In cities on the windswept Kansas prairies, green infrastructure is sprouting up as a way to manage stormwater now and for the future. It blooms as new projects, retrofits, and complementary components of traditional grey infrastructure. In one case, it is the focus of the rebuilding of an entire town.
In Topeka, the Water Pollution Control Division operates two wastewater treatment plants with a combined capacity to treat 28 million gallons of wastewater daily incoming from 840 miles of sewers. The city’s storm sewers system includes 200 miles of storm sewers, 35 miles of channels, and 12 miles of river levees.
One inch of rain over Topeka yields 940 million gallons of stormwater. Adopting a green infrastructure program to help manage that stormwater offers Topeka’s residents more recreational opportunities and improved water quality and also prevents flooding.
“The city has several areas that serve as detention basins for stormwater volume and quantity control measures,” says Sylvia Michaelis, a landscape architect and manager in Topeka’s Public Works Department. “Auburndale Park is a two-acre site owned by the city that functions as a stormwater detention area during times of high water levels in the Kansas River.”
As with other communities that have implemented a broad program of green infrastructure, Topeka’s rationale is that it is cheaper to plan for the city’s stormwater needs before development occurs rather than return after construction to make costly repairs and retrofits. The city manages stormwater in two watershed basins, West Shunga and Wanamaker. Its goal is to detain stormwater on both new development and redevelopment projects.
Michaelis says, “Underground catch basins that collect sediment, debris, and other pollutants, as well as buffer areas alongside nearby streams and grassed detention ponds that hold water and release it at a slower rate, are being installed on a routine basis.”
Called Green Topeka, Topeka’s green infrastructure program is a partnership between state and local governments, nonprofit organizations, Kansas State University, the US Department of Agriculture National Agroforestry Center, and other groups. The program began in November 2000.
Green Topeka’s first project was a pilot project in the Soldier Creek watershed in North Topeka.
Rather than the usual concrete channels and pipes, it used vegetated swales, constructed wetlands, and other green strategies to lessen runoff and improve water quality.
Another project in this watershed involved restoring about 2 miles of the Old Soldier Creek Channel. Invasive Siberian elm trees and other weedy species had taken over, creating an eyesore. The unwanted plants were removed and replaced with native prairie species including little bluestem, sideoats grama, Indian blanket flower, and false sunflower. The result is less maintenance and more infiltration of water.
The Elm Row Demonstration Stream Buffer was created in conjunction with the same project. The Kansas Forest Service supplied enough bareroot seedlings of American plum shrubs and bur oak and red cedar trees to plant four rows approximately 150 feet in length. These trees and shrubs screen views of development across the stream and provide natural filtering for water quality. This project helped Topeka earn the Tree City designation from the National Arbor Day Foundation.
Nearby is the Garfield Park wetland, part of the North Topeka Stormwater Master plan, which was designed to stop flooding in the 2,550-acre North Topeka drainage basin. During heavy rains the old combined sewer system sent overflow to a pump station, where it was pumped over the Kansas River levee and into the river.
Instead of building a new pump station to send only rainwater into the river, the city decided on a green infrastructure solution. Water Pollution Control installed enough grey infrastructure to convey the stormwater separately from the old sewer system into a 3-acre wetland in the Old Soldier Creek Channel. This wetland has various depths so that a variety of native water plants can thrive there. The surrounding area contains short grass prairie, with such native grasses as little bluestem, sideoats grama, and western wheat.
To provide color and food for wildlife, forbs were planted, including purple prairie clover, showy partridge pea, pitcher sage, Indian blanket flower, greyhead prairie coneflower, and plains coreopsis. Educational signs help visitors learn about the importance of wetlands to both wildlife and water quality.
Wetlands and ponds play a multifaceted role, providing not only removal of pollutants from runoff but also wildlife habitats and natural beauty for residents to enjoy. One of the most interesting in Topeka is the Belle Avenue Pond project, began when an existing neighborhood pond broke past two dams in the Shunganunga Creek watershed. The Prairie Trace Homeowners Association asked the city’s help in rebuilding the pond. The Water Control Division agreed to help, and the PTHA agreed that the pond should be enlarged so that it could work effectively in managing stormwater runoff. Surrounding property owners, including Covenant Baptist Church, Southwest YMCA, and French Middle School, were also involved in the project.
