CIVE 445 - ENGINEERING HYDROLOGY SPRING 2004 - MIDTERM 2 - SOLUTION

PROBLEM 2

To convolute the 2-hr unit hydrograph with the effective storm pattern defined at intervals of 3 hr, it is necessary to change the unit hydrograph duration to 3 hr. We use the S-hydrograph method to change the 2-hr UH to 3-hr UH.

To calculate the flood hydrograph, for 3 cm, it is 3 times; for 6 cm, it is 6 times (lagged 3 hr).

Time	2-hr UH	2-hr SH	Lagged 3 hr	3-hr UH	3×UH	6×UH (lagged 3 hr)	Flood hydrograph
(hr)	(mm/hr)	mm/h	(ha)	(m3/s)	(m3/s)	(m3/s)	(m3/s)
0	0	0	0	0.00	0	0	0
1	5	5	0	3.33	10	0	10
2	15	15	0	10.00	30	0	30
3	30	35	0	23.33	70	0	70
4	60	75	5	46.67	140	20	160
5	75	110	15	63.33	190	60	250
6	65	140	35	70.00	210	140	350
7	55	165	75	60.00	180	280	460
8	45	185	110	50.00	150	380	530
9	35	200	140	40.00	120	420	540
10	25	210	165	30.00	90	360	450
11	15	215	185	20.00	60	300	360
12	5	215	200	10.00	30	240	270
13	0	215	210	3.33	10	180	190
14	0	215	215	0.00	0	120	120
15	0	215	215	0.00	0	60	60
16	0	215	215	0.00	0	20	20
17	0	215	215	0.00	0	0	0
∑	430	-	-	429.99	0	0	3870 [= 430 ×9]

Problem 1

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