A 120-acre watershed has a runoff coefficient of 0.45 and time of concentration of 35 min. For a 25-year, 1-hour rainfall intensity of 2.8 in/h, the peak discharge by the rational method is nearest to:

Why is this the answer?

The Rational Method formula is Q = CiA. Using the provided intensity of 2.8 in/h directly (assuming it represents the intensity for the duration equal to Tc), Q = 0.45 * 2.8 * 120 = 151.2 cfs. However, if the 1-hour intensity is 2.8 in/h, the intensity for 35 minutes is typically higher. Given the options provided, there is a discrepancy in the problem statement's intensity values. Based on standard Rational Method application Q=CiA, 151 cfs is the result; none of the options match. If we assume the intended answer is 68 cfs, the calculation is flawed.

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