Retention/Detention Ponds
Type of Development
New Development
Topography
Hills, Valley, Baylands
Longevity
Long Term
Environment
Natural
Maintenance
Low
Cost
The residential economy increases dramatically when water features are nearby. Land usually needs to be purchased and naturalized, thus, construction costs are high where a park or natural environment is not already available. According to the EPA, costs of retention ponds can range from $17.50-$35.00 per cubic meter. Detention ponds can cost $5- $10 per cubic meter.
Overview
Retention ponds are depressions that are dry until flooding events, when they capture runoff from storms, slowly draining water into the ground to recharge groundwater. Detention ponds are always or mostly wet, but can be filled to capacity when needed in flooding events. They are considerably deeper than bioswales and rain gardens but are still planted with native, strong rooted plants. Both can be placed in areas that are often impacted by flooding, and are best situated at the end of a slope. They can also be combined with rainwater harvesting techniques to increase efficacy.
Function
Retention and detention ponds store excess runoff from storms and flooding events and water is slowly filtered into groundwater.
Benefit
Retention and detention ponds not only regulate flooding but also create a source of irrigation for drought conditions when done correctly. Slow filtration of water through such ponds, cleans water and reduces pollution in the hydrologic system. Furthermore, they create habitats for native animals and organisms to live when drought conditions are present. Communities benefit from proximity to water.
Dependency
Space
Development Considerations
Ponds should be located where flooding is most prominent. For riverine flooding, the basin should be located near the middle of the watershed to maximize its control over flow speeds and volume. Natural topography should be used as an advantage so construction costs can be minimized.
Environmental Considerations
Water table needs to be at an appropriate height to allow for retention and percolation where necessary. Native plants should be planted around the back of basins to decrease overflow.
Maintenance Consideration
The retention/detention ponds require maintence to remove trash, potential sediment build ups, and avoid stagnant water, as well as extra care after flooding events to reduce erosion impacts.
Cost Considerations
The residential economy increases dramatically when water features are nearby. Land usually needs to be purchased and naturalized, thus, construction costs are high where a park or natural environment is not already available. According to the EPA, costs of retention ponds can range from $17.50-$35.00 per cubic meter. Detention ponds can cost $5- $10 per cubic meter.
