Rain gardens or bioretention cells, green roofs, planter boxes, bioswales, and other bioretention systems are examples of green infrastructure used in low impact development to make city landscapes more permeable. Rain gardens and other bioretention systems can be implemented on a small scale on individual properties, sites, or neighborhoods, or on a larger scale throughout a city, county, or geographic region. Native and adapted plants can be used in rain gardens and other bioretention systems, since they are tolerant of local climate, soil, and water conditions. Plants and soil layers in such systems filter water before it enters the groundwater system1.
Expected Beneficial Outcomes (Rated)
Reduced water pollution
Other Potential Beneficial Outcomes
Reduced soil erosion
Increased wildlife habitat
Improved mental health
Improved health outcomes
Reduced urban heat island effects
Improved sense of community
Evidence of Effectiveness
There is strong evidence that rain gardens and other bioretention systems reduce stormwater run-off and pollutant concentrations, especially total suspended solids and heavy metals2, 3, 4, 5, 6, 7, 8. Rain gardens and other bioretention systems are also a suggested strategy to reduce soil erosion, protect communities from flooding, improve water quality, recharge groundwater, and preserve habitat, property, and other infrastructure9, 1, 3, 10.
Coordinated efforts to establish many rain gardens throughout an area have a greater effect on water quality than individual rain gardens; combining rain gardens with other low impact development projects such as permeable pavement and infiltration trenches also increases effectiveness11, 12, 13, 14. Bioretention systems are generally more effective in Midwest and Mountain states than in Atlantic and Gulf Coast states, and with steady rainfall rather than extreme storms15.
Rain gardens and other bioretention systems have been shown to be effective in tight soil conditions and cold weather climates when designed, implemented, and maintained properly16; proper design, implementation, and maintenance maximizes benefits2. Using a multilayer or multizone design with enrichments such as iron-enhanced sand can improve overall capture of phosphorus (P), nitrogen (N), and other organic compounds; other designs have varying success capturing N and P4, 16, 5, 17. Rain gardens and other bioretention systems are also more effective for N capture than conventional wet or dry ponds18.
Rain gardens and other bioretention areas increase attractive green spaces, which may improve neighborhood aesthetics and enhance wildlife habitats3. These additional green spaces may also improve mental and physical health for residents, reduce heat island effects, improve sense of community, and reduce crime19, 20. Rain gardens have been shown not to serve as mosquito breeding grounds15.
Models suggest that residential rain garden adoption more than triples with government rebate incentives21. Surveys suggest that non-senior citizen households with higher incomes, higher levels of environmental concern, and gardening experience are more likely to install rain gardens than other households21. Financial incentives and education also influence the likelihood of adopting green infrastructure22.
On average, residential rain gardens cost $3-4 per square foot and commercial gardens range from $10-40 per square foot; costs vary with plants used and other site specifics. Commercial rain gardens and other bioretention systems can cost less than traditional structural stormwater conveyance systems such as stormwater pipes and retention ponds23, 24.
Impact on Disparities
A few states have regulations that encourage sustainable water management, including techniques such as rain gardens and other bioretention systems; California is one example25. Many states and cities have guidelines encouraging stormwater management best practices that include using low impact development and green infrastructure such as rain gardens, bioswales, permeable pavement, green roofs, and rain barrels. Examples include Connecticut26, Minnesota27, Boston28, Los Angeles29, Muncie, Indiana30, San Diego31, and Washington DC32.
Universities, colleges, and nonprofit organizations provide resources, trainings, information, and tools to municipalities, governments, businesses, and individuals to support their efforts to implement bioretention systems, as in Washington33 and Oklahoma34.
WSU-Rain gardens - Washington State University (WSU), Stewardship Partners. 12,000 Rain gardens in Puget Sound: About rain gardens.
URI-Rain gardens - University of Rhode Island (URI), Rhode Island Department of Environmental Management (DEM). Rhode Island stormwater solutions: Simple steps at home: Rain gardens.
UCONN Ext-Rain gardens - University of Connecticut Cooperative Extension System (UCONN Ext). Water quality and the home landscape: Rain gardens in Connecticut: A design guide for homeowners.
NC State-LID 2009 - North Carolina State University (NC State). Low Impact Development (LID): A Guidebook for North Carolina; 2009.
CDC-Water quality - Centers for Disease Control and Prevention (CDC). Healthy places: Water quality.
US EPA-LID - US Environmental Protection Agency (US EPA). Urban runoff: Low impact development (LID).
LSS-Stormwater - Lake Superior Streams (LSS). Tools for stormwater management.
SEMCOG-LID - Southeast Michigan Council of Governments (SEMCOG). Low impact development (LID).
NC State-Stormwater resources - North Carolina State University (NC State), Stormwater Engineering Group. Stormwater publications and resources.
CA DWR-Water efficient - California Department of Water Resources (CA DWR). Model water efficient landscape ordinance.
WEF-Potts 2015 - Potts A, Marengo B, Wible D. The real cost of green infrastructure. Water Environment Federation (WEF), Stormwater Report. 2015.
* Journal subscription may be required for access.
1 US EPA-Green infrastructure - US Environmental Protection Agency (US EPA). What is green infrastructure?
2 Ahiablame 2012* - Ahiablame LM, Engel BA, Chaubey I. Effectiveness of low impact development practices: Literature review and suggestions for future research. Water, Air, and Soil Pollution. 2012;223:4253-4273.
