Rain Gardens
Green Infrastucture
What is a rain garden? A rain garden - a kind of Green Infrastructure - is an engineered sloped area in the landscape that collects rainwater from a roof, driveway or street. Rain gardens remove pollutants, slow down stormwater runoff, and allows rainwater to soak into the ground.
Students just like you are studying (Green Infrastructure) rain garden soils.
-MU engineering students building rain garden tanks to study water filtration into soil and pollutant reduction.-
-Engineering students adding different sizes and types of gravel to study pollutant removal and water flow rates.-
Students just like you are studying rain garden soils and their effectiveness in removing pollutants from stormwater runoff (People Pollution).
To understand the importance of rain gardens, you must first understand how the urban environment impacts the natural water cycle. In nature, rain falls directly onto vegetation and is evenly distributed over the land's surface soaking into the soil, held up in the tree canopy, drank by the plants, and feeds the local waterways.
Rain is essential to our environment. However, when we do not work with nature, in cities, at our homes, and on farms, it causes problems with the rainwater runoff. These problems are caused how fast the water rushes off hard surfaces and by the water picking up pollution.
As the water moves across surfaces such as streets, parking lots, and roofs, it picks up all sorts of pollutants. These pollutants can kill water life and interfere with the delicate balance of the aquatic ecosystem. Scientists estimate that 70% of the pollution in streams, rivers, and lakes is from stormwater runoff. From nutrients like nitrogen and phosphorous that fuel algal blooms. To pesticides, herbicides, oil, grease, heavy metals, harmful bacteria, and trash.
-Students add native plants to study their effect on pollutant removal, soil types & filtration rates in the rain garden tank study.-
-Engineering students fill rain garden tanks with different soil mixes.-
-MU students used a mix of different soil types to see what best-removes pollutants from stormwater runoff.-
-MU engineering students run-time tests for soil drainage filtration (water) rates.-
Why protecting our local waters is important.
Imagine the day after a big storm, walking home from school or running around the playground, and avoiding – or jumping through- all the puddles leftover from yesterday. When rain falls on hard surfaces and not plants, the water forms puddles and cannot be soaked into the ground and up by the plants.
The storm drain system is responsible for carrying all stormwater (rain) from your watershed to local streams. The storm drain system is not connected to the wastewater system, which drains water from the plumbing of your home, school, and friends' house. Storm drains do not send water to a treatment facility where it is cleaned. That means the rainwater and everything it touches – from dirt, motor oil, trash, and pet waste – flows straight into creeks, streams, and local waterways.
- Stormwater runoff, it picks up pollutants from the ground and carries them into the nearest storm drain or drainage ditch alongside the street or parking lot. -
This rainwater, or polluted runoff (people pollution), comes from things we do every day. Anything you dump or drop on the ground adds to polluted runoff. The most common pollutants result from littering. Trash like fast-food wrappers, plastic water bottles, soda cans, plastic cups, foam cups, and even pet waste can end up polluting our local waterways.
-Ditches and storm drains do not connect to a treatment system, so everything that flows down the drain goes directly to the nearest local water body. -
-The most common litter in U.S. streams is household trash, including plastic cups, plastic bags and wrapping materials, fast-food wrappers, plastic bottles, and other plastic containers.-
Toxic chemicals can enter the mix from leaky cars (motor oil and antifreeze) and water running off lawns can carry pesticides and fertilizers. Even the family dog can add to water pollution if you don’t properly dispose of pet waste! Please pick up after your pet!
-Here's what happens to the pollutants swept up in stormwater runoff. The water that gushes off our roofs, driveways, streets, and landscaped yards is to blame for the bulk of the pollution that dirties our local waterbodies. By tonnage, the most significant stormwater pollutants are dirt, oil and grease, nitrogen-containing compounds and phosphorus.-
One way the City of Columbia and Boone County is helping deal with that extra stormwater and the pollutants it carries is by studying how we use what is called “green infrastructure.” Green infrastructure mimics the way grassy fields, forests, and other natural areas absorb and filter water. By researching how green infrastructure works and the best ways to use it, city and county researchers are helping Columbia and Boone County communities reduce or prevent contaminated stormwater from polluting our local waterways.
For example, we are studying how rain gardens — a kind of green infrastructure — planted at the edges of parking lots, driveways, or sidewalks can help. Rain gardens capture runoff and allow it to seep slowly into the ground. Instead of dirty runoff reaching the storm drain, you get flowers!
"The Bonne Femme Watershed Project hosted planting days to help bring our Bioretention basins to life. Water leaving these basins flows into the Gans Creek, which is part of the Greater Bonne Femme Watershed. This Watershed holds a variety of unique natural resources that support farming, wildlife, and residential areas. These native plants will help improve our waterways by slowing down and cleaning stormwater runoff."
Green Infrastructure in Boone County, MO
Volunteers planted over 2,500 plants at the Meyer Industrial Drive Bioretention basins over four days.