Land belonging to the church was used for expansion of the pond. Students from Kansas State University’s College of Architecture drew up several plans for the project, incorporating ideas from neighborhood residents.
Construction on the Belle Avenue Pond began in fall 2004 and was finished in summer 2005. The enhanced pond has a forebay that allows sediment to settle out as runoff flows into the pond. That makes maintenance easier and cheaper.
A wetland shelf extends 30 feet out, providing a shallow area for safety and for water-loving plants to grow. Two fountains add to the beauty and keep the water aerated. Native plants–species of short and tall prairie grass–grow around the pond, treating runoff and stabilizing the steep slopes. They also save the cost of mowing.
Urban Restoration
The existing storm sewer was enlarged, but one traffic lane was converted to bioretention cells with native prairie grasses, trees, and shrubs. A sidewalk with decorative lighting and seating was added so that pedestrians could enjoy the area.
Another urban green infrastructure project is the retrofit of Quinton Heights, an older neighborhood of steep streets and alleys that lacks storm sewers. During heavy storms, the steep grades caused torrents of runoff that flooded streets, buildings, and yards.
The problems were solved by installing two detention areas, two bioretention swales, and some new storm sewers and by reforming some street ditches. Tall grass prairie native plants and water- tolerant grasses grow on the slopes of and within the detention areas and bioretention swales.
Stacy Hutchinson, associate professor of biological and agricultural engineering at Kansas State University, was involved in doing research on the effectiveness of early Green Topeka projects. She recalls efforts “to combine pieces from many different systems into one larger eco-based system.”
Her favorite Green Topeka project is the Quinton Heights system. “It uses the ideas of bioretention, dry detention ponds, and grassed waterways all in one, of course planted with native vegetation in the native soils,” she says.
Gaining Public Acceptance
What has helped to bring about public acceptance? “Surprisingly, one of the most effective tools we have had is our NPDES [National Pollutant Discharge Elimination System] permit,” she says. “By showing this to officials and educating the public on our requirements, they begin to realize this work isn’t some farfetched idea, but actual regulation that we are required to implement.”
Hutchinson agrees with Michaelis, citing “a lack of understanding about the potential for using more eco-based systems that starts with city management and engineering and permeates the rest of the citizenry.”
One reason for this thinking in the heartland of the country, she believes, is that the region does not have “an animal or fish that most people relate to, such as salmon in the Northwest or crab in the Mid-Atlantic. Thus most don’t get the need, but it is getting better as more surrounding areas are starting to use the newer design ideas.”
Green and Grey
To correct the problem, crews recreated the stream’s steep bank and placed coir fiber blocks to reform it. Then they planted native willow and cottonwood seedlings along with other native trees and shrubs to stabilize the bank.
The interceptor project also ruined streamside vegetation along Deer Creek within the Forest Park Retreat Center. The city planted 15 trees and 250 willow and cottonwood stakes along the bank to establish an improved riparian buffer.
Over the years, the city had spent several thousand dollars to clean the sediment out of the box culvert located under SE 29th Street, over a bend in Butcher Creek. To save money and let nature do the work, city crews installed a weir wall to direct low stream flows to the east culvert. During high flows the water goes over the weir wall and into the pond area on the west side of the wall.
The sediment that does accumulate lies in the pond area instead of the culvert. Native switch grass and cord grass were planted to promote more infiltration.
Michaelis attributes the success of Green Topeka to involving the public. “Public buy-in is perhaps our most valuable tool in managing a stormwater program. The city also believes that the public should be given opportunities to play an active role in both the development and implementation of the program.”
Accordingly, in the last few years the city has been evaluating the effectiveness of stormwater projects. “It has also been working on new ordinances that address the community at large and their role in stormwater management,” says Michaelis.
Lake Lenexa
Located near a residential area, the manmade Lake Lenexa covers nearly 35 acres within 240 acres of parkland that includes preserved woods and streams. The dam and spillway facility features three wetlands, trails, docks and a boat ramp, picnic areas, boardwalks, and access to water’s edge for fishing.
A study of the Coon Creek watershed recommended that the lake be created at the bottom of the watershed. Doing that would have removed several hundred acres of bottomland hardwood forest.
