Design Hyetograph for Typhoon Rainstorms in Taiwan

The design flood can be determined by transposing the design storm observed in the region surrounding the project and converting the storm to flow by use of a simple rainfall-runoff relation or a watershed runoff model. In this study, a design hyetograph in a double-triangular shape of 48h duration was derived from rainfall intensity–duration–frequency curve to represent the time distribution of severe typhoon rainstorms. The design floods generated by performing a rainfall-runoff model using design hyetographs as inputs were verified using the flow records from 17 watersheds in Taiwan. The result indicated that the generated design discharge using the proposed hyetograph for specified return periods were close to the discharge obtained from frequency analysis using flow records. The proposed design hyetograph can be applied to areas that are usually threatened by typhoon rainstorms.