Who’ll Stop the Rain?
Bigger storms and wider development are pushing a surge of stormwater into places like UW - Madison's Arboretum. CALS scientists say it will take a community effort to stem the tide.
ON A HILLTOP ON MADISON’S FAR west side, David Liebl stands at the edge of a sea of sparkling new Toyotas. A salesman approaches, but Liebl’s not shopping for cars. A UW-Extension educator and stormwater specialist, he’s more interested in the lot itself, particularly an unpaved corner at the low end of the property. Lined with stones and an assortment of plants, this corner is sculpted into a shallow depression—a high-tech rain garden designed to divert water and the crud it’s carrying from a nearby city storm drain.
“They need to get in here and clean this out,” Liebl says, noting the thick layer of sand, leaves and trash that have collected in the basin. But he’s not complaining too much. Every bit of material that makes its way into the drain becomes his problem. And Liebl has plenty of problems already.
Two and a half miles downhill from the Toyota dealership lies the UW-Madison Arboretum, a 1,200-acre enclave known worldwide for its collection of restored ecological communities. Bordering the shore of Lake Wingra, the arboretum sits at one of the lowest points in Madison, making it the final destination for much of the rain that falls on the city. Decades of rapid development on Madison’s fringes have only worsened the problem. As more fields and woodlands are paved over to create roads, driveways and parking lots, the water arrives at the arboretum faster, dirtier and in greater volume. In one year, 115 million gallons of stormwater pass through an outlet at the western edge of Lake Wingra, reaching speeds of up to 2,244 gallons per second. The torrent has already blown out a pond built to contain it and carved a deep trench leading to the lake. The water brings with it layers of nutrient-rich sediment, which have created a delta that is filling in parts of the lake and are causing algal blooms.
“It’s the same all over the arboretum. We have ponds full of sediment and ponds that are too small to carry these heavy flows,” says Liebl, who chairs the facility’s stormwater committee. The arboretum is already building a larger pond near the west end of Lake Wingra to contain the flow, part of a multimillion dollar effort to deal with stormwater issues. But Liebl says new ponds aren’t the long-term answer.
“The arboretum can’t keep giving up the natural areas it is trying to preserve,” he says. “We need to treat that water and infiltrate that water somewhere closer to where it falls out of the sky and hits the ground.”
BAD THINGS HAPPEN WHEN water travels. Most obvious are floods. When something prevents stormwater from soaking into the ground—say, a roof or a couple acres of asphalt—water follows the path of least resistance until it finds a place to settle. Maybe it’s a lake or a stream, but maybe—in cases where there’s too much water or too little penetrable ground to deal with it—it’s a low-lying field or neighborhood.
But flooding is only part of the problem. Running water erodes the soil and picks up all kinds of nasty contaminants, including hydrocarbons from roads and metals such as zinc from galvanized roofing. Just as importantly, water that doesn’t infiltrate the soil doesn’t recharge groundwater, which contributes to the depletion of aquifers.
In 2002, these concerns led the Wisconsin Department of Natural Resources to issue new rules on stormwater management. Now communities and real-estate developers must have plans to infiltrate significant amounts of the rainfall they receive and reduce contamination in whatever does run off. For new housing developments, for instance, the DNR requires infiltration to be 90 percent of pre-development levels.
But the composition of a typical urban neighborhood makes reaching those goals challenging. Asphalt and rooftops are designed to repel water, and they do their job well. According to one estimate, 16 times more water runs off of a one-acre parking lot than a one-acre meadow. Considering that in an average medium-density residential development 20 to 50 percent of the landscape can be paved or shingled, this puts a lot of water on the loose.
And then there is the weather. Many climatologists are predicting that Wisconsin will experience more frequent violent storms as a result of global climate change. One such system, which hammered southern Wisconsin in June 2008, caused the most expensive weather-related disaster in Wisconsin history, flooding more than 800 square miles, closing hundreds of roads and causing $760 million in damages.
While those storms mostly spared the state’s biggest cities, others haven’t. Half of Milwaukee’s 10 largest rainfalls on record have come during the past 20 years. That fact has stormwater managers worried, says Chris Kucharik, a CALS ecologist who studies the effects of climate change. At a meeting last summer, Kucharik reminded a group of municipal engineers about a storm that dumped 11 inches of rain on Vernon County during one day in August 2007. “I asked the stormwater folks, ‘What would happen if you received 11 inches in Milwaukee?’” he recalls. “They kind of gasped, because they know that their stormwater and sewage systems would be overwhelmed.”
If you ask David Liebl, that’s because most of today’s stormwater systems are based on yesterday’s thinking,
“Traditionally, the idea was to move water as quickly as possible to the nearest surface water to prevent local flooding,” he says. “But as you develop an area and have more and more impervious surface, the amount of water becomes difficult to manage and the impact downstream becomes more of a problem.”
A good example is on the south side of the arboretum, where stormwater pours in from a neighborhood called Arbor Hills. Rain that falls at the top of the development surges down a concrete channel running through a 10-acre, park-like greenway, then under a six-lane highway into the arboretum.
“When the water’s really flowing, it’s like a southwestern arroyo—you don’t even want to be near it,” Liebl says.
