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Light mode 5:15am 15/07/2026 to 5:15am 17/07/2026
You can find out more about Design Rainfall and IFD here.
Observations for this analysis :
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
9.0 mm
5:30pm 16/07/2026
5:45pm 16/07/2026
1 in 1.2 years
85.56 %
30m
12.8 mm
5:30pm 16/07/2026
6:00pm 16/07/2026
1 in 1.3 years
77.03 %
45m
16.2 mm
5:15pm 16/07/2026
6:00pm 16/07/2026
1 in 1.5 years
68.32 %
60m
22.0 mm
4:45pm 16/07/2026
5:45pm 16/07/2026
1 in 2.3 years
43.27 %
90m
30.2 mm
4:30pm 16/07/2026
6:00pm 16/07/2026
1 in 5.1 years
19.67 %
120m
33.6 mm
4:30pm 16/07/2026
6:30pm 16/07/2026
1 in 5.1 years
19.44 %
3h
41.8 mm
4:30pm 16/07/2026
7:30pm 16/07/2026
1 in 7.3 years
13.62 %
4h
47.0 mm
2:45pm 16/07/2026
7:15pm 16/07/2026
1 in 6.0 years
16.76 %
6h
49.4 mm
1:15pm 16/07/2026
7:15pm 16/07/2026
1 in 4.4 years
22.83 %
9h
49.6 mm
12:30pm 16/07/2026
9:30pm 16/07/2026
1 in 2.4 years
42.31 %
12h
49.6 mm
7:15am 16/07/2026
7:15pm 16/07/2026
1 in 1.9 years
53.56 %
18h
49.8 mm
8:00am 16/07/2026
2:00am 17/07/2026
1 in 1.4 years
70.26 %
24h
49.8 mm
3:00am 16/07/2026
3:00am 17/07/2026
1 in 1.2 years
81.9 %
30h
49.8 mm
9:00pm 15/07/2026
3:00am 17/07/2026
1 in 1.1 years
89.07 %
36h
49.8 mm
3:00pm 15/07/2026
3:00am 17/07/2026
1 in 1.1 years
93.15 %
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.
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