thenenergy losses must be added (or subtracted, depending on whether youare working upstream or downstream) to the energy grade line, E. G.
h) Set new E. G. (20) equal to E. G. (11)
V2
2g
[ ]/V2
2g
1275. HYDRAULIC DESIGN OF STORM SEWERS
To fi
nd e
nerg
y lo
ss in
pip
e fri
ctio
n fo
r a g
iven
Q, m
ultip
ly Q
2 by
the
figur
e un
der t
he p
rope
r val
ue o
f n.
Man
ning
Flo
w E
quat
ion:
Q =
(AR2/
3 ) x S1/
2En
ergy
Los
s =
S =
Q2 ( n
)2
n A
R2/3
Tabl
e 5.
1E
nerg
y-lo
ss s
olut
ion
by M
anni
ng’s
form
ula
for
pipe
flow
ing
full
Area
Hydr
aulic
Diam
eter
(m2 )
Radi
us (m
)(m
m)
AR
R2/3
AR2/
3n
= 0.
012
n =
0.01
5n
= 0.
019
n =
0.02
1n
= 0.
024
150
0.02
0.03
80.
112
0.00
236
7757
4692
1911
262
1471
020
00.
030.
050
0.13
60.
004
793
1239
1988
2428
3172
250
0.05
0.06
30.
157
0.00
821
437
760
573
996
530
00.
070.
075
0.17
80.
013
91.2
143
229
279
365
400
0.13
0.10
00.
215
0.02
719
.730
.749
.360
.278
.750
00.
200.
125
0.25
00.
049
5.98
9.35
15.0
018
.32
23.9
360
00.
280.
150
0.28
20.
080
2.26
23.
535
5.67
26.
929
9.04
970
00.
380.
175
0.31
30.
120
0.99
41.
554
2.49
33.
045
3.97
780
00.
500.
200
0.34
20.
172
0.48
80.
762
1.22
31.
494
1.95
190
00.
640.
225
0.37
00.
235
0.26
00.
407
0.65
20.
797
1.04
110
000.
790.
250
0.39
70.
312
0.14
80.
232
0.37
20.
454
0.59
411
000.
950.
275
0.42
30.
402
0.08
90.
139
0.22
40.
273
0.35
712
001.
130.
300
0.44
80.
507
0.05
60.
088
0.14
10.
172
0.22
413
001.
330.
325
0.47
30.
627
0.03
70.
057
0.09
20.
112
0.14
614
001.
540.
350
0.49
70.
764
0.02
50.
039
0.06
20.
076
0.09
915
001.
770.
375
0.52
00.
918
0.01
70.
027
0.04
30.
052
0.06
816
002.
010.
400
0.54
31.
091
0.01
20.
019
0.03
00.
037
0.04
817
002.
270.
425
0.56
51.
282
0.00
90.
014
0.02
20.
027
0.03
518
002.
540.
450
0.58
71.
494
0.00
60.
010
0.01
60.
020
0.02
619
002.
830.
475
0.60
91.
725
0.00
50.
008
0.01
20.
015
0.01
920
003.
140.
500
0.63
01.
978
0.00
40.
006
0.00
90.
011
0.01
522
003.
800.
550
0.67
12.
550
0.00
20.
003
0.00
60.
007
0.00
924
004.
520.
600
0.71
13.
217
0.00
140.
002
0.00
30.
004
0.00
627
005.
720.
675
0.76
94.
404
0.00
070.
0012
0.00
190.
0023
0.00
3030
007.
070.
750
0.82
55.
832
0.00
040.
0007
0.00
110.
0013
0.00
1733
008.
550.
825
0.88
07.
520
0.00
030.
0004
0.00
0 60.
0008
0.00
1036
0010
.17
0.90
00.
932
9.48
40.
0002
0.00
030.
0004
0.00
050.
0006
( n )2 x
10-2
AR
2/3
128 MODERN SEWER DESIGN
Tabl
e 5.
2 H
ydra
ulic
cal
cula
tion
shee
t
12
34
56
78
910
1 112
1314
1516
1718
1920
Inve
rtD
H.G.
Sec-
AK
VQ
V2E.
G.S f
Avg.
Sf
LH f
H bH j
H mH t
E.G.
Stat
ion
mm
mm
tion
m2
m/s
m3 /s
2gm
m/m
m/m
mm
mm
mm
m
0 +
000.
000
28.2
0018
0030
.000
02.
540.
0113
02.
87.
00.
3930
.390
0.01
270.
0 127
33.5
0.42
430
.390
0 +
033.
528
28.6
2418
0030
.424
2.54
0.01
130
2.8
7.0
0.39
30.8
140.
0127
0.01
274.
70.
059
0.05
630
.814
0 +
038.
222
28.7
4018
0030
.540
2.54
0.01
130
2.8
7.0
0.39
30.9
300.
0127
0.0 1
2737
.40.
473
30.9
300
+ 07
5.59
029
.212
1800
31.0
122.
540.
0113
02.
87.
00.
3931
.402
0.01
270.
0266
12.3
0.06
10.
132
31.4
020
+ 07
7.87
629
.805
1400
31.2
051.
540.
0095
04.
57.
01.
0532
.255
0.04
060.
0406
30.5
1.23
832
.255
0 +
108.
356
31.0
4314
0032
.443
1.54
0.00
950
4.5
7.0
1.05
33.4
930.
0406
0.04
0630
.51.
238
0.05
333
.493
0 +
138.
836
32.3
3414
0033
.734
1.54
0.00
950
4.5
7.0
1.05
34.7
840.
0406
0.02
9913
.10.
092
1.08
534
.784
0 +
141.
900
33.7
1112
0034
.911
1.13
0.00
785
3.1
3.5
0.49
35.4
010.
0191
0.01
9135
.00.
669
35.4
010
+ 17
6.90
034
.380
1200
35.5
801.
130.
0078
53.
13.
50.
4936
.070
0.01
910.
0351
13.5
0.12
31.
299
36.0
700
+ 18
0.42
136
.402
1600
37.0
020.
280.
0063
63.
51.
00.
6437
.492
0.05
110.