3 Liu 2014 - Liu J, Sample D, Bell C, Guan Y. Review and research needs of bioretention used for the treatment of urban stormwater. Water. 2014;6:1069-1099.
4 LeFevre 2015* - LeFevre GH, Paus KH, Natarajan P, et al. Review of dissolved pollutants in urban storm water and their removal and fate in bioretention cells. Journal of Environmental Engineering. 2015;141(1).
5 Roy-Poirier 2010* - Roy-Poirier A, Champagne P, Filion Y. Review of bioretention system research and design: Past, present and future. Journal of Environmental Engineering. 2010;136:878-889.
6 Stagge 2006 - Stagge JH, Davis AP. Water quality benefits of grass swales in managing highway runoff. Water Environment Foundation. 2006:5518-5527.
7 Jaber 2015* - Jaber FH. Bioretention and permeable pavement performance in clay soil. In: International Low Impact Development Conference 2015. Reston, VA: American Society of Civil Engineers; 2015:151-160.
8 Carpenter 2016* - Carpenter CMG, Todorov D, Driscoll CT, Montesdeoca M. Water quantity and quality response of a green roof to storm events: Experimental and monitoring observations. Environmental Pollution. 2016;218:664-672.
9 CDC-Water quality - Centers for Disease Control and Prevention (CDC). Healthy places: Water quality.
10 Morsy 2016* - Morsy MM, Goodall JL, Shatnawi FM, Meadows ME. Distributed stormwater controls for flood mitigation within urbanized watersheds: Case study of Rocky Branch Watershed in Columbia, South Carolina. Journal of Hydrologic Engineering. 2016;21(11):5016025.
11 Roy 2014 - Roy AH, Rhea LK, Mayer AL, et al. How much is enough? Minimal responses of water quality and stream biota to partial retrofit stormwater management in a suburban neighborhood. PLOS One. 2014;9(1):e85011.
12 US EPA-LID - US Environmental Protection Agency (US EPA). Urban runoff: Low impact development (LID).
13 Pennino 2016 - Pennino MJ, McDonald RI, Jaffe PR. Watershed-scale impacts of stormwater green infrastructure on hydrology, nutrient fluxes, and combined sewer overflows in the mid-Atlantic region. Science of The Total Environment. 2016;565:1044-1053.
14 Tredway 2016* - Tredway JC, Havlick DG. Assessing the potential of low-impact development techniques on runoff and streamflow in the Templeton Gap watershed, Colorado. The Professional Geographer. December 2016:1-11.
15 Jennings 2016* - Jennings AA. Residential rain garden performance in the climate zones of the contiguous United States. Journal of Environmental Engineering. 2016;142(12):4016066.
16 Dietz 2007* - Dietz ME. Low impact development practices: A review of current research and recommendations for future directions. Water, Air, and Soil Pollution. 2007;186:351-363.
17 Strong 2015* - Strong P, Hudak PF. Nitrogen and phosphorus removal in a rain garden flooded with wastewater and simulated stormwater. Environmental Quality Management. 2015;25(2):63-69.
18 Collins 2010a* - Collins KA, Lawrence TJ, Stander EK, et al. Opportunities and challenges for managing nitrogen in urban stormwater: A review and synthesis. Ecological Engineering. 2010;36(11):1507-1519.
19 Barton 2009 - Barton S. Human benefits of green spaces. University of Delaware Bulletin #137. 2009.
20 UN IL-LHHL - University of Illinois at Urbana-Champaign (UN IL). Landscape and Human Health Laboratory (LHHL).
21 Newburn 2015* - Newburn DA, Alberini A. Household response to environmental incentives for rain garden adoption. Water Resources Research. 2016;52(2):1345-1357.
22 Tayouga 2016 - Tayouga SJ, Gagné SA. The socio-ecological factors that influence the adoption of green infrastructure. Sustainability. 2016;8(12):1277.
23 LIDC-Bioretention costs - Low Impact Development Center (LIDC). Urban design tools: Bioretention costs.
24 Vineyard 2015* - Vineyard D, Ingwersen WW, Hawkins TR, Xue X, Demeke B, Shuster W. Comparing green and grey infrastructure using life cycle cost and environmental impact: A rain garden case study in Cincinnati, OH. Journal of the American Water Resources Association (JAWRA). 2015;51(5):1342-1360.
25 CA SB 7 - California Senate Bill No. 7 (CA SB 7). Part 2.55. Sustainable water use and demand reduction: Chapter 5: Sustainable Water Management. 2009.
26 Fuss & O’Neill 2013 - Fuss & O'Neill. Quinnipac River: Watershed based plan. 2013.
27 MN PCA-Stormwater - Minnesota Pollution Control Agency (MN PCA). Stormwater management: Low impact development and green infrastructure.
28 MAPC-Stormwater - Metropolitan Area Planning Council (MAPC). Stormwater management.
29 LA Stormwater-Rain gardens - City of Los Angeles Stormwater Program. LA’s watershed protection program: Low impact development and rain gardens.
30 MSD-Stormwater management - Muncie Sanitary District (MSD). Stormwater management.
31 San Diego-Water conservation - City of San Diego. Water conservation.
32 DC DDOT-Green infrastructure - Washington DC, District Department of Transportation (DDOT). Green infrastructure.
33 WSC-LID - Washington Stormwater Center (WSC). Low impact development program (LID).
34 OK State-Bioretention - Oklahoma State University (OK State). Bioretention cells and rain gardens.
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