Intensity–Frequency–Duration
The 2016 Intensity–Frequency–Duration (IFD) design rainfalls are provided for use in conjunction with the 2016 edition of Australian Rainfall and Runoff (ARR2016) http://arr.ga.gov.au/arr-guideline
The 2016 IFDs:
- are based on a more extensive database, with more than 30 years of additional rainfall data and data from extra rainfall stations;
- are more accurate estimates, combining contemporary statistical analysis and techniques;
- have an increased probability range from 12 exceedances per year to 1-in-2000 annual exceedance probability;
- provide better estimates of the 2% and 1% annual exceedance probability IFDs than the interim 2013 IFDs.
While access to the ARR87 IFDs will be maintained for a short period, use of these previous estimates should be limited to the guidance provided below.
Should be used:
- in conjunction with ARR2016
- for new flood studies and flood assessments but must be used with the other ARR2016 design inputs
- for sensitivity assessments of older studies and studies already underway
Should be used:
- for old flood studies
- to compare changes between 2016 IFDs and ARR87 IFDs
- if adopting the ARR87 Rural Probabilistic Rational Method