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Light mode 3:45am 13/08/2026 to 3:45am 15/08/2026
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
24.0 mm
6:15pm 14/08/2026
6:30pm 14/08/2026
1 in 3.8 years
26.11 %
30m
24.0 mm
6:00pm 14/08/2026
6:30pm 14/08/2026
1 in 1.6 years
64.16 %
45m
24.0 mm
5:45pm 14/08/2026
6:30pm 14/08/2026
1 in 1.3 years
76.27 %
60m
24.0 mm
5:30pm 14/08/2026
6:30pm 14/08/2026
1 in 1.2 years
84.33 %
90m
24.0 mm
5:00pm 14/08/2026
6:30pm 14/08/2026
1 in 1.1 years
90.07 %
120m
24.0 mm
4:30pm 14/08/2026
6:30pm 14/08/2026
1 in 1.1 years
93.03 %
3h
24.0 mm
3:30pm 14/08/2026
6:30pm 14/08/2026
1 in 1.0 years
95.87 %
4h
24.0 mm
2:00pm 14/08/2026
6:30pm 14/08/2026
1 in 1.0 years
97.59 %
6h
24.0 mm
12:30pm 14/08/2026
6:30pm 14/08/2026
1 in 1.0 years
98.38 %
9h
24.0 mm
9:30am 14/08/2026
6:30pm 14/08/2026
1 in 1.0 years
98.95 %
12h
24.0 mm
6:30am 14/08/2026
6:30pm 14/08/2026
1 in 1.0 years
99.41 %
18h
24.0 mm
12:30am 14/08/2026
6:30pm 14/08/2026
1 in 1.0 years
99.83 %
24h
24.0 mm
6:30pm 13/08/2026
6:30pm 14/08/2026
1 in 1.0 years
99.94 %
30h
24.0 mm
12:30pm 13/08/2026
6:30pm 14/08/2026
1 in 1 years
100.0 %
36h
24.0 mm
6:30am 13/08/2026
6:30pm 14/08/2026
1 in 1 years
100.0 %
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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