Detention ponds or basins are usually dry depressions in the ground that can be vegetated or grey. While usually designed to provide only short term storage of water, their pollutant removal efficiency is higher when they are designed to hold water for longer (they are then called extended detention basins). They do so by allowing sediment to settle and biological processes to take place that destroy nutrients and other pollutants.
Detention basins can be used as multifunctional areas and so provide opportunities for recreation and sport. (2,6,14)
Potentially, pollutants can be adsorbed by vegetation and soil. (9)
Detention basins have a high impact on peak flows and can reduce volume of runoff (20-90%), but are most effective for small storms. Extended detention basins can achieve better outcomes. (7, 8, 10, 11)
Detention basins may influence fluvial floods downstream by reducing the amount of water discharged into rivers. (2)
DB can reduce the UHI effect and store carbon if vegetated. Long storage times, while improving nutrient removal, can increase GHG emissions. (2, 13,16)
Low potential but planting of native vegetation and shrubs can improve habitat conditions for wildlife. Invasive species can be a problem. (6, 13, 15)
Groundwater recharge is possible. (6,13)
Especially high sediment removal (40-70%) but also for metals and insoluble pollutants, but lower for soluble pollutants. Higher for extended detention basins. (3, 4, 7, 10, 11)
Depending on design the aesthetic value can be significant. In highly urbanised areas where grey design is required, this can be enhanced to look appealing and provide multifunctional space. (6,13,15)
Depending on design, detention basins can provide space for cultural activities. (6, 14, 15)
Good design increases property value in close vicinity to detention basins. (11)
Through their impact on reducing and removing surface water runoff, detention basins can reduce severity of surface water floods.
Considering the Bigger Picture
Detention basins act mainly as storage areas and can provide treatment of water from a larger catchment area. Surface water can be stored as part of a routine runoff path (‘on-line component’) or they can act to capture overflow when the usual train of treatment is insufficient (‘off-line’), before it is discharged into the sewer system or further treatment. The intended function influences the design, with on-line components usually being vegetated to provide infiltration and pollutant treatment capacities. To maintain their function, pre-treatment – for example sediment forebays – is necessary. They can be combined with swales, and including small ponds or wetlands can increase treatment performance. In addition, they can provide valuable recreational areas. When dry, they are can be playing fields or amenity areas that are publicly accessible, depending on their design. They can incorporate recreational facilities, other interventions or be themselves part of an existing open space – green or grey.
To provide a comprehensive treatment and management of surface water, detention basins should be seen within the wider landscape. While they are able to store runoff, it is important to understand that their ability to reduce runoff and infiltrate it is limited. If they are placed in natural runoff paths, they can reduce the risk of fluvial flooding by preventing water from entering the stream immediately.
Detention basins provide control of runoff from a large catchment area, but their storage capacity is limited by their design. Combining them with other interventions like swales can reduce sediment loads before runoff enters the basin and so reduce maintenance requirements. Water can further be lead into retention ponds or wetlands to undergo additional treatment or to be stored over a longer period, or be discharged slowly into sewers or other receiving systems.
Below, you see some of the multitude of additional benefits that detention basins provide in the context of the urban landscape.
15-55£/m3 volume, with a lifetime of up to 50 years. Costs depend on the site and context, as well as the scale of the development. (5)
Residential, Commercial, Retrofit. Multiple uses possible and can therefore be incorporated in existing amenity space and used for recreation. (6,14,15)
0.3£/m2/a. Can be part of landscaping. Inlet and outlet need to be cleaned regularly and sediment monitored and removed if necessary. Regular maintenance is necessary. (5)
Trade-offs and Potential Dis-services
Lack of maintenance can lead to swampy areas at the outlet of the basin which can be perceived as dangerous or simply ugly, and can also have an impact on the multi-functionality of the space.
Sediment removal needs to be taken care of if accumulation of metals happens at the bottom of the basin. Otherwise, the soil can become contaminated and high pollution can occur in the outflow of the basin.
Depending on the design, NH4 and CH4 can be emitted, more so when storage times are longer. This should be considered when designing the basin and outlet.
- Ahiablame, L. M., Engel, B. A. and Chaubey, I. (2012) Effectiveness of Low Impact Development Practices: Literature Review and Suggestions for Future Research.
- Ashley, R. M., Nowell, R., Gersonius, B. and Walker, L. (2011) ‘Surface Water Management and Urban Green Infrastructure’, 44(0), pp. 1–76.
- Berwick, N. and Wade, D. R. (2013) A Critical Review of Urban Diffuse Pollution Control : Methodologies to Identify Sources , Pathways and Mitigation Measures with Multiple Benefits.
- Deletic, A. (2005) ‘Sediment transport in urban runoff over grassed areas’, Journal of Hydrology, 301(1-4), pp. 108–122.
- Environment Agency (2015) Cost estimation for SUDS – summary of evidence. Bristol.
- Kellagher, R., Martin, P., Jefferies, C., Bray, R., Shaffer, P., Wallingford, H. R., Woods-Ballard, B., Woods Ballard, B. (2015) The SUDS manual, CIRIA. London.
- Pratt, C. J. (2004) Sustainable Drainage. A Review of Published Material on the Performance of Various SUDS Components. Bristol.
- Lawrence, A. I., Marsalek, J., Ellis, J. B. and Urbonas, B. (1996) ‘Stormwater detention & BMPs’, Journal of Hydraulic Research. Taylor & Francis Group, 34(6), pp. 799–813
- Forest Research (no date) Improving Air Quality.
- Birch, G. F. and Fazelli, M. S. (2006): Efficiency of a Retention/detention Basin to Remove contaminants from Urban Stormwater’, Urban Water Journal, 3.2, 69–77
- J B Ellis, R B E Shutes and M D Revitt (2003) Constructed Wetlands and Links with Sustainable Drainage Systems.
- Lee, J. S. and Li, M. (2009): The Impact of Detention Basin Design on Residential Property Value: Case Studies Using GIS in the Hedonic Price Modeling’, Landscape and Urban Planning, 89.1-2, 7–16
- McPhillips, L. and Walter, T.(2015): Hydrologic Conditions Drive Denitrification and Greenhouse Gas Emissions in Stormwater Detention Basins’, Ecological Engineering, 85 (2015), 67–75
- Susdrain (2016): http://www.susdrain.org/delivering-suds/using-suds/suds-components/retention_and_detention/Detention_basins.html
- CIRIA (2014) ‘Demonstrating the multiple benefits of SuDS – a business case’, (October), p. 45.
- Armson, D., Stringer, P. and Ennos, A. R. (2012) ‘The effect of tree shade and grass on surface and globe temperatures in an urban area’, Urban Forestry & Urban Greening, 11(3), pp. 245–255.