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10.8. In Miami-Dade County, the kinematic-wave equation is recommended for calculating the time of concentration (tC) on asphalt pavements, the minimum slope toward drainage inlets is specified as 0.26. The

IDF curve to be used in drainage design is given by(10.160) where i is the average rainfall intensity in mm/h, t is the rainfall duration, and T is the return period. In lieu of calculating the time of concentration in parking-lot drainage designs, a common approximation is to assume that tc=10 min. (a) Estimate the circular catchment area surrounding an inlet that would have tc=10 min, and the average rainfall intensity and peak runoff from this area corresponding to a return period of 5 yr. (b) If the catchment area surrounding the inlet has a radius of 50 m, what is the actual time of concentration and peak runoff? (c) If tc=10 min were assumed in Part (b), what would be the percentage error in the calculated peak runoff? Would you consider this difference to be of any practical significance? Explain. i=783648.6T-0.11+t(0.5895+T-0.67)mm/h

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