Regionalisation of rainfall temporal patterns in New South Wales for application with the Monte Carlo simulation technique to design flood estimation

![CDATA[The Design Event Approach (DEA), the recommended rainfall-based design flood estimation method in Australian Rainfall and Runoff, has a number of limitations including a probability bias in the final design flood estimates. To overcome these limitations, considerable research has been undertaken recently on the development and application of the Joint Probability Approach (JPA)/Monte Carlo Simulation Technique (MCST) to design flood estimation. The previous applications of this method with Victoria and Queensland data have shown that MCST can overcome some of the limitations associated with the DEA and this can produce more accurate design flood estimates. The wider application of the MCST, however, needs regionalisation of various input variables to the runoff routing model which include rainfall parameters such as duration, intensity, temporal pattern and losses. This paper focuses on the regionalisation of the rainfall temporal patterns in New South Wales, Australia using 86 pluriograph stations so that this can be applied with the MCST to obtain design flood estimates for both gauged and ungauged catchments in NSW. It has been found that the use of at-site and regional temporal patterns can give up to 10% differences in flood quantile estimates using the MCST. In this study, a new random variable, rainfall inter-event duration, has been tested along with other randomly distributed random variables (i.e. rainfall duration, rainfall intensity, initial loss, continuing loss and runoff routing model parameter) in the MCST, which has provided reasonable results. Future study focuses on the applicability of the MCST to a larger catchment data set in NSW to test the applicability of various derived regional input variables in the MCST.]]