What is the purpose of a detention basin?

A detention basin serves the specific purpose of temporarily storing runoff water to manage excess stormwater during and shortly after rainfall events. This temporary storage helps to reduce peak flow rates, preventing downstream flooding and allowing the water to be released at a controlled rate. By doing so, it mitigates the impact of sudden surges of water that could overwhelm drainage systems or stream channels.

This function is essential in managing the quantity of water entering the drainage infrastructure, thereby protecting water quality and reducing erosion and sediment transport. The design of a detention basin typically includes outlets that allow for the gradual release of water once the storm event has passed, ensuring that the basin does not serve as a permanent reservoir but as a dynamic management tool for stormwater.

In contrast to the other options, a detention basin is not intended for permanent storage, immediate release, or sole filtration of stormwater. These alternative functions are typically associated with other types of water management practices, like retention basins or treatment swales, which focus on longer-term water quality enhancement and greater water retention.