STORM and MUSIC can both be used to assess stormwater treatment performance, but they are designed for different levels of project scale and complexity.
A STORM-style assessment is generally suited to smaller developments with straightforward runoff catchments and relatively simple treatment measures.
MUSIC modelling is generally used where a project contains larger or multiple catchments, connected treatment trains, more complex runoff pathways or subdivision-scale stormwater infrastructure.
The original Melbourne Water STORM Calculator has now been replaced by BlueFactor for suitable small developments. However, the term “STORM assessment” remains common in existing planning permits, council correspondence and project discussions.
The choice should not be based solely on which method is faster or simpler. The accepted assessment depends on the development, the proposed treatment system and the requirements of the relevant council or drainage authority.
STORM and MUSIC occupy the same broad technical territory: both can be used to demonstrate how a development treats stormwater runoff and performs against applicable water-quality objectives.
The main difference is the level of detail each method can represent.
A simple townhouse development may be capable of being represented using roof catchments, rainwater tanks, a driveway treatment and a small number of untreated areas.
A larger subdivision may involve multiple sub-catchments, roads, sediment ponds, wetlands, raingardens, harvesting systems and staged drainage infrastructure. That type of project is more likely to require MUSIC modelling.
For a broader overview of STORM reports and treatment assessments, visit the Certified Energy STORM Knowledge Hub.
A STORM assessment is a simplified method of evaluating the stormwater-quality performance of a development proposal.
It commonly considers:
The original STORM Calculator produced a relative score indicating how the proposed treatment strategy performed against the relevant best-practice objective.
Victorian planning guidance historically described STORM as most appropriate for small-scale subdivisions, typically below one hectare, while recognising that more sophisticated modelling may be preferable for larger developments.
MUSIC stands for Model for Urban Stormwater Improvement Conceptualisation.
It is a more detailed modelling platform used to represent how rainfall, runoff, pollutant loads and stormwater treatment measures interact over time.
A MUSIC model can represent:
MUSIC is therefore better suited to projects where the order, connection and performance of several stormwater measures need to be modelled explicitly.
The distinction is not simply that STORM is used for residential projects and MUSIC is used for commercial projects.
The more useful dividing line is stormwater system complexity.
A smaller project may be suitable for a simplified assessment where:
MUSIC may be more appropriate where:
A simplified treatment assessment may suit a relatively small and uncomplicated development.
Examples may include:
The treatment strategy may include a small number of elements such as:
Even where a project appears simple, the relevant council should confirm that the proposed assessment method is acceptable.
MUSIC becomes more relevant as the stormwater system grows in scale or complexity.
It may be required for:
Melbourne Water maintains dedicated MUSIC modelling guidelines for models submitted to it. The current guidance addresses matters such as rainfall data, model inputs, high-flow bypasses, overflows and treatment-node configuration.
A treatment train is a sequence of stormwater treatment measures through which runoff passes.
For example, runoff may travel through:
The order of these measures can affect their operation and treatment performance.
MUSIC can model the connection between individual treatment nodes and show how runoff and pollutant loads move through the system.
A simplified STORM-style assessment is less suitable where the project depends on a detailed sequence of pre-treatment, primary treatment, bypasses, overflows and downstream assets.
Melbourne Water describes a treatment train as a sequence of treatments selected and ordered to maximise performance and protect downstream assets from pollutants such as litter and coarse sediment. :contentReference[oaicite:1]{index=1}
Project area is an important indicator, but it is not the only consideration.
Victorian planning guidance has historically described STORM as most appropriate for small subdivisions, typically below one hectare, and MUSIC as suitable for more complex subdivision, neighbourhood or regional-scale projects. :contentReference[oaicite:2]{index=2}
However, a small site can still require MUSIC where it has:
Conversely, the suitability of a simplified method for any larger site should not be assumed merely because the proposed treatments appear simple.
The assessment method should reflect both scale and complexity.
Melbourne Water replaced its original STORM Calculator with BlueFactor in December 2025.
BlueFactor now occupies the simplified-assessment role for suitable small developments, while MUSIC remains available for projects requiring more detailed modelling. :contentReference[oaicite:3]{index=3}
This means that a new project may be described as requiring:
Older planning permits and council correspondence may still request:
Where the wording refers to the former tool, the project team should confirm whether the responsible authority will accept the current BlueFactor output or requires another assessment method.
Not necessarily.
The assessment method may be nominated by:
A project should not use a simplified method merely to avoid the additional work associated with MUSIC where the stormwater system cannot be represented adequately.
