Design for stormwater treatment Print

Design Outcome

Design Checklist

  1. The development preserves existing topographic and natural features to help manage stormwater
  2. The landscape design minimises stormwater runoff and treats as much stormwater as possible on site



​​Stormwater is the rainwater runoff from buildings and the areas surrounding them. If left untreated and uncontrolled, it can cause pollution and destruction of Auckland’s waterways and flooding on neighbouring sites.

Integrating treatment processes within landscape design is an effective method of addressing stormwater pollution, particularly within large-scale developments.

A ‘water sensitive design’ (WSD)​ looks at using natural systems and processes to manage the quantity and quality of stormwater. There are many approaches to WSD, depending on the site, these may consist of a combination of natural systems and conventional devices.

Considering WSD at the start of the design process may save time and money by avoiding the need to upgrade infrastructure. It can be cheaper and more effective to use natural systems before using devices or ‘built in’ systems. Raingardens (engineered gardens that are designed to hold (detain) and treat stormwater) are one particularly effective method of regulating the volume and quality of stormwater leaving a site. They also increase the amenity of a site through their landscaping element.

Technical information on stormwater treatment and devices can be found here.

Better Design Practice

Protect, enhance and work with the natural hydrological conditions of a site.

Effective methods of working within the natural hydrological conditions of a site include:

  • Protecting and providing buffer planting alongside watercourses
  • Maintaining overland flow paths within the site
  • Avoiding large scale earthworks and working with the slope of the site​
  • Identifying areas of the site that can naturally absorb water (known as ‘soakage’) and using these to absorb stormwater. 

Mimic natural systems and processes for stormwater management.
  • Consider the use of living roofs and walls for stormwater filtering and transpiration
  • Direct stormwater across gardens, vegetated flowpaths, swales and filter strips to reduce the flow, detain, and filter water
  • Treat stormwater runoff in bioretention devices or underground detention tanks
  • Minimise impervious areas by limiting the building footprint and using permeable surfaces wherever possible. ​

Address the effects of stormwater as close to the source as possible.

Design the footprint of the building to protect existing soils and vegetation that contribute to stormwater management.

Avoid building materials that contribute toxins, metals and other harmful substanc​​es to stormwater runoff. 
Using materials that leach contaminants such as zinc or copper may require expensive onsite treatment to remove it. 

Retain roof or balcony runoff for reuse in buildings and landscapes.

Use rainwater tanks to water the garden. Rainwater may also be used for washing clothes and flushing the toilet.​

Consider the ma​intenance of stormwater systems at an early stage. 
A low maintenance system will save money in the long term.

Rules of Thumb

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