1:45pm 25/08/2026 to 1:45pm 27/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
4.8 mm
8:15am 27/08/2026
8:30am 27/08/2026
1 in 1.1 years
93.29 %
30m
9.2 mm
8:15am 27/08/2026
8:45am 27/08/2026
1 in 1.5 years
65.49 %
45m
13.2 mm
8:15am 27/08/2026
9:00am 27/08/2026
1 in 2.3 years
44.21 %
60m
17.8 mm
8:15am 27/08/2026
9:15am 27/08/2026
1 in 3.8 years
25.98 %
90m
24.0 mm
8:15am 27/08/2026
9:45am 27/08/2026
1 in 6.4 years
15.69 %
120m
29.6 mm
8:00am 27/08/2026
10:00am 27/08/2026
1 in 9.0 years
11.07 %
3h
37.6 mm
7:45am 27/08/2026
10:45am 27/08/2026
1 in 12.4 years
8.09 %
4h
45.0 mm
7:45am 27/08/2026
12:15pm 27/08/2026
1 in 13.3 years
7.49 %
6h
48.6 mm
7:30am 27/08/2026
1:30pm 27/08/2026
1 in 11.5 years
8.71 %
9h
49.0 mm
4:30am 27/08/2026
1:30pm 27/08/2026
1 in 6.9 years
14.46 %
12h
51.0 mm
1:30am 27/08/2026
1:30pm 27/08/2026
1 in 5.6 years
17.8 %
18h
51.0 mm
7:30pm 26/08/2026
1:30pm 27/08/2026
1 in 3.7 years
27.16 %
24h
51.0 mm
1:30pm 26/08/2026
1:30pm 27/08/2026
1 in 2.9 years
34.4 %
30h
51.0 mm
7:30am 26/08/2026
1:30pm 27/08/2026
1 in 2.5 years
40.6 %
36h
51.0 mm
1:30am 26/08/2026
1:30pm 27/08/2026
1 in 2.2 years
45.62 %
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.

