Flood level refers to the height of flood water measured in metres to Australian Height Datum (AHD).

Flood extent refers to how far flood water will reach.

Flood depth across a property is measured from the ground levels of the property and can vary considerably, depending on the landform of the property – for this reason, when providing individual property information, we provide property owners with the estimated minimum and maximum depth on their property.

The impact of a flood at your property depends on the flood depth but also the clearance between the ground and the floor of your house or other buildings.

If you would like to find out the specific flood information for your property you can call us on 131 722 or email [email protected]

To make a request for the specific flood information for your property, please call 131 722 or email [email protected], and our team will be able to lodge a request on your behalf.

Please provide your full name, property address and email address. A flood information letter with this information will be sent out to you. Please note, this can take up to 14 days. 

Melbourne Water will provide the flood level and depth for a flood event that has a one percent chance of occurring in any given year. This is known as a 1% Annual Exceedance Probability (1% AEP). We will provide this information for the new 2024 and 2100 scenarios. The depth of flooding across a property can vary considerably, depending on the landform of the property – we therefore provide the minimum and maximum depth for your property.

The extent to which buildings are impacted by a flood event depends on the flood level and also the clearance between the ground and the floor of the building.

Individual property owners may wish to engage a licensed surveyor to determine their floor level and whether any of the structures on their property are below the flood levels advised by Melbourne Water.

Please note, the flood information letter is not a formal Flood Certificate for planning and development purposes or for a ‘section 32’ property statement prepared to support the sale of land. 

Individual property owners could engage a licensed surveyor to determine their floor level and whether any of the structures on their property are below the flood levels advised by Melbourne Water.

To make a request for information on flood level and flood depths for your property, please call 131 722 or email [email protected], and our team will be able to lodge a request on your behalf. Please note, our time frames for this information may take up to 14 days.

The extent to which buildings are impacted by a flood event depends on the flood depth and also the clearance between the ground and the floor of the building.

The modelling by Jacobs finds the flood wall resulted in an average increase of flood extent across the catchment of 1 per cent in the October 2022 flood event. This includes an increased depth ranging from 0.8 to 3 cm (an average of 1.7 cms) for approximately 240 properties in the Maribyrnong township area - in an area where the overall flood depth was 80 cm. 

The racecourse flood wall did not lead to flooding of the Kensington Banks community in the October 2022 flood event. 

You can find more information on the assessment of the racecourse wall impact in the October 2022 event undertaken by the Independent Review Panel here.

Modelling by Jacobs finds that under the projected 2024 scenario – which maps a flood event with a one per cent chance of occurring in any given year – the average impact in the Maribyrnong township is 3.8cms of extra depth in a flood that is an average of 130 centimetres deep.

The analysis finds that in Kensington Banks there is no added depth because of the wall – and in fact the wall has the effect of reducing the estimated flood depth by 5.1cms in this location.

Note the projected 2024 flood event with a one per cent chance of occurring is more significant than the Maribyrnong River flood of 2022.

The Jacobs modelling finds in the 2100 scenario there is little or no impact from the flood Wall on Maribyrnong township or Kensington Banks as water overtops the flood wall.

You can find the report here.

The evidence we have, including the findings of the Independent Review of the 2022 flood, does not justify removal of the Flemington flood wall. 

However, we will now incorporate an examination of the mitigations associated with the flood wall into our broader investigation of potential mitigation measures across the catchment.   

You can find more information about the mitigation study above.

Melbourne Water's responsibility is to provide advice on flood risk to support flood awareness and preparation, to inform planning decisions and consider potential mitigations such as retarding basins, drainage or levees.

This new modelling represents the flood risk that exists – and is used to help mitigate that risk.

These climate change impacts are global issues that the insurance industry has been dealing with and taking into account in setting their premiums. 

We would advise householders to engage with their insurance companies to understand their own circumstances.

It is Melbourne Water’s responsibility to ensure that planning and emergency agencies, communities and individual landholders are able to understand their flood risk so that as a community we can best prepare before any flood and in the event of any flood.

Melbourne Water is not best placed to speculate or comment on property values.  

We are releasing modelling information so that we can prepare for the impacts of climate change and plan for the future. 

This new modelling represents the flood risk that exists – and is used to help mitigate that risk.  

