Detention/ Retention Ponds: Dry/ Wet Ponds
Detention/ Retention two different kinds of ponds are often used for flood mitigation and stormwater runoff treatment: wet ponds and dry ponds. Both systems function to temporarily hold stormwater runoff and release into the drainage system at a pre-developed flow rate.
Wet ponds are also called retention ponds and they hold back water similar to water behind a dam. The retention pond has a permanent pool of water that fluctuates in response to precipitation and runoff from the contributing areas. Maintaining a pool discourages resuspension and keeps deposited sediments at the bottom of the holding area. We commonly use Retention ponds when the client needs more dirt or wants a water feature. Dry ponds are also called detention ponds are the most common and serve as an important flood control feature. They are usually dry except during or after rain events. Their purpose is to slow down water flow and hold it for a short period of time such as 48 -72 hours. In the greater Houston area, the cities and counties rely on these structures to reduce peak runoff rates associated with storms, decreasing flood damage. Dry ponds can be designed for a variety of storm events and purposes. The land area available for construction, slope of the site and contributing area are all factors to be considered. Also, an emergency spillway is usually required to allow for safety during flood events. Although detention ponds can vary in size and shape, they all function to settle stormwater particles and reduce peak flows.