Lake Cathie (Sewerage Treatment Works) - IFD

5:30am 21/05/2026 to 5:30am 23/05/2026

You can find out more about Design Rainfall and IFD here.

Maximum observed rainfall by duration, estimated return period and AEP

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.