Stormwater management Print

Desi​gn Checklist

  1. Existing topographic and natural features are preserved, including watercourses and wetlands, to ensure the long term resilience of the ecosystem to manage stormwater
  2. Stormwater volumes and flow rates are minimised from urban developments and the amount of runoff managed on-site is maximised
  3. Minimum amounts of sediment, pollutants or contaminants are discharged to the urban stormwater drainage system, both during and after construction
  4. The impact of residential development and associated infrastructure on natural waterways is minimised

Better Design Practice

Protect and enhance the values and functions of natural ecosystems by:

  • ​​Protecting and buffering the ecosystems of a site, including soils, groundwater interactions, vegetation, and watercourses.

Considering overland flows within the site and the impacts of modifying these on sub-catchment hydrology.

​Address stormwater effects as close to the source as possible by:
  • Designing the construction footprint to protect existing soils and vegetation that contribute to stormwater management.
  • Minimising impervious areas through limiting building footprints and reinstating the building curtilage with permeable surfaces wherever practicable.

​Avoid inappropriate building materials that contribute toxins, metals, etc. to stormwater runoff. 

Using materials that leach contaminants such as zinc or copper may require expensive onsite treatment to remove it. Use inert materials instead. 

Retain roof and balcony runoff for reuse in buildings and landscaped areas. 

Consider the use of living roofs and walls. These can protect roofs, insulate buildings, and manage stormwater. 

Mimic natural systems and processes for stormwater management by:
  • Considering living roofs and walls for stormwater filtering and transpiration.
  • Conveying stormwater runoff across vegetated flowpaths, swales, and filter strips to attenuate, detain, and filter it.
  • Infiltrate or treat stormwater runoff in bioretention devices or underground detention tanks.

​Implement erosion and sediment controls during construction to reduce sediment discharge from the site by:
  • Minimising the area of site disturbance and earthworks.
  • Incorporating appropriate vegetation into the landscaping.
  • Creating stable flowpaths to convey water at non erosive speeds.
  • Using sediment and erosion control measures such as silt fences, sediment ponds and mulching.

​Consider the maintenance of systems at an early stage of design development and provide a maintenance plan that considers:
  • Actions required for maintenance of the system.
  • Frequency of inspections.

​Consider the following to promote interdisciplinary planning and design in stormwater management:
  • ​The relative benefits of at-source stormwater management compared with centralised stormwater features that contribute to ecology, recreation, or amenity values.
  • Including operation and maintenance professionals in the design of stormwater infrastructure.​
  • Aligning stormwater function with the appropriate level of public and private open space.

Rules of Thumb

The most harmful contaminants in Auckland’s stormwater are suspended solids, a range of heavy metals, organochlorines, polynuclear aromatic hydrocarbons and human pathogens.

Sand and gravel erode more easily than silt and clay, but silt and clay are difficult to trap with sediment control practices once they are in suspension.

Steep slopes contribute a disproportionately large level of sediment for the area disturbed.

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