Design Rainfalls

Design flood support

Hundreds of millions of dollars are spent annually on hydraulic structures in Australia, ranging from small drains and culverts to bridges and large dams used for town water supply and irrigation.

Rainfall intensity, frequency and duration (IFD) data plays an integral part in the design of these structures and the Bureau has completed a major revision of the information it provides in this domain as part of Australian Rainfall and Runoff 2016 (ARR2016).

The Bureau now provides design rainfall information in the form of:

  • Very Frequent design rainfall information, related to a range of water-sensitive urban design (WSUD) applications and some stormwater design
  • Intensity–Frequency–Duration (IFD) information, used in the design of gutters, culverts and stormwater drains
  • Rare design rainfall information, used in the design of bridges and spillway adequacy assessment of existing dams
  • Probable Maximum Precipitation (PMP) estimates for the design of high-consequence infrastructure such as large dams

2016 IFD information NEW

The Bureau of Meteorology released the new IFD design rainfall estimates in 2016 which replace the interim 2013 IFD estimates.

The 2016 IFDs are based on a more extensive database, with more than 30 years of additional rainfall records and inclusion of data from an extra 2300 rainfall stations across Australia. By combining contemporary statistical analysis and techniques with this expanded rainfall database, the 2016 IFDs provide more accurate design rainfall estimates for Australia. In addition, the 2016 IFDs provide better estimates of the 2% and 1% annual exceedance probability (AEP) IFDs than the interim 2013 IFDs.

Very Frequent and Rare design rainfall information NEW

In addition, the suite of design rainfalls has been expanded to include:

  • Very Frequent design rainfalls with probabilities from 2 to 12 exceedances per year (EY)
  • Rare design rainfalls with probabilities less than 1% AEP (1-in-100 to 1-in-2000 AEP)

This makes them applicable to a wider range of applications.

The new design rainfalls should be used in conjunction with the other design inputs contained in the 2016 edition of Australian Rainfall and Runoff (ARR2016).

Access the new design rainfalls.

For more information on the new design rainfalls see the Frequently Asked Questions.

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