ABSTRACTNumerous concepts of surface water lag time have been developed and applied in the past. In this report, hydraulic solutions of a lag time derived by Overton 1970 are presented for several idealistic surfaces using the kinematic wave equations. These surfaces are: (1) a uniform plane; (2) hillslope as a cascade of planes; (3) V‐shaped watershed; (4) V‐shaped watershed with hill‐slopes; (5) converging surface; (6) concave surface.The lag times are shown to be related to roughness, length and catchment slope, and the input rate. These relations may be used immediately in predicting lag time as the parameter in a unit response function. A lag relation has been developed for a nonuniform catchment in terms of the lag of a uniform plane and a convergence factor. A numerical procedure is shown whereby the convergence factor can be evaluated for any nonuniform catchment from observed input and output
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