The sediment eroded by that water has nearly filled a retention pond built in the 1980’s. The pond will be rebuilt, but Liebl already knows it won’t be enough. Detaining all of the water from Arbor Hills would require a pond three or four times as big as what’s there now. So instead, Liebl is focusing on upstream solutions. “We estimate that up to one half of the stormwater reaching the arboretum from Arbor Hills could be infiltrated,” he says.
To get that done, Liebl reached out to Anita Thompson, a professor in CALS biological systems engineering department. With colleague John Panuska PhD’06, Thompson assembled and advised a team of students to study the route the water travels, and find alternatives to get it into the ground. The students’ proposal calls for the creation of three dry basins in the greenway to collect and infiltrate the water. Two of them would contain native plantings, like large-scale rain gardens. The third would double as a soccer field. The students estimate that this system could infiltrate as much as 80 percent of the water pouring into the greenway.
ONE INTRIGUING ASPECT of the system is that it came out of a discipline that marries biology and engineering. Agricultural engineers have been wrestling with runoff and sedimentation issues on farmlands since the 1930s, and now that much of that land is growing houses, their expertise is coming in handy.
It’s a natural fit, says Panuska, an extension specialist who works on nonpoint pollution projects in both urban and rural settings. “People in the soil and water area have an ideal skill set for this kind of work, because they have a background in biology, as well as engineering and hydrology. Runoff, erosion, water quality — all of these are areas that we have always dealt with.”
Jeremy Balousek BS’97 MS’03 can vouch for that. After earning degrees in agricultural engineering, he now works as an urban conservation engineer for Dane County, dealing with everything from manure spills to runoff from golf course communities. “The practices really aren’t any different. We’re applying the same principles,” he says. He points to a project he’s doing with Panuska to convert software designed to predict agricultural erosion to work as a modeling tool for construction sites. “The soil loss equations were developed for agricultural land uses. We have to modify them to use for urban areas, but the science is the same. Some of the practices we use are different, because construction isn’t done on an annual basis, but the science of how erosion occurs is exactly the same.”
Over in King Hall, CALS’ soil scientists are also finding the scope of their work expanding. Once dominated by agricultural research, the department is now home to researchers such as Nick Balster, a self-described “urban soil scientist.” Much of Balster’s work focuses on soils that have been altered by human activity, such as the highly compacted soils in most residential lawns. “Today houses are being built quickly and they’re being built year-round,” he says. “When you get equipment in there during the wet season moving around in the soil, you can cause pretty severe compaction, and you can disrupt the connection between pores in the soil.“ These kinds of activities squeeze shut the channels that carry water through healthy soil, making the earth as impervious as pavement.
That could turn out to be an important factor in the success of rain gardens, one of the most widely adopted home remedies for dealing with stormwater. Balster points out that to date, the published research on rain gardens has been done on newly planted gardens. He’s currently watching over 12 rain-garden plots to try to understand the longer-term interactions between plants and soil. Do rain garden plantings help reopen those channels to filter water into the soil? And if so, which kinds of plants work best? And under what conditions?
“Rain gardens evolve. Soil and plants are in a dynamic marriage that’s constantly changing,” he says. “Our goal is to look at how these different gardens behave and learn what controls that behavior.”
BUT THERE IS ANOTHER KIND of behavior that can aid or hinder efforts to deal with stormwater: human behavior. Back at the arboretum, David Liebl knows that the facility’s water problems would be significantly reduced if residents in the Arbor Hills neighborhood took steps on their own properties to reduce runoff. The arboretum is working with Bret Shaw, an assistant professor of life sciences communication, to encourage neighbors to take steps such as planting rain gardens or installing rain barrels in their yards.
“The goal of that effort is to encourage people to take stewardship of water on their own property.” Liebl says. “The hope is that as they begin to see the problem, they are motivated to do something about it, and they’ll also support efforts like the greenway project.”
And Arbor Hills residents did need some convincing. “The neighbors were concerned about conflicts with recreational uses,” says John Panuska. “They don’t want things that will infringe upon their use of the area or the aesthetics.” But the neighborhood ultimately signed on, and with that approval in hand, city engineers intend to move ahead with the students’ design.
Shaw, who has conducted environmental awareness campaigns in several Wisconsin communities, says the Arbor Hills project demonstrates the unique challenge to getting the public to participate in stormwater management. “With stormwater, what’s done in the uplands affects people down below, so the impacts are not visually salient,” he says. “That’s what makes this situation interesting. In Arbor Hills, (the damage) is out of sight across the highway.”
Last fall, students in Shaw’s environmental communication class conducted surveys in Arbor Hills to gauge opinions on stormwater issues. The results show huge variations in awareness of the problems and readiness to address it—gaps that the students hope to close with a marketing effort targeted in the neighborhood. Shaw’s near-term expectations are modest: He’d be thrilled if he could lift the number of rain gardens in the neighborhood by 10 percent.
“A lot of what I see my work doing is both improving immediate short-term outcomes, but also influencing a cultural shift,” he says. “Let’s be honest: How many people are really thinking about stormwater management today? But I think we’re at the start of a nascent movement, where it’s one more thing to do in an effort to live sustainably.This article was posted in Communities, Environment, Features, Summer 2009 and tagged Arboretum, Rain gardens, Soil science, Stormwater, Water.