A detention basin is an stormwater management facility installed on, or adjacent to, tributaries of rivers, streams, lakes or bays that is designed to protect against flooding and, in some cases, downstream erosion by storing water for a limited period of a time. These basins are also called “dry ponds”, “holding ponds” or “dry detention basins” if no permanent pool of water exists. Some detention ponds are also “wet ponds” in that they are designed to permanently retain some volume of water at all times. In its basic form a detention basin is used to manage water quantity while having a limited effectiveness in protecting water quality, unless it includes a permanent pool feature.[1]

A retention basin, is a type of best management practice (BMP) that is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. Sometimes called a wet pond or wet detention basin, it is essentially an artificial lake with vegetation around the perimeter, and includes a permanent pool of water in its design.[1] [2]

It is distinguished from a detention basin, sometimes called a dry pond, which temporarily stores water after a storm, but eventually empties out at a controlled rate to a downstream water body. It also differs from an infiltration basin which is designed to direct stormwater to groundwater through permeable soils.

Wet ponds are frequently used for water quality improvement, groundwater recharge, flood protection, aesthetic improvement or any combination of these. Sometimes they act as a replacement for the natural absorption of a forest or other natural process that was lost when an area is developed. As such, these structures are designed to blend into neighborhoods and viewed as an amenity.[3]