These ponds, which can vary in size and shape, help slow, heavy water flows to avoid floods and improve the quality of urban runoff from roads, parking lots, and commercial and industrial areas by filtering water.
The terms detention pond and retention pond are used interchangeably when referring to these ponds or basins since they capture and store runoff; they can even be similar in design.
However, detention ponds and retention ponds differ in purpose.
What is a retention pond?
The definition of retention is “the capacity to hold; the state of being retained.” So a retention pond is designed to hold a permanent pool of water that fluctuates in response to precipitation and runoff.
Usually, retention ponds have drainage leading to another location when water levels reach beyond a certain point. However, they continue to maintain a specific water capacity.
Maintaining a water pool can also help keep deposited sediments at the bottom of the holding area, improving water quality.
What is a detention pond?
On the other hand, detention means to “momentarily withhold something” or “delay an action.” In this case, a detention pond—or dry pond—is an area where excess stormwater is stored or held temporarily and then slowly drains when water levels in the receiving channel recede.
In essence, the water in a detention basin is briefly detained—over 24 hours, for example—until the additional room becomes available in the next conduit. These are extensive in the Ocean & Monmouth County areas of southern NJ.
Detention ponds come in handy during large storm events, which can contribute to a significant volume of runoff moving at an increased speed, raising the potential for erosion and flooding, particularly downstream. When the rain stops, detention ponds will be empty shortly afterward.
The area saw much more rain through July 8 of last year than it saw in all of 2019 and 2020. A meteorologist in charge of the Northeast weather service, Keith Stellman, says even if the area gets only average rainfall the rest of the year, it will still be one of the top ten wettest years on record.
Maintenance makes them work.
To operate successfully, both detention ponds and retention ponds require regular maintenance. Inspections, debris removal, vegetation management, bank stabilization, and structural checks are essential to ensure detention and retention ponds are ready to do their jobs when storms or heavy rains occur. If you need help installing or maintaining your backyard pond, we are here for you.