Stormwater Australia certifies the first SQID in the Stormwater Quality Improvement Device Evaluation Process (SQIDEP)

Stormwater Australia, after many years of diligent work and consultation, has released the first product to have passed the full assessment of Stormwater Quality Improvement Device Evaluation Protocol (SQIDEP). The device – the SPELBasin has passed the full assessment under the Body of Evidence Pathway (BOE) of the SQIDEP. 

BoE Pathway3
Image Courtesy of Stormwater Australia

The process included assessment by two peer industry experts and the certification was overseen by the Governance Panel.  The whole process is designed to increase the the transparency and integrity of performance claims for manufactured stormwater treatment devices.  The full Independent Evaluation report has been published on the SQIDEP website.  

We have been busy at InSite Water – integrating the SQIDEP Devices.  We are aiming to make it easier to size and use SQIDs as part of stormwater design.

Simply choose ‘Manufactured Devices’ in the InSite tool as your treatment option and select and size your device.  Sizing is done by matching the nominal flow for the device to the runoff of your impervious area from a 4EY design storm (contact us if you would like the device to be sized to a 1EY storm).

To find out more about the SPELBasin, just click on the image after selecting a SPELBasin in your project the InSite tool, or click here.

If you would like to learn more about stormwater design requirements for individual lots and about the recent upgrades and changes to InSite Water please book into our upcoming live webinar training

For support in using the tool as a private professional or as a Council, please purchase a license

Swinburne Method of OnSite Detention (OSD) tank sizing

We have been very busy these last few weeks integrating the Swinburne Method of OSD calculation into the Australian version InSite Water (This upgrade has not been implemented into the SA tool).

For those non-engineers out there, the Swinburne Method is a popular way of sizing stormwater detention tanks.  Unfortunately the only software that calculates the Swinburne Method, OSD4W was withdrawn from sale.  We are stepping into the gap to allow you to continue using this methodology, originally developed by Bruce Bowditch and Dr. Donald Phillips at the Swinburne University of Technology.

For the civil engineers out there – enjoy! For the non-engineers – please leave the FLOW settings as ‘defaults’ unless otherwise instructed by your Council / consulting Engineer. The default settings are suitable for most sites.

You can still print reports from previous projects, and there is the option to keep using our previous OSD methodology (Boyd’s equation).

Details of Recent Upgrades:
​Recent changes include:
– Integration of SQIDEP approved devices​
– Optimisation of the UI to reduce visual clutter
– ​Upgrade of the server – the site now runs much more smoothly 
– Integration the Swinburne Method into reporting
– Upgrade of our PSD algorithms – the Swinburne Method calculations now run much faster.
– Allowing ‘uncontrolled areas’ to be part of OSD calculations.
– Removal or the ‘calculate’ button. The new more powerful server meant that this was not necessary as the 20 year rain tank water balance and irrigation simulation runs almost instantaneously without lag. All calculations run automatically whenever any relevant input is changed.

FAQ: Why do I not get exactly the same number as the OSD software?

Some notes for engineers and hydrologists with experience with the Swinburne Method: 

InSite now is very close to other Swinburne Method software (usually +/-10%) however there are a few reasons the numbers are not exactly the same.

  • We are using the 2016 IFDs from the BoM instead of the 1987 IFDs. This will give slightly different (but more valid) answers.
  • The BoM no longer publishes ARIs (Average Return Interval) for 5 and 10 year storms. Instead they publish: 20%AEP (Annual Exceedance Probability) which is roughly a 1 in 4.5 ARI storm; and a 10%AEP which is roughly a 1 in 9.5 year ARI. We have used 20%AEP and 10%AEP in our calculations where previously OSD4 would have used 5 and 10 year ARIs. Further details on the new probability terminology can be found in Book 1; Chapter 2; Section 2.2 Terminology of ARR2019
  • We calculate the pervious area runoff coefficient for each site rather than using the default of 0.13.  This is using the standard formula of 0.1+(0.7-0.1) x (i – 25)/(70 – 25) as per the Rational Method (where i is the 1 hour 20%AEP IFD intensity for the site). This is important, as this changes a lot as you head north in Australia.

Please purchase a license for further support or attend training for more information.


For more information on the role of OSD in flood prevention.

Book 9: Runoff in Urban Areas: Coombes, P., and Roso, S. (Editors), 2019 Runoff in Urban Areas, Book 9 in Australian Rainfall and Runoff – A Guide to Flood Estimation, Commonwealth of Australia, ©Commonwealth of Australia (Geoscience Australia), 2019.

