COLUMBIA — As a scientist, Jason Hubbart has not been a political player in the three-year standoff between local government agencies and MU with the federal government over the water quality in Hinkson Creek.
But the MU assistant professor of forest hydrology sees a potential solution in floodplain reforestation as an affordable way to meet a federal mandate to reduce pollution in the stream. The city likes his idea.
Hubbart, a member of the Hinkson Creek Science Team, is working with the city on plans to return part of the Forum Nature Area along Hinkson Creek to forest. In his EPA-financed research, Hubbart found that trees can increase the soil's ability to hold water by as much as 30 percent.
The pilot project would divert rainwater from Hinkson into the field targeted for reforestation that would act as a natural filtration system, preventing pollutants from entering the creek and reducing the amount of water flowing into the stream.
Plans call for a swale, a low stretch of land, planted with native plants to carry water away from the creek. Water from the swale would enter into a concrete curb, or "level spreader," which spreads the water out over a large area so it can be absorbed faster. Once trees are allowed back, they would consume more water through transpiration.
"I don’t think this solution will solve all of our water quality problems," Hubbart said. "But it could help a lot, and it’s cheap. Really cheap. If we just step back from the floodplain, and don’t touch it, trees are going to come back all by themselves."
The Environmental Protection Agency declared Hinkson Creek to be impaired, or polluted, in 1998. To help relieve pollution and erosion, the agency ordered the city to reduce runoff by nearly 40 percent. Ideas included the construction of large reservoirs and other holding basins and cost estimates to meet the targets ranged from $30 million to $300 million.
The reforestation and level spreader would cost an estimated $25,000. If the Forum Nature Area project is successful, the approaches used there could be implemented up and down Hinkson Creek.
"It's inexpensive compared to other storm drain projects," said Tom Wellman, an engineering specialist with the city Department of Public Works and a member of the Hinkson Creek Science Team. "This concept is pretty adaptable."
In a historical context, floodplains were normally forested, Hubbart said. But agriculture and urban development led to deforestation. This image of non-forested banks has been around for hundreds of years and has become a popular conception of how they should look, he said.
"As it turns out, in our area, having anything other than forest next to a creek takes a lot of maintenance," Wellman said. The Department of Parks and Recreation manages the Forum Nature Area and would like to "bow to the obvious" and start letting that southeast area reforest, he said.
Although the soil has been drained of nutrients from agriculture, enough remain to allow trees to grow, Hubbart said. Bottomland trees such as cottonwood, willow, poplar and sycamore would work well because they tolerate flooding, consume a lot of water and transpire a lot.
"It’s such a no-brainer; it’s so cheap," Hubbart said of reforestation. "You have marginal floodplain lands, plant trees, and there is virtually no maintenance cost."
Deforestation and urbanization have led to increased erosion, which can pollute streams with soil and other pollutants. Erosion causes smaller particles that have more surface area, which allow more chemicals to be absorbed and washed into the creek.
Reforestation would slow down the volume of water going into the creek, therefore the peak flows may be lessened, and therefore the amount of erosion in the stream and the amount of suspended sediment might be reduced, Hubbart said.
To make the reforestation more effective, water would be diverted into the nature area with a 250-foot concrete curb that would release water slowly into the field, which would act as a natural filtration system. The plan would address about 115 acres, a fraction of the 90 square miles that drain into Hinkson Creek.
"The importance of something like this is more in what we can learn from it and how it can be applied in other areas," Wellman said.
The spreader would be designed to accommodate small- and medium-sized storms. These storms, 1.3 inches or less, make up 90 percent of rainfall in Columbia, according to Wellman.
Although smaller storms don't place as much stress on streams as bigger rains, more erosion occurs as a result of small storms because of their regularity.
"In the past, someone like me would have been focusing on 3.5-inch storms or 5-inch storms, the big ones, to prevent flooding, but in the meantime, all these little ones have been causing damage," Wellman said.
Wellman also needs to keep a small amount of water running through the original ditch that leads into Hinkson Creek to support the ecosystem there.
"There are critters living in that creek, in that little flow line, that depend on that water," Wellman said. "So, we don’t want to cut it off entirely."
The next step for the reforestation and the level spreader would be getting approval from the Hinkson Creek Stakeholder Committee and, eventually, Public Works and the Department of Parks and Recreation. A public hearing would precede a decision by the Columbia City Council.
Wellman said that a lot of people view Hinkson Creek as a large drainage ditch that is terribly polluted.
"It’s not lifeless," Wellman said. "It’s actually really pretty. It’s a beautiful resource right through the center of town. We think it’s one of the better urban streams you could ever find, so it’s a resource worth protecting."
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