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Runoff Impacts

Stormwater & Runoff Impacts

Back when our land was covered with forests, prairies, and wetlands, rain water fell and either infiltrated into the ground, evaporated off of plants, or ran off into the nearest stream or river. Now, when it rains, water runs off of our roofs, parking lots, streets, and lawns instead of soaking into the soil the way it did before development. This water, along with everything it picks up along the way, flows into storm drains and ditches that discharge to streams, rivers, and lakes. Salt from roads, bacteria from pet waste, lawn nutrients, spilled gas, oil, and other pollutants are all washed into local waterways.

The EPA has determined that up to 70 percent of the pollution in our surface waters is carried there by storm water runoff. Some studies show that about 50 percent of that pollution comes from individuals and homeowners due to yard care, yard waste, and chemical pollution from household activities. Most modern American cities are built in such a way that when it rains, all of the water is directed into storm sewers via gutters, curbs, and ditches, and then the water flows directly into nearby creeks and streams without being treated or filtered.

In addition to carrying pollution, the stormwater runoff is usually warm, causing a pulse of warmer water to flow down the stream. In a natural system, water enters a stream through a slow and steady release from groundwater. Groundwater has a fairly cool temperature, which allows water to hold more oxygen and keeps stream habitat stable. Many sensitive creatures, such as trout, cannot survive in a stream with fluctuating or warmer temperatures. While groundwater release is slow and fairly steady, storm water runoff occurs all at once. The large volumes of warm water flushing downstream cause erosion and flooding, carry dam-forming debris, and scour the stream bed.

Creating a rain garden or growing native plants along your shoreline is a great way you can make a difference and start correcting these problems.  Click on the two graphics below to view a visual representation of where runoff goes in a typical suburban area versus one utilizing native plantings.

Benefits to Water Quality

Although rain gardens and shoreline plantings may contain a variety of plants, native species are highly recommended.  Native plants, those that are originally from this area, are more beneficial to our environment and are also lower maintenance than species from other parts of the United States or the world.  Certain native plant species are also very efficient at absorbing nutrients, and using them in your landscaping can really optimize the benefits the area provides.  For example, several rush and bulrush species (which look similar to the reeds you might have seen growing in wetlands) perform well in rain gardens and along shorelines and also do a great job of absorbing nitrogen and phosphate, the main nutrients in lawn fertilizers.

Rain gardens reduce the amount of pollution reaching bodies of water by holding storm water and allowing it to infiltrate into the ground or be absorbed by plants rather than run off.  Native species are especially well suited for this purpose – their deep roots create root channels through which water can infiltrate.  Additionally, natives that are adapted to growing along shorelines are thirsty and take up water at a rapid pace.  Native shoreline plantings slow down storm water runoff, absorbing it and allowing it to infiltrate into the ground or be taken up by plants rather than fill up retention ponds, streams, and reservoirs.  This is extremely important as more and more areas are developed.  We are losing natural areas that used to provide flood control and need these native shoreline plantings begin to remedy those effects.

Native Plantings and Wildlife

Native plantings like rain gardens and shoreline plantings can also provide unique habitat for native wildlife.  The caterpillars of butterflies and moths rely on native plants like milkweed for their diet, adult butterflies feed on nectar from colorful blooms, and songbirds enjoy the seeds provided by native flowers and grasses.  Natural shorelines can also benefit fish, frogs, and ducks, all species we like to watch and enjoy.

Canada Geese are becoming a serious problem in our urban areas.  They can be very aggressive, especially when they have a nest nearby.  Additionally, their droppings contribute nutrients and bacteria like E. coli to the water.  Canada Geese tend to avoid native plantings – they are afraid of the taller vegetation because predators could be hiding there.  If geese are a problem in your yard or neighborhood, landscaping with native plants could help; some neighborhoods have completely eliminated their goose populations by surrounding their ponds with native plantings.


Do your actions matter?

Of course they do!  Here's how.

    How do rain gardens work?

    See this helpful visual explanation of how rain gardens function.

      Ready to install your own rain garden?

      To build your own rain garden, just follow these simple steps!

        Want to limit impacts on your shoreline?

        If you live along a shoreline, chances are it can be enhanced. Find out how to improve your shoreline and do shoreline plantings.   

          How does nutrient runoff affect you?

          To find out, watch The Choice is Yours: Clean or Green Water.