It is Melbourne Water’s responsibility to ensure that planning and emergency agencies, communities and individual landholders can understand their flood risk so that as a community we can best prepare before any flood event. The models and detailed maps will help inform decisions about flood mitigation infrastructure such as drainage, levees and retarding basins, and other options to manage flood risk. 

This new modelling represents the flood risk that exists – it is not creating more risk. Melbourne Water is releasing the modelling information so that we can prepare for the impacts of climate change and plan for the future. 

It is Melbourne Water’s responsibility to ensure that planning and emergency agencies, communities and individual landholders are able to understand their flood risk so that as a community we can best prepare before and in the event of any flood event.

We are not best placed to speculate or comment on property values or insurance premiums. These climate change impacts are global issues that the insurance industry has been dealing with and taking into account in setting their premiums.

We would advise householders to engage with their insurance companies to understand their own circumstances.

In regard to renovations and redevelopment - once the new flood data is incorporated into planning schemes, any modifications to a property or new builds which would trigger the need for a planning permit, would need to be considered in light of the new flood information. Assessment would include what appropriate design measures and floor levels might be needed to appropriately manage risk in a flood event.

For flood modelling to be used in land use planning and development decisions, it needs to be translated in appropriate zones and overlays in planning schemes. This is done by a Planning Scheme Amendment (PSA) process. In line with Victorian Planning Policy directions for climate change, the new 2100 flood information is used to underpin planning scheme controls.

We’ll be working with Local and State Government to use the new model to update municipal planning schemes. The planning scheme amendment process ensures there is an opportunity for community feedback via a public exhibition process. We’re anticipating the amendment process will commence in the second half of this year.

You can find out how to retrofit your home with flood resilient design approaches and materials that reduce the impact of flooding by downloading our Flood Resilient Guide to Retrofitting Your Home on our website here. The guide has been developed for homeowners who have experienced flooding and want to reduce the impacts of future flood events. It is for information purposes only.

For resources and community education sessions on how to be prepared for a flood, including how to sign up to flood alerts and create your own flood emergency plan, visit our website here. 

The function of a flood model is to simulate the behaviour of stormwater and flood flows within drainage and waterway networks and determine urban and floodplain inundation.  

A flood model is a suite of hydrologic and hydraulic computations that have been programmed into a computer model.  Typically, the hydrologic model determines how much water is delivered into the drainage network or riverine system.  The drainage network is represented in the hydraulic model.   

The flood model takes as input:  

• a representation of the terrain and landform features, land use types, waterways and drainage network, flood control infrastructure and boundary conditions (e.g. starting water levels), and   
• a suite of “design” rainfall events that are based on historic rainfall and climate conditions for the location.  

A flood model provides (as output) flood extent (the areas impacted), depth (how high flooding might occur) and velocity (how quickly an area might flood) across the range of rainfall events that are modelled.    

Updating flood models ensures up to date flood information is available to inform flood risk and build community resilience across the region. The information from flood modelling helps the state government, local councils, developers, businesses and the community understand how best to minimise the impact of flooding.     

An important part of minimising flood risk is to ensure new development takes account of the flood risk in the area.  Melbourne Water uses flood information to comment on development and subdivision applications and, if necessary, place conditions on planning permits. This ensures that all new developments are designed to protect occupants from flooding and that Melbourne’s drainage system functions like it should.

The Australian Rainfall and Run off guidelines were updated in 2019 (ARR 2019) – since then we have increased our budget for flood modelling to $13 million over 5 years and implemented a program to update all models by 2026.

We now have the technology to do more sophisticated modelling more regularly – in the past it would not have been possible to continuously update flood models across Melbourne.

Melbourne Water has adopted the recommendations of the independent Maribyrnong River Flood Review, and will review the models every 5 years and update them every 10. Any major flood event experienced within this timeframe, will also trigger a review of our flood modelling.

The 2022 flood event was the first major flood since the Maribyrnong River modelling was last updated. The flood itself provided an enormous amount of data that will help us plan and prepare for future floods – including being an important source of information for our updated model.

