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Fish passage

Stormwater management ponds and wetlands

Stormwater ponds and wetlands are used to remove sediment, heavy metals and other contaminants from stormwater. ARC has a preference against the use of on-line ponds, which discharge into natural stream environments, but these may be the only option in highly developed catchments.

Issues

Rising manhole outflow for a stormwater pond, note the vertical sides and lack of flow in most conditions

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Vertical outflow structures – rising manholes are often used as overflow structures to control the water level in stormwater ponds. The vertical, smooth concrete surfaces and intermittent flows over these structures can be barriers to climbing species.

Lack of shade or deep water – shallow ponds with little vegetation can be subject to high water temperature in summer, which native fish are unable to tolerate.

Options

  • Spat ropes – these ropes have been shown to be effective for climbing fish species to wriggle up and over obstacles. This may be one of the only options where access for climbing species through vertical rising manhole structures is required.
    Spat ropes (223.8 KB PDF)

  • Designing stormwater ponds to include deeper areas in the centre and surrounding the edges with native vegetation can help make these devices more fish-friendly. Further advice on stormwater pond design can be obtained by ringing ARC on 09 366 2000 and asking to speak to a member of the Stormwater Action Team.

Note: the pdf documents on this page are excerpts from ARC Technical Report 2009/084: “Fish Passage in the Auckland Region – a synthesis of current research".