0511
35.5
1.81
40.
032
37.4
920
+ 21
5.89
238
.248
1600
38.8
480
0.28
0.00
636
3.5
1.0
0.64
39.3
380.
0511
39.3
38
n =
Varia
ble
K =
2g(n
2 )S f =
K (
V2 ) /R
4/3
2
g�
H frict
ion =
6.1
91
�H fo
rm =
2.6
57
1295. HYDRAULIC DESIGN OF STORM SEWERS
i) Determine conduit invert (2). In the example we are designing for fullflow conditions; therefore, H. G. (4) is at crown of pipe and invert (2) isset by subtracting, D (3) from H. G. (4).
j) Continue to follow the above procedure taking into account all formhead losses.
k)Complete profile drawing; showing line, grade and pipe sizes. This savestime and usually helps in spotting any design errors.
Energy LossesStation 0 + 033.528 to 0 + 038.222 (Bend)
Hb = K
b , where K
b = 0.25
, central angle of bend = 30o
Kb = 0.25 = 0.1443
Hb = 0.1433 (0.39) = 0.056 m
Station 0 + 075.590 to 0 + 077.876 (Transition)
Ht = 0.2
= 0.2 (1.05 - 0.39)= 0.132 m
Station 0 + 108.356 (man hole)
Hm = 0.05
= 0.05 (1.05) = 0.053mStation 0 + 138.836 to 0 + 141.900 (Junction)
30o
1
3
2
Q1 = 3.5 cms
A1 = 1.13 m2
D1 = 1200 mm
Q2 = 7.0 cms
A2 = 1.54 m2
D2 = 1400 mm
Q3 = 3.5 cms
A3 = 1.13 m2
D3 = 1200 mm
= 30oI 0I 0
3090
[ ]V2
2g
[ ]V12
2g
V22
2g ,
Expansion
V1 > V
2
0
90I
[ ]V2
2g
130 MODERN SEWER DESIGN
( )( )
3.52 cos 30o
1.13 (9.81)3.52
1.13 (9.81)
1.13 + 1.542
( )Hj + D
1 — D
2 = — —( )A
1 + A
2
2Q
22
A2g
Q1
2
A1g
Q32 cos
A3g
I 0
(Hj + 1.2 — 1.4) =
(7.0)2
(1.54) (9.81)
( )1.335 H
j — 0.2 (1.335) = 3.243 — 1.105 — 0.957
1.335 Hj — 0.267 = 1.181
Hj = 1.085 m
• P = • M (Pressure plus momentum laws)
Fittings and elbows are easily fabricated in all sizes.
1315. HYDRAULIC DESIGN OF STORM SEWERS
Station 0 + 176.900 to 0 + 180.421 (Junction)
70o
70o
1 2
3
4
In this example, the head losses at junctions and transition could also havebeen accommodated by either increasing the pipe diameter or increasingthe slope of the pipe.
This backwater example was designed under full flow conditions butcould also have been designed under pressure; allowing surcharging in themanholes, which would have reduced the pipe sizes. Storm sewer systems,in many cases, can be designed under pressure to surcharge to a tolerablelevel.
0.705 Hj — 0.6 (0.705) = 1.105 — 0.364 — 0.123 — 0.125
0.705 Hj — 0.423 = 0.493
Hj = 1.299 m
Station 0 + 215.892 (manhole)
Hm = .05 = 0.5 (0.64)
= 0.032 m
Total friction Hf throughout the system = 6.191 m
Total form losses = 2.657 m
Q42 cos 0
4
A4g
Q32 cos 0
3
A3g
Q1 = 1.0 m3/s
A1 = 0.28 m2
D1 = 600 mm
Q4 = 1.0
A4 = 0.28
D4 = 600
04 = 70o
Q2 = 3.5
A2 = 1.13
D2 = 1200
Q3 = 1.5
A3 = 0.64
D3 = 900
03 = 70ϒ
(Hj + D
1 — D
2)
=( )A
1 + A
2
2Q
22
A2g
Q1
2
A1g
(Hj + 0.6 — 1.2)
= (1.0)2
(0.28) (9.81)(3.5)2
(1.13) (9.81)
(1.0)2 cos 70o
(0.28) (9.81)(1.5)2 cos 70o
(0.64) (9.81)
( )0.28 + 1.132
( )V2
2g
132 MODERN SEWER DESIGN
Flow
Channel
0 +
000.
000
0 +
033.
528
BC
FLO
W
7.0
m3 /
s7.
0 m
3 /s
0 +
180.
421
0 + 215.892
M.H.
0 + 108.356
M.H.
0 + 077.876
0 + 075.590
0 + 038.222 EC
1.5 m3/s
3.5 m3/s
0 + 138.836
0 + 141.900
1.0 m3/s
1.0
m3 /
s 70
o
3.5
m3 /
s 30
o
Fig
ure
5.1
Pla
n a
nd
pro
file
fo
r st
orm
se
we
r
1335. HYDRAULIC DESIGN OF STORM SEWERS
0 + 215.892
M.H.
0 + 108.356
M.H.
0 + 180.421
0 + 176.900
0 + 141.900
0 + 138.836
0 + 077.876
0 + 075.590
0 + 038.222
0 + 033.528
0 + 000.00
E.G
.
GR
OU
ND
SU
RFA
CE
H.G
.L. a
tC
row
n
H.G
. 00
+ 03
50
+ 07
0Tr
ansi
tion
junc
tion
junc
tion
0 +
105
0 +
140
0 +
175
0 +
210
0 +
245
.37
m
.30
m
.23
m
600
mm
CPS
1400
mm
CPS
1800
mm
CPS
1200
mm
CPS
Fig
ure
5.2
Pla
n a
nd
pro
file
fo
r st
orm
se
we
r
134 MODERN SEWER DESIGN
[ ]
= +
13 n2 LQ2 (16)2g ≠2 D16/3
Hf = = for K
f = 2n2
METHODS OF DETERMINING EQUIVALENT HYDRAULICALTERNATIVESA method has been developed to aid the designer in quickly determiningequivalent pipe sizes for alternative material, rather than computing thebackwater profiles for each material.
