Water sensitive urban design

Water sensitive urban design planning requirements

Amendments to the Victoria Planning Provisions (VPP) were gazetted on 26 October 2018, expanding stormwater management requirements to:

  • Commercial subdivisions and developments

  • Industrial subdivisions and developments

  • Public use developments

  • Residential multi-dwelling subdivisions and developments

These updated provisions require all new developments falling in the above categories to meet the following stormwater management objectives:

  • To minimise damage to properties and inconvenience to the public from stormwater

  • To ensure that the street operates adequately during major storm events and provides for public safety

  • To minimise increases in stormwater and protect the environmental values and physical characteristics of receiving waters from degradation by stormwater

  • To encourage stormwater management that maximises the retention and reuse of stormwater

  • To encourage stormwater management that contributes to cooling, local habitat improvements and provision of attractive and enjoyable spaces

To do this, the amended provisions state that the stormwater management system should be:

  • Designed and managed in accordance with the requirements and to the satisfaction of the relevant drainage authority

  • Designed and managed in accordance with the requirements and to the satisfaction of the water authority where reuse of stormwater is proposed

  • 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)

  • Designed to ensure that flows downstream of the site are restricted to pre-development levels unless increased flows are approved by the relevant drainage authority and there are no detrimental downstream impacts

  • Designed to contribute to cooling, improving local habitat and providing attractive and enjoyable spaces

For more information:

What is water sensitive urban design?

Urban development impacts the natural water cycle by creating impervious surfaces that affect the quantity and quality of stormwater. This in turn generates increased pollution and erosion. In Moreland, stormwater runoff is discharged to Port Phillip Bay via Merri Creek, Edgars Creek and Moonee Ponds Creek. Stormwater runoff and pollutants are detrimental to these creeks, the Bay and the ocean.

Water sensitive urban design mitigates these impacts while reducing water bills and creating greener urban areas. 

Meeting the above VPP requirements can be done via adopting water sensitive urban design principles.

Benefits of water sensitive urban design

Water sensitive urban design also provides many social, economic and environmental benefits including:

  •  Minimising impact on receiving waters

  •  Reducing potable water use

  •  Recharging local groundwater through the infiltration of stormwater

  •  Creating greener urban environments with high visual amenity, and

  •  Passive cooling through increased vegetation cover.

Best practice

The Victorian Urban Stormwater Best Practice Environmental Management Guidelines (Victorian Stormwater Committee, 1999) mentioned in the VPP's define best practice stormwater pollutant removal as:

  • 80% reduction in the typical urban load of total suspended solids

  • 45% reduction in the typical urban load of total phosphorous

  • 45% reduction in the typical urban load of total nitrogen

  • 70% retention of typical urban load of litter.

In addition, the VPP require flow from the site to be:

  • Designed to ensure that flows downstream of the site are restricted to pre-development levels unless increased flows are approved by the relevant drainage authority and there are no detrimental downstream impacts.

Moreland City Council is located in the middle reaches of Merri Creek and Moonee Ponds Creek, with downstream flows impacting the lower reaches of the Yarra River. Meeting the stormwater quality objectives is important to maintain the health of the downstream Yarra River, Bay and Ocean. Meeting the stormwater flow objectives is important to ensure the health and stability of the Merri and Moonee Ponds creeks.

To find out more visit the Melbourne Water website.

Demonstrating meeting best practice

Meeting the VPP requirements can currently be demonstrated in two ways:

Either:
Submitting a MUSIC model demonstrating a treatment train that achieves                     the above targets.

OR:
Submitting a STORM report achieving a score of 100% or above

When submitting an application to Council, be sure to include all the information required in the WSUD response check list:

See WSUD submission checklist (PDF 310Kb).

Water sensitive urban design treatments

A range of water sensitive urban design treatments can be used to demonstrate best practice stormwater management. 

Moreland has created a hierarchy to demonstrate which treatments are considered to meet the intent of the VPPs and have a good track record of successful implementation within the Moreland municipality.WSUD hierarchy

See WSUD treatment options (PDF 753Kb) for further details on each of these treatments

See WSUD treatment standard drawings (PDF 1Mb) for standard drawings of some WSUD treatment options that may be used in a WSUD response to Moreland.

Recommended WSUD approaches in Moreland

Recommended WSUD approaches to meet the VPP intent are shown below for the three most common types of development experienced in Moreland. Council’s preferred approaches are highlighted. Following Council’s preferred approaches will result in an easier process of approval.

