The Benefits of Rain Gardens

By Gabriel Halm

Rain Garden in Parking Lot. Source: BrianAsh

Rain or Stormwater gardens are specifically designed gardens that help collect and filter rainwater run-off naturally in urban areas with highly impervious surfaces. The gardens primary purpose is to help reduce pollution by filtering out and storing or breaking down chemicals and other pollutants that collect on these impervious surfaces such as parking lots, roads, or rooftops. In addition to their primary purpose, these rain gardens have countless other benefits. One notable positive side-effect is the increased capacity for water absorption and retention. This benefit is essential in helping reduce soil erosion in local habitats and to prevent flooding of urban areas. With climate-change increasing the strength of storms and the amount of rainfall per storm, raingardens can act as a first line of defense in reducing the damages caused by these downpours. A second benefit is the increased biodiversity it can bring back to an urban landscape. The collected water and flowering plants can act as an oasis for pollinators and other wildlife in an urban desert.

Rain gardens have been gaining popularity in several countries such as the U.S., UK, and Australia at the private household level. These little gardens have been a way to have a well-designed landscape in your garden while still being environmental conscious since in most cases there is a focus on using plants native to the region. This development of rain gardens in private households has been further promoted by local governments giving financial incentives such as rebates or tax deductions to homes that have built a rain garden in their yard.

A place where Sustainable Design Alliance believes we can magnify the benefits of rain gardens is in the business and government sectors. With regular construction and remodel of buildings and maintenance on roads and landscape in a city, there are opportunities abound to reap the benefits of these gardens on a larger scale. When a new building is being designed, if there is a plan to include a small greenspace or a parking lot on the building site, a rain garden can be a perfect addition. Alongside the additional greenspace benefit the garden provides, it can also potentially reduce some maintenance costs in the long run for the building site. Since the garden will collect and hold rainwater, it will prevent standing water in unwanted locations, on cement or walkways, that will be damaged by continual standing water exposure. By design, most rain gardens are made to handle being inundated with water as well as having dry periods. This allows the building to use less water in dry months to keep its greenspace maintained. In the government domain, rain gardens can also help dramatically with reducing costs of the city. Swales for example, the strip of greenspace next to roads, is a perfect location to add a rain garden. A primary benefit is the filtering of harmful pollutants into major bodies of water around the city and a decreased burden on the sewer system. When a storm hits, instead of all the water inundating the sewers and city water facilities all at once, the converted swales would be able to reduce the amount of water entering the system. This removes strain on the sewer system and helps reduce maintenance costs and potential overflow pollution.

A perfect swale to add a rain garden. Source: NRCS

Rain gardens can be an easy natural way to solve existing problems that we have in our urban environments. While there can be an upfront cost, their natural tendency to low maintenance and the cost savings they can help with elsewhere in the system can make up for the initial cost quickly. Additionally, it is an attractive method to demonstrate that you as a city, business, or household are wanting to make an environmental difference. To help all that are interested in learning more about rain gardens we have added links to resources from around the globe.

Rain Garden at State University of New York. Source: David A. Sonnenfeld. Creative Commons License

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