Puhinui Stream Restoration

Puhinui Stream Restoration - Concept Plan Prepared by D.J. Scott Associates Ltd.

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Puhinui Stream Restoration - Click to enlarge
Puhinui Stream Restoration - Concept Plan (PDF 1.74m)

Background | Project Brief | Management Issues

Project Background

The Manukau City Council Draft Parks Strategy states as one of its key goals “coastal and riparian access and protection - the completion of a continuous link around the coast and along the primary streams to provide access to and protection of the coastal and riparian environment”.

Consistent with this strategy Manukau City Parks is seeking the restoration of the Puhinui Stream and the development of a walkway linking Totara Park and Puhinui Reserve.

The key aim of the Puhinui Stream Restoration Project is the establishment of a cross-city walkway. The development of this concept plan is to act as a guide for the restoration of the stream and the development of a walkway. Another key aim is to foster partnerships within the community and between local interest groups and Council to provide a recreational and educational resource for the entire community.

What is restoration?
The Society for Ecological Restoration defines ecological restoration as “ the process of intentionally altering a site to establish a defined indigenous, historical ecosystem. The goal of this process is to
emulate the structure, function, diversity and dynamics of the specified ecosystem.”

The Society also describes ecological restoration as: “The process of intentionally compensating for damage by humans to the biodiversity and dynamics of indigenous ecosystems by working with and sustaining natural regenerative processes in ways which lend to the reestablishment of sustainable and healthy relationships between nature and culture”.

Site Description
The Puhinui catchment includes approximately 2220m2 of land extending from within Manukau City from Redoubt Road and Mills Road out to the Manukau Harbour at the Puhinui Reserve. The stream in approximately 12.0 kilometres in length, a significant proportion of which is in Council ownership. Land use within the catchment is predominately residential with commercial and light industrial areas around Cavendish Drive.

The Puhinui stream has undergone extensive modification and in a number of locations has been channelled and lined in concrete, resulting in a loss of ecological, recreational and amenity values. Further modification to the Puhinui Stream is anticipated with the future construction of State Highway 20 across several sections of the stream.

Project Brief

This report has been prepared in order to provide a general concept plan for the restoration of the Puhinui Stream. A series of 13 Concept Plans and corresponding Cross-Sections are the basis of this report and outline the area of restoration in addition to the proposed species composition and layout. The main factors which have contributed to the layout and planning of the stream restoration include:

  • The identification of target areas suitable for public planting initiatives
  • The enhancement of the ecological, environmental and aesthetic values of the stream
  • The creation of a green corridor connection Manukau City with the Manukau Harbour
  • The social and recreational development of the stream for recreation and public enjoyment and use
  • The connection of the restoration project with existing open space areas and future opportunities for additional linkages
  • The development of costings and staging for the project over the next 10 years

Project Goals
The key goals of the stream restoration project include:

  • The reduction of flood damage along the stream corridor
  • The reduction of damage from stream bank erosion
  • The preservation / restoration of the historic and cultural resource
  • The return of birds and wildlife in urban environment
  • The development of pedestrian links along and across the stream
  • The upgrade of urban and neighbourhood environments
  • The provision of greenbelts, open space and parks
  • The inclusion of safety issues along the proposed pedestrian walkway
  • The creation of educational opportunities for local schools
  • The restoration and improvement of water quality
  • The replacement of culverts and concrete-lined channels with natural stream channels
  • The improvement of water quality and habitat

Management Issues

The key management issues relating to the stream include:

  • The protection and enhancement of habitat along the stream
  • The extensive modification of the meander of the stream and the relining of the stream channel with concrete lining in a number of locations
  • In the highly developed commercial areas adjacent to the stream there is limited opportunity for restoration due to the close proximity of built form
  • Sedimentation of the stream due to new development and adjacent land uses (i.e. agricultural)
  • The future development of State Highway 20
  • The positioning of the proposed pedestrian walkway along the stream corridor
  • Existing stock access to the stream in a number of locations
  • Safety issues for pedestrians utilising the proposed pedestrian walkway

The proposed management for the restoration of the Puhinui Stream includes:

  • The removal of exotic and invasive weed species within the stream corridor and along the stream banks
  • The revegetation of the stream corridor and floodplain with appropriate native species
  • The removal of rubbish and waste from the stream corridor
  • The provision of canopy trees to provide shading to the stream channel Linkage with adjacent public open and recreational space
  • The repair and construction of fencing along the stream in order to ensure that stock are kept out of the floodplain
  • The identification of target areas suitable for public planting initiatives

As outlined above, there are a number of management issues which are critical to the ecological restoration of the stream. The main priority in the restoration of the stream and consequently in the development of the concept plan has been to improve the existing ecological quality and links along the stream.

The ecological restoration of the stream will initially involve the ‘clean up’ of the stream, the removal of exotic and invasive weed species, the revegetation of the riparian areas of the stream along with the ongoing maintenance and ‘release’ of the revegetation plantings. Another key consideration in respect to the restoration of the Puhinui Stream is the management of adjacent land and the prevention of additional ecological damage due to issues related to new development adjacent to the stream corridor, waste disposal, rubbish dumping and land use.

The management of the stream will initially require the revegetation of the stream corridor with appropriate native species. The establishment of native species along the stream channel and throughout the floodplain will initially require the removal of existing and extensive weed coverage along the stream.

The Puhinui Stream has for the most part been neglected and as a result, extensive weed invasion has taken over much of the floodplain area. In order to rid the proposed areas of revegetation of weeds, several applications of herbicide spray will be necessary. Initial site preparation of the stream may also require additional work in the form of clearing invasive tree species, cleaning out the stream channel of rubbish, dredging of the stream and regrading of the floodplain. As portions of the stream are revegetated a thorough maintenance programme will also need to be adhered to over a period of 4 to five years in order to aid in the successful establishment of new plantings. Maintenance will include releasing new plantings from weed growth, interplanting as a result of plant loss (over 10%) and the removal of rubbish from the stream.