Detention Storage over 2D Laboratory Watersheds at Concentration Time

Abstract

AbstractWater balances, for two-dimensional (2D) laboratory experiments with long-duration rainfalls over planar aluminum surfaces, indicate that at time of concentration the detention storage comprises about 70% of the accumulating inflow. Under the applied experimental conditions, its spatially averaged depth is 1 to 6 mm. This depth increases with rainfall intensity and decreases with main watershed slope. The time of concentration is defined here from rainfall commencement until the outflow begins a gradual approach towards the equilibrium state. It was shown, in an earlier paper, that the ratio of peak runoff discharge to rate of supply attributable to rainfall of a shorter duration is linearly related to the ratio of rainfall duration to time of concentration. Such a relation led to the formulation of the 120-year-old Rational Formula, commonly used for hydrologic design of populous districts. The similarity between laboratory and field results allows considering the detention depths in the laborato...