The derivation shown below allows the designer to assign representativevalues for loss coefficients in the junctions and length of average reachbetween the junctions, and develop a relationship for pipes of differentroughness coefficients. In this manner the designer need only perform adetailed hydraulic analysis for one material, and then relatively quicklydetermine conduit sizes required for alternative materials. The relation-ships for hydraulic equivalent alternatives in storm sewer design may bederived from the friction loss equation.
The total head loss in a sewer system is comprised of junction losses andfriction losses:
where: Hj = K
j
V2
2g
Q2
A2 2g
HT = H
j + H
f
= Kj
Q2 16≠2 D4 2g
= Kj
where:
2n2 LV2
R4/3 2g
HT = H
j + H
f
13 n2 LQ2 (16)2g ≠2 D16/3
16Q2 Kj
2g ≠2 D4
= 8Q2
g ≠2
Kj D4/3 + 13 n2 L
D16/3
1355. HYDRAULIC DESIGN OF STORM SEWERS
Thus, for comparison of concrete and steel:
The flow Q for each conduit will be the same, therefore the relationshipsimplifies to:
Average values for conduit length between manholes (L), and junctionloss coefficient (K
j), must next be selected. Representative values may be
derived for the hydraulic calculations that will have already been performedfor one of the materials.
In this example the average conduit length is 90 metres with an averagejunction loss coefficient of 1.0. With the selected L, n and K
j values the
equations are determined for a series of pipe diameters. The results areshown in Table 5.3. These figures are then plotted on semi-log paper, fromwhich hydraulically equivalent materials may be easily be selected. (Fig-ures 5.3 and 5.4)
[ ]8Q2
g≠
Combination increaser, manhole and elbow in one length of pipe.
=8Q2
g≠K
j (D
c)4/3 + 13(n
c)2 L
(Dc)16/3 [ ]K
j (D
s)4/3 + 13(n
s)2 L
(Ds)16/3
Kj (D
c)4/3 + 13(n
c)2 L
(Dc)16/3
Kj (D
s)4/3 + 13(n
s)2 L
(Ds)16/3=
136 MODERN SEWER DESIGN
Table 5.3 Methods of determining equivalent alternatives
Junction and Friction Losses
Kj = 1.0 L = 90m
Smooth Pipe Annular CSP Pipe Helical CSP Pipen = 0.012 n = 0.024 n var. (see Table 4.9)
Diameter D4/3 + 0.168 D4/3 + 0.674 D4/3 + 1170 n2
(mm) D16/3 D16/3 D16/3
n values200 1525.30 4226.21 1525.30 0.012250 529.86 1351.46 486.12 0.011300 227.03 537.74 245.01 0.013400 61.39 128.38 95.04 0.019500 22.79 43.17 26.61 0.015600 10.28 17.99 13.50 0.018700 5.29 8.68 6.71 0.018800 3.00 4.66 3.98 0.02900 1.82 2.71 2.43 0.021
1000 1.17 1.67 1.52 0.0211200 0.55 0.74 0.68 0.0211400 0.29 0.37 0.35 0.0211600 0.17 0.21 0.19 0.0211800 0.10 0.12 0.12 0.0212000 0.07 0.08 0.08 0.0212200 0.05 0.05 0.05 0.0212400 0.03 0.04 0.03 0.021
Note: Pipe diameter in metres in above equations.
Philadelphia Airport, 16 x 26mm fiber-bonded, full bituminous coated and full pavedCSP with semi-corrugated bands with O-ring gaskets, provides storm drainage forairport— 5800 m of 2000mm, 2200mm, 2400mm, 2700mm diameters, 14 - 16 gauge,2 - 3m of cover.
1375. HYDRAULIC DESIGN OF STORM SEWERS
00.
20.
40.
60.
81.
01.
21 .
41.
61.
82.
02.
2
1000
0
1000 10
0 10 1
0.1
0.01
Dia
met
re in
met
res
Fig
ure
5.3
E
quiv
alen
t alte
rnat
ives
with
ann
ular
CS
P w
here
C =
13n
2L
Sm
ooth
pip
e
CS
P
EX
AM
PLE
:G
iven
: 0.8
m d
iam
eter
CS
P,
hydr
aulic
ally
equ
ival
ent t
o 0.
7m
di
amet
er s
moo
th p
ipe
D4/3 + CD16/3
138 MODERN SEWER DESIGN
00.
20.
40.
60.
81.
01.
21.
41.
61.
82.
02.
2
1000
0
1000 100 10 1
0.1
0.01
Dia
met
res
in m
etre
s
Fig
ure
5.4
E
quiv
alen
t alte
rnat
ives
with
hel
ical
CS
P (
n va
riabl
e) w
here
C =
13n
2L
EX
AM
PLE
:G
iven
: 0.9
m d
iam
eter
CS
P,
hydr
aulic
ally
equ
ival
ent t
o 0.
8m
di
amet
er s
moo
th p
ipe
D4/3 + CD16/3
Sm
ooth
pip
e
CS
P
1395. HYDRAULIC DESIGN OF STORM SEWERS
DESIGN OF STORM DRAINAGE FACILITIES
System LayoutThe storm drainage system layout should be made in accordance with theurban drainage objectives, following the natural topography as closely aspossible. Existing natural drainage paths and watercourses such as streamsand creeks should be incorporated into the storm drainage system. Thusthe storm design should be undertaken prior to finalization of the streetlayout in order to effectively incorporate the major-minor drainage con-cepts.
Topographic maps, aerial photographs, and drawings of existing serv-ices are required before a thorough storm drainage design may be under-taken.
Existing outfalls within the proposed development and adjacent landsfor both the minor and major system should be located. Allowances shouldbe made for external lands draining through the proposed development bothfor present conditions and future developments.
The design flows used in sizing the facilities that will comprise the drain-age network are based on a number of assumptions. Flows that will occurunder actual conditions will thus be different from those estimated at thedesign stage; “the designer must not be tempted by the inherent limitationsof the basic flow data to become sloppy in the hydraulic design.”(1) Alsothe designer should not limit his investigation to system performance un-der the design storm conditions, but should assure that in cases where sewercapacities are exceeded such incidents will not create excessive damage.
