Detention basin

Detention ponds that are designed to permanently retain some volume of water at all times are called retention basins.

[2] The basins are typically built during the construction of new land development projects including residential subdivisions or shopping centers.

The ponds help manage the excess urban runoff generated by newly constructed impervious surfaces such as roads, parking lots and rooftops.

[3] A basin functions by allowing large flows of water to enter but limits the outflow by having a small opening at the lowest point of the structure.

The size of this opening is determined by the capacity of underground and downstream culverts and washes to handle the release of the contained water.