Rain gardens & other bioretention systems

There is strong evidence that rain gardens and other bioretention systems reduce stormwater run-off and pollutant concentrations, especially total suspended solids and heavy metals, and reduce soil erosion (Sharma 2021, Wadzuk 2021, Gilbreath 2019, Guo 2019, Wang 2019, Ahiablame 2012, Liu 2014, LeFevre 2015). Rain gardens can effectively treat stormwater run-off over the long-term (Johnson 2019). Rain gardens and other bioretention systems are also a suggested strategy to protect communities from flooding, improve water quality, recharge groundwater, and preserve habitat, property, and other infrastructure (CDC-Water quality, US EPA-Green infrastructure, Sharma 2021, Liu 2014, Morsy 2016).

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 effectiveness (Roy 2014, US EPA-LID, Pennino 2016, Tredway 2016, Kim 2018). A San Francisco-based study shows bioretention systems along urban transit corridors can reduce pollutant loads to nearby water bodies and help meet area water quality goals (Gilbreath 2019). Bioretention systems are generally more effective with lighter, steady rainfall rather than extreme storms (Qin 2020, Jennings 2016). Rain gardens in urban park spaces can also reduce stormwater run-off (Feldman 2019). However, individual rain gardens have limited capacity to reduce urban flooding (Qin 2020).

Proper design, implementation, and maintenance of rain gardens maximizes benefits and preserves long-term effectiveness (Sharma 2021, Ahiablame 2012). In some cases, rain garden effectiveness at capturing nitrogen (N) and phosphorus (P) even improves over time (Johnson 2019). Studies show that soils of all types remove N and P from run-off and can retain various levels of N and P, although generally rain gardens retain P more effectively than N (Wadzuk 2021). The amount of soil nutrients captured by rain gardens varies over time, with the intensity and duration of rain events (Guo 2019), and depending on the bioretention system’s design (LeFevre 2015, Dietz 2007, Roy-Poirier 2010, Strong 2015). Nitrogen retention after capture is especially difficult, since N is highly soluble; however, optimizing rain garden design can prevent N leaching (Osman 2019).

Properly sized and graded water basins can increase residential rain garden water storage capacity, pollutant removal, and erosion control. Deeper rain gardens can also improve effectiveness and capture more run-off; however, deeper rain gardens require more time and labor, more soil disposal, and knowledge of how to avoid safety issues when implemented near buried utilities on private property. Studies suggest most native soil types, except for clay soils, can be used in rain gardens to capture rainwater, with some variation in volume reduction (DelVecchio 2020). Plants used in bioretention systems increase soil permeability, water conductivity, and N removal (Dagenais 2018). Some studies show using multiple plant species can improve biodiversity, ecosystem resilience, and rain garden functionality, including phosphorus uptake and capture and increased flooding tolerance (Morash 2019). Available evidence has not yet determined if using native plants in rain gardens is more effective than using exotic species; however, native plants may be more resilient and enhance local biodiversity (Dagenais 2018). In Illinois, rain gardens with native prairie grasses, sedges, and other plantings are associated with improved habitat and a noticeable increase in birds, bees, and butterflies (Kim 2018).

Rain gardens and other bioretention areas increase attractive green spaces, which may improve neighborhood aesthetics and enhance wildlife habitats (Kim 2018, Liu 2014). These additional green spaces may also improve mental and physical health for residents, reduce heat island effects, improve sense of community, and reduce crime (Barton 2009, UN IL-LHHL). Available evidence shows rain gardens do not serve as mosquito breeding grounds (Jennings 2016).

Experts suggest bioretention systems can be designed to maximize their potential for carbon sequestration in the soil (Kavehei 2019). However, the effectiveness of bioretention as a means to mitigate climate change may be limited, since biological processes in the soil also produce greenhouse gases, which can include nitrous oxide, methane, and carbon dioxide, in amounts that vary depending on water saturation over time (Kavehei 2021) and soil temperature (Shrestha 2018). In general, bioretention systems appear to sequester more carbon and nitrogen than the soil releases as greenhouse gases (Shrestha 2018).  

Models suggest that residential rain garden adoption more than triples with government rebate incentives (Newburn 2015). Surveys suggest that non-senior citizen households with higher incomes, higher levels of environmental concern, and more gardening experience are more likely to install rain gardens than other households (Newburn 2015). Financial incentives and education also influence the likelihood of adopting green infrastructure (Tayouga 2016).

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 ponds (LIDC-Bioretention costs, Vineyard 2015). A benefit-cost analysis for Grand Rapids, Michigan suggests many green infrastructure projects are cost-effective, and identifies rain gardens as a low cost and attractive option, especially for small sites such as homes or street corners (Nordman 2018).