This requirement can only be practically achieved if the designer real-izes that a dual drainage system exists, comprised of the minor system andthe major system. Utilizing both systems, the pipe system may be providedfor smaller, more frequent rainfall events, and an overland system for ex-treme rainfall events.
In the layout of an effective storm drainage system, the most importantfactor is to assure that a drainage path both for the minor and major sys-tems be provided to avoid flooding and ponding in undesirable locations.
Minor SystemThe minor system consists chiefly of the storm sewer comprised of inlets,conduits, manholes and other appurtenances designed to collect and con-vey into a satisfactory system outfall, storm runoff for frequently occur-ring storms (2 to 5 year design).
Storm sewers are usually located in rights-of-way such as roadways andeasements for ease of access during repair or maintenance operations.
Major SystemThe major drainage system will come into operation when the minor sys-tem’s capacity is exceeded or when inlet capacities significantly controldischarge to the minor system. Thus, in developments where the majorsystem has been planned, the streets will act as open channels draining theexcess storm water. The depth of flow on the streets should be kept withinreasonable limits for reasons of safety and convenience. Considerationshould be given to the area of flooding and its impact on various streetclassifications and to public and private property.
Typical design considerations are given in Table 5.4.
140 MODERN SEWER DESIGN
Multiple inline storage installation.
Table 5.4 Typical maximum flow depths
Storm Return Frequency (Years)
Location* 5 25 40
Walkways, Minor surface flow As required for As required forOpen spaces up to 25mm deep overland flow outlets overland flow outlets
on walkways
Minor, Local and 1m wide in gutters or 100mm above crown 200mm above crownFeeder Roads 100mm deep at low
point catch basins
Collector and Minor surface flow up to crown 100mm above crownIndustrial Roads (25mm)
Arterial Roads Minor Surface flow 1 lane clear up to crown(25mm)
*In addition to the above, residential buildings, public, commercial and industrial buildingsshould not be inundated at the ground line for the 100 year storm, unless buildings areflood-proofed.
To prevent the flooding of basement garages, driveways will have tomeet or exceed the elevations corresponding to the maximum flow depthat the street.
The flow capacity of the streets may be calculated from the Manningequation, or Figure 5.5 may be used to estimate street flows.
When designing the major system it should be done in consideration ofthe minor system, with the sum of their capacities being the total system’scapacity. The minor system should be first designed to handle a selectedhigh frequency storm, (i.e., 2-year) next the major system is designated fora low frequency of flood storm, (i.e., 100-year). If the roadway cannothandle the excess flow, the minor system should be enlarged accordingly.
1415. HYDRAULIC DESIGN OF STORM SEWERS
4
3.5 3
2.5 2
1 .5 1
0 .5 0
010
2030
4 050
60
Cap
acit
y –
(m3 /
s)
Slope – percent
Fig
ure
5.5
H
ydra
ulic
cap
acity
of r
oadw
ays
Not
e: B
lvd.
= B
oule
vard
Streetline
Streetline
150m
mBl
vd.
n =
0.0
5B
lvd.
n =
0. 0
13P
avem
ent
W.L
.Maj
or s
yste
m
15mrightofway-8mPavement(2%Blvd)
20mrightofway-9mPavement(2%Blvd)
15mrightofway-8mPavement(4%Blvd)
15mrightofway-8mPavement(6%Blvd)
20mrightofway-9mPavement(4%Blvd)
20m
right
ofway
-9mPav
emen
t(6%
Blvd)
142 MODERN SEWER DESIGN
HYDRAULIC DESIGN EXAMPLE OF MINOR-MAJOR SYSTEM
Description of SiteThe site for this design example is shown on Figure 5.6.
The site is about 15 hectares in size consisting of single family and semidetached housing as well as a site for a public school. The site slopes gen-erally from west to east, where it is bounded by a major open water course.To accommodate the principles of the “minor-major’’ storm drainage sys-tems, the streets have been planned to conform as much as possible to thenatural contours of the lands. Where sags in roadways between intersec-tions could not be avoided, overflow easements or walkways have beenprovided to permit unobstructed surface runoff during major storms, asshown on Figure 5.7.
Selected Design Criteria
Minor SystemBased on a reasonable level of convenience to the public, a two-year de-sign curve is considered adequate as a design basis for the minor systemwithin this development.
Storm Sewer installation involved 1300 m of full bituminous coateded full pavedpipe arch.
1435. HYDRAULIC DESIGN OF STORM SEWERS
Figure 5.6 Site plan with route of surface runoff
N
GreenBelt
GreenBelt
School
144 MODERN SEWER DESIGN
N
GreenBelt
Culvert
Watercourse
Culvert
School
GreenBelt
Headwall
OverflowEasement
OverflowEasement
Drainage Areaof Design Example
Storm Sewer Section
Major SystemThe major (or overflow) system will be checked together with the minorsystem against a 100-year storm intensity. The combination of these twosystems shall be able to accommodate a 100-year storm runoff.
Minor SystemFor the limited extent of area involved, designing on the principles of theminor-major drainage concept without gravity connections to foundationdrains permits considerable tolerance in the degree of accuracy of runoffcalculations such that the rational formula Q = k•C•i•A is considered ad-
Figure 5.7 Storm drainage areas
1455. HYDRAULIC DESIGN OF STORM SEWERS
equate. The values for the two year rainfall intensity curve obtained fromlocal records are shown in Table 5.5.
The following steps should be followed in the hydraulic design of theminor system:1. A drainage area map should be prepared indicating the drainage limits
for the site, external tributary areas, location of imported minor systemand carryover flows, proposed minor-major system layout and directionof surface flow.
2. The drainage area should be divided into sub-areas tributary to the pro-posed storm sewer inlets. In this case the inlet shall be located at theupstream end of each pipe segment.