Rainfall probability terminology

BoM updates Storm Intensity Frequency Duration Terminology

The probability terminology used in InSite Water for the 2016 design rainfalls (IFD rainfall or Intensity Frequency Duration) is consistent with the probability terminology for the new edition of Australian Rainfall and Runoff (ARR2019). Further details on the new probability terminology can be found in Book 1; Chapter 2; Section 2.2 Terminology of ARR2019

The main terms used to describe design rainfalls are:

  • Exceedances per year (EY): the number of times an event is likely to occur or be exceeded within any given year.
  • Annual exceedance probability (AEP): the probability or likelihood of an event occurring or being exceeded within any given year, usually expressed as a percentage.

The table below lists the probability terminology used for the 2016 design rainfalls and shows in bold the standard EY and AEP values for which design rainfalls are available. Generally, EY terminology is used for Very Frequent design rainfalls used in Water Sensitive Urban Design sizing, AEP (%) terminology is used for Frequent and Infrequent design rainfalls, and AEP (1 in x) terminology is used for Rare design rainfalls (major floods).

IFD Equivalencies for Exceedances per Year (EY), Annual exceedance probability (AEP) and Average Return Interval (ARI) source:


  • The 50% AEP IFD does not corresponds to the 2 year Average Recurrence Interval (ARI) IFD. Rather it corresponds to the 1.44 ARI.
  • The 20% AEP IFD does not corresponds to the 5 year Average Recurrence Interval (ARI) IFD. Rather it corresponds to the 4.48 ARI.
  • The 10% AEP IFD does not corresponds to the 10 year Average Recurrence Interval (ARI) IFD. Rather it corresponds to the 9.49 ARI.

For more information and to view the IFD data visit the Bureau of Meteorology (BoM) design rainfalls page.

Planning Amendments for Integrated Water Management implemented in Victoria

Much has changed in Victorian Stormwater policy and law and many stormwater professionals have been working hard to understand the changes. Key changes are to Victorian Planning Policies and to the EPA laws the State Environmental Protection Policies (SEPPs)

Planning Policy Amendment VC154

New integrated water management planning policies were gazetted in October 2018.

The key elements include:

  • A new definition of stormwater 73.01 General terms
    • Stormwater: The net increase in run-off from urban development due to water not being able to seep into the ground because of impervious surfaces, such as roofs and roads.
  • New Integrated water management clause in the state’s Planning Policy framework (PPF) to embed IWM objectives and strategies into urban land-use planning.
  • New provisions, under the Victoria Planning Provisions (VPP), to expand the current stormwater management requirements to:
    • commercial subdivisions and developments
    • industrial subdivisions and developments
    • public use developments
    • residential multi-dwelling subdivisions and developments including townhouses
  • In particular Standard B9 55.03-4 Permeability and stormwater management objectives  (26/10/18 VC154) requires assessment of smaller developments such as townhouses:
    • The site area covered by the pervious surfaces should be at least:
      • The minimum area specified in a schedule to the zone, or
      • If no minimum is specified in a schedule to the zone, 20 percent of the site.
    •  The stormwater management system should be designed to:
      • Meet the current best practice performance objectives for stormwater quality as contained in the Urban Stormwater – Best Practice Environmental Management Guidelines (Victorian Stormwater Committee, 1999).
      • Contribute to cooling, improving local habitat and providing attractive and enjoyable spaces.

Details of changes can be found at

New Environmental Protection Act – SEPP (Waters)

The SEPP (Waters) formally commenced on 19 October 2018. This is the largest change in stormwater regulation related to Councils in over a decade.

The SEPPs outline the uses and values of the environment that the community want to protect (these are called beneficial uses) and define the quality of the environment required to protect these.  SEPPs also identify the rules for decision makers and obligations on industry in order to protect water environments.

Section 34 – Management of Urban Stormwater of the new SEPP (Waters) nominates Councils as the authority responsible for ensuring that all new developments meet the environmental objectives of the Best Practice Environmental Management Guidelines (BPEM) for Urban Stormwater to implement source control measures to:

  • Minimise the quantity of stormwater leaving the property boundary;
  • Hold or use it as close to where it is generated as possible; and
  • Minimise the pollution of stormwater.

The SEPP (Waters) also requires that owners and managers of assets created to protect water quality (including constructed sediment ponds and wetlands) must ensure those assets are designed well and maintained properly.

Section 34 of the SEPP (waters) can be found here

How InSite Water allows designers to demonstrate compliance

For redevelopment sites under 1 hectare, InSite water allows designers to quickly and effectively demonstrate requirements of the Integrated Water Management Planning Policies and the SEPP (Waters). InSite allows this because it takes a multi criteria approach, where one stormwater device – such as a water tank or WSUD device such as a raingarden or infiltration pit can demonstrate how it meets both hydrology and environmental requirements. In addition we allow users to calculate Volume reduction to minimise the quantity of stormwater leaving the property boundary.

