The Brown Hill Keswick Creek Stormwater Project is designed to provide flood protection to the community in the event of a 100 year average recurrence interval (ARI) flood event. The Project requires the delivery of a series of infrastructure works across the Brown Hill and Keswick Creek catchment, which is largely contained within the Cities of Adelaide, Burnside, Mitcham, Unley and West Torrens in metropolitan Adelaide.
Currently, a 100 year ARI flood event would impact over 2,000 properties and result in significant impact to the Adelaide Airport, Ashford Hospital, major arterial roads and freight corridors. Whilst a flood event of this magnitude has not occurred in the catchment since 1930, the high flow events of 2005 and 2016 have provided recent reminders of the flood risk.
Objectives of the Stormwater Management Plan
The Stormwater Management Plan is designed to substantially reduce the number of properties within the catchment that would be affected by very large Adelaide flood events, up to and including a 100 year average recurrence interval (ARI) flood.
A 100 year ARI flood — also referred to as a one in a 100 year event — is a flood that has a 1% chance of occurring in any given year. It is the most commonly applied standard in Australia for providing an acceptable level of flood protection for the community.
The Stormwater Management Plan identifies six primary objectives:
- Protection from flooding
- Quality runoff and effect on receiving waters
- Beneficial reuse of stormwater runoff
- Protection of watercourses and riparian ecosystems
- Effective planning outcomes
- Management of stormwater infrastructure.
What the Plan involves
Approved by the Stormwater Management Authority — a statutory corporation that acts as a state-wide planning and prioritisation body for stormwater management — in February 2017, the Stormwater Management Plan requires delivery of a series of sub-projects that include both structural and non-structural flood mitigation measures. The sub-projects are described in more detail here.
Important environmental and community benefits of the outcomes of the Stormwater Management Plan are also identified including:
- Improved quality of stormwater discharge into marine receiving waters;
- Beneficial re-use of stormwater, particularly for greening of urban open space areas;
- Creek rehabilitation and protection of biodiversity; and
- Improved recreational amenity in open space areas traversed by watercourses.
The works outlined in the Stormwater Management Plan present urban renewal opportunities that enable communities to better use the land corridors through which stormwater is designed to be conveyed — for example linear parks, wetlands and shared use paths.