Likewise, a relatively simple project should not automatically be burdened with detailed MUSIC modelling where an accepted simplified assessment can answer the relevant planning question.
A STORM-style report generally provides a concise account of:
A MUSIC submission may provide substantially more technical detail, including:
For Melbourne Water submissions, the model itself and justification of key inputs may be required rather than screenshots or a short summary alone. :contentReference[oaicite:4]{index=4}
Consider a three-townhouse proposal with:
The catchments and treatment measures are limited and can be described clearly.
Subject to council acceptance, this type of project may be suitable for a simplified BlueFactor or STORM-style assessment.
The assessment can test whether the tanks, reuse demands, raingarden and untreated areas collectively achieve the required stormwater treatment result.
Now consider a larger subdivision containing:
This system depends on the connections between several catchments and treatment assets.
MUSIC is more likely to be appropriate because it can model the treatment train and the movement of runoff and pollutant loads through the connected system.
No. STORM, BlueFactor and MUSIC primarily assess stormwater treatment performance.
They do not automatically provide:
A project may require a stormwater treatment model and separate civil, hydraulic or flood-related documentation.
Victorian planning guidance distinguishes stormwater-quality treatment from the minor and major drainage systems needed to convey runoff and manage larger storm events. :contentReference[oaicite:5]{index=5}
Not necessarily.
MUSIC provides a more sophisticated representation of the system, but the quality of the result still depends on:
A detailed model using unrealistic inputs is not inherently more reliable than a well-prepared simplified assessment for an appropriately simple project.
Melbourne Water’s MUSIC guidance requires current modelling approaches and input parameters, and it no longer accepts new models based on its superseded 2018 templates or guidance. :contentReference[oaicite:6]{index=6}
Selecting the wrong assessment method can delay a planning submission or create unnecessary redesign.
A simplified assessment may be inadequate where:
Detailed modelling may be unnecessarily complex where:
Early confirmation of the required method helps the project team prepare the correct information and reserve suitable space for the treatment measures.
Determine whether the council has asked for a STORM report, BlueFactor result, MUSIC model, WSUD response or Stormwater Management Strategy.
Consider the overall development area, number of catchments and extent of roads, roofs and other impervious surfaces.
Identify whether runoff passes through one treatment or several connected measures.
Shared wetlands, sediment ponds, harvesting systems and downstream assets often indicate the need for more detailed modelling.
A project referred to Melbourne Water or another drainage authority may need to follow specific modelling guidelines and submission requirements.
Confirm whether civil drainage plans, detention calculations or flood assessment are required in addition to the water-quality model.
New small-development assessments should reflect the transition from STORM to BlueFactor, while MUSIC models should use the applicable current modelling guidance.
A STORM-style or BlueFactor assessment may be appropriate where:
MUSIC modelling may be appropriate where:
Where the requirement is unclear, the available plans and council correspondence should be reviewed before the assessment scope is confirmed.
Certified Energy can review the proposed development and help determine whether a focused STORM-style or BlueFactor assessment is appropriate.
For suitable projects, this may include:
A simplified STORM assessment should not be presented as an alternative to MUSIC where the scale, treatment system or authority requirements call for detailed modelling.
Explore the STORM Assessment Knowledge Hub or send through the current plans and council correspondence for an initial review.
STORM is a simplified stormwater treatment assessment for suitable smaller projects. MUSIC provides more detailed modelling of runoff catchments and connected treatment systems.
The original STORM Calculator has been replaced by BlueFactor for suitable small developments. The STORM term remains common in existing reports, permits and council requests.
It may suit a relatively small project with a limited number of clearly defined catchments and treatment measures, subject to council acceptance.
MUSIC may be needed for larger developments, multiple catchments, treatment trains, subdivision infrastructure or where the relevant authority specifically requests it.
No. It may also be used for complex commercial, industrial, institutional or mixed-use developments where detailed catchment and treatment modelling is needed.
Yes. Although many townhouse projects are relatively straightforward, MUSIC may be required where the site, drainage arrangement or treatment system is unusually complex or council specifically requests it.
Suitability should not be assumed. Larger developments are more likely to require detailed modelling, particularly where they contain multiple catchments or treatment trains.
No. A MUSIC model may form part of a broader Stormwater Management Plan, but the plan may also address drainage, detention, discharge, maintenance and implementation.
They primarily address stormwater treatment performance. Flooding, drainage capacity and overland flow may require separate assessment.
The appropriate method is influenced by the planning controls, project complexity and the requirements of the relevant council, Melbourne Water or drainage authority.