InSite water includes clear targets in line with Integrated Water Management requirements, and measures performance of a design to show whether those targets have been met.

Australian Rainfall and Runoff Book 9 published

Geoscience Australia has just released the final draft of Book 9 – the Urban Book of the ARR 2016 guide – a guide to flood estimation. ARR is the main standard used by civil engineers and hydrologists in Australia for design of stormwater infrastructure. This is the first major update of this standard since 1987, and it is a step change in how stormwater infrastructure is designed. In the last 30 years, stormwater approaches have evolved significantly, and the 2016 ARR guide introduces multiple objectives as well as flood mitigation (e.g. resilience, WSUD, liveability, sustainability and affordability) and the perspective of other disciplines such as aquatic ecology and landscape design[1].

The ARR Urban Book (book 9) was completed and published on 4 December 2018. The link is provided as follows:

Online Version

PDF Version

Figure 2       Potential overlapping volume management design objectives (ARR 2016 figure 9.4.1.)

What has changed in stormwater design?

Strategic use of water efficiency, rainwater, stormwater infiltration and wastewater recycling at multiple scales can supplement the performance of centralised water supply and drainage systems to provide more sustainable and affordable outcomes (ARR 2016). These integrated strategies reduce the requirement to transport water, stormwater and wastewater across regions with associated reductions in costs of extension, renewal and operation of infrastructure. In particular, the concept of volume management has been emphasised (ARR 2016, Book 9, Ch. 4).

The historical practice of designing urban stormwater systems has focused on peak flows, stormwater detention, and conveyance in hydraulically efficient pipes and channels. It is now recognised that volume of stormwater runoff, urban amenity and water quality treatment also need to be managed.

The ARR 2016 guide discourages the use of stormwater detention in favour of VOLUMEmanagement, except in clear cases where existing local street level pipe infrastructure needs protection in the face of increased impermeability through ongoing urban redevelopment.

The ‘volume management’ engineering design procedures that are talked about in the ARR can be found in this textbook:

Water Sensitive Urban Design: Basic Procedures for ‘Source Control’ of Stormwater A Handbook of Australian Practice Edited by John Argue, University of South Australia available for download at:

This Handbook is
a compilation of basic approaches that aim at
solving everyday problems of small-scale, i.e.,
not basin-wide, stormwater management. The
document is a collaboration of the Australian
Water Association, the Stormwater Industry
Association and the University of South

This is achieved through design and installation of volume management and water treatment devices, such as rainwater retention tanks, rainwater infiltration systems, and unlined biological treatment devices such as raingardens, tree pits and bioswales.

The design of volume management and stormwater treatment trains must include objectives that are relevant to the site, the surrounding catchment and receiving waterways. An adequate number of facilities are required to be built and maintained in catchments to ensure that stored, harvested or infiltrated stormwater will significantly reduce peak discharges at catchment outlets, or where existing downstream infrastructure is overwhelmed by redevelopment.

Typically, compliance with ARR 2016 book 9 is also requires meeting stormwater QUALITY targets.

The InSite tool uses the targets from the Urban stormwater: Best practice environmental management guidelines[1] (BPEM, CSIRO Publishing 1999). By including a stormwater quality calculation engine, InSite water allows designers to demonstrate they are meeting stormwater quality guidelines using treatments such as raingardens, bioswales, rainwater retention tanks, and infiltration.

Limiting FLOW from a site using On-Site Detention (OSD), is still allowed to extend the usable life of existing Council stormwater pipe assets.

With the release of the new ARR 2016, Engineers Australia recommends all stormwater practitioners, including Councils, revisit and revise their stormwater management practices, methodology, policies and guidelines to include volume management and water quality targets.

How InSite Water meets the requirements of ARR 2016

InSite water has been designed from the ground up to help engineers and designers meet the requirements for the ARR2016 urban book standards. We allow projects to quickly optimise for the 4 multiple criteria targets of VOLUME management (retention), peak FLOW control (detention), stormwater QUALITY, and EFFICIENCY for drought resilience. For example we allow designers to optimise the size and setup of a rainwater to meet retention, detention, stormwater quality and water efficiency targets with the one device. Our mission is to make Integrated Water Management quick to calculate, cost effective to implement, while maintaining the engineering rigour of the ARR 2016 standard.

[1] Engineers Australia (2016) Australian Rainfall and Runoff:A guide to flood estimation, Book 9, Chapter 3 Philosophy of urban stormwater management.

[2] Urban
Stormwater: Best Practice Environmental Management Guidelines. CSIRO 1999.
Electronic edition published by CSIRO PUBLISHING, 2006.