Dark mode
Light mode 7:15am 16/07/2026 to 7:15am 18/07/2026
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
33.0 mm
9:30pm 17/07/2026
9:45pm 17/07/2026
1 in 7.3 years
13.7 %
30m
33.0 mm
9:15pm 17/07/2026
9:45pm 17/07/2026
1 in 2.2 years
46.25 %
45m
33.0 mm
9:00pm 17/07/2026
9:45pm 17/07/2026
1 in 1.5 years
64.76 %
60m
33.0 mm
8:45pm 17/07/2026
9:45pm 17/07/2026
1 in 1.3 years
74.69 %
90m
33.0 mm
8:15pm 17/07/2026
9:45pm 17/07/2026
1 in 1.1 years
88.03 %
120m
33.0 mm
7:45pm 17/07/2026
9:45pm 17/07/2026
1 in 1.1 years
92.96 %
3h
34.0 mm
6:45pm 17/07/2026
9:45pm 17/07/2026
1 in 1.0 years
96.56 %
4h
34.0 mm
5:15pm 17/07/2026
9:45pm 17/07/2026
1 in 1.0 years
98.64 %
6h
34.0 mm
3:45pm 17/07/2026
9:45pm 17/07/2026
1 in 1.0 years
99.35 %
9h
35.0 mm
12:45pm 17/07/2026
9:45pm 17/07/2026
1 in 1.0 years
99.84 %
12h
36.0 mm
9:45am 17/07/2026
9:45pm 17/07/2026
1 in 1.0 years
99.97 %
18h
36.0 mm
3:45am 17/07/2026
9:45pm 17/07/2026
1 in 1 years
100.0 %
24h
36.0 mm
9:45pm 16/07/2026
9:45pm 17/07/2026
1 in 1 years
100.0 %
30h
36.0 mm
3:45pm 16/07/2026
9:45pm 17/07/2026
1 in 1 years
100.0 %
36h
36.0 mm
9:45am 16/07/2026
9:45pm 17/07/2026
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.
Install
