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6Use the landscape to reduce stormwater

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Design Checklist

  1. The development preserves existing topographic and natural features to help manage stormwater.​​
  2. The site keeps stormwater runoff to a minimum, keeps and treats as much stormwater as possible on site and minimises any effects on the wider environment.

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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.
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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 by: 
  • Protecting and providing buffer planting alongside watercourses.
  • Maintaining overland flow paths within the site.
  • Avoiding large scale earthworks, work with the slope of the site and avoid large retaining walls where possible.
  • Identifying areas of the site that can naturally absorb water (known as ‘soakage’) and using these to absorb stormwater. 

Control runoff during construction to avoid sediment entering the stormwater system by: 
  • Avoiding unnecessary excavation and excavation on steep slopes, which creates a disproportionately large level of sediment runoff for the area disturbed.​
  • Consider the underlying ground conditions and avoid disturbing soil prone to sediment runoff. Sand and gravel erode more easily than silt and clay, but silt and clay are difficult to trap with sediment control devices. ​
  • Installing appropriate retention devices to control sediment runoff. 

Mimic natural systems and processes for stormwater management by: 
  • Considering the use of living roofs and walls for stormwater filtering and transpiration.
  • Directing stormwater across gardens, vegetated flowpaths, swales and filter strips to reduce the flow, detain, and filter water.
  • Treating stormwater runoff in bioretention devices or underground detention tanks. 

Address the effects of stormwater as close to source as possible by: 
  • Designing the footprint of the building to protect existing soils and vegetation that contribute to stormwater management.
  • Minimising impervious areas by limiting the building footprint and using permeable surfaces wherever possible. 

Avoid building materials that contribute toxins, metals and other harmful substances 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 areas by: 
  • Using living roofs and walls for stormwater management, and to protect roofs and insulate buildings.
  • Use rainwater tanks to water the garden. Rainwater may also be used for washing clothes and flushing the toilet.

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Consider the maintenance of stormwater systems at an early stage. 
Include how complex or expensive this will be. A low maintenance system will save money in the long term.