Many people are often puzzled when they first hear about requirements to detain a few thousand litres of rainwater, especially when further told this rainwater must be slowly released down the drain. While this seems like a waste of precious water, there are good reasons for stormwater detention that this article will explore.
What is Stormwater Detention?
Stormwater detention is about having a storage tank which is configured to temporarily hold rainwater and then slowly release it into the stormwater system. This helps to prevent local stormwater drains exceeding their capacity and causing flash floods.
Detention means the water will be “detained” for a limited period. Stormwater detention tanks are intended to remain empty, except during periods of rainfall and for a short time thereafter.
Why Detain Stormwater?
During heavy downpours a lot of stormwater can be generated increasing the risks of flash floods. This risk of such is worsened by higher density residence, industrial and commercial buildings which create a lot of hard surfaces water runs off. This places increased pressure on underground drainage infrastructure.
One solution is to increase the capacities of existing drainage to cater to increased stormwater flow, however councils consider this infeasible due to space and cost constraints. Some burden of responsibly is therefore placed on homeowners to help make the stormwater from their properties more manageable.
The solution to this is stormwater detention – the general idea being to always have empty storage which stormwater can fill. One might think simply storing water in a rainwater tank might be a good solution for reducing stormwater, however in heavy downpours rainwater tanks can quickly fill up. The emptying of stormwater in a detention tank system keeps space available for water to be detained in consecutive downpours.
The slow release of water into drains from stormwater detention tanks helps to assist your local area with more manageable loads of water runoff, helping to prevent flash flooding. This may not prevent flooding, but if consistently applied to residential properties in an area it can help to significantly reduce and/or prevent flash flooding.
While water detention tanks are a solution, they are more like last line of defence in dealing with stormwater runoff. You can effectively plan your property to be more sensitive to stormwater runoff by combining natural detention solutions with effective design.