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7.8 A rectangular paved area 150 m x 450 m has a longitudinal drain along one of its longer edges. The time of concentration for the area is estimated to be 30 minutes1dealiızed outflow hydrographs for D =5 and 40 nutes.
7.8 A rectangular paved area 150 m x 450 m has a longitudinal drain along one of its longer edges. The time of concentration for the area is estimated to be 30 minutes and consists of 25 minutes for over land flow across the pavement to the drain and 5 minutes for the maximum time from the upstream end of the drain to the outlet at the other end. (a) Construct the isochrones at 5 minutes interval for this area. (b) A rainfall of 7 cm/h occurs on this plot for D minutes and stops abruptly. Assuming a runoff coefficient of 0.8 sketch idealized outflow hydrographs for D = 5 and 40 minutes.