Retention basins, also known as “wet ponds”, are typically used for flood control in subdivisions and on commercial properties to decrease peak flows and slowly release collected rainfall runoff over a longer period to reduce local flash flooding. Wet ponds can also be designed for “extended” storage, which detains water evenly above the permanent pool storage and then released over 24 hours. Wet extended detention ponds consume less space while serving the same pollutant removal as typical wet ponds. 

Detention basins, also known as “dry ponds”, capture stormwater runoff for a determined period of time after a storm event. Water is temporarily impounded in a dry pond and then discharged. Dry ponds typically feature low-flow concrete channels that convey temporary water to outlets and are often planted with turf grass or prairie species.