Stormwater is the rain that meets the ground surfaces. What starts as rainwater harvested from the rooftops into a rainwater tank, quickly becomes stormwater that overflows from the tank onto the ground or into a drain. This is why residential and commercial buildings need to plan for stormwater detention.
What is stormwater detention?
Stormwater detention is the place where rainwater flowing across ground surfaces like driveways, paths and drains is captured and stored before being released. The stormwater is stored on a special water tank known as a stormwater detention tank. The tank usually has a slow-release valve which allows the water to drain slowly.
Why detain stormwater?
During heavy downpour of rain or storms, a lot of stormwater can be generated. It increases the risk of floods in urban areas. It is worsened by increasing residential densities and expanding industrial and commercial buildings as they increase pressure on existing underground drainage infrastructure.
It has been observed that increasing the capacity of existing drainage for increased stormwater flow can be infeasible because of space and cost limitations. Thus, the onus is on homeowners to manage the stormwater.
How is stormwater detained?
When a property is being developed and designed, a sensitive stormwater design is made. Also, new houses often need to have on-site detention facilities made as a part of their home drainage system. Some of them include water tanks or concrete basins beneath driveways for capturing stormwater runoff from the residential area and hold it for some time to reduce the impact of flooding.
The stored water is then drained slowly from a small opening near the base of the tank. It is said that when most homes in the flood-prone area have detention systems, the flood peak during storms can be reduced and thereby flood damage can be minimised.
Solutions for onsite stormwater detention
• Stormwater detention tanks
These are specially designed tanks which have split storage inside. One compartment is for storing rainwater, and another is for detaining stormwater.
• Underground storage tanks
These tanks are used for storing stormwater runoff. They are designed with your rainwater harvesting system to receive excess water overflowing from a rainwater tank or placed under driveways where a lot of stormwater runoff can be received.
• Rainwater tanks
These large water storage tanks can satisfy most council requirements.
When the new houses are built in areas where councils need homeowners to help with, stormwater needs to get stormwater detention tank made. Detention means that the water will be detained for a limited period of time. These tanks must remain empty except during the periods of rainfall and for a short period thereafter.
What makes these detention tanks different is that they are specially fitted with a valve to release the water over time slowly. There are two options with a stormwater detention tank solution:
• Use two water tanks- one to harvest rainwater and other for stormwater detention.
• Use a specially made dual-use water retention/detention system.
Since a detention tank is supposed to be always empty, it will be prepared for storing more water in consecutive downpours. If storm stops pouring down rain for an hour or two, it should be ready to detain another 2000 litres of water by the time storm returns as this allows drainage network in your areas to the better manager water runoff during heavy storms.
Stormwater detention needs can vary from one council to another; thus, it is important to discuss with your local council before you implement any stormwater solution. Getting a suggestion from experts about the detention tank can also be a good idea.
Analyse the type of property you have and get a stormwater detention tank installed based on your specific needs.