Townhouse style developments

Preferred solution

  • Direct as much roof space as possible to rainwater tanks for reuse in toilet flushing, laundry and irrigation.
  • Driveway and backyard paving to be “permeable paving”

Example WSUD response for townhouse development - preferred (PDF 230Kb)

Less preferred solution

  • Direct as much roof space as possible to rainwater tanks for reuse in toilet flushing, laundry and irrigation
  • Other roof space directed to planterbox raingardens
  • Driveway and backyard paving to be “permeable paving”

Example WSUD response for townhouse development – less preferred (PDF 473Kb)

Least preferred solution

  • Direct as much roof space as possible to rainwater tanks for reuse in toilet flushing, laundry and irrigation
  • Other roof space untreated
  • Backyard paving to be “permeable paving”
  • Driveway to be treated by in-ground raingarden

Note re. in-ground raingardens for townhouse developments. In general, townhouse developments do not have sufficient space to ensure an in-ground raingarden can function effectively and avoid potential flooding problems. In-ground raingardens therefore require a significant amount of “up front” civil engineering to assess whether they are a viable proposition. If in-ground raingardens are specified for a townhouse style development within Moreland, they should be accompanied by engineering work to demonstrate:

  • They will not cause any flooding issues
  • Untreated water can adequately drain into the raingarden
  • Treated water can adequately be discharged to the legal point of discharge (note Moreland will not accept pumping from a raingarden to the legal point of discharge)

If Civil Engineering details covering these issues are not submitted as part of the planning application, then it is likely that an in-ground raingarden will be rejected in favour of one of the two above more preferred WSUD treatment solutions.

Example WSUD response for townhouse development – least preferred (PDF 468Kb)

Apartment style development

Preferred solution

  • Direct as much roof space as possible to rainwater tanks for reuse in toilet flushing, laundry and irrigation.
  • Runoff from balconies NOT to go to rainwater tanks
  • Other impervious ground surfaces (e.g. driveway or paving) to be “permeable paving”

Example WSUD response for an apartment building - preferred (PDF 304Kb).

Large sub-division style development

Preferred solution

  • Direct as much roof space as possible to rainwater tanks for reuse in toilet flushing, laundry and irrigation.
  • Large-scale WSUD treatment (e.g. unlined raingarden or wetland). Note these should be designed to meet the VPP objectives of “contribute to cooling, improving local habitat and providing attractive and enjoyable spaces”
  • Other impervious ground surfaces (e.g. roads, driveway or paving) to be “permeable paving”

Note: re in-ground raingardens for large sub-division developments. In general, large sub-division style developments may have sufficient space to ensure an in-ground raingarden can function effectively and avoid potential flooding problems, however sites may still be constrained and so these problems still pose significant risks. In-ground raingardens therefore require a significant amount of “up front” engineering to assess whether they are a viable proposition. If in-ground raingardens are specified for a sub-division development within Moreland, they should be accompanied by engineering work to demonstrate:

  • They do not cause any flooding issues
  • Untreated water can adequately drain into the raingarden
  • Treated water can adequately be discharged to the legal point of discharge (note Moreland will not accept pumping from a raingarden to the legal point of discharge)

Example WSUD response for large residential development - preferred (PDF 684Kb).

How to develop a response

A water sensitive urban design (WSUD) response must clearly demonstrate how stormwater runoff will managed in accordance with the VPP Stormwater Management objectives.

Step 1: When should you develop a WSUD response?

WSUD responses should be developed as early as possible in the development process to allow WSUD to be fully integrated with the site design, such as roof shape and the site levels. This will result in a better WSUD response and easier assessment process.

Step 2: Determine catchment area and discharge point(s)

Identify and measure the area of all outdoor “hard” surfaces on your site plan.  Hard surfaces include roofs, balconies, verandas, pergolas, concreted and paved areas.  (Note that permeable paving does not count as a hard surface with respect to generating stormwater runoff). 

Depending upon the type of roof construction, sections of the roofed areas may drain to different points of the development, and therefore may need to be separated into sub-roof areas. Sub-roof areas may be combined where the roof runoff will be diverted to a common WSUD treatment, i.e. rainwater tank.

The legal point of discharge for the property should also be identified. Discharges from WSUD treatments will need to be conveyed to this point.

Step 3: Choosing WSUD infrastructure

Select which WSUD treatment will be used to treat runoff from each hard surface using the above hierarchy, such as a rainwater tank or a raingarden. Take into account any constraints on available space and site levels relative to the legal point of discharge.

Step 4: Size rainwater tank and/or treatment system

Two assessment tools are available to assist applicants to size WSUD infrastructure to meet the stormwater quality standards:

  • STORM Calculator
  • MUSIC

Option 1: STORM Calculator

The STORM Calculator is a user friendly, free online tool developed by Melbourne Water.  It is designed to be suitable for applicants without any formal training on using the calculator or designing stormwater treatment systems.

STORM Calculator inputs include the total development area and all impervious areas (including impervious areas where no treatment will be provided for stormwater runoff). The calculator enables users to select from a range of WSUD treatment types.

An overall STORM score of at least 100% is required to demonstrate that best practice Stormwater Management has been achieved.

Option 2: MUSIC

The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) is a modelling tool that uses historic rainfall data to estimate catchment runoff and predict the performance of WSUD infrastructure. It enables a significantly higher degree of modelling complexity and flexibility compared to the STORM calculator. 

The MUSIC model should only be used by those with appropriate expertise.  MUSIC models used to prepare WSUD Responses for the City of Moreland must be developed in accordance with Melbourne Water MUSIC Guidelines.

MUSIC users must have a software licence and a minimum level of training and competency to develop a MUSIC model. MUSIC training is provided by eWater.  MUSIC is generally used by professionals with stormwater treatment expertise.  MUSIC is generally the most suitable assessment tool for complex and/or large developments (e.g. large multi-lot subdivisions) and any proposal that involves stormwater harvesting. 

See WSUD submission checklist (PDF 310Kb).

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