Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Infiltration – indices and equations
Question Statement:
The 6-hour unit hydrograph of a watershed is represented by an isosceles triangle with the peak of 180 m³ s⁻¹ and time to peak of 18 hours. The phi-index (φ) of this watershed is 3.0 mm h⁻¹ and the constant baseflow is 20 m³ s⁻¹. The accumulated rainfall received in this watershed at 6 h and 12 h from the start of the storm are 38 mm and 106 mm, respectively. The resulting peak of the flood hydrograph due to this storm event is _______ m³ s⁻¹.
Official Answer Key:
1280 to 1280
Step-by-Step Solution & Explanation
Rainfall increments: 0–6 h = 38 mm; 6–12 h = 106 − 38 = 68 mm.
Loss per 6-h block at φ = 3 mm h⁻¹: 18 mm.
Effective rainfall: ER₁ = 38 − 18 = 20 mm = 2.0 cm; ER₂ = 68 − 18 = 50 mm = 5.0 cm. Total ER = 7.0 cm.
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.