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Light mode 3:45pm 23/08/2026 to 3:45pm 25/08/2026
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
7.0 mm
1:45pm 25/08/2026
2:00pm 25/08/2026
1 in 1.2 years
83.31 %
30m
7.0 mm
1:30pm 25/08/2026
2:00pm 25/08/2026
1 in 1.0 years
97.56 %
45m
7.0 mm
1:15pm 25/08/2026
2:00pm 25/08/2026
1 in 1.0 years
99.38 %
60m
7.0 mm
1:00pm 25/08/2026
2:00pm 25/08/2026
1 in 1.0 years
99.91 %
90m
13.4 mm
5:30am 25/08/2026
7:00am 25/08/2026
1 in 1.1 years
88.95 %
120m
13.4 mm
5:00am 25/08/2026
7:00am 25/08/2026
1 in 1.1 years
95.22 %
3h
18.2 mm
4:00am 25/08/2026
7:00am 25/08/2026
1 in 1.2 years
86.47 %
4h
27.6 mm
2:30am 25/08/2026
7:00am 25/08/2026
1 in 1.8 years
57.11 %
6h
29.2 mm
1:45am 25/08/2026
7:45am 25/08/2026
1 in 1.6 years
63.85 %
9h
38.2 mm
2:00am 25/08/2026
11:00am 25/08/2026
1 in 2.0 years
49.7 %
12h
47.0 mm
2:45am 25/08/2026
2:45pm 25/08/2026
1 in 2.5 years
39.35 %
18h
49.8 mm
9:00pm 24/08/2026
3:00pm 25/08/2026
1 in 2.1 years
47.52 %
24h
49.8 mm
3:00pm 24/08/2026
3:00pm 25/08/2026
1 in 1.7 years
59.13 %
30h
50.0 mm
9:00am 24/08/2026
3:00pm 25/08/2026
1 in 1.5 years
66.68 %
36h
50.0 mm
3:00am 24/08/2026
3:00pm 25/08/2026
1 in 1.4 years
72.23 %
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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