Direction: One hour triangular unit hydrograph of a watershed has the peak discharge of 60 m³/sec.cm at 10 hours and time base of 30 hours. The f index is 0.4 cm per hour and base flow is 15 m³/sec.
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If there is rainfall of 5.4 cm in 1 hour, the ordinate of the flood hydrograph at 15th hour is
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- 225 m³/sec
- 240 m³/sec
- 249 m³/sec
- 258 m³/sec
Correct Option: B
Rainfall excess = Rainfall – φ index
= 5.4 – 0.4 = 5 cm
Base flow = 15 cm³/s
| Ordinate at 15th hour = 5 × | × 15 + 15 = 240 m³/s. | |
| 30 - 10 |