A few states have regulations that encourage sustainable water management, including techniques such as rain gardens and other bioretention systems; California is one example (CA-SB 7). 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 Connecticut (Fuss & O'Neill 2013), Minnesota (MN PCA-Stormwater), Boston (MAPC-Sustainable water), Los Angeles (LASAN-Green infrastructure), Muncie, Indiana (MSD-Stormwater management), New York City (NYC-Green infrastructure), San Diego (San Diego-Water conservation), and Washington, D.C. (DC DDOT-Green infrastructure). The U.S. Environmental Protection Agency’s Soak Up the Rain initiative also has many examples of rain gardens, bioretention systems, and other green infrastructure projects in residential developments, elementary schools, college campuses, commercial buildings, federal facilities, and along city streets throughout New England (US EPA-Soak up the rain examples).

Universities, colleges, and nonprofit organizations provide resources, trainings, information, and tools to support efforts by local governments, businesses, community organizations, and individuals to implement bioretention systems, as in Washington (WSC-LID) and Oklahoma (OK State-Bioretention).

CA DWR-Water efficient - California Department of Water Resources (CA DWR). Model water efficient landscape ordinance.

CDC-Water quality - Centers for Disease Control and Prevention (CDC). Web Archive: Healthy places: Water quality.

LSS-Stormwater - Lake Superior Streams (LSS). Tools for stormwater management.

McFarland 2019 - McFarland AR, Larsen L, Yeshitela K, Engida AN, Love NG. Guide for using green infrastructure in urban environments for stormwater management. Environmental Science: Water Research and Technology. 2019;5:643-659.

NCSU-Stormwater resources - North Carolina State University (NCSU), Stormwater Engineering Group. NCSU Stormwater publications and resources.

RI DEM-Rain gardens - Rhode Island Department of Environmental Management (RI DEM). Rain gardens.

SEMCOG-LID 2008 - Southeast Michigan Council of Governments (SEMCOG). Low impact development (LID) manual for Michigan: A design guide for implementers and reviewers. 2008.

UCONN Ext-Rain gardens - University of Connecticut Cooperative Extension System (UCONN Ext). Rain gardens: A design guide for Connecticut & New England homeowners.

US EPA-LID - U.S. Environmental Protection Agency (U.S. EPA). Urban runoff: Low impact development (LID).

US EPA-Soak up the rain - U.S. Environmental Protection Agency (U.S. EPA). Soak Up the Rain: Municipal and community resources and resources for residents.

WEF-Potts 2015 - Potts A, Marengo B, Wible D. The real cost of green infrastructure. Water Environment Federation (WEF), Stormwater Report. 2015.

WMEAC-Calculator - West Michigan Environmental Action Council (WMEAC). Rainwater rewards: Green infrastructure benefits calculator.

WSU-Rain gardens - Washington State University (WSU), Stewardship Partners. 12,000 Rain gardens in Puget Sound: About rain gardens.

* Journal subscription may be required for access.

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.

Atchison 2006 - Atchison D, Potter K, Severson L. Design guidelines for stormwater bioretention facilities. University of Wisconsin Civil & Environmental Engineering; 2006.

Barton 2009 - Barton S. Human benefits of green spaces. University of Delaware Bulletin #137. 2009.

CA-SB 7 - California Legislative Information. Senate Bill (SB) 7. Part 2.55. Sustainable water use and demand reduction: Chapter 5: Sustainable Water Management. 2009.

CDC-Water quality - Centers for Disease Control and Prevention (CDC). Web Archive: Healthy places: Water quality.

Dagenais 2018* - Dagenais D, Brisson J, Fletcher TD. The role of plants in bioretention systems; does the science underpin current guidance? Ecological Engineering. 2018;120:532-545.

DC DDOT-Green infrastructure - Washington, D.C., District Department of Transportation (DDOT). Green infrastructure.

DelVecchio 2020* - DelVecchio T, Welker A, Wadzuk BM. Exploration of volume reduction via infiltration and evapotranspiration for different soil types in rain garden lysimeters. Journal of Sustainable Water in the Built Environment. 2020;6(1).

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.

Feldman 2019* - Feldman A, Foti R, Montalto F. Green infrastructure implementation in urban parks for stormwater management. Journal of Sustainable Water in the Built Environment. 2019;5(3).

Fuss & O'Neill 2013 - Fuss & O'Neill. Quinnipac River: Watershed based plan. 2013.

Gilbreath 2019* - Gilbreath A, McKee L, Shimabuku I, et al. Multiyear water quality performance and mass accumulation of PCBs, mercury, methylmercury, copper, and microplastics in a bioretention rain garden. Journal of Sustainable Water in the Built Environment. 2019;5(4).

