26/06/2025
Can you design drains so they don’t overflow?
It is not feasible for all stormwater to be collected in underground drainage systems. The drains required would have to be enormous and expensive. Pipe drainage systems are generally designed to accommodate stormwater runoff in a 1 in 5 (20%) AEP event according to standards.
In a 1 in 100 year event, the piped system will overflow and rely upon the natural drainage paths towards a larger waterway. In this instance – the Broken River using roads and reserves. Roadways play an important role in flood management and are designed to carry floodwater in a 1 in 100 AEP event, which is standard practice across Victoria.
All properties will be required to be filled 300mm above the 1 in 100 AEP levels to ensure that they do not flood in a major storm event.