A robust approach to the derivation of intensity-frequency-duration (IFD) curves for a large region

Rainfall intensity-frequency-duration (IFD) curves are often used by engineers and environmental modellers for the design of a wide range of hydraulic structures and for environmental studies. Current practice of deriving the IFD curves for any Australian location is based on the design criteria of the Australian Rainfall and Runoff (ARR). With the advancement of knowledge as reported in the literature, and extensive fine scale data availability, it is high time to review the ARR methodology. This paper presents a robust approach to the derivation of the IFD curves for any location in Australia. The new approach is based on stochastic disaggregation of daily rainfall data to any fine timescale. The disaggregation model incorporates repetition techniques and a proportional adjusting procedure into a regionalized hybrid model. A novel approach of the capping of the simulation time scale depths to improve the IFD curve estimation is presented. The disaggregation model is linked to SILO Data Drill Facility that generates long-term (1889 to date) daily rainfall data for any location within Australia. Initial results of the derivation of the IFD curves for selected locations in Australia are very encouraging.