Client: Cardinia Council

Project Summary:

In this project, Afflux Consulting was asked to undertake an options analysis to control erosion and sediment within Gembrook Park, Redwood Road, Gembrook. Council, along with the Friends of Gembrook Park have become increasingly concerned about the development of erosion along the main valley line running through the Park from Redwood Road well into the forest. Not only are there developing erosion heads down in the forest floor, there are also large accumulations of sediment and gravel in bands across the valley.

Engineering constraints within the project included:

  • Large trees to be protected.
  • Steepness of catchment and ground levels limiting possible WSUD locations.

Project recommendations:

Four options were presented to Council and ultimately the several forward steps were recommended:

  • A Storage volume of 140m3. This results in a flow reduction from the ~10yARI to the 2yARI.
  • Basin deepened and moved so that batter slopes and tree plate of large Eucalypt did not clash.
  • Pipework and hydrology reviewed and revised.
  • New outfall proposed to enter existing gully line.
  • Diversions of minor and major flow routes.
  • The following design parameters have been achieved with the final design:
  • A sediment dropout area of 140m2. For a design particulate size of 125┬Ám this will meet a 95% solid removal for the 3mth ARI.
  • A recommended cleanout rate of around 8 years is recommended based on contemporary sediment loads. However, given the vegetation present in this location bark removal may need to be more frequent.

Key Features and Innovations:

  • Working closely with the community to understand their needs.
  • Stepped-down WSUD treatment train to deal with steep slopes and minimise erosion.