Stormwater as a Resource

Detention basins and native plantings help an Illinois community control flooding, improve water quality and recharge aquifers
Stormwater as a Resource
The Montgomery, Ill., area has integrated natural landscapes to reduce flood loss.

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In July 1996, a millennial storm hit the Village of Montgomery, Ill., unleashing 17 inches of rain in 24 hours — half the area’s average annual rainfall for a year.

The flooded village was devastated, and the experience led local officials to revamp the stormwater management program. The results include higher standards for stormwater detention; the use of native plantings and best management practices; and a new philosophy on valuing stormwater as a community asset.

Montgomery is located 40 miles west of Chicago and has seen more than 300 percent population growth in the last decade, from 5,100 to 18,000. The development boom provided an opportunity for the village to design a progressive stormwater management and biodiversity program that encourages natural landscapes and helps reduce flood losses.

The program has received awards from the Illinois Association for Floodplain and Stormwater Management (IAFSM), the U.S. EPA, regional conservation group Chicago Wilderness and the Chaddick Institute for Metropolitan Development at DePaul University in Chicago.

 

Storm cleanup

After the 1996 storm, the Federal Emergency Management Agency (FEMA) declared Montgomery a disaster area. Although it lies at the bottom of a few watersheds and had some flood-prone areas, the village had never encountered such a catastrophe.

As an immediate solution, officials saw that the best way to prevent flooding problems in flood-plain areas affected by the storm was to remove as many homes as possible. With federal, state and local funding, the village offered to buy out 50 damaged homes at 95 percent of their market value. Thirty homeowners accepted.

The purchased homes were destroyed, and the land was turned into open park space. To address longer-term impacts throughout the community, the village board committed to higher standards of flood control. The board passed regulations to reduce flooding in newly developed areas, which set an example for the entire region.

“Local flooding is a traumatic experience,” says Pete Wallers, village engineer from Engineering Enterprises in Sugar Grove, Ill. “It is heart-wrenching to see the look on someone’s face who just had a home completely flooded. The board wanted to avoid people being in harm’s way in the future.”

Montgomery manages stormwater by collecting it and moving it through detention basin systems, then discharging it back to the local drainage system and ultimately to the Fox River.

 

Guidelines for development

In 2004, to prevent flooding problems in new development areas, officials from Montgomery’s engineering and community development departments contracted Planning Resources, Inc. in Wheaton, Ill., to write Naturalized Stormwater Management Facility Design, Planting and Management Plan Guidelines for developers. Even before the official guidelines had been created, the village started implementing these concepts in 2000.

At the time, there were some county ordinances encouraging best practices for flood control and stormwater management, and Montgomery used them as a stepping-stone to develop the more comprehensive guidelines now in place. Since 2007, the guidelines have been codified into the zoning ordinances for new subdivisions, and they are optional for new nonresidential projects. The guidelines are updated periodically to meet new environmental needs and are posted on the village’s website at www.ci.montgomery.il.us.

An important part of the guidelines specifies the inclusion of detention basins that hold back water and maintain a consistent level of discharge over property so that downstream flows remain consistent. In 1996, the release rate required for detention basins in Kane County (where Montgomery is located) was 0.15 cubic feet per second per acre (ft3/s/acre). That rate was based on the amount of water that runs off undeveloped property.

However, county research studies determined that to prevent flood profiles from increasing from the sheer amount of new development in the county, the recommended release rate should be lowered to 0.10 ft3/s/acre. The change posed a challenge for turfgrass, which was commonly used to line the detention basins.

 

Different vegetation

“A slower release rate meant that after a storm, the detention basins would draw down slower, sometimes exceeding the survivability of conventional turfgrass,” Wallers says. “A traditional option to combat this problem was to construct a ring of rock around the detention basin, but that solution was expensive to install and not very attractive.”

Montgomery officials realized that native wetland and prairie plants on the shoreline and prairie plants along the slopes of the detention basins would help with cost and aesthetics. Planning Resources identified native wetland grasses and flowers such as fox sedge, Torrey’s rush, rice cutgrass, and Common Water Plantain as hardy plants that would stand up to longer submergence. Maintenance costs are minimal because they don’t require frequent mowing.

