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Light mode 7:45am 23/08/2026 to 7:45am 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
6.0 mm
1:45am 25/08/2026
2:00am 25/08/2026
1 in 1.1 years
91.67 %
30m
9.8 mm
1:30am 25/08/2026
2:00am 25/08/2026
1 in 1.2 years
80.1 %
45m
12.2 mm
1:30am 25/08/2026
2:15am 25/08/2026
1 in 1.3 years
74.5 %
60m
14.0 mm
1:15am 25/08/2026
2:15am 25/08/2026
1 in 1.4 years
71.64 %
90m
17.6 mm
1:15am 25/08/2026
2:45am 25/08/2026
1 in 1.6 years
64.1 %
120m
20.6 mm
1:00am 25/08/2026
3:00am 25/08/2026
1 in 1.8 years
57.14 %
3h
23.2 mm
12:45am 25/08/2026
3:45am 25/08/2026
1 in 1.7 years
58.65 %
4h
27.8 mm
10:45pm 24/08/2026
3:15am 25/08/2026
1 in 1.9 years
52.47 %
6h
30.2 mm
10:15pm 24/08/2026
4:15am 25/08/2026
1 in 1.9 years
53.51 %
9h
31.6 mm
9:15pm 24/08/2026
6:15am 25/08/2026
1 in 1.6 years
64.34 %
12h
31.8 mm
7:15pm 24/08/2026
7:15am 25/08/2026
1 in 1.4 years
72.15 %
18h
31.8 mm
1:15pm 24/08/2026
7:15am 25/08/2026
1 in 1.2 years
84.95 %
24h
31.8 mm
7:15am 24/08/2026
7:15am 25/08/2026
1 in 1.1 years
89.7 %
30h
31.8 mm
1:15am 24/08/2026
7:15am 25/08/2026
1 in 1.1 years
92.5 %
36h
31.8 mm
7:15pm 23/08/2026
7:15am 25/08/2026
1 in 1.1 years
94.67 %
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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