Guo 2019* - Guo C, Li J, Li H, Li Y. Influences of stormwater concentration infiltration on soil nitrogen, phosphorus, TOC and their relations with enzyme activity in rain garden. Chemosphere. 2019;233:207-215.

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.

Johnson 2019 - Johnson JP, Hunt WF. A retrospective comparison of water quality treatment in a bioretention cell 16 years following initial analysis. Sustainability. 2019;11(7).

Kavehei 2019* - Kavehei E, Jenkins GA, Lemckert C, Adame MF. Carbon stocks and sequestration of stormwater bioretention/biofiltration basins. Ecological Engineering. 2019;138:227-236.

Kavehei 2021* - Kavehei E, Iram N, Rezaei Rashti M, et al. Greenhouse gas emissions from stormwater bioretention basins. Ecological Engineering. 2021;159.

Kim 2018* - Kim J. Exploring green infrastructure benefits at house and neighborhood scale: Case study of Illinois, USA. Landscape and Ecological Engineering. 2018;14:165-174.

La Crosse-Stormwater - La Crosse, Wisconsin. Stormwater utility: Stormwater credits & forms.

LASAN-Green infrastructure - City of Los Angeles, LA Sanitation & Environment (LASAN). Watershed protection program: Low impact development, green infrastructure, and more.

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).

LIDC-Bioretention costs - Low Impact Development Center (LIDC). Urban design tools: Bioretention costs.

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.

MAPC-Sustainable water - Metropolitan Area Planning Council (MAPC). Environment: Sustainable water management.

MN PCA-Stormwater - Minnesota Pollution Control Agency (MN PCA). Stormwater management: Low impact development and green infrastructure.

Morash 2019 - Morash J, Wright A, LeBleu C, et al. Increasing sustainability of residential areas using rain gardens to improve pollutant capture, biodiversity and ecosystem resilience. Sustainability. 2019;11.

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.

MSD-Stormwater management - Muncie Sanitary District (MSD). Stormwater management.

Newburn 2015* - Newburn DA, Alberini A. Household response to environmental incentives for rain garden adoption. Water Resources Research. 2016;52(2):1345-1357.

Nordman 2018* - Nordman EE, Isely E, Isely P, Denning R. Benefit-cost analysis of stormwater green infrastructure practices for Grand Rapids, Michigan, USA. Journal of Cleaner Production. 2018;200:501-510.

NYC-Green infrastructure - New York City (NYC) Environmental Protection. Green infrastructure.

OK State-Bioretention - Oklahoma State University (OK State). Bioretention cells and rain gardens.

Osman 2019 - Osman M, Yusof KW, Takaijudin H, et al. A review of nitrogen removal for urban stormwater runoff in bioretention system. Sustainability. 2019;11.

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.

Qin 2020 - Qin Y. Urban flooding mitigation techniques: A systematic review and future studies. Water. 2020;12.

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.

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.

San Diego-Water conservation - City of San Diego. Water conservation.

Sharma 2021* - Sharma R, Malaviya P. Management of stormwater pollution using green infrastructure: The role of rain gardens. WIREs Water. 2021;8.

Shrestha 2018 - Shrestha P, Hurley SE, Adair EC. Soil media CO2 and N2O fluxes dynamics from sand-based roadside bioretention systems. Water. 2018;10(185).

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.

Tayouga 2016 - Tayouga SJ, Gagné SA. The socio-ecological factors that influence the adoption of green infrastructure. Sustainability. 2016;8(12):1277.

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.

UN IL-LHHL - University of Illinois at Urbana-Champaign (UN IL). Landscape and Human Health Laboratory (LHHL).

US EPA-Green infrastructure - U.S. Environmental Protection Agency (U.S. EPA). What is green infrastructure?

US EPA-LID - U.S. Environmental Protection Agency (U.S. EPA). Urban runoff: Low impact development (LID).

US EPA-Soak up the rain examples - U.S. Environmental Protection Agency (U.S. EPA). See who’s soaking up the rain: Connecticut, Massachusetts, New Hampshire, Rhode Island, Vermont, and Beyond New England.

UW Ext-Rain gardens - University of Wisconsin Cooperative Extension (UW Ext). Southeast Wisconsin rain garden resources.

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.

Wadzuk 2021* - Wadzuk B, DelVecchio T, Sample-Lord K, Ahmed M, Welker A. Nutrient removal in rain garden lysimeters with different soil types. Journal of Sustainable Water in the Built Environment. 2021;7(1).

Wang 2019* - Wang R, Zhang X, Li MH. Predicting bioretention pollutant removal efficiency with design features: A data-driven approach. Journal of Environmental Management. 2019;242:403-414.

WSC-LID - Washington Stormwater Center (WSC). Low impact development program (LID).