The basins also become focal points for some neighborhoods. With the development of such natural habitat, Montgomery is seeing a big increase in wildlife, fish, frogs and birds. An additional benefit to the native plantings is improved water quality. The plants have root systems that can go down 20 feet, helping take up stormwater before it discharges to the drainage system.

“The main focus for the native plantings is flood control, but it gets into more water-quality issues,” says Mike Pubentz, public works director. “Wetland and prairie plants clean the water and filter it before it gets into the system.”

 

Valuing stormwater

Recognizing that stormwater isn’t a nuisance to eliminate but a community asset, Montgomery set its guidelines to balance the needs for flood control and water quality. That means addressing release rates, cleaning water before it goes back into streams, and allowing stormwater infiltration to recharge shallow groundwater aquifers.

“We use an integrated management approach to look at the water supply, stormwater and water quality together,” Wallers says. “It’s not enough to just control the rate of runoff from a property. That used to be a good local solution to flooding, but that volume transfers to a problem downstream. We need to address it upstream of the watershed. Also, we don’t want the resource to leave our area without giving some benefit to recharge the aquifers. An integrated management approach treats stormwater as a resource, not a liability.”

As outlined in Montgomery’s guidelines, developers must not only follow construction criteria, but also comply with longer-term performance standards for detention basin drawdown times and establishment of native plants. During the typical three- to five-year establishment period for native plants, the basins undergo semi-annual surveys to evaluate whether they are meeting the criteria for plant coverage, weed levels and plant diversity. Developers are required to monitor and maintain the plants.

Once the plants are deemed established, the village takes over long-term maintenance, using Pizzo & Associates, an ecological restoration company in Leland, Ill. At present, the village maintains 24 basins. This work is funded through a special service area line item levied on property taxes for each resident in an affected subdivision.

Although the cost to develop a basin with naturalized plants is greater than a typical turf basin, the cost to maintain naturalized areas versus turfgrass is lower over time because mowing and weed care are minimal. When weeds are controlled properly early in basin development, the established native plants can out-compete them. The village mows basins once a year to remove old plant material and uses a controlled burn about every two years.

By using native plants instead of turfgrass, village staff estimates annual basin maintenance savings per acre from $500 during years when controlled burns are performed, up to approximately $2,500 in non-burn seasons. These figures are based on comparing one acre of naturalized basin plantings maintenance against an acre of turfgrass that is mowed, aerated, treated for weeds and insects, and repaired as necessary. Annual savings are similar for larger basins but are generally realized earlier in the life of the basin, often as soon as two to three years after development.

 

Wildflower or weed?

When homes in a new subdivision are being built and sold, the native plants are usually still being established, appearing coarse, weedy and unkempt to an untrained eye. This can cause confusion and anger from residents. To gain public acceptance of native plants, Montgomery educates residents about the benefits of the naturalized basins.

“We want the public to take a different look at stormwater management from the traditional hole in the ground with grass around it,” Wallers says. “Some people may never like this type of design. Some people love it and want to do it everywhere. There’s a group in the middle who may not understand it, so we try to educate them and have them see the benefits.”

Montgomery shares information through its website, newsletters and public basin education sessions that target homeowner associations and other local groups.

“We tell people what they can expect to see and how it is beneficial so they have a better understanding of what is outside their back door,” says Michael Brown, senior planner in Montgomery’s Community Development Department.

One sign that public education is working is growing interest in a basin stewardship program in which residents living near the basins can take part in their upkeep. This involves educating volunteers on weed control, plant monitoring and plant identification.

“We have interest from residents who want to get involved and have a personal connection to the basins,” Pubentz says. “It’s a good sign for the program and the future of these types of basins.”

 

More best practices

Looking ahead to future stormwater management challenges, the village expects to use more best management practices that reduce pollutants before they get into the stormwater system, such as permeable pavers, plant-lined bioswales, rain gardens and reduced road salt usage. For now, Montgomery officials are confident they have implemented good policies and ordinances to keep people safe from flooding.

“Our combined commitment to naturalized basins, proper floodplain elevation requirements and proper release rates help us minimize flood damage,” Wallers says. “Over the last decade, we haven’t had any drainage complaints in any of the new development areas. That alone tells us that the system is working pretty well.”



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