The Rain Garden: A  beautiful  contribution to cleaner water

By Steve Hoogenakker, Concierge Landscape and Jenn Morrow.

Many folks are not aware that the rain that runs to our storm sewers does not go to the municipal plant for treatment. It used to, but as growing communities increased pressure on treatment plants, cities nationwide disconnected storm sewers and routed them directly to the nearest lake or stream. In Minnesota, pride in our natural resources is strong, and residents are willing and eager to do their part to protect water quality.

Raingardens are a fabulous way for property developers/managers to protect water quality. It is a garden or landscaped area with a very slight depression (usually 6-8 inches). A raingarden is designed to capture stormwater from rooftops, driveways and even streets, allowing it to soak into the ground along the deep root channels of beautiful plants (some native and some conventional).

Some of the benefits to CICs include an aesthetically appealing landscape feature, increased bird and butterfly activity, and credit for reduction of stormwater -which some cities are beginning to charge fees for! The list of benefits to the environment is long.

The current system of storm sewer pipes contributes largely to flooding and poor water quality in all water bodies. The water runs off so fast, our natural systems cannot absorb it. Prior to urbanization, stormwater soaked into the ground. Some of it made it all the way down to aquifers and some of it flowed slowly and laterally through the ground to lakes and streams. By the time rainwater reached a surface water, it was scrubbed clean by soil and microbes and cooled to the temperature that fish and other aquatic critters enjoy. Gutters and pipes allow over-heated stormwater to flush all the pollutants that collect on impervious surfaces to water bodies that are not able to treat or absorb the impurities nor are they able to accept the sheer volume – leading to serious flooding. Raingardens begin to repair the natural mechanism that slows, cleans and cools stormwater.

What about all the stormwater ponds that CICs have, aren’t those meant to protect water quality? The quick answer is, yes, they were originally intended as an answer to the Clean water Act mandate that stormwater be treated on site in new construction over five acres.  They do keep stormwater and pollutants out of local lakes and streams, unfortunately they merely collect and concentrate those pollutants.  They, just like natural ponds, do not have the capacity to treat stormwater. In addition they often become eyesores. 

To intercept the stormwater that is piped directly into storm ponds (and would not be served by a buffer), raingardens can be installed in the path of down spouts and near the curb with curb cuts.  These curbside raingardens allow water from streets to flow into the garden.  They are designed to over flow back into the street if their capacity is exceeded, not into the lawn. All raingardens are designed to be dry within 24-36 hours after a storm to keep mosquitoes from breeding in them. Mosquito larvae need seven to twelve days of standing, stagnant water to mature. Raingardens actually act as ‘traps’ when mosquitoes lay eggs in them and the water drops since they cannot mature! In contrast, raingardens provide vital habitat for many desirable critters like birds and butterflies.

The city of Burnsville recently studied the effectiveness of raingardens.  They installed 17 residential raingardens to capture street and roof runoff and measured an 82% reduction in runoff in 2004!  They measured a 90% reduction in 2005 and a 93% reduction in 2006- illustrating that as the plants mature (and the root structures create more channels) the infiltration rate increases! The city of Maplewood has actively employed raingardens in city street reconstruction projects for over 10 years! Cities across the country are embracing simple raingardens to address serious stormwater problems including Kansas City, MO (with its 10,000 raingarden program launched in 20060, Portland OR and Chicago IL.  The ‘ground work’ has been laid and practitioners have learned how to make raingardens work and look beautiful!

With both raingardens and shoreline plantings, proper plant selection and installation and maintenance are critical to their success. There is a wide pallet of colors and textures that will tolerate the water fluctuations common to these landscapes. Raingardens can be designed to be virtually indistinguishable from conventional gardens and landscapes while performing an important community service!  Be sure to consult a contractor that is familiar with native plants and shorelines when pursuing projects like these.

Even if raingardens and ponds are not part of your landscape, a native garden can achieve environmental goals and can be incorporated into any plan. A simple butterfly garden can bring bright bold colors and delightful wildlife to an outdoor living space. They require less water and no fertilizers or weekly mowing and in that way, conserve water and other resources as well as protect water quality!

If your CIC is searching for ways to help the environment, they need not look far.  Take a close look at how stormwater is ‘treated’ in your community as ask, ’is there a better way?’.

Jenn Morrow is currently is an Ecologist with Urban Ecosystems, a division of Top Notch Treecare.  Jenn feels that a properly designed and installed raingarden is an inexpensive investment in our future. Jenn can be reached at 763-253-8733, or at Jmorrow@topnotchtree.com

Steve Hoogenakker is landscape consultant/contractor with 20 years experience working with cic properties and can be reached at 763-213-2410 or Steve@Landscape.Pro

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