Rain Gardens

Rain Gardens

Stormwater runoff is excess precipitation that flows into water bodies and local storm sewer systems largely due to the prevalence of hard surfaces, such as impervious concrete. Large quantities of water that would ordinarily be absorbed into the ground in the natural environment instead enter streams and lakes. Stormwater runoff collects pollutants, chemicals and debris as it flows over paved surfaces and into water bodies. It also causes erosion, decreases groundwater recharge and alters aquatic environments.Rain gardens are gardens designed with a depression to capture stormwater runoff and reduce flooding. Generally used in residential landscaping, the rain garden absorbs and stores rainwater temporarily as it flows off building roofs, pavement and other hard surfaces. Most rain gardens are intended to hold water for one to two days.


The Environmental Protection Agency estimates that stormwater runoff is responsible for 70% of all water pollution in lakes, rivers and creeks. Rain gardens mimic natural processes for filtering and storing precipitation, thereby reducing the amount of stormwater runoff in an area. Less stormwater runoff reduces the impact on surrounding water bodies and minimizes erosion while increasing groundwater recharge

Sustainability Principles

Stormwater management, water quality, bioretention, sedimentation, eutrophication, human health, biodiversity, water cycle, forest ecology

Effort Required

The effort required for rain garden installation can very according to the complexity of the design. Generally speaking, most rain garden projects require very little effort, but they may require consultation with horticulturist or plant nursery.


  • Improved water quality in surrounding water bodies. Rain gardens reduce stormwater runoff rates and volumes. Reductions in stormwater lessen the transfer of pollutants and chemicals into nearby water bodies
  • Flood prevention. Rain gardens collect, temporarily store and eventually absorb stormwater runoff, making flood events less likely
  • Groundwater recharge. As water seeps into the soil it is stored underground and available for human use through well construction
  • Aesthetic appeal. Rain gardens can contain a variety of plants, shrubs and grasses, providing greenspace for the local community
  • Less interference with aquatic ecosystems. Stormwater runoff is often warmer than the water in streams, lakes, and rivers. As runoff enters water bodies, the increase in temperature negatively impacts aquatic ecosystems. For example, studies show that temperature changes among sensitive fish species can cause increased feeding, disorientation, increased metabolism, reduced reproduction and possible mortality
  • Wildlife habitat. Vegetated areas such as rain gardens provide a habitat for animals, organisms and insects
  • Minimization of erosion. Stormwater quantity reductions minimize erosion in the nearby area and along the banks of water bodies


If rain gardens are not constructed or maintained properly, pests such as mosquitoes may become a problem. However, rain gardens are not intended to house standing water for more than a couple of days and mosquitoes need at least 5 days for establishment.

Action Agents

Landscape architect, property owner, horticulturist, plant nursery, soil scientist (pedologist)


The main costs associated with rain gardens are plant costs, which depend on the type and number of plants. Other costs include stones, mulch, soil and planting tools. Cost is not high compared to many other landscaping strategies.





Toolkits & Templates

Reports & Guides

Region II

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Region VI

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Region VIII

Region I

Region IX

Region X

100,000 - 750,000

750,000 - 2 million

greater than 2 million



Rain Gardens