Client: Stormy Water Solutions

Project Summary:

Afflux Consulting have been engaged by Stormy Water Solutions to conduct a 2-dimensional flood investigation of the proposed Alira Development and associated floodplains. The primary focus of the investigation was to:

• Examine 9.5%, 1% and 0.2% AEP event flood levels in Alira Waterways so that pathways, road levels, lot levels and extreme flow event emergency provisions can be assessed and confirmed.
• Confirm the 9.5%, 1% and 0.2% AEP flood levels as previously determined by Water Technology.
• Examine the various degrees of blockage to the syphon system to ensure the proposed freeboard provisions are adequate.
• Clearly define both the 1% AEP and 3-month ARI flood flow velocities in the wetland system.

The study was intended to act as both a review of the substantial previous work undertaken in this reach, but also to better understand the hydraulics of the Hallam Valley Contour Drain (HVCD) and associated floodplains.

The interaction of both the peak flows through the HVCD, and the volume of water within the floodplains combine to set the flood levels in the whole system. This complex interaction is difficult to simplify, and as such a significant number of detailed models were constructed and run for this study. 

Project Recommendations:

The hydraulic modelling was used to refine existing flow characteristics of the creek. Several flood risk management strategies were consequently adopted as a result of this project, including increasing retarding volumes of 4 retarding basins, flood levee works, staging of wetland and levee works, and setting floor levels for affected residents. 

Key Features and Innovations:

• Collaboration with Melbourne Water and Stormy Water Solutions.
• Modelling of levee staging and numerous scenario runs.
• Vastness of HVCD modelled to understand downstream flood impacts.