ABSTRACT
Stormwater storage facilities are designed to pass unsteady runoff flows. A hydrograph presents variations of flow rate versus time. At a stream gauge station, the flow depths in the river over a period of time can be directly measured, recorded, and then converted into observed hydrographs. With the advance of computing technologies, many numerical algorithms have been derived to convert a rainfall hyetograph into its runoff hydrograph generated from the specified tributary watershed. The unit hydrograph (UH) method is one of the numerical approaches developed to predict rainfall-induced runoff flows. Although the procedure of the UH was intuitively derived based on the assumption of a linear relationship between runoff flow and excess rainfall depth, the predicted runoff hydrographs can be used for the purpose of engineering designs.
