Love In the Time of Rain Gardens
Have you ever heard of a rain garden?
The following is an introduction to this widely-used best-management practice.
What is a rain garden?
A rain garden is a depressed area filled with plants designed to collect stormwater flows off impervious surfaces and hold it until the water can be absorbed by the ground. Impervious surfaces might include driveways or parking lots, roofs, and greenspace with soil too compact to allow water to percolate into the soil.
The vegetation selected for rain gardens is recommended to be species native to the region. The native species, already adapted for the local climate, soil and water conditions, are more likely to thrive and grow than non-natives. Drought-resistant native vegetation, called succulents, are commonly used in a rain garden because they do not require any additional water than the stormwater it collects.
Stormwater naturally picks up fertilizers, oils, trash, and other contaminants in its journey across impervious surfaces leading to storm sewer drains. However, rain gardens can serve as barriers preventing the contaminants from flowing directly into storm sewer drains, and our water supply. When diverted to a rain garden, stormwater and its contaminants are instead isolated there and allowed to percolate down through the soil profile while being naturally filtered and cleansed prior to entering the water supply.
How is a rain garden different from a detention pond or a bioswale?
The biggest difference is rain gardens are not primarily designed to manage stormwater. A detention pond is designed to collect and gradually drain stormwater and bio-swales are for clearing silt and debris from stormwater, on its overland journey to a storm drain. Rain gardens, on the other hand, are actually designed to allow rainwater to infiltrate directly back into the soil profile instead of running through a city’s storm sewer system to the river, and ultimately an ocean. The key to remember is that rain gardens remove the storm sewer drain component from the stormwater management process.
What are the benefits of a rain garden?
- They’re attractive! Rain gardens actually have the potential to raise land values or improve the marketability of property. Much like traditional landscaping, a rain garden adds a nice visual aesthetic. But, unlike most traditional landscaping, rain gardens provide an additional tool to manage stormwater and commonly require little to no watering once established.
- Rain gardens help offset the effects of urbanization. Natural drainage patterns have depressions that collect stormwater and perform the exact function of a rain garden, but when land is paved over and built upon, these natural depressions are eliminated, and stormwater flows over the new impervious surfaces at higher than natural velocities.The higher flow velocity can create ruts, outwashes and create erosion which can reduce the amount beneficial organics and topsoil, and increase the amount of contaminants in the water.This will, in turn affect water quality for municipalities.
- Rain gardens are flexible in their size and functionality. They can be large enough to handle an entire big-lot store parking lot or small enough to take the rainwater from your residential home gutters.
What about creating places for mosquitos?
This is a common concern and no one wants to provide additional breeding grounds for a disease-carrying pest, like mosquitos. However, with proper design, the rain water collected doesn’t stay around long enough for mosquito larvae to hatch.
Creating a Rain Garden
For home and small business owners who are willing to get their hands dirty, it is possible to create to your own rain garden with minimal effort and cost. There are plenty of online resources to guide you through the process.
Homes, developments, or businesses that are larger will likely need to contact a local engineering firm to have a rain garden designed to meet their needs. Several items one may want to consider in designing rain gardens include calculating their size, capacity, location, soil conditions as well as suitable plants and compliance with city or regional requirements.
It is not difficult to see how one would benefit from a rain garden; helping to reduce the negative impacts of urbanization, improving water and soil quality, and increasing property values.