Station‐Year Approach: Tool for Estimation of Design Floods

Abstract

The processing of composite samples by the station‐year approach either coupled or not coupled to the systematic use of Hershfield's formula can be very helpful when studying design floods. Therefore, a station‐year approach is applied to rainfall and discharge data from Indonesia, Malaysia, and the Philippines to define regional distributions for observed maxima. After a cluster analysis defining groups of homogeneous stations, a double distribution concept is used to properly take into account the existence of outliers. Results are compared with information available on probable maximum precipitation (PMP) and design floods. Concerning Indonesian rainfall data, the estimate of 10,000‐year daily rainfall was consistent with the application of Hershfield's method for computing PMP. Hershfield's PMP was between 73% and 115% of the 10,000‐year daily rainfall. The processing of discharge data yields results that are confirmed by project inflow design floods. The method provides a bridge between statistical and hydrometeorological approaches. Regional analysis obliges to weigh the occurrence of outliers. Data clustering is recommended for applications involving large amounts of information.