3. The coverage of each sub-area should be calculated.4. The appropriate runoff coefficient should be developed for each sub-
area. The example has been simplified in that impervious areas discharg-ing to grass areas have been given a runoff coefficient equal to the grassedarea runoff coefficient. The runoff coefficient in this example has beendetermined based on 0.20 for grassed areas and areas discharging to grasssuch as roof, patios and sidewalks) and 0.95 for impervious surfaces(streets and driveways), which for this site results in an average runoffcoefficient of 0.35 for all the sub-areas.
5. The required capacity of each inlet should be calculated using the ra-tional method, with the initial time of concentration and the corres-ponding intensity. In this example,T
c = 10 minutes.
i = 72 mm/hr (2-year storm) (Table 5.5).Inlets will be located at the upstream manhole for each length of con-duit.
Table 5.5 Rainfall intensity duration frequency
Time 2 Year Return 100 Year Return(Min) (mm/hr) (mm/hr)
5 105 26210 72 17915 57 14620 48 12225 42 10930 37 9735 34 8940 30 8145 28 7450 26 6955 24 6460 22 5965 21 5570 19 5175 18 4780 16 4485 15 4190 13 3995 12 38
100 11 33125 10 32150 9 25175 7 23200 7 22
146 MODERN SEWER DESIGN
6. Commencing at the upstream end of the system, the discharge to becarried by each successive segment in a downstream direction is calcu-lated. The initial time of concentration is 10 minutes at the most up-stream inlet. Added to this value is the required travel time in the con-duit to the next inlet. The resulting time of concentration is then used todetermine a new intensity at that point.
Also, a weighted area x C value must be determined at each succes-sive inlet.
At a confluence of two or more conduits, the longest time of con-centration is selected and the procedure continues downstream. The abovecomputations are summarized in Table 5.6.
7. With computed discharges at the upstream end of each pipe segment, atentative pipe size to accommodate friction losses only is selected usingthe friction flow charts in Chapter 4. In this design example, a helical68mm x 13mm CSP with variable roughness coefficient (Table 4.9) hasbeen selected as the conduit material. The corresponding velocities forthe expected flow are determined to calculate the pipe flow time. Thistime added to the upstream time of concentration results in the new timeof concentration for the downstream segment as described in Step 6.Design velocities in storm sewers should be a minimum of 1.0 m/s whenflowing half full to full to attain self cleaning velocities and to preventdeposition, to a maximum of 4.5 m/s to avoid erosive damage to theconduit.
Recharge trench installation showing junction box.
1475. HYDRAULIC DESIGN OF STORM SEWERS
Culvert design technology and open-channel flow design are increasingly applied tourban storm water management. Triple structural plate pipe-arches enclose streamunder roadway, and industrial land development.
Note: If upon completion of the hydraulic design (and backwater cal-culations), the times of concentrations have varied enough to alter thedischarges, new flow values should be determined. In most cases theslight variance in the T
c will not significantly affect the peak flows.
8. As the preliminary design proceeds downstream, some account must bemade for the manhole and junction losses. Certain rules of thumb maybe used before the detailed hydraulic analysis. In this design examplethe following manhole drops were assumed:
15 mm for straight runs45 mm for 45ϒ junctions75 mm for 45ϒ to 90ϒ junctionsAlso crowns of incoming and outgoing pipes at manholes were kept
equal where the increase in downstream diameter met or exceeded theabove manhole drops.
The preliminary minor system design is shown in Table 5.6 with thetentative pipe sizes and manhole drops.
9. The hydraulic analysis should next be performed on the proposed minorsystem to ensure that it operates as expected. The hydraulic grade is setat the crown of the outlet conduit, with hydraulic calculations proceed-ing upstream. The energy loss equations shall be used following the sameprocedure as in the Hydraulic section. The detailed hydraulic calcula-tions are computed for each station, on pages 153 and 154, with theresults summarized in Table 5.7. In this example the initial pipe sizesdid not change, but rather manhole drops were adjusted to account forthe junction losses. If junction losses would have resulted in the eleva-tion of the pipe crown exceeding the minimum cover criterion, then the
148 MODERN SEWER DESIGN
hydraulic grade line may have been lowered by increasing the pipesize. The hydraulic grade line may be permitted to exceed the crownwhere some surcharging in the storm system can be tolerated.
10. The designer may now estimate the required pipe sizes for a minorsystem for an alternative conduit material or roughness coefficient.There is no need to perform a detailed hydraulic analysis for the alter-native conduit, but rather use the method of “Equivalent Alternatives”as described earlier in this chapter. In this example the average lengthof conduit is estimated to be 90m with an average manhole junctionloss coefficient of 1.0. The alternative conduit will have constant n =.012. Therefore the alternative material may be determined. The re-sults are summarized in Table 5.8.
Large storm drain projects under runways at a major airport.
1495. HYDRAULIC DESIGN OF STORM SEWERS
Increasers are easily fabricated for correct field location.
Pipe-arch sewer installation in a residential area satisfying minimum headroomrequirement; however it has adequate capacity and strength.
150 MODERN SEWER DESIGN
Leng
thTo
tal
Tota
lIn
tens
ityof
Size
Fall
M.H
.U p
Dow
nAc
tual
M.H
.M
.H.
Area
Sect
ion
Trun
kI
QPi
pePi
peSl
ope
Drop
Stre
amSt
ream
Cap.
Vel.
Sect
.Ac
cum
.Fr
omTo
(ha)
CA
x C
A x
CA
x C
(mm
/hr)
(m3 /s
)(m
)( m
m)
%(m
)(m
m)
(m)
(m)
Q(m
3 /s)
(m/s
)M
in.
Min
.
12
0.74
0.35
0.26
0.26
720.
0590
200
0.84
0.76
231.
590
230.
830
0.05
1.03
1.47
11.4
72
31.
100.
350.
390.
6567
0.12
8030
01.
301.
0475
230.
755
229.
715
0.1 2
1.71
0.77
12.2
43
41.
040.
350.
361.
0165
0.18
8140
00.
980.
7975
229.
640
228.
850
0.1 8
1.58
0.85
13.0
94
50.
830.
350.
291.
3062
0.22
9340
01.
5 01.
3075
228.
775
227.
475
0.22
1.96
0.79
13.8
8
67
1.06
0.35
0.37
0.37
720.
