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Light mode10:45am 24/07/2026 to 10:45am 26/07/2026
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
25.0 mm
10:00am 26/07/2026
10:15am 26/07/2026
1 in 2.4 years
41.12 %
30m
25.0 mm
9:45am 26/07/2026
10:15am 26/07/2026
1 in 1.3 years
75.57 %
45m
25.0 mm
9:30am 26/07/2026
10:15am 26/07/2026
1 in 1.1 years
88.21 %
60m
25.0 mm
9:15am 26/07/2026
10:15am 26/07/2026
1 in 1.1 years
92.17 %
90m
25.0 mm
8:45am 26/07/2026
10:15am 26/07/2026
1 in 1.0 years
95.85 %
120m
25.0 mm
8:15am 26/07/2026
10:15am 26/07/2026
1 in 1.0 years
97.1 %
3h
25.0 mm
7:15am 26/07/2026
10:15am 26/07/2026
1 in 1.0 years
98.32 %
4h
25.0 mm
5:45am 26/07/2026
10:15am 26/07/2026
1 in 1.0 years
98.71 %
6h
25.0 mm
4:15am 26/07/2026
10:15am 26/07/2026
1 in 1.0 years
98.98 %
9h
25.0 mm
1:15am 26/07/2026
10:15am 26/07/2026
1 in 1.0 years
99.38 %
12h
25.0 mm
10:15pm 25/07/2026
10:15am 26/07/2026
1 in 1.0 years
99.68 %
18h
25.0 mm
4:15pm 25/07/2026
10:15am 26/07/2026
1 in 1.0 years
99.83 %
24h
25.0 mm
10:15am 25/07/2026
10:15am 26/07/2026
1 in 1.0 years
99.9 %
30h
25.0 mm
4:15am 25/07/2026
10:15am 26/07/2026
1 in 1.0 years
99.95 %
36h
25.0 mm
10:15pm 24/07/2026
10:15am 26/07/2026
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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