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Abstract

Estimates of design floods are required for the design of hydraulic structures and to quantify the risk of failure of the structures. Most of the methods currently used for design flood estimation in South Africa were developed in the late 1960s and early 1970s and are in need of updating with more than 40 years of additional data currently available and with new approaches used internationally. This has resulted in the initiation of a National Flood Studies Programme (NFSP) which, to date, has updated 1-day design rainfall and probable maximum precipitation estimation, identified and recommended the best probability distribution to use for flood frequency analyses, developed regionalised quantile regression and index flood approaches to flood estimation at a national scale, determined locally derived Curve Numbers for the SCS model using both observed and simulated flows, developed an ensemble approach for the SCS-SA model in a pilot study, and developed a continuous simulation approach to flood estimation on a national scale. This presentation will summarise the development of a continuous simulation approach to flood estimation and the use continuous simulation to improve the performance of the event-based SCS-SA model when applied using default parameters extracted from a national quinary catchment scale parameter database, thus enabling the SCS-SA model to be applied for design flood estimation at any location in South Africa.