Melbourne Water engaged Jacobs Consulting, a global modelling consultant, to perform the detailed flood modelling work. This work was independently peer-reviewed by HARC consulting at key milestones of development. The work of both consultancies was also informed through access to an independent academic panel (two leading hydrologists) enabling an additional layer of review and challenge to ensure a robust modelling outcome. Furthermore, a leading flood modelling specialist, Mark Babister also considered the model as part of the Pagone Independent Review and commented positively on its integrity at the Victorian Parliamentary Inquiry.

The new Maribyrnong River Flood Model is a riverine flood model and provides the latest flood information for the Maribyrnong River. It uses the most up to date data about rainfall and run-off, the physical features of the floodplain and nearby urban areas, and the most recent flood in October 2022 for accurate results.

As a more advanced 2-dimensional model than the previous model, it can simulate water flow across an entire area and in multiple directions. With this improved capability, the model gives a more accurate picture of how water flows, which helps predict flood patterns and their effects.

The new modelling has been prepared according to the current climate change guidelines, including recommended values for rainfall intensity increases and sea level rise, and latest standards and industry best practice set out in the ARR 2019.

Current flood modelling methods are very sophisticated using the latest computing and other technology to map millions of data points through the catchment. The approach and the methodology for the hydrology (RORB) and the hydraulic (TUFLOW) modelling used to develop the flood mapping was reviewed by Melbourne Water and external industry experts (as mentioned above) as part of a comprehensive quality assurance process to provide confidence in the modelling results.

Melbourne Water has committed to a significant uplift in its mapping and modelling program delivery.    

We know with climate change there will be more frequent and severe events, there will also be impacts from rising sea levels in some coastal areas. This is why we are using the best available information to update flood modelling.     

Melbourne Water is updating modelling to take account of the impacts of climate change, in line with the Australian Rainfall and Runoff Guidelines 2019, and this will be used to update land use planning controls in Planning Schemes and subsequently to inform planning and development decisions.  The new information will also be used to update municipal Flood Emergency Management Plans and community Local Flood Guides. 

Melbourne Water has committed to updating all flood models for every catchment in Melbourne by 2026 (both riverine and overland flow model). These updates will include climate change assumptions projected to the year 2100.    

The Australian Rainfall and Runoff Guidelines (ARR) 2019 sets out best practice for flood modelling in Australia, including climate change assumptions.

ARR 2019 notes that a number of factors considered in flood model development will be impacted by climate change, including rainfall intensity, duration, the conditions of the catchment the rain falls onto, and downstream conditions affected by sea level rise.

Current guidance focuses on changes to rainfall intensity and Melbourne Water is consistent with national guidelines.

A planning horizon to 2100 has been selected by Melbourne Water for consistency with Victorian State Planning Policy.

Now that the new modelling is complete, a comprehensive identification and assessment of mitigation options is being progressed, including looking at previously identified traditional solutions, as well as any new innovative solutions for the riverine flood hazards.  This work began last year with a preliminary desktop review of past flood mitigation studies for the Maribyrnong River, which you can read more about in this report.

The study will consider feasible flood mitigation solutions for the riverine flood hazards, that prioritise the safety and resilience of the communities within the catchment and have the greatest impact on reducing the flood risk, both now and anticipated by the year 2100 and beyond. Consideration of applicability and scalability of options to the Melbourne-wide context will also be made. 

Mitigation measures cannot be progressed in isolation for just one area, as adverse impacts on other areas neighbouring or upstream will also need to be considered, within a total catchment context.

The community will be invited to participate in the development and assessment of options later this year.  

Now the new Maribyrnong River flood modelling has been completed, detailed assessment of long-term sustainable flood mitigation options is being progressed. A timeframe will be confirmed once a preferred contractor is selected to conduct the study and their work methodology is agreed. The community and stakeholders will be invited to participate in the development and assessment of options later this year.

Yes, in some cases there may be cause to remodel the flood extents after mitigation works. However, this will be subject to the mitigation solutions that might ultimately be implemented.

We know that the community will want to have a say in the options analysis. Over the coming months we will seek community input into this work and will also ensure the community is kept up-to-date and provided opportunities to participate throughout the study.

We encourage the community to register interest in the mitigation study by completing our short survey here.