0790
200
1.70
1.53
231.
610
230.
080
0.07
1.47
1.04
11.0
47
8–
––
––
0.07
9020
01.
701.
5375
230.
005
228.
475
0.07
1.47
1.04
12.0
88
91.
500.
350.
530.
9066
0.16
7530
02.
201.
6545
228.
430
226.
780
0.16
2.23
0.56
12.6
4
1011
1.80
0.35
0.63
0.63
720.
1390
300
1.40
1.26
230.
360
229.
100
0.13
1.77
0.86
10.8
611
120.
710.
350.
250.
8869
0.17
8330
02.
401.
9915
229.
085
227.
095
0.17
2.32
0.60
11.4
612
130.
420.
350.
151.
0367
0.19
8140
01.
100.
8975
227.
020
226.
130
0.19
1.68
0.80
12.2
6
59
0.43
0.35
0.15
1.45
600.
2481
500
0.76
0.62
7522
7.40
022
6.78
00.
241.
470.
9214
.80
913
0.53
0.35
0.19
2.54
580.
4081
600
0.62
0.50
150
226.
630
226.
130
0.41
1.41
0.96
15.7
613
142.
280.
350.
804.
3756
0.67
150
600
1.70
2.55
7522
6.05
522
3.50
50.
682.
321.
0916
.85
1415
0.55
0.35
0.19
4.56
550.
6915
060
01.
802.
7015
223.
490
220.
790
0.70
2.39
1.06
17.9
115
162.
350.
200.
475.
0353
0.74
3570
01.
200.
4275
220.
715
220.
295
0.74
1.99
0.28
18.1
916
O
utfa
ll–
––
5.03
530.
7415
080
00.
681.
0275
220.
220
219.
200
0.74
1.61
1.58
19.7
7
Tabl
e 5.
6P
relim
inar
y st
orm
sew
er d
esig
n
Q=
Flow
A=
Area
in H
ecta
res
C=
Coef
ficie
nt o
f Run
off
I=
Inte
nsity
of R
ainf
all f
or P
erio
d in
mm
/hr
Loca
tion
R
unof
fIn
verts
Tim
e(E
ntry
: 10
Min
.)
1515. HYDRAULIC DESIGN OF STORM SEWERS
Installing 1,800mm diameter CSP to be used as an underground detention chamberfor stormwater runoff.
152 MODERN SEWER DESIGN
Tabl
e 5.
7H
ydra
ulic
cal
cula
tion
shee
t
12
34
56
78
910
1112
1314
1516
1718
1920
Inve
rtD
H.G.
Sec-
AK
VQ
V2E.
G.S f
Avg.
Sf
LH f
H bH j
H mH t
E.G.
M.H
.m
mm
mtio
nm
2m
/sm
3 /s2g
mm
/mm
/mm
mm
mm
mm
Outle
t21
9.20
080
022
0.00
00
0.50
0.00
636
1.47
30.
740.
111
220 .
111
0.00
6022
0.11
116
220.
149
800
220.
949
00.
500.
0063
61.
473
0.74
0.11
122
1.06
00.
0060
0.00
6015
00.
900
0.03
30.
016
221.
060
1522
0.59
370
022
1.29
30
0.38
0.00
636
1.92
40.
740.
189
221 .
482
0.01
230.
0092
350.
322
0.02
222
1.48
214
223.
478
600
224.
078
00.
280.
0063
62.
442
0.69
0.30
422
4 .38
20.
0243
0.01
8315
02.
745
0.02
50.
015
224.
382
1322
7.42
860
022
8.02
80
0.28
0.00
636
2.37
10.
670.
287
228.
315
0.02
290.
0236
150
3.54
00.
034
0.37
622
8.31
59
228.
912
600
229.
512
00.
280.
0063
61.
415
0.40
0.10
222
9.61
40.
0081
0.01
5581
1.25
60.
008
0.22
022
9.61
45
229.
586
500
230.
086
00.
200.
0044
11.
223
0.24
0.07
623
0.16
20.
0054
0.00
6881
0.55
10.
007
0.01
623
0.16
2
1222
8.99
440
022
9.39
40
0.13
0.00
385
1.51
30.
190.
117
229.
511
0.00
970.
0163
811.
320
0.01
0.03
622
9.51
111
230.
798
300
231.
098
00.
070.
0033
22.
406
0.17
0.29
523
1.39
30.
0310
0.02
0483
1.68
90.
015
231.
393
1023
3.18
230
023
3.48
20
0.07
0.00
332
1.84
00.
130.
173
233.
655
0.01
820.
0246
902.
214
0.17
233.
655
823
0.57
930
023
0.87
90
0.07
0.00
332
2.26
50.
160.
261
231.
140
0.02
740.
0178
751.
335
0.03
10.
001
231.
140
723
3.92
720
023
4.12
70
0.03
0.00
283
2.22
90.
070.
253
234.
380
0.03
890.
0332
902.
988
0.26
234.
380
623
7.67
820
023
7.87
80
0.03
0.00
283
2.22
90.
070.
253
238.
131
0.03
890.
0389
903.
501
0.25
238.
131
423
0.70
840
023
1.10
80
0.13
0.00
385
1.75
20.
220.
156
231.
264
0.01
290.
0092
930.
856
0.16
623
1.26
43
231.
593
400
231.
993
00.
130.
0038
51.
433
0.18
0.10
523
2.09
80.
0087
0.01
0881
0.87
50.
0123
2.09
82
232.
737
300
233.
037
00.
070.
0033
21.
700
0.12
0.14
723
3.18
40.
0154
0.01
2180
0.96
80.
074
0.00
223
3.18
41
234.
551
200
234.
751
00.
030.
0028
31.
592
0.05
0.12
923
4.88
00.
0198
0.01
7690
1.58
40.
