7:15pm 15/08/2026 to 7:15pm 17/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
26.2 mm
3:00pm 17/08/2026
3:15pm 17/08/2026
1 in 122.2 years
0.82 %
30m
26.2 mm
2:45pm 17/08/2026
3:15pm 17/08/2026
1 in 28.0 years
3.57 %
45m
26.6 mm
2:30pm 17/08/2026
3:15pm 17/08/2026
1 in 14.3 years
6.98 %
60m
26.8 mm
2:15pm 17/08/2026
3:15pm 17/08/2026
1 in 9.1 years
11.01 %
90m
27.4 mm
1:45pm 17/08/2026
3:15pm 17/08/2026
1 in 5.3 years
18.85 %
120m
29.4 mm
1:15pm 17/08/2026
3:15pm 17/08/2026
1 in 4.5 years
22.24 %
3h
30.6 mm
12:15pm 17/08/2026
3:15pm 17/08/2026
1 in 2.7 years
36.49 %
4h
37.0 mm
10:45am 17/08/2026
3:15pm 17/08/2026
1 in 3.3 years
30.67 %
6h
37.2 mm
10:00am 17/08/2026
4:00pm 17/08/2026
1 in 2.3 years
43.94 %
9h
37.8 mm
10:15am 17/08/2026
7:15pm 17/08/2026
1 in 1.6 years
62.28 %
12h
37.8 mm
7:15am 17/08/2026
7:15pm 17/08/2026
1 in 1.3 years
75.21 %
18h
37.8 mm
1:15am 17/08/2026
7:15pm 17/08/2026
1 in 1.1 years
90.69 %
24h
37.8 mm
7:15pm 16/08/2026
7:15pm 17/08/2026
1 in 1.0 years
96.21 %
30h
37.8 mm
1:15pm 16/08/2026
7:15pm 17/08/2026
1 in 1.0 years
98.32 %
36h
37.8 mm
7:15am 16/08/2026
7:15pm 17/08/2026
1 in 1.0 years
98.9 %
Note: A '1 in 1.0 years' estimate means that it is almost certain to occur at least once in a year, and could occur much more than once per year on average. For smaller values like this the Annual Recurrance Interval (ARI) may be of more relevance, but it is complex to calculate for common events.
IFD describes how rainfall intensity relates to how long it lasts and how often it happens. It is the basis for design rainfall used in engineering and flood studies.
- Duration: the length of the rainfall burst, from a few minutes to several days.
- AEP (Annual Exceedance Probability): the chance, in any one year, of a rainfall of that depth or greater. A 1% AEP event has a 1 in 100 chance each year - what is often loosely called a '1 in 100 year' event.
- The curves show design rainfall depths for a range of AEPs. The observed maximums for this location and period are plotted against them so you can see how rare the event was.
Design rainfall data is sourced from the Bureau of Meteorology.

