What is the function of a stormwater detention basin?

The function of a stormwater detention basin is to temporarily store stormwater and release it at a controlled rate. This process mitigates flooding by managing runoff during periods of heavy rainfall. When stormwater flows into the basin, it is held temporarily, allowing for sedimentation and settling of pollutants to occur before the water is gradually released into downstream waterways. This controlled release helps prevent surges of water that can overwhelm drainage systems and cause erosion, flooding, and other environmental issues. It is an essential component of stormwater management as it balances the volume of runoff with the capacity of the surrounding ecosystem to handle it.

Other options reflect misunderstandings of the purpose of a detention basin. While permanent storage of stormwater may seem beneficial, it does not align with the primary goal of managing peak runoff flows. Filtering all contaminants is a more complex process typically associated with treatment systems rather than the primary function of a detention basin. Furthermore, immediate drainage does not account for the need to regulate the flow rate, which is crucial for flood prevention and environmental protection.