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Light mode 3:50pm 23/08/2026 to 3:50pm 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
10m
4.6 mm
1:10pm 25/08/2026
1:20pm 25/08/2026
1 in 1.1 years
94.23 %
20m
7.6 mm
1:10pm 25/08/2026
1:30pm 25/08/2026
1 in 1.2 years
86.87 %
30m
8.8 mm
1:10pm 25/08/2026
1:40pm 25/08/2026
1 in 1.1 years
89.07 %
60m
10.6 mm
1:00pm 25/08/2026
2:00pm 25/08/2026
1 in 1.0 years
96.19 %
90m
12.4 mm
12:20pm 25/08/2026
1:50pm 25/08/2026
1 in 1.0 years
97.62 %
120m
13.0 mm
12:10pm 25/08/2026
2:10pm 25/08/2026
1 in 1.0 years
98.97 %
3h
15.2 mm
10:50am 25/08/2026
1:50pm 25/08/2026
1 in 1.0 years
99.53 %
4h
17.0 mm
9:20am 25/08/2026
1:50pm 25/08/2026
1 in 1.0 years
99.95 %
6h
20.0 mm
1:50am 25/08/2026
7:50am 25/08/2026
1 in 1.0 years
99.91 %
9h
26.4 mm
5:00am 25/08/2026
2:00pm 25/08/2026
1 in 1.0 years
99.62 %
12h
37.2 mm
1:50am 25/08/2026
1:50pm 25/08/2026
1 in 1.0 years
95.84 %
18h
38.2 mm
8:10pm 24/08/2026
2:10pm 25/08/2026
1 in 1.0 years
99.2 %
24h
38.2 mm
2:10pm 24/08/2026
2:10pm 25/08/2026
1 in 1.0 years
99.94 %
30h
38.2 mm
8:10am 24/08/2026
2:10pm 25/08/2026
1 in 1 years
100.0 %
36h
38.2 mm
2:10am 24/08/2026
2:10pm 25/08/2026
1 in 1 years
100.0 %
48h
38.2 mm
3:50pm 23/08/2026
3:50pm 25/08/2026
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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