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 ^$\phi$ index is 0.4 cm per hour and base flow is 15 m³m/sec.

If there is rainfall of 5.4 cm in 1 hour, the ordinate of the flood hydrograph at 15^th hour is

Effective rainfall = 5.4 - (0.4 * 1) = 5.0 cm. The ordinate of the flood hydrograph = (Effective Rainfall * Unit Hydrograph Ordinate) + Base Flow. At 15 hours, the UH ordinate is calculated by linear interpolation: at 10h it is 60, at 30h it is 0. So at 15h, it is 60 * (30-15)/(30-10) = 60 * 15/20 = 45. Flood hydrograph = (5 * 45) + 15 = 225 + 15 = 240 m^3/s.