1323
4.88
0
n =
Varia
ble
S f = K
(V2 ) /R
4/3
K =
2g(n
2 )
2g
1535. HYDRAULIC DESIGN OF STORM SEWERS
( )
(Hj + 0.5 — 0.6) = —
Kb = 0.25 = 0.117
M.H. 16 0 = 45ϒ From Figure 4.13 K = 0.3
Hb = K = 0.3 x 0.11 = 0.033m
Ht = 0.2 — = 0.2 x (.19 — .11) = 0.016m
M.H. 15
M.H. 14 Kb = 0.25 = 0.083
( )V1
2
2gV
22
2g
Ht = 0.2 — = 0.2 (.30 — .19) = 0.022m( )V
12
2gV
22
2g
Hb = K
b = 0.083 x .30 = 0.025m
Hm = 0.05 = 0.05 x .30 = 0.015m
( )V2
2g
V2
2g( )M.H. 13
Hb = K
b = 0.117 x (.29) = 0.034m( )V2
2g
0 = 90ϒ cos 90ϒ = 0
(Hj + 0.6 — 0.6) = —
Hj = 0.376m
(Hj + D
1 — D
2) = — — cos 0( )A
1 + A
2
2Q
2 2
gA2
Q1
2
gA1
Q3
2
gA3
( )0.28 + 0.282
(0.67) 2
9.81 (0.28)
Hj = 0.220m
M.H. 9 Hb = K
b = x 0.10 = 0.008mV 2
2g1090
0 = 90ϒ cos 90ϒ = 0
( )0.20 + 0.282
( )V2
2g
1090
2090
0 = 90ϒM.H. 5
(0.4) 2
9.81 (0.28)
(0.4) 2
9.81 (0.28)
(0.24) 2
9.81 (0.20)
Detailed Hydraulic Calculations for Step No 10 in Minor System Design
0.25( )
154 MODERN SEWER DESIGN
( )
( )
V2
2
2gH
m = 0.1 — = 0.1 (.26 — .25) = 0.001m( )
Hb = K
b = x 0.08 = 0.007m
Ht = 0.2 — = 0.2 (.16 — .08) = 0.016m
V2
2g ( )
( )V1
2
2gV
22
2g
1090
M.H. 12
Ht = 0.2 (.3 — .12) = 0.036m
Hm = 0.05 = 0.05 (.3) = 0.015m( )V2
2gM.H. 11
K = 1.0M.H. 10
Hm = K
= 1.0 (.17) = 0.17mV2
2g
Hb = (.26) = 0.031m20
90M.H. 8
V1
2
2g
0 = 90ϒM.H. 7
From Figure 4.13 K = 1.04
Hb = 1.04 (.25) = 0.260m
K = 1.0M.H. 6
Hm = K = 1.0 (.25) = 0.250m
0 = 90ϒM.H. 4
From Figure 4.13 K = 1.04
Hb = 1.04 (.16) = 0.166m
( )V2
2
2gH
t = 0.2 — = 0.2 (.15 — .10) = 0.010m
V1
2
2gM.H. 3
0 = 60ϒM.H. 2
From Figure 4.13 K = 0.49
Hb = 0.49 (.15) = 0.074m
( )V2
2
2gH
t = 0.1 — = 0.002m
V1
2
2g
K = 1.0M.H. 1
Hm = K = 1.0 x 0.13 = 0.13
( )
( )
( )V2
2g
( )V2
2g
0.25 1090
0.25Hb = x .12 = 0.010m
0.25
1555. HYDRAULIC DESIGN OF STORM SEWERS
Major SystemVarious manual methods can be used to estimate the major system flows.As a preliminary estimate, designers often apply the Rational formula, us-ing the rainfall intensity for a 100 year storm and a C factor 60 percent to85 percent higher than what would be used for a 2-year or 5-year storm.The increase in value is basically to allow for a change in the antecedentmoisture condition. Except in special circumstances, a C factor above 0.85need not be used.
In this design example the C factor of 0.35 used for the design of theminor system will be increased to 0.60, an increase of about 70 percent.The results are shown in Table 5.9.
In cases where this method results in flows in excess of the acceptableroadway capacity, a more detailed method should be applied, such as theSCS Graphical Method or a suitable hydrological computer model.
If properly laid out the major system can tolerate the variability in flowsestimated by the various methods. A minor increase in the depth of surfaceflow will greatly increase the capacity of the major system, without neces-sarily causing serious flooding. The designer must also consider the re-maining overland flow accumulated at the downstream end of the develop-ment; adequate consideration must be given for its conveyance to the re-ceiving water body. This may involve increasing the minor system andinlet capacities or providing adequate drainage swales.
Table 5.8 Equivalent alternative n = .012
Location
M.H. M.H. Pipe SizeStreet From To mm
1 2 2002 3 3003 4 4004 5 4006 7 2007 8 2008 9 300
10 11 30011 12 30012 13 4005 9 5009 13 600
13 14 60014 15 60015 16 70016 Outfall 800
156 MODERN SEWER DESIGN
Tabl
e 5.
9 M
ajor
sys
tem
flow
s fo
r 10
0 ye
ar s
torm
Runo
ffTo
tal
Tim
e of
Inte
nsity
Tota
l Run
off
Sew
er*
Maj
or S
yste
mRo
adSu
rface
Loca
tion
Area
Sect
ion
Conc
entra
tion
IQ
Capa
city
(ove
rland
flow
)Gr
ade
Capa
city
**M
H to
MH
(ha)
CA
x C
A x
Cm
in.
(mm
/hr)
(m3 /s
)(m
3 /s)
(m3 /s
)%
(m3 /s
)
1-2
0.74
0.60
0.44
0.44
10.0
179
0.22
0.07
0.15
2.00
5.15
2-3
1.10
0.60
0.66
1.10
11.5
174
0.5 3
0.11
0.42
2.00
5.15
3-4
1.04
0.60
0 .62
1.72
12.8
160
0.76
0.14
0.63
2.00
5.15
4-5
0.83
0.60
0.50
2.22
14.2
151
0.93
0.14
0.79
1.90
5.09
6-7
1.06
0.60
0.64
0.64
10.0
179
0.31
0.11
0.21
2.00
5.15
7-8
––
––
11.5
169
0.00
0.00
0.00
2.20
5.41
8-9
1.50
0.60
0.90
1.54
13.0
159
0.67
0.14
0.53
2.00
5.15
10-1
11.
