How are significant storm events measured?

    Flood events are referred to in measurements known as an Annual Exceedance Probability (AEP) which is a statistical measure of an event occurring in any given year. Flood mapping is based on a 1% AEP event which is a high-intensity storm that has only a 1% statistical chance of occurring in any one year. During a storm of this intensity, heavy rainfall can exceed the capacity of Council’s drainage network, leading to stormwater flowing over land, and impacting properties and infrastructure.

    My property has never flooded, why is it considered at risk of flooding now?

    We have less than 200 years of flood records in Australia. While there may be no memory or record of your property flooding it does not mean that the land has not flooded in the past, or that it won’t flood in coming years. Floods bigger than those we have experienced previously may occur. Using the rainfall records that are available, catchment topographic data and sophisticated computer models we can now accurately predict the possible extent of flooding for the full range of rainfall intensities that lead to possible flood events. 

     The data identifies areas in Maroondah that area at risk of flooding. Flooding occurs across Melbourne and we want to mitigate this risk as best we can to minimise the impact to your property or land and enable you to prepare for potential flood events.

     It also means that if you want to redevelop or build on your land you will be able to do so in a way that is appropriate to the flood risk, ensuring that your investment is better protected from potential future damage. It also ensures that buildings do not make flooding worse for neighbours.

    My property is on a hill, can it still flood?

    Hills or elevated land are not always free of floods. Flooding can generally occur on these types of properties in two ways:

    • Creeks and rivers can rise several metres when they flood. Land that is considered to be safe from flooding often ends up well under water due to the final flood level. 
    • When water is running down a hill to a creek or river it will find the easiest path to follow or collect in low points on your property and store in these locations. When pipes, kerb or guttering cannot handle all the water in a severe storm, the water will find its own path.

    Why can’t all floods be prevented?

    It is not possible to completely eliminate flooding, particularly due to extreme weather events. These events are unpredictable and can exceed scientific expectations and adopted engineering and town planning standards. 

     Council is planning for and implementing upgrades of drainage infrastructure for areas with extreme flood risk, however we cannot upgrade all of Maroondah’s infrastructure due to:  

    • High cost of major drainage upgrade works. While Council plans for these drainage upgrade works, Council’s Annual Capital Budgets are allocated to a wide range of infrastructure projects across its extensive asset base.  The cost of constructing these drainage upgrades can often extend into the millions of dollars and Council must consider how it allocates in capital funding to provide the most cost-effective outcome and service level for its community;
    • Service clashes with other underground utilities. Clashes with other existing underground services that physically impact the installation of larger underground drainage infrastructure can limit the ability to provide effective flood protection. These clashes may limit the extent of flood mitigation that can be provided and, in some cases, make drainage works to minimise flood unfeasible;
    • Insufficient capacity of the downstream drainage and creek network to accept and takeaway increased stormwater from larger infrastructure;
    • Availability of land to manage drainage infrastructure works. The availability of land particularly in relation to the installation above ground storage options such as retarding basins and availability of drainage easements through private land can limited flood mitigation options; and
    • Social impacts. Undertaking major drainage upgrade works may disturb people, their homes, traffic and access to key services. 


    Although we can’t prevent all floods, we’re continually working to reduce their severity and impacts and educate the community on the management of flooding.

    What will flood mapping do to my property value?

    If your property has been identified as having a flood risk, it should be noted that the existing flood risks to your property have not changed. 

    Flooding is one of many factors that can influence the value of a property both negatively and positively. Property values are determined by many factors including planning considerations such as zoning and requirements, lot sizes, types of surrounding properties, the level of infrastructure, amenities and services in the surrounding area, tenancy opportunities, prevailing trends in the ‘market cycle’, the social profile of areas and the quality and maintenance of individual buildings.


    Will the flood mapping impact my insurance premiums?

    If your property has been identified as having a flood risk, it should be noted that the existing flood risks to your property have not changed. 

    Council is unable to provide advice on insurance and recommends that you contact your insurance provider directly.

    What is Council doing to reduce the risks and impacts of flooding?

    Council is continually working to reduce the risks and impacts of flooding in the municipality. Some of the ways we are doing this include:

    • Drainage improvement works through Council’s Annual Capital Works Program such as the installation of new drainage, flood retarding basins and stormwater harvesting/reuse works;
    • Maintenance and renewal of drainage assets including pipe and pit cleaning, street sweeping to minimise leaf debris, and repairing of Council managed stormwater drains and pits;
    • Providing flood management and prevention advice to landowners;
    • Supporting the work of the SES in preparing for emergency flood events, assistance during events, and cleaning up after floods;
    • Educating and preparing our community through flood information; and
    • Ensuring that new developments appropriately consider flood events/impact and that any required drainage upgrades are implemented through the development construction.