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.

2016 IFDs (new)

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

ARR87 IFDs

Should be used:

  • for old flood studies
  • to compare changes between 2016 IFDs and ARR87 IFDs
  • if adopting the ARR87 Probabilistic Rational Method

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