Afflux Consulting was engaged by OpenCorp to investigate the flood impact of a proposed development at 757-763 Toorak Rd, Hawthorn East. The subject site is currently a large residential block. Gardiners Creeks lies approximately 150m west of the site and is subject to flood swelling from the creek.
The development site also lies within Land Subject to Inundation Overlay. Consequently, Melbourne Water objected to the development citing loss of floodplain storage and increase to flood levels of neighbouring properties. Melbourne Water requirements were summarised as:
- A minimum 40% of the site to be retained at natural surface.
- No development below 7.31m AHD.
- A Finished Floor Level (FFL) of 8.91m AHD to allow for 600mm freeboard above the 1% AEP flood level (8.31m AHD).
The primary concerns raised by Melbourne Water were flood volume reduction as a result of development, and for the development to adopt a Finished Floor Level of 8.91m AHD. 2D modelling, using parameters prescribed by Melbourne Water, did not find significant flood storage on the development site, and recommended that Melbourne Water retract their flood volume requirements. In regard to FFL however, it was agreed that the minimum FFL of 8.91m to be adopted. Given the thoroughness of the flood investigation undertaken to model Gardiners Creek, Melbourne Water had confidence that the safety of inhabitants and surrounding neighbours have been prioritised and the proposed development pose no additional flood risk to the area.
Key Features and Innovations:
- Came to an agreement with Melbourne Water and Client.
- Thorough modelling of Gardiner Creek swelling in a 1% AEP.