The Bureau of Meteorology has released the new 2013 Intensity-Frequency-Duration(IFD) design rainfalls as part of the revision of ARR. While these are new design IFD rainfall estimates, careful consideration is needed when using these estimates with other 1987 ARR techniques. Advice on what to do in the interim with the new IFD rainfall estimates (before the rest of the ARR design inputs are released) has been developed by EA and BOM and is provided on the BOM website and can also be viewed here. The IFD rainfall estimates can be downloaded at the Bureau of Meteorology.

Project 1 Scope

Detailed IFD relationships across the country were last investigated prior to the publication of the 1987 edition of Australian Rainfall and Runoff. These design IFD relationships across the country were determined using the rainfall data recorded up to 1983. For the analysis it was assumed that the statistical distribution for the developed series was a Log Pearson Type III, skew of the record was a regional feature and could be applied to all durations and frequencies, the data sample at each location was representative of the long-term conditions at that station, and climatic trends had negligible effect on the intensities. Since these data records were analysed, techniques for dissemination of information have changed, the length of data record has increased, new techniques for estimation of the statistical properties of the rainfall have been developed, and the needs of the profession for IFD related information have changed. Project 1 also includes Climate Change research and the goals of this are to:

• Quantify possible changes and uncertainties in rainfall intensity-frequency-duration (IFD) curves due to anthropogenic climate change.
• Provide interim advice to practitioners on how these changes can be included into design and planning decisions.

In this project, the main objective will be to provide interim advice to practitioners on how possible changes in the magnitude and uncertainty of rainfall IFD under anthropogenic climate change can be incorporated into design and planning. In order to estimate these potential changes, IFD curves for the current climate will be compared to IFD curves estimated for a future climate. Current IFD curves will be generated using different regional climate models and alternative statistical methods, and they will be benchmarked against the IFD curves currently being prepared by the BoM as the baseline. Any difference between the generated IFD curves and those prepared by the BoM will be investigated for systematic errors and, if there are biases, the generated IFDs will be corrected to be equivalent to the ARR IFDs. The project will also include two sub-components that will focus on (a) assessing wheter sub-daily rainfall in the study region is non-stationary and (b) using a combination of station and radar data to evaluate the how well dynamically downscaled output reproduces the spatial extent of observed rainfall extremes. The project will focus on the greater Sydney region due to availability of data. A future stage will focus on South East Queensland.

Important documents

Conference Papers Relating to Project 1

Climate Change Guidelines