Expanded design rainfalls to aid infrastructure design

Bridge over reservoir

Cairn Curran Reservoir (Alison Pouliot)

We’ve recently expanded the range of design rainfall estimates to assist water infrastructure design around Australia. This means users can now go to a single web page to access design rainfalls for probabilities ranging from 12 exceedances per year to a 1-in-2000 chance of being exceeded annually, for any location in Australia.
The latest release complements the 2016 Intensity–Frequency–Duration (IFD) design rainfalls, published last November, and includes:
  • Very frequent design rainfalls for probabilities from 12 Exceedances per Year (EY) to 0.2 EY
  • Rare design rainfalls for probabilities from 1-in-100 Annual Exceedance Probability (AEP) to 1-in-2000 AEP
Very frequent design rainfalls have not previously been available. These estimates extend the range of the design rainfalls to cover water-sensitive urban design purposes.
The rare design rainfalls replace the existing CRC-FORGE estimates and provide estimates derived using a consistent database and method across Australia. Rare design rainfalls are used in the design of bridges and are also an integral part of the spillway adequacy assessment of existing dams.
The complete suite of design rainfall estimates is available from the Bureau's website and should be used in conjunction with the 2016 edition of Australian Rainfall and Runoff: A Guide to Flood Estimation (ARR2016) released by Geoscience Australia.