800.
601.
081.
0810
.017
90.
530.
130.
411.
854.
9611
-12
0.71
0.60
0.43
1.51
11.5
169
0.70
0.14
0.57
2.00
5.15
12-1
30.
420.
600.
251.
7612
.016
00.
780.
120.
662.
205.
41
5-9
0.43
0.60
0 .26
2.48
15.7
142
0.98
0.12
0.85
2.00
7.79
9-1
30.
530.
600.
323.
6217
.113
61.
360.
121.
242.
007.
7913
-14
2.28
0.60
1.37
6.75
18.4
130
2.41
0.22
2.19
2.50
8.78
14-1
50.
550.
600.
337.
0820
.912
02.
340.
232.
112.
007.
7915
-16
2.35
0.60
1.41
8.49
23.4
113
2.65
0.23
2.43
0.50
3.96
16-O
utfa
ll–
––
8.49
24.0
112
2.62
0.23
2.39
0.50
3.96
*As
sum
ing
suffi
cien
t inl
et c
apac
ity**
Refe
r to
Figu
re 5
.5
1575. HYDRAULIC DESIGN OF STORM SEWERS
Foundation DrainsTo establish the groundwater level, piezometer measurements over a 12month period were taken, indicating the groundwater table would be safelybelow the footing elevations for the proposed buildings, minimizing theamount of inflow that can be expected into the foundation drains.
The municipal requirements include detailed lot grading control, thusfurther reducing the possibility of surface water entering the foundationdrains. Accordingly a flow value of 7.65 x 10-5 m3/s per basement is used.See the discussion on Foundation Drains in Chapter 2 of this text. For de-tailed calculations see Table 5.10.
Computer ModelsThere is a wide range of computer models now available for analyzingsewer networks. The complexity of the models varies from straightforwardmodels which use the rational method to estimate the peak flow to compre-hensive models which are based on the continuity and momentum equa-tions and are capable of modeling surcharge, backwater, orifices, weirsand other sewer components.
Table 5.11 lists several of these models and their capabilities.
Smooth-lined CSP storm sewer being installed.
158 MODERN SEWER DESIGN
Tabl
e 5.
10 F
ound
atio
n dr
ain
colle
ctor
des
ign
shee
t Unit
Flow
Tota
lFr
omTo
Area
Dens
ityTo
tal
Cum
.Pe
r Uni
tFl
owLe
ngth
Grad
ient
Pipe
Dia
.Ca
paci
tyVe
loci
tyLo
catio
nM
.H.
M.H
.(h
a)(p
er h
a)Un
itsUn
its(m
3 /sx1
0-5 )
(m3 /s
x10-
3 )(m
)%
(mm
)(m
3 /s)
(m/s
)
Cres
cent
‘G’
1A2A
1.20
218
187.
65 1
.38
119
0.98
200
0.03
11.
12Cr
esce
nt ‘G
’2A
3A0.
722
1129
7.65
2.2
294
1.51
200
0.03
71.
37Cr
esce
nt ‘G
’3A
4A1.
492
2251
7.65
3.9
015
20.
5020
00.
022
0.79
Cres
cent
‘G’
4A5A
0.60
29
607.
65 4
.59
930.
5520
00.
023
0.82
Cres
cent
‘G’
1A6A
1.52
223
237.
65 1
.76
152
1.39
200
0.03
61.
28Cr
esce
nt ‘G
’6A
7A0.
932
1437
7.65
2.8
390
2.25
200
0.04
01.
67Cr
esce
nt ‘G
’7A
8A0.
582
946
7.65
3.5
210
51.
3120
00.
035
1.28
Stre
et ‘F
’9A
10A
1.54
330
307.
65 2
.30
137
1.20
200
0.03
41.
21St
reet
‘F’
10A
11A
0.85
317
477.
65 3
.60
133
1.20
200
0.03
41.
21
Stre
et ‘A
’5A
8A0.
633
1310
67.
65 8
.11
821.
8120
00.
041
1.52
Stre
et ‘A
’8A
11A
0.51
310
116
7.65
8.8
775
4.34
200
0.06
32.
31St
reet
‘A’
11A
13A
0.94
319
135
7.65
10.3
013
31.
4220
00.
036
1.34
Sour
ce: P
aul T
heil
Asso
ciat
es L
td.
1595. HYDRAULIC DESIGN OF STORM SEWERS
Table 5.11 Computer models – Sewer system design and analysis
Model Characteristics
Model Purpose:Hydraulic Design • • • •Evaluation/Prediction • • • •
Model Capabilities:Pipe Sizing • • • •Weirs/Overflows • • • •Surcharging • • •Pumping Stations • • •Storage • • •
Hydraulic Equations:Linear Kinematic Wave • •Non-Linear Kinematic Wave • •St. Venant’s – Explicit •St. Venant’s – Implicit •
Ease of Use:High • •Low • • • •
1. Wright, K.K., Urban Storm Drainage Crite-ria Manual, Volume 1, Wright-McLaughlinEngineers, Denver, Colorado, 1969.
2. Dept. of the Army, CE Storm Users Manual,Construction Engineering Research Labora-tory, Champaign, Illinois, 1985.
3. Hydrograph Volume Method of Sewer Sys-tem Analysis, HVM Manual, Dorsch ConsultLimited, Federal Republic of Germany, 1987.
4. Terstriep, M.L., Stall, J.B., Illinois UrbanDrainage Area Simulator (ILLUDAS), Illi-nois State Water Survey, Bulletin 58, Urbana,Illinois, 1974.
5. Huber, W.C. Heaney, J.P. and Cunningham,B.A., Stormwater Management Model (SWMMVersion IV) Users Manual, U.S.Envioronmental Protection Agency, 1986.
6. Wallingford Storm Sewer Package (WASSP),Users Guide, Hydraulics Research Laboratory,Wellingford, UK, 1984.
REFERENCES
HV
M D
orsc
h3
CE
Sto
rm2
ILLU
DA
S4
SW
MM
-Ext
ran5
SW
MM
-Tra
nspo
rt5
WA
SS
P-S
IM6