“As a part of a larger, more sustainable set of goals, the lake and dam were pulled up in the watershed to an acreage that was predominately rangeland and downsized,” says Patti Banks, RLA, LEED, principal-in-charge of Patti Banks Associates, the firm charged with designing the project. This plan “preserved the old growth hardwood bottomland and made better use of the existing high-quality stream corridor to manage stormwater flows. In addition, it left a recreational amenity for the citizens of Lenexa, all in the Rain to Recreation initiative,” explains Banks.
Walking onto a pedestrian bridge across the dam and spillway affords visitors a dramatic view of the landscape’s cascading pools and a fountain. Each key element features sweeping curved lines, turning what could have been a boring, albeit functional, project into a bold work of art that enhances the surrounding park and natural areas.
The design is the opposite of conventional dam design. The dam arches upstream instead of downstream and the bridge goes down rather than upstream. Such unusual effort required extra attention to principles of physics, hydraulics, and geotechnology to make the dam both a design and an engineering success.
The project’s most challenging aspects, Banks says, were “balancing natural resource preservation while providing recreation and stormwater management for a suburban community, and making sure that while engineering the details we didn’t lose sight of the overall community’s sustainability goals.”
This innovative project demonstrates to residents how stormwater runoff can be managed not only to prevent costly flooding and to bring about improved water quality, but also to protect wildlife habitat and create natural beauty along with recreational opportunities.
The project has received numerous awards and recognitions:
- US Society on Dams (USSD) 2009 Project of the Year Award
- USSD 2008 Award of Excellence in the Constructed Project
- American Concrete Institute Technical Innovation Award for the Lake Lenexa Spillway, 2006
- American Council of Engineering Companies National Engineering Excellence Award, given to Black and Veatch for the design of Lake Lenexa, 2006
- American Builders and Contractors’ Heart of America chapter Excellence in Construction Award, Heavy Site Work/Demolition, given to Mega Industries Corporation for phase 1 of Black Hoof Park, 2006
Another Rain to Recreation project in Lenexa is Mize Lake, which offers residents trails, protected forest, fish and wildlife habitat, and native plants to enjoy. A treatment train filters and infiltrates stormwater runoff from upstream development before it enters the lake.
The 7-acre lake now has three sediment forebays, three wetlands, and two bioretention cells. It is located along Mize Boulevard, a four-lane major arterial street, which serves as the dam for the lake.
The wetlands are in subwatersheds of Cedar Creek. They can hold and treat storm runoff that falls on the entire drainage area directly upstream from the lake. Runoff flows through a pretreatment forebay before entering the wetland. Much of the runoff flows through a winding path of native wetland vegetation until it is discharged into the lake, while some is permanently ponded throughout the wetland. A sediment forebay and wetland are at each channel entering the lake.
The wetlands are immediately downstream and one foot lower than the sediment forebays. The water enters the sediment forebay then spills over a weir into the constructed wetland. Plants filter pollutants and nutrients in the wetland, and then the filtered water is controlled and released slowly through an inline water-level control structure. A stacked stone weir at the downstream end of the wetlands controls flow rate.
Banks says Lenexa’s Rain to Recreation program “set the bar nationally on how cities should combine stormwater management and other public infrastructure like parks and open space preservation.”
The Coon Creek watershed in a riparian/upland area upstream of Lake Lenexa offers fishing and an extensive system of trails for recreation. Visitors can both enjoy the beauty of the Coon Creek Wetlands project and learn about natural stormwater management from its educational signage.
Lenexa stormwater specialist Mandy Stark says “Several places include open green space and wildlife habitat, including bluebird and wood duck nesting boxes. Large flat areas serve as informal play fields in addition to increasing infiltration.”
The Coon Creek Wetlands project covers 3 acres. The three wetland sites, measuring 0.75 acre, 1 acre, and 1.25 acres, follow a sinuous route to slow runoff flow. Stark says the carefully located instream wetlands “include a unique overflow dam design with vegetated riprap. Existing vegetation was preserved where possible, though the wetlands and surrounding areas were also seeded with native plant seed mixes.”
The Coon Creek Wetlands project fits in with Lenexa’s overall systems approach for green infrastructure. Stark explains that the project “was combined with stream restoration projects, open space preservation, prairie restoration, and lake development to create an effective treatment train for stormwater runoff and flood control.”