The basins are a demonstration project for the Greater Bonne Femme Watershed Project and are open for the public to visit.
These deep-rooted plants and amended soils act as a living filter by allowing water to soak in and remove pollutants, including oil, gas, road salt, trash, and other contaminants, from stormwater runoff, leaving Meyer Industrial Dr.
Clean water leaves the basins before entering Gans Creek, keeping the stream healthy and safe. At the same time, these basins provide a beautiful wildlife habitat for butterflies and bees to thrive.
Rain gardens, wetlands, stream buffers, and ponds are some examples of other water quality features that can be used for treating and reducing stormwater runoff.
What are rain gardens?
-Why the soil matters. Rain gardens function by allowing water to slowly infiltrate the soil instead of running off into city storm drains or contributing to flooding on a property. They act like shallow, permeable containers that drain water through their flat bottom and back into the soil. -
Rain gardens are designed to mimic the layered conditions of a forest floor, which naturally filters pollutants from water. The rain garden consists of a vegetated or stone ponding area, a mulch layer, a planting soil layer, a sand bed, and a gravel base.
Why the soil matters. Rain gardens function by allowing water to slowly infiltrate the soil instead of running off into city storm drains or contributing to flooding on a property. They act like shallow, permeable containers that drain water through their flat bottom and back into the soil. The soil, therefore, is the true foundation of how the rain garden functions.
The soil has to be graded, or shaped, so it can act like a container, and the soil has to have the right composition for the water to slowly infiltrate it. Once the soil foundation is set, plants will help maintain the soil function over time.
Building a rain garden is a fun way to help keep your waterways healthy and learn about the water cycle!
Rain gardens are part of the water cycle.
-When planted with native grasses and flowering perennials, rain gardens can be cost-effective, low maintenance and a beautiful way to reduce and filter runoff from your property.-
When planted with native grasses and flowering perennials, rain gardens can be cost-effective, low maintenance and a beautiful way to reduce and filter runoff from your property.
Rain garden soils act like sponges that soak up water while also letting the water pass through to the native soil layers below the rain garden. In order to do this, they need to have a mixture of high organic content and sand to improve the coarseness and texture of the soil. For rain gardens, the ideal soil mix is 35 to 40 percent compost and 60 to 65 percent coarse sand. Once you have created the proper mix of soil for the rain garden, it is not necessary to continuously add these amendments.
Rain gardens slowly drain rainwater and should not hold water for more than 48 hours. Therefore, it’s critical that the soil mix in the rain garden allows for adequate infiltration. If your existing soil did not perform well in your infiltration rate test, here are two approaches to creating the correct soil mix.
Rain gardens remove (People) pollution.
-One of the most prevalent categories of runoff pollution is oil and grease from leaking cars and spills at gas pumps, vehicle exhaust, and burning wood and fossil fuels.-
One of the most prevalent categories of runoff pollution is oil and grease from leaking cars and spills at gas pumps, vehicle exhaust, and burning wood and fossil fuels. The contaminants include petroleum hydrocarbons, and a category of environmentally hazardous chemicals called polycyclic aromatic hydrocarbons, or PAHs.
The scientists found that rain gardens do a great job catching metal pollutants and oil and grease — in some cases trapping more than 90 percent of the pollutants — keeping them out of streams and lakes where they harm wildlife and contaminate water for swimming, fishing, and other human uses. Rain gardens, often called bioretention systems, swales, or bioswales in the scientific literature, have a mixed record in terms of capturing bacteria based on tests done in the field.
Once the pollutants are trapped in the rain garden soil, what happens to them next?
The soil in rain gardens is safe for kids and pets. That said, people are advised to wash their hands after working or playing in any soil, which can contain naturally occurring metals, fecal waste from the neighbor’s dog, or any number of compounds one wouldn’t want to ingest. And remember that while rain gardens are attractive landscape features, the plants and soil are also doing an important job, so they need to be treated with some care.
-The scientists found that the rain gardens do a great job catching metal pollutants and oil and grease — in some cases trapping more than 90 percent of the pollutants — keeping them out of streams and lakes where they harm wildlife and contaminate water for swimming, fishing, and other human uses.-
Adsorption. Certain dissolved pollutants stick to particles floating in the stormwater or settled into the soil.
Absorption. Stormwater and pollutants soak deeper into the soil. Pollutants may accumulate in the soil, percolate through it with the water, or dissipate through microbial action, adsorption, or volatilization.
Microbial action. Bacteria and other microorganisms break down pollutants in the water or soil, often into forms that are less environmentally harmful.
Plant resistance and uptake. Decaying plant material increases adsorption and provides a good habitat for microbes that gobble pollution. Plants may also suck up pollutants from the soil through their roots, though not in large amounts.
Volatilization. Pollutants, particularly some of those associated with petroleum or oil and grease, evaporate.
Sedimentation. In the case of standing water, heavier particles settle into the soil below.
