CIVE 445 - ENGINEERING HYDROLOGY FALL 2008 - 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 6 cm, it is 6 times; for 12 cm, it is 12 times (lagged 3 hr).

Time	2-hr UH	2-hr SH	Lagged 3 hr	3-hr UH	6×UH	12×UH (lagged 3 hr)	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	20	0	20
2	15	15	0	10.00	60	0	60
3	30	35	0	23.33	140	0	140
4	60	75	5	46.67	280	40	320
5	70	105	15	60.00	360	120	480
6	60	135	35	66.67	400	280	680
7	55	160	75	56.67	340	560	900
8	45	180	105	50.00	300	720	1020
9	35	195	135	40.00	240	800	1040
10	25	205	160	30.00	180	680	860
11	15	210	180	20.00	120	600	720
12	5	210	195	10.00	60	480	540
13	0	210	205	3.33	20	360	380
14	0	210	210	0.00	0	240	240
15	0	210	210	0.00	0	120	120
16	0	210	210	0.00	0	40	40
17	0	210	210	0.00	0	0	0
∑	420	-	-	420.00	2520 [= 420×6]	5040 [= 420×12]	7560 [= 420×18]

Problem 3

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