Evolution of Kinematic Wave Time of Concentration Formulas for Overland Flow

Time of concentration of overland flow is an important parameter in many hydrologic design methods. This technical note traces the evolution of the kinematic wave time of concentration formulas for overland flow only. It commenced with Henderson and Wooding’s 1964 formula for a single plane. This formula, however, cannot be easily applied in practice because the parameters were not related to the physical characteristics of an overland plane. Nearly four decades later, in 2002, Wong developed a powerful formula, which can be applied to a series of planes which are of different lengths, different slopes, different roughnesses, different flow regimes, different soil types and infiltration rates resulting in different net rainfall intensities, and for planes subject to different net rainfall intensities, and a combination of all these variables. Finally, a comparison of Wong’s 1996 formula with Overton’s 1971 formula shows that Overton’s formula for a series of planes is incorrect.