Variability of Rainfall Temporal Patterns and Its Impacts on Design Flood Estimation

Design rainfall temporal pattern is an important input to the rainfall-based flood estimation methods. Although temporal patterns generally show a high degree of variability from storm to storm, an average temporal pattern is generally used in the Design Event Approach, the recommended rainfall-based design flood estimation method in Australian Rainfall and Run-off. This paper examines the variability of temporal patterns and its impacts on design flood estimates in the Gold Coast region in Queensland, Australia. In particular, it investigates the expected differences in design flood estimates if observed temporal patterns are adopted instead of recommended design temporal patterns. It has been found that the observed temporal patterns generally produce design floods that are notably different than those obtained from the design temporal patterns. This highlights the limitations of the average temporal patterns in design flood estimation as recommended in the Design Event Approach.