“Slow it, sink it, spread it” is an informal way of talking about a three-tiered approach to rainfall management: “Retain, Detain, and Convey.” This approach recognizes that there is a range in storm sizes and that there will always be a storm which is bigger than the collection system we’ve built to manage it. The tiered approach aims to:
- Retain rainfall on site in natural proportions
- Detain or temporarily store excess rainfall (when the amount is too large to retain), and
- Safely convey anything that cannot be detained (these are large events) via regional green (constructed wetlands) or grey (stormwater pipes and channels) detainment and conveyance systems.
Using this tiered approach we can reduce the severity of impact human development has on the balance of water.