Stormwater woes, and how rain gardens can help

University of Illinois Extension

MACOMB, Ill. — What is a watershed?

No matter where you live, you are in a watershed. All of Illinois, minus that sliver of land bordering Lake Michigan, is in the Mississippi River Watershed. But we can break down this massive watershed into more local streams and rivers.

For instance, I grew up in Adams County in the Mill Creek watershed. But watersheds can go even smaller. Perhaps one of the most local watersheds is the one over your head – the roof, a human-designed watershed. As rain pours across the entire roof, it is sloped to channel that water into a single point of concentration – the downspout. From the peak of a roof to the downspout would be the watershed of your home.

Landcover in Illinois has changed, quite dramatically, over the past centuries. Historically, Central Illinois was a vast, flat prairie, with much of the state being an extensive wetland in the spring and fall. European settlement and the advances in agriculture technology changed all of it. The invention of the moldboard plow by John Deere wiped the prairie clean and replaced it with row crop agriculture. To prevent crops from rotting with the high water table, ag fields had networks of clay (now plastic) piping called field tiles installed to drain the extra water away.

Human development replaced natural spaces with buildings, roads, and parking lots which took a landscape that absorbed water and now sheds it off. Cities and towns sprawled into the countryside, creating more and more impermeable surfaces.

To meet the demand for all this stormwater runoff, engineers developed infrastructure to collect, convey, and discharge water into rivers and streams. This method of stormwater management treated stormwater as a nuisance that must be rid of as soon as possible.

The problem with all these changes to our landscape is it now concentrates water at greater and greater volumes. When comparing streams of pre-development versus post-development, the increase in impermeable surfaces created an increase in flash flooding events. This problem is exacerbated by more intense rain events caused by climate change.

Most infrastructure is not sized appropriately for the volume of water moving through it. Plus, most stormwater infrastructure is beyond its design lifespan, with no money to have it replaced.

A problem this big requires a diverse set of solutions. One such option is to return to the watershed of our roof. Examine how and where the water moves during a rain event. Is there a way this water can be diverted from entering the stormwater system? One method being employed by homeowners across the country is building a rain garden to slow stormwater so it can be absorbed by their soil. Some municipalities are even offering incentives to homeowners to build rain gardens on their property.

When dealing with stormwater runoff, there are a lot of things to consider. Such as how big to make the garden or how deep to dig the rain garden basin. And then what type of plants can go in a rain garden?

You can have answers to all these questions. Illinois Extension will be the host of a rainscaping workshop in Hancock County. During this series of classes, participants can learn landscape design and management practices that reduce runoff. This four-part workshop will take place on September 12, 14,
19, and 21 from 5:30-7:30 p.m. at 130 Young, Nauvoo, in Building A. Not only will you learn about how to design, install and maintain a rain garden, we are going to build a rain garden.

This program is free but registration is required for ordering program materials. Register at or call the Illinois Extension Hancock County office at 217-357-2150.

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