CIVE 445 - ENGINEERING HYDROLOGY SPRING 2010 - 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)	Composite Flood hydrograph
(hr)	(m3/s)	(m3/s)	(m3/s)	(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	20	0	30
3	30	35	0	23.33	70	0	70
4	60	75	5	46.67	140	20	160
5	70	105	15	60.00	180	60	240
6	60	135	35	66.67	200	140	340
7	55	160	75	56.67	170	280	450
8	45	180	105	50.00	150	360	510
9	35	195	135	40.00	120	400	520
10	25	205	160	30.00	90	340	430
11	15	210	180	20.00	60	300	360
12	5	210	195	10.00	30	240	270
13	0	210	205	3.33	10	180	190
14	0	210	210	0.00	0	120	120
15	0	210	210	0.00	0	60	60
16	0	210	210	0.00	0	20	20
17	0	210	210	0.00	0	0	0
∑	420	-	-	420.00	1260 [= 420×3]	2520 [= 420×6]	3780 [= 420×9]

Problem 3

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