Stormwater Ponds

Stormwater ponds are the workhorse practices of watershed protection: constructed basins that hold a permanent pool of water, settle out sediment and attached pollutants, and meter out storm flows slowly enough to protect downstream channels. The family covers wet ponds, wet extended detention ponds, micropool designs and multiple-pond systems. Ponds suit drainage areas of roughly ten acres and up, tolerate nearly any soil group, and deliver some of the most reliable monitored performance of any practice group — median removal of about 80 percent of suspended sediment and half of total phosphorus. The trade-offs are land consumption, permanent standing water with its safety and mosquito considerations, and embankments that turn the structure into a regulated dam above certain heights. The fact sheets in this group cover applicability, design criteria, outlet works, landscaping and the maintenance schedule that keeps a pond performing past its first decade; the pond design calculator works the full sizing sequence interactively.