|| 21 Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com- pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are marked in Fig. P 2.27 (a). Assume: (i) Run-off coefficient for the entire area 0.30 (ii) Velocity of flow in sewers flowing full = 0.75 m/sec (iii) 5-year average frequency curve may be used, Fig. P 2.27 (b), (iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2. Table 2.2 Hydraulic elements for a circular pipe flowing full Discharge (lps) 400 600 690 1500 2000 1A=0.016 km Inlet time = 5 min, A=0.032. km Inlet time = 5 min 1 Diameter (mm) Manhole 1 120 m sewer, 180 m- sewer BManhole 2 A=0.024 km Inlet time = 8 min 450 525 1050 1350 1450 (a) Watershed system Most remote point Manhole 3 200 Rainfall intensity, mm/hr Discharge 175 150 125 100 75 50 Slope of Pipe (m/m) 25-year ave! frequency 10-year ave! frequency 5-year ave. frequency Velocity (m/sec) 0.025 0.020 0.00055 0.75 0.001 1.55 0.001 1.20 [690 lps, 0.75 m/s, 1 m laid at 1 in 1800] 2.7 2.8 0 5 10 20 30 40 50 60 70 80 90 100 110 120 Duration of rainfall, min (b) Rainfall intensity-duration curves for computation of storm water runoff Fig. P2.27 Storm water drainage project
|| 21 Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com- pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are marked in Fig. P 2.27 (a). Assume: (i) Run-off coefficient for the entire area 0.30 (ii) Velocity of flow in sewers flowing full = 0.75 m/sec (iii) 5-year average frequency curve may be used, Fig. P 2.27 (b), (iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2. Table 2.2 Hydraulic elements for a circular pipe flowing full Discharge (lps) 400 600 690 1500 2000 1A=0.016 km Inlet time = 5 min, A=0.032. km Inlet time = 5 min 1 Diameter (mm) Manhole 1 120 m sewer, 180 m- sewer BManhole 2 A=0.024 km Inlet time = 8 min 450 525 1050 1350 1450 (a) Watershed system Most remote point Manhole 3 200 Rainfall intensity, mm/hr Discharge 175 150 125 100 75 50 Slope of Pipe (m/m) 25-year ave! frequency 10-year ave! frequency 5-year ave. frequency Velocity (m/sec) 0.025 0.020 0.00055 0.75 0.001 1.55 0.001 1.20 [690 lps, 0.75 m/s, 1 m laid at 1 in 1800] 2.7 2.8 0 5 10 20 30 40 50 60 70 80 90 100 110 120 Duration of rainfall, min (b) Rainfall intensity-duration curves for computation of storm water runoff Fig. P2.27 Storm water drainage project
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
Related questions
Question
(Civil engineering hydrology)
![||
21 Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com-
pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are
marked in Fig. P 2.27 (a). Assume:
(i) Run-off coefficient for the entire area 0.30
(ii) Velocity of flow in sewers flowing full = 0.75 m/sec
(iii) 5-year average frequency curve may be used, Fig. P 2.27 (b),
(iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2.
Table 2.2 Hydraulic elements for a circular pipe flowing full
Discharge
(lps)
400
600
690
1500
2000
1A=0.016 km
Inlet time = 5 min,
A=0.032.
km
Inlet time
= 5 min
1
Diameter
(mm)
Manhole 1
120 m
sewer
180 m-
sewer
BManhole 2
A=0.024 km
Inlet time = 8 min
450
525
1050
1350
1450
(a) Watershed system
Most remote
point
Manhole 3
Rainfall intensity, mm/hr
Discharge
200
175
150
125
100
75
50
Slope of Pipe
(m/m)
Velocity
(m/sec)
25-year ave! frequency
10-year ave! frequency
5-year ave. frequency
0.025
0.020
0.00055
0.75
0.001
1.55
0.001
1.20
[690 lps, 0.75 m/s, 1 m laid at 1 in 1800]
2.7
2.8
0 5 10 20 30 40 50 60 70 80 90 100 110 120
Duration of rainfall, min
(b) Rainfall intensity-duration curves for
computation of storm water runoff
Fig. P2.27 Storm water drainage project
22 Explain step by step the procedure you would adopt to prepare the depth area-duration curves](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F04aa96a8-f797-4f02-a591-d0e36329df37%2F237436ad-3a91-40ae-a62b-109c4c5db44c%2F6rgsvcf_processed.jpeg&w=3840&q=75)
Transcribed Image Text:||
21 Using rational method, rainfall intensity-duration curves and the data given in Fig. P 2.27 com-
pute the diameter of the outfall sewer. The length of lines, drainage areas, and inlet times are
marked in Fig. P 2.27 (a). Assume:
(i) Run-off coefficient for the entire area 0.30
(ii) Velocity of flow in sewers flowing full = 0.75 m/sec
(iii) 5-year average frequency curve may be used, Fig. P 2.27 (b),
(iv) Hydraulic elements for circular pipes flowing full are given in Table 2.2.
Table 2.2 Hydraulic elements for a circular pipe flowing full
Discharge
(lps)
400
600
690
1500
2000
1A=0.016 km
Inlet time = 5 min,
A=0.032.
km
Inlet time
= 5 min
1
Diameter
(mm)
Manhole 1
120 m
sewer
180 m-
sewer
BManhole 2
A=0.024 km
Inlet time = 8 min
450
525
1050
1350
1450
(a) Watershed system
Most remote
point
Manhole 3
Rainfall intensity, mm/hr
Discharge
200
175
150
125
100
75
50
Slope of Pipe
(m/m)
Velocity
(m/sec)
25-year ave! frequency
10-year ave! frequency
5-year ave. frequency
0.025
0.020
0.00055
0.75
0.001
1.55
0.001
1.20
[690 lps, 0.75 m/s, 1 m laid at 1 in 1800]
2.7
2.8
0 5 10 20 30 40 50 60 70 80 90 100 110 120
Duration of rainfall, min
(b) Rainfall intensity-duration curves for
computation of storm water runoff
Fig. P2.27 Storm water drainage project
22 Explain step by step the procedure you would adopt to prepare the depth area-duration curves
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