Question

2. For the drainage system as shown in figure below, determine the design flow and determine the pipe size for each of the sewer section by rational method. The rainfall intensity (in/hr) is given by the IDF curve in second figure. The design frequency storm is 10-year storm. Flow from each area is shown by an arrow. The flow velocity in each pipe can be calculated by Manning's equation or Hazen-William equation by assuming a full pipe condition for peak flows. Assume that the pipe material is concrete. Verify all the pipe flow velocities and time of concentration at the end of calculation Unit Area(ac) Runoff Coefficient, C Overland flow time (min) 0.5 B 0.9 0.9 D 1.4 1.4 F 1.0 0.7 0.4 0.60+0.0X 0.65+0.0X 0.75+0.0X 0.70+0.0X 0.80+0.0X 0.70+0.0X 0.65+0.0X 0.75+0.0X X-last-digit of your Student ID. 10 12 14 Pipe Lengths | Feet-lop- 1-2 2-3 3-5 4-5 500 0.004 480 0.0075 600 0.0075 1100 0.0065 6-7 600 0.0055 7-8 400 0.0036 8-5 600 0.0075 5-9 700 0.008
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Answer 1

Pipe Length	Feet	Slope
1-2	500	0.004
2-3	480	0.0075
3-5	600	0.0075
4-5	1100	0.0065
6-7	600	0.0055
7-8	400	0.0036
8-5	600	0.0075
5-9	700	0.008

Unit	Area (ac)	Area (ft2)	Runoff coefficient, C	Overland Flow time	Q=CiA (ft3/min)	ft3/sec
A	0.5	21780	0.6	5	63.52137	1.058689
B	0.9	39204	0.65	11	123.8667	2.064445
C	0.9	39204	0.75	10	142.9231	2.382051
D	1.4	60984	70	12	20750.31	345.8386
E	1.4	60984	0.8	14	237.1464	3.952441
F	1	43560	0.7	11	148.2165	2.470275
G	0.7	30492	0.65	8	96.34074	1.605679
H	0.4	17424	0.75	6	63.52137	1.058689

Pipe	Carries Discharge of Areas	Net Discharge	Pipe Diameter (in.)	Pipe Diameter (rounded)(in.)	Velocity (ft/sec)	Time to travel (min)
1-2	A	1.0586895	6.171	7	10.54	0.8
2-3	A+B	3.123134025	8.184	9	17.69	0.46
3-5	A+B+C	5.5051854	10.153	11	20.26	0.5
4-5	D	345.83857	50.469	51	51.49	0.36
6-7	F	2.4702755	7.978	8	14.72	0.68
7-8	F+G	2.4702755	8.704	9	12.37	0.54
8-5	F+G+H	5.134644075	9.887	10	19.92	0.51
5-9	A+B+C+D+E+F+G+H	360.4308403	49.129	50	56.63	0.21

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