Melbourne Water as the ‘flood plain manager’ is responsible for: 

• Catchment level and coastal flood modelling of 1% AEP flood risk (note, DEECA with CSIRO have undertaken the most recent coastal hazard mapping). 
• Melbourne Water is responsible for modelling for riverine floods. 
• Melbourne Water is responsible for modelling stormwater flooding/overland flow above 60 ha and local councils are responsible for less than 60ha, reflecting ownership of these drainage assets.  
• Together this modelling is used as inputs into land use planning controls, Councils’ Municipal Flood Emergency Plans, VICSES local flood guides, and in assessing feasible mitigation solutions.  
• A referral authority for planning and building permits in relation to flood risk (see below for further info on our role in land use planning).  
• Running flood prediction models in real time before and during an event and providing that information to other agencies to inform flood warnings and emergency response actions.  

Melbourne Water does not: 

• Issue warnings to the community - this is done by Bureau of Meteorology and VICSES, using Melbourne Water flood predictions.
• Issue planning or building permits - these decisions are made by local councils or the Minister for Planning
• Lead recovery from flood events, except where we own or are responsible for the assets. 

Melbourne Water has key roles in land use planning for flood resilience in the context of climate change:

• Undertake flood modelling and determine development controls in partnership with Councils
• As Floodplain management authority under the Water Act 1989 and related functions under the Planning and Environment Act 1987 (PE Act) and the Building Regulations 2018
• Assesses permit proposals and requires conditions of permit to ensure developments are compatible with any flood risk. If the flood risk is determined too high, Melbourne Water can recommend refusal of a permit.
• Provide advice to other government agencies and authorities where development and infrastructure is proposed in flood affected areas.

In terms of Melbourne Water’s role as a referral authority, there are two types of referral authorities:

• A determining referral authority
• A recommending referral authority

Melbourne Water is usually a determining referral authority which means if we object, the responsible authority e.g. Council) must refuse to grant a permit, and if a determining referral authority specifies conditions, those conditions must be included in any permit granted.

It is a shared responsibility between many organisations to manage flood risk in the Port Phillip and Westernport region, including Melbourne Water, councils, state government and emergency management services. All have responsibilities for protecting people, infrastructure, assets, economic activity and the environment. As part of Melbourne Water’s responsibility to minimise the impact of flooding where possible, we have a flood mitigation program that determines appropriate responses on flood risk.

Councils may implement mitigation infrastructure at the local scale and in some instances, other government agencies and/or developers may be responsible for the funding the infrastructure.

Infrastructure, land use planning and education programs are all mitigation options that are delivered to reduce flood risk. There are actions in the Flood Management Strategy that cover all of these mitigation options.

The Maribyrnong River flood model is a riverine model, it does not include flooding associated with the stormwater drainage system (overland flow flooding). Where possible, flood modelling to predict stormwater flooding is undertaken jointly with local Councils who own much of the related drainage infrastructure. 

At Melbourne Water, we manage various types of flooding including that of our river systems (riverine flooding), our drainage infrastructure (overland and flash flooding) and along our coastlines (coastal flooding or tidal inundation and sea level rise). 

Melbourne Water prepares flood models for different types of flooding (outlined below). 

• Riverine flooding – happens when widespread, prolonged rain falls over the catchment of a river. Inundation of normally dry land occurs when water overflows the natural or artificial banks of a stream, river, estuary, lake or dam. Riverine flooding generally excludes watercourses constructed with pipes or artificial channels considered as stormwater channels. Riverine flooding can be a slower process, occurring at a rate that allows advance warning. Flood waters may last for days. 
• Creek flooding – happens when intense ran falls over a creek catchment. Run-off from houses and streets also contributes to creek flooding. The combination of heavy rainfall, run-off and the existing water in the creek causes creek levels to rise. Flood water from creek flooding can rise quickly and be very fast moving, and then recede quickly. 
• Flash (stormwater) flooding – Inundation by local runoff caused by heavier than usual rainfall. Inundation can be caused by local runoff that exceeds the capacity of urban stormwater drainage systems; overland flows that are on the way to waterways; or riverine flooding causing urban stormwater drainage systems to back up and overflow. Flash flooding from the stormwater system tends to be rapid and dangerous due to the speed and depth of flows and difficulty in providing a timely warning to people. 
• Coastal flooding – Increases in coastal water levels above the predicted tide level resulting from a range of storm-related factors such as wind and waves. Coastal flooding in a storm surge gives some advance notice but sea level rise will mean some areas are permanently underwater.