Oakley Creek – Stream Ecological Valuation

Client:  Auckland Council
Date:  2019

We were engaged by Auckland Council (Healthy Waters Department) to undertake a Stream Ecological Valuation (SEV) assessment of the Upper Oakley Creek stream corridor located in War Memorial Park, Keith Hay Park and Molley Green Reserve in Mount Roskill.  The key objective of this assessment was to determine the ecological potential for restoration of the watercourse through these reserves to inform a stream restoration conceptual design and offset the loss of ecological values from development, and/or the provision of infrastructure elsewhere in the region.

We conducted ecological assessments using the SEV methodology which assigns scores based on key ecological functions.  It was determined which ecological functions were limited by the current stream design and the stream had low ecological value.  Fish survey and macroinvertebrate surveys were also conducted to determine instream fauna present.  As such the following opportunities were identified across each park.

  • Removal of concrete lining to restore connectivity to groundwater in the hyporheic zone and natural flow regimes.
  • Riparian planting should be undertaken to the maximum extent possible.
  • Broader enhancement opportunities were also been identified to improve the amenity and aesthetic values of the reserve.
  • Meanders could be incorporated into the lower, straightened section of the watercourses to increase channel sinuosity, flow diversity and instream habitat.
  • Bioengineered features could be incorporated into the stream banks, such as boulders, tree trunks and root wads to provide hydraulic heterogeneity, instream habitat, organic matter and roughness.
  • Pool-riffle-run sequences can also be incorporated into the channel to provide flow diversity, roughness and increased habitat.
  • Daylight piped tributaries into the channel and provide riprap sections to improve aesthetics and water quality.
  • Focus habitat enhancement for those species present.

A high-level planning assessment was conducted concerning the proposed works against the requirements of the relevant local national regulations.  In addition, a high-level geotechnical assessment was conducted to outline the geology and site ground condition, as well as potential risks with the proposed works.  A high-level engineer’s costing was also conducted to guide the cost of the proposed works to restore the stream.

Key Aspects:

  • Stream restoration planning
  • Ecological considerations in watercourse design and engineering solutions
  • Environmental offsetting and mitigation
  • Stream Ecological Valuation
  • Macroinvertebrate sampling
  • Fish surveys including electric fishing and trapping
  • Consent and planning advice
  • Geotechnical assessment

Client:  Auckland Council
Date:  2019

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