Two key terms are used in the Flood Mapping Study that it may be helpful to understand:

‘Overland stormwater flow’ is commonly known as flash flooding, which occurs when extreme rainfall overloads gutters, downpipes and pipe drains and causes excess stormwater to flow over land - streets, laneways, and properties.  This is very different from flooding that rises up from rivers and creeks. Areas that are at risk from rivers, creeks and main drains have previously been identified by Melbourne Water and are designated in the Boroondara Planning Scheme as a Special Building Overlay (SBO) or a Land Subject to Inundation Overlay (LSIO).

To find out if your property is already in one of these types of overlay:

  1. Visit Planning Maps Online and search for the address of your property. The Planning Maps Online page displays a map of the property.
  2. Select Get Report. Follow the prompts to create and open a Planning Property Report.
  3. Read the report to see whether the property falls in any overlays

‘1 in 100 year rainfall (ARI) event’ is a term you may have read or heard in the media when we have extreme weather events. It refers to an infrequent high-intensity storm that has a statistical probability of happening again once in one hundred years. Another term sometimes used for the same type of event is a ‘1% Annual Exceedance Probability (AEP) event’.

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