Identifying Representative Parameters of IUH

Abstract

A simple procedure is proposed, using a linear transform, for obtaining a single representative effective rainfall hyetograph (ERH) and the corresponding direct runoff hydrograph (DRH) by processing multistorm data. Using these representative ERH and DRH, the representative parameters of the two-parameter gamma distribution instantaneous unit hydrograph (IUH) is determined by either the proposed optimization method or the conventional method of moments. The optimization method is found superior to the method of moments and yields reliable IUH. However, the method of moments is easier to apply and yields acceptable results. A two-parameter gamma distribution is used for the parametric representation of the IUH, which yields a smooth shape of the IUH. A linear programming or a least-squares approach does not yield a IUH and the UH it identifies does not have a smooth shape (oscillations are observed in the tail of the UH). The new method yields a reliable representative IUH. The use of the methods is illustrated using the published data sets.