MUSIC & DRAINS Modelling Consultants

Behind almost every stormwater condition on a NSW development consent sits a model. DRAINS answers the quantity question — how much runoff, how fast, and whether the pipes, pits and detention storages can handle it. MUSIC answers the quality question — how much sediment, nutrient and gross pollutant load your site generates, and whether the proposed treatment train reduces it enough to meet council’s targets. Councils do not take these answers on trust: they expect a properly constructed model, built on accepted parameters, submitted in a form their engineers can interrogate.

Contrive Consultants provides MUSIC and DRAINS modelling as a standalone specialist service and as the analytical core of our wider stormwater work. We model for architects and builders who need a compliance report attached to a DA, for developers whose consultants need the numbers checked or reworked after an RFI, and for projects from single dwellings to industrial subdivisions and masterplanned estates. Based in Rouse Hill and working across Greater Sydney and NSW, we know which councils demand MUSIC-link submissions, which publish their own modelling guidelines, and how each tends to review what lands on its desk.

When council requires it

DRAINS modelling is effectively assumed whenever piped drainage or on-site detention must be justified — at DA stage for the stormwater concept on larger or constrained sites, and at CC stage to verify pipe capacities, hydraulic grade lines and OSD performance before construction plans are stamped.
MUSIC modelling is triggered by council water quality policies, typically once a development exceeds an impervious-area or lot-size threshold set in the DCP or WSUD policy. Medium-density residential, commercial, industrial and subdivision applications are the usual candidates.
MUSIC-link councils — a growing list of NSW councils require MUSIC models to be lodged through MUSIC-link, which locks input parameters to the council’s template and generates a standard compliance report. A model built outside those settings will be rejected regardless of its conclusions.
RFI and peer-review situations — councils frequently issue RFIs where a lodged model uses unsupported parameters, the wrong rainfall template or an unrealistic treatment train; consent authorities and developers also engage us to review models prepared by others.

What we deliver

DRAINS models of minor and major drainage systems, with hydraulic grade line analysis, pit and pipe sizing and overflow checks
OSD modelling across the full range of ARR 2019 storm durations and temporal patterns to identify the critical case
MUSIC models of the site and its treatment train — rainwater tanks, bioretention, gross pollutant traps, proprietary cartridge devices and vegetated measures
MUSIC-link submissions using the relevant council template, with the generated compliance report ready for lodgement
Water quality compliance reporting documenting pollutant source loads, treatment performance and residual loads against council targets
Treatment train optimisation — resizing or substituting devices so compliance is achieved with the least cost and land take
Model audits and peer reviews of third-party MUSIC or DRAINS models, with a plain-language findings memo
Updated modelling and RFI responses when council queries a lodged model or the design changes mid-assessment

Software & standards

We model in DRAINS and MUSIC, the two packages NSW councils overwhelmingly nominate for site-scale stormwater assessment. DRAINS models are built on ARR 2019 design rainfall, temporal patterns and loss parameters. MUSIC models follow the parameter guidance adopted by the assessing council — via MUSIC-link where the council participates — because source-node and treatment parameters, not just the treatment train, determine whether a model is accepted. Drainage components feeding the models are designed to AS/NZS 3500.3:2021, road drainage elements reference Austroads guidance, and every model is checked against the specific council DCP or WSUD policy, since both the pollutant reduction targets and the accepted modelling assumptions differ between LGAs.

Our process

Brief and requirements check — we confirm what your council actually requires: DRAINS only, MUSIC only, or both; MUSIC-link or standard submission; and which policy version applies.
Data assembly — survey, architectural and landscape plans, catchment boundaries and impervious area take-offs, so the model reflects the real proposal rather than a convenient simplification.
Model build and analysis — DRAINS and/or MUSIC models constructed to the council’s accepted parameters, run, sense-checked and internally reviewed by a senior engineer.
Design iteration — where the first run fails, we adjust the drainage layout or treatment train with your design team until compliance is achieved efficiently, not just achieved.
Reporting through to certification — compliance reports and model files issued for lodgement, RFIs answered, and models updated at CC stage so the certified design matches what was approved.

Why Contrive

Approvals-first modelling — models built the way your council reviews them, in the format it requires, which is what turns a model into an approval.
Design and analysis under one roof — because we also design the drainage, OSD and WSUD measures (and coordinate with ARQI, URBA and our surveying partners across the Contrive group), model findings translate straight into buildable design changes.
Sydney and NSW-wide — current experience across MUSIC-link and non-MUSIC-link councils throughout Greater Sydney and regional NSW.
Senior-led review — every model is checked by an experienced engineer before it leaves, because a model is an argument, and arguments need scrutiny.

Frequently asked questions

What pollutant reduction targets does my MUSIC model need to meet?

NSW councils set percentage load-reduction targets for gross pollutants, total suspended solids, total phosphorus and total nitrogen, comparing the developed site with treatment against the developed site without it. Broadly similar target sets are adopted across much of the state, but the exact percentages, and the thresholds that trigger them, are set by each council’s DCP or WSUD policy and are revised over time — so we always confirm the current targets with your consent authority before modelling.

What is MUSIC-link and do I have to use it?

MUSIC-link is a facility within MUSIC that loads a participating council’s template — rainfall data, source-node parameters and compliance criteria — and generates a standardised report showing whether the model passes. If your council participates, using it is effectively mandatory: models built on other assumptions are routinely sent back. We hold current MUSIC licensing and lodge MUSIC-link submissions regularly.

Can you fix a MUSIC or DRAINS model that council rejected?

Yes, and it is a substantial part of our workload. Common failures include the wrong rainfall template, optimistic source-node parameters, treatment devices modelled at sizes that cannot physically fit the site, and DRAINS models that ignore the hydraulic grade line. We diagnose the objection, rebuild or repair the model, and where necessary adjust the design itself so the resubmission holds up.

Do small projects like duplexes need MUSIC modelling?

Often not — many councils only require MUSIC above an impervious-area or development-scale threshold, relying on standard measures such as rainwater tanks for smaller sites. But thresholds vary considerably between LGAs, and some apply water quality requirements to surprisingly small developments. We check your council’s trigger before you pay for modelling you may not need, and tell you honestly if you don’t.

Related services

Need a MUSIC or DRAINS model council will accept? Call Contrive Consultants on +61 497 848 111, email info@contriveconsultants.com.au or reach us through the contact page with your plans and council name for a same-week fee proposal.