The surface of a 2-ha catchment is characterized by a runoff coefficient of 0.5, a Manning n for overland flow of 0.25, an average overland flow length of 60 m, and an average slope of 0.5%. The time of concentration can be calculated by the kinematic-wave equation. The drainage channel is to be sized for the peak runoff resulting from a 10-year rainfall event, and the 10-year IDF curve is given by i=150/(t+8.96)^.78

where i is the average rainfall intensity in cm/h and t is the duration in minutes. The minimum time of concentration is 5 minutes. Determine the peak runoff rate.