Stormwater Management - Building Design for a Sustainable Future

Stormwater managementBuilding design for a sustainable future

This fact sheet will assist you in making informed decisions aboutStormwater Management practices to minimise negative impacts onthe environment.

What’s included in this fact sheet:

• Why do we need to change our Stormwater Management practices?
• How will best practice Stormwater Management benefit me?
• How does my choice of Stormwater Management strategies impact on the environment?
• Some basic guidelines to manage stormwater:
• Rainwater tanks
• Porous paving
• Raingardens
• Drought tolerant landscaping
• Measuring Stormwater Management performance
• Where can I find out more?
• Mandatory Requirements
• Council’s Best Practice Standard.

Why do we need to change our StormwaterManagement practices?

Melbourne’s continued urbanisation and expansion has resulted in a dramatic increase in areas of hard and impervious surfaces, such as buildings, roads and car parks. Consequently, the majority of the rain that falls in urban areas is converted into run off, or stormwater.

Traditional stormwater management practices direct stormwater into urban waterways, which carries pollutants that ultimately enter our rivers and Port Phillip Bay.

The increase in stormwater negatively affects the health and amenity of our waterways for people, plants and animals. Additionally, the large volumes of stormwater entering our waterways can cause flooding that damages both natural and built environments.

How will best practice Stormwater Managementbenefit me?

Water Sensitive Urban Design (WSUD)can capture, treat and reuse stormwateronsite to dramatically improve thequality and quantity of water enteringour waterways. Integrating WSUD intoyour development will minimise itsdownstream impacts and also enablesyou to conserve potable (drinking) waterby substituting it with rainwater. WSUDstrategies allow you to achieve thefollowing outcomes and helps Melbournetransition to a water sensitive city:

• improve water quality in streams and in groundwater
• protect stream and riparian habitats for native plants and animals
• prevent erosion of banks along our waterways
• reduce flooding risk
• protect the scenic and recreational values of streams
• conserve potable water by providing an alternative water source for uses such as, irrigation and toilet flushing.

How does my choice of Stormwater Management strategies impact on the environment?

There is enormous scope for creativitywhen building or renovating toincorporate a variety of WSUD strategiesinto your design.

Some simple measures to eliminate thenegative impacts of stormwater andconserve potable water are outlinedbelow:

Rainwater tanks

Rainwater tanks are perhaps the easiestway to reduce the amount of stormwaterleaving your property. They also havethe added benefit of providing a watersource that can replace drinking(potable) water in certain uses such asoutdoor use, toilet flushing and clotheswashing. By using stormwater to replacedrinking water, savings of up to 90% canbe achieved.

Tanks come in many different colours,materials and designs. They can beinstalled above ground, under ground,below outdoor decks, under buildings(if space allows), or even hidden withinplanter boxes.

Sizing rainwater tanks is contingent ona number of variables namely, rainfall,roof catchment area and proposeduses. There are now a number of freetools, such as Tankulator and STORM,available to assist people in sizing theirtanks and delivering best practice WSUDoutcomes. For more information on watertanks, see the resources section of thisfact sheet and refer to fact sheet 3.0Water Efficiency.

Porous paving

Porous paving allows rainwater to passthrough the pavers and soak into theground, unlike standard concrete orblock pavers. By using porous paversyou can:

•reduce the amount of ‘impervious’ surfaces on your block

•increase groundwater recharge by allowing the water to soak through the soil

•improve stormwater quality by filtering stormwater and reducing pollutant loads

•reduce high flows during peak rain events entering the waterway from urban areas causing stream erosion and habitat scouring.

Porous paving is installed in the sameway as traditional paving and is availablein many forms. They can be used toreplace asphalt, concrete or otherimpervious pavers.

Drought tolerantlandscaping

The average Victorian family uses almosttwenty percent of their drinking waterin the garden. You can not only reduceyour water consumption by reusinghousehold water or rainwater, but also bymaintaining a water-efficient garden. Thiscan be done through simple measures,such as using mulch, maintaining healthysoil or installing a more efficient wateringsystem.