Building on a Tornado
The average tornado is 150 feet wide. This tornado spanned 1.7 miles, brought winds of 205 miles per hour, and hovered for eight long minutes, essentially destroying the town. Ninety percent of the residential and commercial buildings were demolished, along with trees, vehicles, and infrastructure.
Before the tornado struck, Greensburg (population 1,400) was declining, like many small towns in rural areas. Older farmers were retiring, selling their farms to owners of bigger farms, and most young people left for better jobs elsewhere. The tornado provided the final reason for more residents to move away.
But other Greensburg residents never thought of leaving and soon were talking about not just rebuilding their town, but rebuilding it better and greener, with power from clean energy. Such a major environmental model might attract both corporate and federal dollars and give tourists a reason to visit.
Kansas Governor Kathleen Sebelius told Greensburg’s residents, “We have an opportunity to be the greenest town in rural America.”
Greensburg’s residents knew that it would take years to implement the green plan they had drawn up for their town. Part of that plan involved stormwater management based on the natural flow of runoff there. Greensburg is located near the center of the Rattlesnake Creek watershed. Annual precipitation measures about 22 inches. Runoff comes both from this precipitation and from the watershed south of town. Low-lying areas had ponds after storms.
Greensburg had some disadvantages to effective stormwater management. Its flat topography, inadequate aboveground curb and gutter system, and undersized culverts couldn’t handle runoff from heavy storms.
The new overall stormwater management plan considers Greensburg’s unique topography and the direction of water flow. This natural water treatment train takes in all of Greensburg and is suited to the plants, soils, and climate of the city as well. It’s a truly integrated plan and all future development must follow its guidelines.
Standing water problems have been drastically reduced, and water quality and recharging of local aquifers have been increased greatly. Water flows from the most urban areas that have incorporated green infrastructure to infiltrate (native plants) or capture (cisterns and rain barrels) as much of it as is possible. Rain gardens, bioswales, and other BMPs next intercept the runoff as it moves into residential areas and parks.
Runoff that doesn’t infiltrate or evaporate there next flows through open areas of native prairie grasses whose extensive root systems make them highly efficient at both infiltrating and purifying it. The next phase of the treatment train is wetland systems that allow settling of sediment (decreasing erosion of stream banks) and further purification. Any remaining runoff, now cleansed, flows into local streams or reservoirs.
Choosing the right design for Greensburg’s main thoroughfare–Main Street–and the downtown streets nearby was important for two reasons. The layout of this area had to attract visitors’ attention to green infrastructure. It also had to feel comfortable to the town’s residents and business owners, to enable them to easily interact easily with each other.
Some designs that included a large open green plaza were rejected because, although the open land would have let more stormwater infiltrate, its length and breadth would have made crossing the street less convenient. Even on paper, the two sides of the street seemed more distant from each other, definitely not evoking the interconnectedness of Greensburg’s residents.
The chosen design for the Main Street Streetscape provides an inviting area for people, with trees to cool the area and help absorb stormwater. Native plantings break up the sidewalk areas. The streets themselves are slightly narrower with curb bump-outs of native plants.
The first three blocks of South Main Street were rebuilt with a water catchment system to capture and filter stormwater and store it underground for irrigating the Streetscape plantings. On-street parking was preferred to surface lots, and the number of spaces available is sufficient so that separate lots are not needed.
Green infrastructure installed in Greensburg includes LED for every streetlight in town (more than 300) and a community wind farm that produces enough power to meet all of the city’s current and near-future needs.
Stormwater installations in Greensburg are also impressive. Rain gardens with native plants flourish at many locations, including the public schools, Kiowa County Memorial Hospital, City Hall, and the Sun Chips City Business Incubator. Greensburg Schools also have systems for catching and reusing stormwater. The hospital does, too, along with efficient irrigation and graywater use.
City Hall harvests rainwater to reuse onsite. The Kiowa County Courthouse, one of the greenest historic buildings in the country, includes a water collection system with underground cistern for reuse.
Topeka, Lenexa, and Greensburg are three Kansas cities that clearly demonstrate the benefits–both short term and long term–of not only using green infrastructure to manage stormwater, but also making it the foundation of stormwater management plans for a watershed.
