The role of WSUD in flood management
WSUD can be effective in mitigating the impacts of climate change so that the level of service provided by existing drainage can be sustained into the future.
Flooding in City of Melbourne will be exacerbated by increasing sea levels and storm intensity due to climate change. In some places, the existing drainage is over capacity and there is limited space to provide above ground flooding solutions. WSUD assets such as raingardens and permeable pavement can assist with flood management and also support greening and improve water quality.
While WSUD assets are not a replacement for traditional flood mitigation measures, they can provide stormwater retention and are well suited for reducing storm event flow volumes. If designed well, they can reduce the risks and costs of flooding, particularly in the 5-20% AEP flood event (refer to blue box on right for explanation).
Where possible, a combination of responses across a catchment provides better resilience for a diversity of storm events.
- Rainwater tanks are best for short high-intensity events.
- Green infrastructure with infiltration is better for longer low-intensity events.
Previously flood events were described using an average recurrence interval (ARI), such as a ‘1-in-100 year event’. This suggest that there will be an elapsed time between each event. We now use annual exceedance probability (AEP) to indicate the likelihood a flood event can happen in any given year.
- Flooding and defences