Dark mode
Light mode 8:30pm 24/08/2026 to 8:30pm 26/08/2026
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
7.6 mm
12:30am 26/08/2026
12:45am 26/08/2026
1 in 1.1 years
95.19 %
30m
10.8 mm
11:30pm 25/08/2026
12:00am 26/08/2026
1 in 1.1 years
91.12 %
45m
12.4 mm
11:15pm 25/08/2026
12:00am 26/08/2026
1 in 1.1 years
92.7 %
60m
17.0 mm
11:45pm 25/08/2026
12:45am 26/08/2026
1 in 1.4 years
71.58 %
90m
22.2 mm
11:15pm 25/08/2026
12:45am 26/08/2026
1 in 1.8 years
56.73 %
120m
23.8 mm
11:15pm 25/08/2026
1:15am 26/08/2026
1 in 1.6 years
63.21 %
3h
24.8 mm
11:00pm 25/08/2026
2:00am 26/08/2026
1 in 1.3 years
76.5 %
4h
30.0 mm
10:30pm 25/08/2026
3:00am 26/08/2026
1 in 1.4 years
71.09 %
6h
36.8 mm
11:15pm 25/08/2026
5:15am 26/08/2026
1 in 1.7 years
58.32 %
9h
40.6 mm
11:15pm 25/08/2026
8:15am 26/08/2026
1 in 1.5 years
65.09 %
12h
42.6 mm
11:15pm 25/08/2026
11:15am 26/08/2026
1 in 1.4 years
71.05 %
18h
50.2 mm
9:00pm 25/08/2026
3:00pm 26/08/2026
1 in 1.5 years
68.0 %
24h
52.4 mm
8:15pm 25/08/2026
8:15pm 26/08/2026
1 in 1.3 years
74.37 %
30h
52.6 mm
2:15pm 25/08/2026
8:15pm 26/08/2026
1 in 1.2 years
84.19 %
36h
52.6 mm
8:15am 25/08/2026
8:15pm 26/08/2026
1 in 1.1 years
89.51 %
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
