We normally require minimum habitable floor levels to be at least 0.5m above the estimated 1% Annual Exceedance Probability (AEP) or 100-year Average Recurrence Interval (ARI) flood level, with consideration of climate change, for the site.
This minimum level is called the Flood Planning Level (FPL).
For more detail see Chapter C2.3.2 Areas Affected by Flood - of Development Control Plan 2014(PDF, 2MB)
We also require non-habitable floors to be at or above the 5% AEP (20-year ARI) flood level to provide a reasonable level of protection to these areas.
Non habitable floor example:
You can apply for a flood information certificate if you are in an area that has an adopted flood study or flood management plan. This provides information for your property on flood levels and the 2050 and 2100 FPL.
See Flood Information Certificates
For other areas, you may need to engage a suitable qualified engineer with experience in flood assessments to determine the appropriate flood heights and minimum floor level.
See section Chapter C2.3.5 Areas Affected by Flood - of Development Control Plan 2014