Melbourne Water’s floodplain manager responsibilities are:

• Coordinating flood management
• Maintaining the regional drainage network
• Managing infrastructure
• Monitoring flood data and undertaking modelling and mapping
• Providing flood information and advice
• Assessing severity of flooding
• Boosting community preparedness
• Informing the design of new suburbs

Melbourne Water does not: 

• issue warnings to the community – this is done by Bureau of Meteorology and VICSES using our 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.

Find out more.

Melbourne Water has key roles in land use planning for flood resilience in the context of climate change, as floodplain management authority under the Water Act 1989 and related functions under the Planning and Environment Act 1987 and the Building Regulations 2018.

We:

• undertake flood modelling and determine development controls in partnership with councils
• assess permit proposals and place conditions on permits to ensure developments are compatible with any flood risk. If the flood risk is determined too high, we 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 our role as a referral authority, there are two types of referral authorities:

• a determining referral authority
• a recommending referral authority.

We are usually a determining referral authority. This means that if we object, the responsible authority (e.g. council) must refuse to grant a permit; and if we specify conditions, these must be included in any permit granted.

Melbourne Water is updating modelling to take account of the impacts of climate change, in line with the Australian Rainfall and Runoff Guidelines (ARR) 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.

For flood modelling to be used in land use planning and development decisions, it needs to be translated into appropriate zones and overlays in planning schemes.  

This is done by a Planning Scheme Amendment (PSA) process, usually undertaken by the local Council at the request of Melbourne Water.

A Planning Scheme Amendment process includes a public exhibition stage where anyone can make a submission, and review stage by an independent Planning Panel.

There are different planning scheme zones and overlays which are applied to reflect varying levels of flood risk. These include the Urban Flood Zone, Floodway Overlay, Land Subject to Inundation Overlay and Special Building Overlay.

The predicted depth and velocity of flood waters determine the level of flood risk and flood hazard categories are applied in accordance with industry best-practice guidelines (Australian Rainfall and Runoff Guidelines)

Flood hazard categories are then translated into the most appropriate planning scheme zones and overlays, in accordance with State Government planning guidelines.

Many organisations share responsibility for managing 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 our responsibility to minimise flood impacts where possible, we have a flood mitigation program that determines appropriate responses to flood risk.

Councils may build local mitigation infrastructure, and in some instances, other government agencies or developers may fund it.

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

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

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

View more information on the Independent Review Panel's assessment of the racecourse wall impact in the October 2022 flood.

Modelling by Jacobs finds that under the projected 2024 scenario – which maps a flood event with a 1% chance of occurring in any given year – the average impact in the Maribyrnong township is 3.8cm of extra depth in a flood that is an average of 130cm 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 5.1cm in this location.

Note the projected 2024 flood event with a 1% 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 the Maribyrnong township or Kensington Banks, as water overtops the flood wall.

Download the report (PDF, 30.6MB).

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.   

Find out more about the flood mitigation study.