Drought tolerant plants are also anexcellent way to save water in thegarden. They are better suited to our dryenvironment and create an attractive andlow-maintenance garden.

Raingardens

Installing a raingarden on your propertyis an easy way to reduce pollutant loadsin stormwater while providing attractivelandscaping. Raingardens are designedto capture, filter and reduce the flowrate of stormwater from roofs or hardsurfaces.

For more information on raingardens, seethe resources section of this fact sheet.

“Generally, the size of the raingarden should beapproximately two percent of the run-off area. Onesquare meter of raingarden commonly treats 50 squaremeters of hard surface.”

Measuring StormwaterManagement performance

To address and measure stormwaterquality outcomes, the Best PracticeEnvironmental Guidelines (BPEG)were developed and published bythe Victorian Stormwater Committee.These guidelines establish specificstormwater quality objectives, to assistin determining the level of stormwatermanagement necessary to meet theState Environment Protection Policy(SEPP) requirements. These guidelinesare now a referenced document in theState Planning Policy Framework. Thebest practice performance objectivesfrom the BPEG aim to remove:

•80% of suspended solids

•45% of total Nitrogen

•45% of total Phosphorus

•70% of typical urban annual litter load.

When applying for a planning permit,you may be required to demonstrate thatyour development proposal will meetthese performance targets. This can bedone through the use of different tools.

For small and medium sizeddevelopments, Melbourne Waterdeveloped STORM, a free and simpleonline stormwater calculator that helpsyou assess and improve your design’sstormwater performance. Exceeding the100% benchmark in the STORM toolconfirms that your building design willmeet Council’s performance targets.

For large sized developments, werecommend using proprietary toolssuch as MUSIC and Urban Developer tosimulate urban stormwater systems andtheir performance. These tools require asound knowledge of urban stormwatermanagement principles and practices.

Mandatory Requirementsand Council’s Best Practice Standard

Environmental Sustainable Design (ESD)Principles

There are two levels of compliance whenit comes to ESD principles – mandatoryand best practice.

Mandatory RequirementsTo meet Victoria’s 6-Star buildingstandard, new developments may berequired to install a rainwater tank. For asingle dwelling, a rainwater tank must:

•have a storage capacity of at least 2,000 litres

•drain a roof area of at least 50 square meters

•be connected to all internal toilets.

Council’s Best Practice StandardTo meet best practice standards,you must:

•Exceed Victoria’s best practice standards by achieving a STORM rating of at least 100% or equivalent modelling results (MUSIC, Urban Developer).

•Install appropriate sized rainwater tanks and connect as much roof area as possible to them. Use the harvested water for high demand areas such as toilets, irrigation and washing machines.

Developments, which seek to varyfrom these best practice standards,must demonstrate how best practicestormwater management can besatisfactorily achieved.

Where can I find out more?

• STORM calculator Melbourne Water
• Tankulator Alternative Technology Association
• Raingardens Melbourne Water
• Stormwater Sensitive Home Fact Sheets Melbourne Water
• Sustainable Landscaping and a listof water saver garden centresDepartment of Sustainability andEnvironment
• Stormwater Management EducationProgramsClearwater
• Information about Victoria’s waterenvironmentsEnvironmental Protection AuthorityVictoria
• Information about water andwastewater servicesWater Services Association of Australia

WSUD GuidelinesRefer to individual Council websites

Other Fact Sheets in this series arealso available to provide guidanceon the 10 Key Sustainable BuildingCategories. For further informationon Stormwater Management,consider the Fact Sheets entitled:

•Water Efficiency

•Urban Ecology

This fact sheet is not designed to replace project specific advice from building designand sustainability professionals, Council does not take responsibility for any issues thatmay occur due to the facts and guidance provided in this fact sheet.

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