7:00am 28/07/2026 to 7:00am 30/07/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
6.0 mm
12:30pm 29/07/2026
12:45pm 29/07/2026
1 in 1.0 years
95.3 %
30m
6.0 mm
12:15pm 29/07/2026
12:45pm 29/07/2026
1 in 1.0 years
99.76 %
45m
7.0 mm
12:00pm 29/07/2026
12:45pm 29/07/2026
1 in 1.0 years
99.8 %
60m
7.0 mm
11:45am 29/07/2026
12:45pm 29/07/2026
1 in 1 years
100.0 %
90m
10.8 mm
11:15am 29/07/2026
12:45pm 29/07/2026
1 in 1.0 years
98.56 %
120m
11.6 mm
11:30am 29/07/2026
1:30pm 29/07/2026
1 in 1.0 years
98.84 %
3h
16.4 mm
9:45am 29/07/2026
12:45pm 29/07/2026
1 in 1.1 years
94.65 %
4h
21.2 mm
8:15am 29/07/2026
12:45pm 29/07/2026
1 in 1.1 years
87.75 %
6h
22.8 mm
7:30am 29/07/2026
1:30pm 29/07/2026
1 in 1.1 years
89.34 %
9h
22.8 mm
4:30am 29/07/2026
1:30pm 29/07/2026
1 in 1.0 years
95.94 %
12h
23.4 mm
6:15am 29/07/2026
6:15pm 29/07/2026
1 in 1.0 years
97.59 %
18h
25.4 mm
8:45pm 28/07/2026
2:45pm 29/07/2026
1 in 1.0 years
98.3 %
24h
27.0 mm
1:30pm 28/07/2026
1:30pm 29/07/2026
1 in 1.0 years
98.44 %
30h
27.6 mm
12:15pm 28/07/2026
6:15pm 29/07/2026
1 in 1.0 years
98.72 %
36h
28.4 mm
4:00pm 28/07/2026
4:00am 30/07/2026
1 in 1.0 years
98.86 %
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.

