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CIVE 445 - ENGINEERING HYDROLOGY
SPRING 2005 - MIDTERM 2 - SOLUTION
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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 9 cm, it is 9 times; for 15 cm, it is 15 times (lagged 3 hr).
| Time | 2-hr UH | 2-hr SH
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Lagged 3 hr | 3-hr UH | 9×UH | 15×UH
(lagged 3 hr) | Flood
hydrograph
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| (hr) | (mm/hr) | mm/h
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(ha) | (m3/s) | (m3/s) | (m3/s) | (m3/s)
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0 | 0 | 0 |
0 | 0.00 | 0 | 0 | 0
| 1 | 5 | 5 |
0 | 3.33 | 30 | 0 | 30
| 2 | 15 | 15 |
0 | 10.00 | 90 | 0 | 90
| 3 | 30 | 35 |
0 | 23.33 | 210 | 0 | 210
| 4 | 60 | 75 |
5 | 46.67 | 420 | 50 | 470
| 5 | 70 | 105 |
15 | 60.00 | 540 | 150 | 690
| 6 | 60 | 135 |
35 | 66.67 | 600 | 350 | 950
| 7 | 55 | 160 |
75 | 56.67 | 510 | 700 | 1210
| 8 | 45 | 180 |
105 | 50.00 | 450 | 900 | 1350 |
| 9 | 35 | 195 |
135 | 40.00 | 360 | 1000 | 1360
| 10 | 25 | 205 |
160 | 30.00 | 270 | 850 | 1120
| 11 | 15 | 210 |
180 | 20.00 | 180 | 750 | 930
| 12 | 5 | 210 |
195 | 10.00 | 90 | 600 | 690
| 13 | 0 | 210 |
205 | 3.33 | 30 | 450 | 480
| 14 | 0 | 210 |
210 | 0.00 | 0 | 300 | 300
| 15 | 0 | 210 |
210 | 0.00 | 0 | 150 | 150
| 16 | 0 | 210 |
210 | 0.00 | 0 | 50 | 50
| 17 | 0 | 210 |
210 | 0.00 | 0 | 0 | 0
| ∑ | 420 | - |
- | 420.00 | 3780
[= 420×9] | 6300
[= 420×15] | 10080
[= 420×24]
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Problem 3
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