Flood mapping

Flood mapping helps us understand potential impacts of flash flooding in Boroondara.

We use it to:

• identify if your property is at risk
• give you advice about your property
• help you prepare for building works.

Flood mapping study

Our study identified properties at risk of flooding during rare rainfall events. These events are known as 1% annual exceedance probability (AEP) storms. Read our full definition in the Definitions section on this page.

While these events are rare, it's important you understand flood risks. This helps you (and us) to reduce potential impacts.

How this affects properties

We notified the owners of properties that are at risk of flooding when we completed the study. We've included the results of the study in Property Information Statements. Find out how to request property information on our Copies of Building Permit plans and reports page.

If your property is affected, your statement will say that your property is subject to flooding under Building Regulation 153 which you can read about on the Australasian Legal Information Institute website.

Any property within Boroondara could be at risk of flooding, even if it wasn't identified in our study.

We recommend that you:

• check your requirements for building on flood-prone land by reading our Building and developing on flood-prone land page
• check if your insurance policy covers flash flooding from overland stormwater flow.

To request flood mapping data about your property, contact us by emailing [email protected].

Study method

Our study used radar images and Council asset information. We created a topographic and hydraulic model of surface levels. This helps us understand the estimated flow, water level and velocity of water over land. We used the model to predict stormwater flows that could result from rainfall events.

This included rainfall scenarios from Geoscience Australia’s Australian Rainfall and Runoff, which you can learn about on the Australian Rainfall and Runoff website.

We looked at:

• areas at risk of flooding due to a 1% AEP rainfall event
• how rainfall with lesser and greater frequency could affect the model.

We also tested it against:

• the forecast effects of climate change at the time
• flood studies from Melbourne Water.

Definitions

Overland stormwater flow

This is when excess stormwater flows over land into streets, laneways, and properties. This happens when extreme rainfall overwhelms gutters, downpipes and drains. It can result in flash flooding.

This is different to flooding that rises up from rivers and creeks.

1% annual exceedance probability (AEP) rainfall

This is an infrequent high-intensity storm that has a 1% probability of being exceeded in any one year.

These events are not cyclical. They might happen more than once in a given year, or there might be several years without any events.

More information

To find out more, call us on (03) 9278 4444 or email [email protected].