2576 - SBSMP-01 (Feb 2026)

4.2       Design Storm Events

The major storm was identified as the 1% AEP + CC storm in accordance with Noosa Shire
Council Planning Scheme Section SC6.7.6 d (Engineering Design Standards – Stormwater
Management). This event is also known as the defined flood event (DFE).


Peak stormwater discharge for pre- and post-development conditions were modelled using
the Australian Rainfall and Runoff (ARR) guidelines and data from the Bureau of Meteorology
(BOM) Design Rainfall Data System. The hydrological model was developed using Watershed
Bounded Network Model (WBNM) 2019, using the 10 location-specific temporal patterns
provided by ARR Data Hub.

The analysis assessed the following annual exceedance probability (AEP) events. Annual
recurrence interval (ARI) and exceedances per year (EY) are alternative measures.


          63.2% AEP (1 EY, 1-year ARI)
          50% AEP (1.44-year ARI)
          20% AEP (4.48-year ARI)
          10% AEP (9.49-year ARI)
          5% AEP (20-year ARI)
          2% AEP (50-year ARI)
          1% AEP (100-year ARI) (Major, DFE)

A 20% increase in rainfall depth has also been applied across all design rainfall data to
account for climate change as specified in Noosa Shire Council Planning Scheme Section
SC6.7.6 d.


All permutations of the 10 ARR temporal patterns and storm durations (10 min – 7 days) were
simulated. The critical storm pattern and duration for each node was used to calculate the
peak discharge.




2576-SBSMP-01_Version 1.0 (February 2026)                                       Page 15 of 23
SX/TB